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Essentials for Dry Eyes

Simple facts in dry eyes lead to various complaints. The causes are relatively clear ... but many risk factors play a role. Tear film disorders with dryness are crucial - they lead to tissue damage Unfortunately dry eyes worsen if they don't receive adequate and timely treatment !

  • => go directly to dry eye … or just continue here to stroll along the questions & answers (recommended)

Facts are relatively simple

Complaints are different

Risk factors are important

The cause of dry eyes is a disturbance of tissue wetting - But how is the eye kept moist ... and where does the dryness come from ?

Drought has various causes

Damage is caused by the drought

Worsening is typical of dry eyes

Therapy - there are many options

What are dry eyes ?

Dry eyes, or rather dry eye disease, is a chronic irritation and damage to the tissue on the surface of the eye due to a disturbance in surface wetting by several reasons. The tissue irritation is typically sensed as “dryness“ … All this will be explained in more detail on this page !

In order to stay healthy, the surface of the eye must be moist - always and everywhere !!! - Even with open eyelids to see . Therefore, the surface of the eye is covered by a tear film.

Dry eyes are typically caused by any lack of the tear film on the eye. 

This leads to irritation of the eyes and symptoms such as a gritty sandy feeling, sticky clogged eyes, burning sensation, and pain etc…

Especially at the beginning of the disease and in elderly people, the irritation can also lead to wet watery eyes and tears running down the cheeks.

Chronic Dry Eye Disease is closely related to blockage od the Meibomian oil glands inside the eyelids (Meibomian gland dysfunktion, MGD - this is the main cause for dry eyes) and with chronic eyelid inflammation (chronic blepharitis).

=> Here you can find a short overview about dry eyes

What is Keratoconjunctivitis sicca ?

The ophthalmologist also describes dry eye disease as keratoconjunctivitis sicca.

Sicca means 'dry' and keratoconjunctivitis indicates ´inflammation of the cornea and conjunctiva´. Keratoconjunctivitis Sicca thus means "dry inflammation of the cornea and conjunctiva".  

This term is sometimes misleading, as many dry eye patients may first have a wet and watery eye with tears running down their cheeks.

On the other hand, it has been scientifically proven In recent years that inflammation actually develops in dry eyes, which makes the disease significantly worse.

What is the Sicca Syndrome ?

Sicca syndrome is another medical term for dry eye disease.

Here, too, the term ´ Sicca ´ focuses on ´dryness´ of the eye - although many patients, at least initially, may have a wet eye.

The term ´syndrome´ describes that a bundle of different complaints occurs in the patient. These various complaints may appear uncharacteristic and unrelated at first glance - this can make the diagnosis of dry eye difficult.

What is Sjogren's Syndrome ?

Sjogren´s syndrome is a rare inflammatory damage to the lacrimal gland

How common are dry eyes ?

Dry eyes are regarded as the most common disease condition in ophthalmology :

  • About 1/6 of the population is affected on average in Central Europe and North America

  • With about 1/3 of the population, the frequency in Asia is about twice as high

  • With around 2/3 of the population, the frequency of meibomian gland disorders in the eyelids is twice as high.

  • The frequency of dry eye disease is increased, e.g.

Not every dry eye is recognized correctly in first case, as the symptoms are often initially inconspicuous and the onset is often gradual.

Dry eye complaints

How do I recognize dry eyes ? - What are typical symptoms of dry eyes ?

The symptoms of dry eyes can vary widely and are therefore often unspecific. Most of the symptoms are explained by the irritation of the eye and by the disruption of the tear film:

Irritation and pain can be very different

Although the origin of the disorder is always on the surface of the eye, the patient often perceives disturbing feelings or pain in different places, e.g.:

  • on the surface of the eye itself

  • but also ´peri-orbital´

    • on the eyelids

    • around the eye

    • occasionally even behind the eye

Disorders of the tear film can also cause blurred vision and photophobia

For the reliable detection of dry eye disease and to exclude more severe issues, you should contact an eye doctor, who can examine this more closely with clinical tests.

Therapy

=> Here is information on the therapy of dry eye.

Timely and adequate treatment of dry eye is important to avoid permanent damage. The good news is that every patient can do a lot to help alleviate the symptoms of dry eye.

Drought feeling - dry eyes - the parched desert on the eye

With severe dryness and soreness of the eyes, the feeling of a parched desert floor which cracks open painfully can set in.

The feeling of dryness of the eyes is the most common complaint in patients with surface wetting disorders.

This is where the term “dry eye” comes from.

... however, the irritation may sometimes also lead to a wet watery eye.

The feeling of dryness is related to increased friction during eye movements and especially during eyelid blinks.

Therefore, the feeling of dryness is closely related to a gritty sandy feeling, foreign body sensation and itchy eyes.

If the dryness persists, there is often a feeling of heavy eyelids and tired eyes

If this persists chronically, this can also lead to slimy and sticky eyes with difficulty opening the eyes in the morning.

Gritty sandy feeling and rubbing in the eye indicates reduced lubrication and increased friction

A lack of tears in dry eyes typically typically causes reduced lubrication between eyelids and eyeball with thus increased mechanical friction that causes gritty sandy feeling and foreign body sensation.

A gritty sandy feeling and rubbing, as if small foreign bodies were in the eye, are frequent and annoying complaints with dry eyes.

Due to the typical lack of tears or, more precisely, due to the impaired wetting of the surface there is worse lubrication between the eyelids and the eyeball.

This creates increased friction with increased mechanical stress in all movements of the eye and especially in the frequent normal eyelid blinks, which spread the tear film.

Any lack of tears leads to damage to the ocular surface.

The increased friction leads to constant micro-injuries of the superficial cell layer on the eye, which leads to subliminal pain. We experience this as rubbing, gritty sandy sensation or itch and it may result in a feeling of pressure and tired eyes.

Eventually chronic irritation can turn into pain of different degrees of severity.

Therapy

There are various options for therapy in dry eye. In the case of a foreign body sensation and rubbing, a tear supplementation (artificial tears), possibly with an oil addition, can often immediately improve the symptoms.

In addition, it is worth trying to approach potential underlying risk-factors by some simple ´home remedies´.

Eye redness

Eye redness is caused by the chronic irritation of the ocular surface, mainly due to increased friction. Micro-injuries of the cell surface are seen here as green spots of wounded cells.

Eye redness is caused by the chronic irritation of the ocular surface, which is mainly due to increased mechanical friction on the dry surface.

  • A typical effect are micro-injuries of the epithelial cell surface that can be seen as green spots in clinical vital staining of wounded cells (see image)

  • Another typical effect is the dilatation of the blood vessels in the conjunctiva that leads to reddening of the eye. This represents a first step of an inflammatory response.

The reddening of the eye, which is usually only moderately pronounced in dry eyes.

Therapy

There are various options for therapy in dry eye. In the case of a eye redness, a tear supplementation (artificial tears), possibly with an oil addition, can often immediately improve the symptoms.

In addition, it may be worth trying to approach potential underlying risk-factors by some simple ´home remedies´.

When the tear film on the eye breaks-up ´the cells of the surface of the eye become dry. Such a dry spot causes irritation and burning or stinging of the eye. => the development of a dry spot, as seen here, and the subsequent damage to the underlying tissue, is shown in an animated figure further down.

The tear film has to remain stable for a certain time so that the surface is always moist while the eyelids are open to see.

In dry eyes, the stability of the tear film is typically reduced.

Burning eyes are a typical complaint of dry eyes with an unstable tear film, especially when the salt concentration in the tears is too high. A thinning of the tear film finally causes a ´break-up´ of the thin fluid layer with a dry spot on the tissue (see image). Dry spots can lead to increased mechanical friction and increased salt concentration.

If the tear water evaporates too quickly, there is a locally increased concentration of dissolved salts and proteins in the tear film. This is referred to in the specialist literature as increased osmolarity / hyperosmolarity.

Both mechanical and chemical stress typically lead to cell injury and activation of adjacent nerve fibers. Such signals are felt as irritation or pain. "Burning and stinging" is mainly suspected as a sign of hyperosmolarity.

Both mechanical stimuli and chemical stimuli can trigger an inflammatory reaction.

Therapy

There are various options for therapy in dry eye. A tear supplementation (artificial tears) can often immediately improve the symptoms. In case of burning and stinging eyes, an oil addition often makes sense because it aims to replace missing oil in the tear film. A hypotonic tear supplement that contains less salts than the normal tear film can be of advantage for more effective dilution of hyper-osmolar tears. In addition, it is worth trying to approach potential underlying risk-factors by some simple ´home remedies´.

Time-of-day-dependent symptoms and nocturnal dry eyes

The time of day when most symptoms occur can vary. This depends on which risk factors are relevant in an individual person.

  • in the case of desiccating environmental factors and activities (e.g. office work or games at the computer screen with ´Office Eye´) or driving a car, especially at night, the symptoms of dryness and irritation will be felt most intensely during such activities

  • usually the severity of the symptoms of dry eye increases during the day.

  • some people experience the worst dryness of the eyes at night and sometimes pain and problems opening their eyes can occur. This can be explained by the fact that the natural aqueous tear production is lowest at night and the eye practically runs dry for a while. The composition of the tears also changes then.

Therapy

For more severe dry eyes and particular for problems at night it can be generally recomendable to apply a tear supplement with high viscosity, i.e. a gel or an ointment, in the evening before sleep. This will typically last overnight.

=> In the event of severe pain, an ophthalmologist should be contacted to ensure a reliable diagnosis of dry eye and to exclude or treat recurrent damage to the upper epithelial layer of the cornea !

Tired eyes, heavy eyelids, pressure, irritation and pain

  • The constant dryness and irritation on the surface of the eyes leads to the sensation of "tired eyes" and "heavy lids"

  • A feeling of pressure and pain may be felt in different places in and around the eye.

  • This may be best explained by increased mechanical friction between the eyelids and the globe during the necessary eyelid blinks. This makes the eyelids sluggish and tires the frequent eyelid blinks with its constant irritation.

  • Occasionally, the secretion of the conjunctiva and the edge of the eyelid is increased and the eyes become clotted and sticky.

Therapy

There are various option for therapy in dry eye. In addition to simple ´home remedies´, as well as regular hygiene and care of the eyelids, a tear supplementation (artificial tears), possibly with an oil addition, can often improve the symptoms.

The edge of an eyelid is shown here in schematic cross section. On the lid margin with the eye lashes are yellowish brown deposits of oil, dust and tear remnants. This is a typical reason for the sensation of slimy, sticky and clotted eyes.

A temporary increased build-up of mucus or serous fluid in the case of chronic surface damage may lead to clotted and sticky eyes and to difficulties opening the eyes in the morning.

Changes in oil residues in the event of a disruption of the meibomian glands or deposits from excessive growth of bacteria on the edge of the eyelid in the case of chronic eyelid inflammation (blepharitis) can also contribute to clotted eyes (please see image).

Therapy

There are several options for treating dry eye and blepharitis. If there are deposits on the edge of the eyelid, regular hygiene and care of the eyelids can improve the symptoms. Usually a tear supplementation (artificial tears), possibly with an oil additive, is useful.

If mucus buildup and clotting occurs suddenly and severely, an ophthalmologist should be seen to rule out a potentially dangerous infection !

Chronic eyelid inflammation - Chronic blepharitis

Deposits and crusts on the edge of the eyelid and on the eyelashes occur in practically all forms of dry eye, especially in connection with chronic eyelid inflammation (chronic blepharitis).

Signs of chronic blepharitis (see figure) are typically, depending on the severity :

  • redness and possibly swelling of the eyelids, especially of eyelid margins (see figure)

  • dilatation of the vessels (teleangiektasia)

  • blocked meibomian oil-gland orifices

  • loss of eyelashes (madarosis)

  • deposits, mucus and crusts on the eyelid margin

The deposits on the edge of the eyelids and on the eyelashes contain inflammation-promoting substances that can irritate the tissue and disrupt the tear film.

This can make the condition worse.

=> Here you can find more extensive information on chronic blepharitis.

Therapy

Regular daily and thorough eyelid hygiene and eyelid care are therefore typically an important part of the treatment. Since blepharitis is typically associated with dry eye disease, other typical therapy options for dry eyes may be applied.

If the eyelid inflammation persists despite regular eyelid hygiene and lid care, possibly due to demodex hairmites infestation, an ophthalmologist should be consulted.

Visual disturbances, photophobia, sensitivity to glare

Visual disturbances in dry eyes typically get better after blinking the eye - but only temporarily.

The thin and even tear film is disturbed in dry eyes. Since the tear film is not only important for humidification but also for perfect visual acuity, many patients have visual disorders such as e.g.:

  • blurred vision

  • fluctuating visual acuity

  • glare sensitivity

  • photophobia

After one or more eyelid blinks, the visual acuity usually improves ... but typically only temporarily (see animated image).

Therapy

Usually a tear supplementation (artificial tears), possibly with an oil additive, can provide immediate improvement. There are various therapy options for dry eye that can usually significantly improve symptoms.

THERAPY - EYELID BLINK EXERCISE

Visual disturbances in dry eyes usually improve after one or more strong eyelid blinks, which spread a new tear film.

The new tear film is typically more stable because strong eyelid blinks help to squeeze out more oil of the meibomian glands in the eyelids and thus to increase the thickness of the tear film lipid layer, as studies have shown.

At the same time, this is a good test of whether visual disturbances are caused by a tear film disorder (in dry eyes) or whether a refraction correction (adjustment / change of glasses or contact lenses) is necessary.

If the visual acuity does not improve after eyelid blink exercise, an eye doctor should be contacted in order to exclude more serious reasons for visual disturbance !

Wet watery eyes and tear dripping

Paradoxical ' wet' dry eye due to excessive reflex tear formation

Initially, the irritation of the surface of the eye can also lead to a wet eye, often with tears trickling down the edge of the eyelid. This ´moist´ dry eye is sometimes also referred to as ´paradoxical´ dry eye. This is of course somewhat confusing for a patient who was informed of the diagnosis of "dry eye"

A common reason for wet eyes

  • is an increased flow of tears as a protective reaction (tearing reflex*) with the constant irritation of the eye

  • the irritated eye tries to wash away the irritation through strong tear production, as it often works with a foreign body. Unfortunately, this does not work if the eye itself is chronically irritated.

  • ... this then leads to the tears (Epiphora) overflowing over the edge of the eyelid (see animated illustration).

Other causes of wet eyes that are less common can include:

  • Changes in the shape or position of the eyelid, e.g. inward of outward curling of the edge of the eyelid.

  • Disturbances in the flow of tears into the nose, either because the lid margin protrudes slightly from the eye (which inhibits suction of the tears from the eye) or because a blockage inside the lacrimal drainage system.

=> here is more information on moist eyes and epiphora

THERAPY → A detailed examination by an eye doctor and respective therapy, if it applies, is recommended for every wet eye and for any eye problems in general !

Since watery eyes are typically, but not always, based on increased irritation of the eye, it is generally useful to apply tear supplementation (artificial tears), even though it may appear counter-intuitive. The rationale is that tear supplements are superior in many aspects to stress tears that contain mainly water. Tear supplements improve the lubrication and stabilize the tear film - and thus reduce the irritation of the tissue.

Problems with contact lens wear start or get worse

  • Contact lenses place increased demands on the volume and quality of the tear film and increase the evaporation of watery tears. Therefore, dry eyes become increasingly intolerant to contact lens wear, especially to soft hydrogel contact lenses

  • In addition, contact lenses lead to increased friction on the eye. Therefore, according to various studies , they contribute to changes in the surface of the eye that can promote dry eyes.

  • Many patients first try to compensate for the lack of tear fluid with tear supplements. However, this is usually not a recommended permanent solution. It is better not to wear contact lenses anymore, or at least not to wear them permanently, but to replace them with glasses.

  • Glasses are also beneficial for dry eyes as they offer some protection against drying air currents. If this is not enough, additional protection against evaporation can be installed.

Risk factors for dry eye

Some general remarks

Negative factors influencing the moisturizing of the eye are possible risk factors for dry eye.

Internal risk factors in the body and also external risk factors in the environment can have a negative impact.

  • Internal risk factors inside the body itself often arise from normal aging processes or general chronic illnesses. The eye complaints have usually existed for a longer time and are typically not sufficiently relieved by an improvement of drying environmental factors alone.

But ... the good news is that many essential risk factors for the onset or worsening of dry eye are outside the body in the environment (see below) and can often be easily influenced by simple means !

( 1 ) Internal Risk Factors

Advanced age - hormonal changes - disorders of the eyelids - chronic diseases - medication

  • Advanced age may lead to inevitable changes in the tissue and its function also on the surface of the eye. Thus, an increased age is one of the main ´risk factors´ in the body, which increases the likelihood of a dry eye.

    • ... at least there remains a consolation that ´wisdom´, which usually increases with age, helps to accept such changes better ;-)

  • Disorders or changes in hormones occur naturally with increasing age and can increase the risk of dry eye:

    • especially a relative lack of male hormones and an excess of female hormones

    • This also applies to drugs that affect hormones, such as anti-androgens (in tumor therapy in men) and estrogen replacement therapy (during and after the female menopause).

  • Disorders of the eyelids and eyelid blinking can occur due to changes in the tissue with increasing age, but also due to injuries or disorders of nerve regulation.

  • Chronic illnesses and some drugs against it can negatively affect the eye

  • various skin diseases, e.g. facial flushing (rosacea), neurodermatitis / atopic dermatitis etc.

  • Elevated blood sugar levels ( diabetes mellitus ) can worsen dry eyes, as chronic damage to the blood vessels and nerves occurs, which also affects the surface of the eye.

  • Addition of pollutants , for example when ´ smoking ´, also with passive smoking. This is doubly harmful, as it releases pollutants / smoke particles into the air in addition to internal poisoning.

  • chronic inflammation of the eyelid (chronic blepharitis)

  • chronic inflammatory rheumatic diseases and other systemic inflammatory diseases

  • Some medications that are given topically to the eye, usually as eye drops , can also promote dry eye. Medication prescribed by a doctor should not be discontinued without authorization !

  • serious malnutrition, e.g. with Vitamin A, an important for mucosal health, may lead to a primary surface damage which then negatively affects the tear film stability and wetting and can lead to a dry eye condition.

  • Various medications , often for chronic diseases , that are given systemically (via the digestive tract or via the blood) can make dry eyes more likely

    • e.g.: beta blockers for high blood pressure,

    • e.g. anti-histamines for allergies

    • eg drugs that act on the nervous system

    • ... and many other drugs.

Medications that have been prescribed by a doctor should not be discontinued on their own initiative if they suspect that they could possibly promote dry eye. This should be presented to a doctor who will carefully weigh the necessary therapeutic effect against potential side effects !

Many risk factors for dry eyes are also outside the body. This usually allows a chance way to influence them positively. Desiccating environmental conditions, such as those found in the natural environment, in homes and in many workplaces, play an important role , e.g.

  • Drought, dry room air, with aggravation in the heating season in winter

  • Drafts, wind, fans, air conditioning systems and blowers, e.g. when driving a car

  • as well as air pollution, smoke, own smoking

  • Concentrated visual tasks - as these external factors can trigger internal malfunctions (rare eyelid blinking)

Often several risk factors come together (e.g. drafts and infrequent eyelid blinks) - then dry eyes can develop particularly easily. For example, when driving a car or when working on a computer screen in the office as an “office eye”.

The same is of course also true for private, concentrated screen activity in computer games - this is known as the “ gamer's eye ”.

=> here is more information about home remedies for environmental risk factors

  • Previous eye surgery can trigger or promote dry eye

    • For example, after removing a cataract (cataract surgery), many patients notice a dry eye for the first time. Due to the very small surgery, however, is is likely that the dryness existed before and was just not noticed.

    • Refractive surgery (e.g. LASIK, LASEK, PRK) to improve visual acuity while avoiding glasses or contact lenses are known to typically cause dry eyes. This generally applies to those types of eye surgery in which many corneal nerves are inevitably cut. Usually, however, the dryness improves more or less in the further course.

  • Medications that get onto the surface of the eye from the outside, e.g. as eye drops, can damage the tissue on the surface of the eye and contribute to dry eyes. Especially if eye drops are used permanently and / or frequently per day (e.g. in the case of increased eye pressure/ glaucoma, dry eyes, allergies etc.). But preservatives in eye drops can also be harmful.

  • Also preservatives in various eye drops can damage the tissues of the eye surface and contribute to dry eye. The more often such eye drops are used, the greater the risk of possible damage.

  • Therefore, preservative-free eye drops are generally to be preferred if they are available for the intended purpose!

=> Here you will find an overview of the most common risk factors & home remedies , how you can easily improve them.

Cause of dry eye

What causes dry eyes ? - How does dry eye occur?

=> The decisive factor is a disturbance in the wetting with a damage of the tissue at the ocular surface ! ... and this typically arises from a deficiency of the tear film

The basic causes of tear film deficiency are, in turn, any lack of tear fluid production by the glands of the eye and / or any deficiency in the spreading of the tear fluid to form an even, thin, stable tear film through the eyelid blink.

=> Here you can find more information on basic causative factors of tear film disorders.

Why do I always have dry eyes ??? - The key factors that lead to dry eye may vary be

Although the tear film deficiency with insufficient wetting of the ocular surface tissue is known to be the cause of dry eye disease, many different risk factors in the body and in the environment can contribute to dryness of the eye. Therefore, the main decisive factors that cause or aggravate dry eye in an individual can be very different.

An exact diagnosis of dry eye is necessary for effective therapy in every person .

The surface of the eye, or in more professional terms the “ocular surface”, mainly consists of the clear cornea in the middle and the conjunctiva around it. The latter forms the main part of the moist ocular surface (see animated figure).

The cornea is the clear tissue in the center and serves the entrance and refraction of light to see.

The conjunctiva is the most important auxiliary tissue to keep the cornea moist and healthy. It covers the front of the eyeball and the back of the eyelids - hence it forms the conjunctival sac (see animated figure). When the eye is irritated, e.g. by dryness, the conjunctival vessels fill up and cause the typical reddening.

The tissue surface has a delicate fine structure that is easily damaged by dryness.

=> Here you can find more information about the ocular surface and its function.

Augenoberfläche mit Hornhaut als BANNER für EyeCare_3_20-72_2 + Tropfen_Zettel_kurz_.jpg

The shine of the ocular surface is created by the tear film, which ensures that the mucous membrane remains constantly moist and we can have a perfectly clear vision.

The tears are formed by various glands that are somewhat hidden and also belong to the surface of the eye.

The eyelids protect the moist mucous membrane and distribute the tear fluid to the thin even tear film. Disorders of the eyelids and eyelid blinking can lead to dry eyes or contribute to their aggravation.

The ocular surface must be kept constantly moist by an stable tear film

Only a moist cornea is transparent.

Our ocular surface, which is the medical term for the surface of the eye, is a mucous membrane, similar to that of the mouth. It is constructed in such a way that it has to be permanently moist - ´always and everywhere´ - so that it stays healthy and so that the cornea, the transparent window of the eye, remains really clear.

The moisture is known as tears* and it is produced by the glands that are part of the ocular surface.

But the tissue surface must also be intact and covered with water-binding mucins so that it can be wetted by the aqueous tear film.

Only the regular eyelid blink transforms the tear fluid into an intact stable tear film. Only a stable tear film enables the surface to remain moist, even when the eyelids are open to see.

The tear film is, so to say, the ´ tip on the scale ´ and its stability determines whether the eye is wet or dry.

Since we live in a dry environment with an air atmosphere, it is very laborious for the eye to maintain this small artificial moist ´ecological niche´ on the surface - ´ always and everywhere´ !

If the ocular surface is no longer adequately moistened, the sensitive tissue is damaged with symptoms of irritation .

* In addition to keeping us moist, we can also use tears to convey emotional signals to our fellow human beings. For example that we are particularly sad ... or particularly happy - Hmmm ... doesn't it say ´Tears don´t lie´? ... but with this we leave the sure ground of science and therefore do not pursue it any further !

What is the tear film?

The tear film is of the utmost importance for health and function ... we have to take a closer look at it below !

Schematic representation of the ocular surface n cross section. The eyelid blink distributes the tear fluid on the eye into a thin homogeneous tear film. Disturbances of the regular eyelid blinking are therefore a typical reason for disturbances of the tear film and thus for a dry eye !

What are the tears ? - They consist of the secretion of the eye glands!

  • The tear fluid is produced by the ocular glands

  • and runs along the ocular surface from the sides into nose

  • ... but tears alone are not enough to keep the eye healthy

What is the tear film made of ?

How is the tear film formed? - The eyelids spread the tear film:

  • by the eyelid blink

  • the tear fluid on the eye within the interpalpebral fissure (i.e. beween the eyelids)

  • is pulled out into a very thin and very even liquid FILM - the tear film

  • the different components of the tear fluid (mainly mucus, water and oil) are thereby arranged into layers

    The tear film

  • covers the surface of the eye and keeps it moist, even while the eyelids are opened to see

  • is unfortunately only stable for a short time (about 10 - 20 seconds)

  • then it breaks-up - and a new eyelid blink is necessary, which forms a new tear film … or the tissue dries out and is damaged, which leads to symptoms of eye irritation ..

Where are the tears? - they flow off into the nose!

  • more precisely tears are first sucked up by a little opening (lacrimal punctum) at the nasal side of each upper and lower eyelid

  • from the tear lake (meniscus),

  • and are eventually guided through a canalicular system into the nose - since this system is narrow it may become obstructed leads to a wet eye.

The GLANDS and the TEARS

The moisture in the tears comes from the glands of the eye

Glands of the ocular surface: The lacrimal gland lies in the lateral upper part behind the upper eyelid and small accessory tear glands (Krause & Wolfring) are distributed along the eyelid tissue. Goblet cells, which produce the important mucin for water binding and wettability of the eye, are scattered as single cells (pink dots) along the conjunctiva. The Meibomian glands form individual long strands inside both eyelids.

The tear fluid is produced by several glands, that are part of the ocular surface.

Three different types of glands are necessary because the tear film on the eye, in simplified terms, consists of at least three different types of substances:

Water from the lacrimal gland

Oil from the Meibomian glands

Slime made from mucin molecules bind water

The epithelial cells of the conjunctiva with a interspersed goblet cell are shown schematically here. The mucins in the goblet cell and in the tear film are marked in pink, corresponding to a well-known histological stain ;-). The fine finger-like cell extensions (microvilli) enlarge the surface and thus improve the wettability.

  • Mucins ensure the binding of water and thus the wettability of the surface of the eye!

  • In order to improve the wetting the mucins in fact form 2 layers:

    • Integral mucins are firmly anchored in the surface (cell membrane) of the cells (please see figure) and provide the wettability of the tissue surface

    • Secretory mucins come mainly from individual small goblet cells (please see figure) that are interspersed between the other cells in the mucous membrane of the conjunctival sac.

    • The secretory mucins are swimming in the tear water thus forming a mucin-water gel. The mucin gel provides wetting and lubrication.

The different gland products are arranged in layers in the tear film on the eye.

Disturbances in tear production by the glands (with respect to the quantity and/ or quality of the substances) can lead to disturbances of the important tear film ... and thus to dry eyes.

Any disturbance of the tear film will lead, sooner or later, to a damage of the delicate tissue structure (see image) and will thus negatively influence binding and stability of the tear film.

=> Here you will find more detailed information on the microscopic structure of the surface of the eye

The meibomian glands are of particular importance for the surface of the eye

Meibomian oil retards the evaporation of tear water and increases the stability of the tear film .

Every single gland of the about 50 Meibomian glands that occur in an eye (shown here as yellow streaks) can release a little drop of oil onto the lid margin and tear film.

The meibomian glands form many, individual, long strands inside the eyelids (see also the figure). They produce lipids that are liquid at body temperature and thus form an oil. The regular eyelid blinks promote the expression of oil from the glands onto the edge of the eyelid and tear film.

Meibomian glands are of particular importance for the health of the ocular surface, as their oil delays the evaporation of the watery tears and increases the stability of the tear film.

In the dry environment in which we live, the watery tears evaporate from the surface of the eye faster than the lacrimal gland can produce them. Therefore we need a layer of oil on the surface of the tear film to sufficiently inhibit evaporation.

A lack of oil on the tear film and / or environmental factors that increase evaporation ... both favor dry eyes.

Tears - the magic juice that keeps the surface of the eye healthy

Tears are the ´magic juice´ - a liquid that is necessary for many, many, many purposes on the surface of the eye.

The tear fluid is produced by the different ocular glands and accordingly consists of different substances. It also contains components from the blood. The main amount, however, is water.

Tears not only serve to moisten the tissue surface, but they also contain substances, eg for

Tears can perform many of their functions only when they are spread out into an even thin film of tears

The moistening of the ocular surface is probably the most obvious function of the tears and dry eye disease is the condition when such moistening is disturbed. Therefore tear supplements, particularly of the aqueous type that replace water, are the most immediate therapy option and are still the backbone of dry eye management.

There are basically different treatment options for dry eyes. What really helps against dry eyes ... cannot be answered that easily. Because the choice of therapy depends on which disease factor is most important in a particular person and disturbs the humidification the most.

The predominant volume of the tear fluid is watery and comes from the lacrimal gland, located upwards lateral in the bony eye socket. From there the tears get into the conjunctival sac (see figure).

The tears flow to the nasal side of the eye. This takes place behind the eyelids and in the tear lake along the edge of the eyelid.

Through the blink movement of the eyelids, the tears are distributed into a thin film of tears over the visible frontal part of the eye to keep the tissue moist.

On the side of the nose, the "used" tears are then sucked up through two small holes (lacrimal puncta). One punctum each lies on the nasal edge of the upper and lower eyelids and dips into the tear lake.

The tears reach the nose through the draining tear ducts (see animated figure).

The lacrimal punctum that sucks up the tears is easily visible, for example in a mirror.

If large amounts of tears get into the nose, when we cry, they can run backwards into the throat, where we can perceive their salty taste.

Changes of the eyelids e.g. when the lacrimal puncta not dip into the tear lake, or e.g. any obstruction of the lacrimal ducts, often with bacterial infection, can cause "wet eyes" and overflow of tears. A wet eye with tearing should always be presented to an ophthalmologist to exclude any serious reason !

The EYELIDS and the Eyelid BLINK

The eyelids and eyelid blinks are just as important as the tears

The eyelid blink spreads the tear fluid into the tear film within the interpalpebral fissure. The tear fluid flows behind the lid and in the tear lake (tear strip/ tear meniscus - is located at the contact point between the inner lid margin and the eyeball. It is present at both the lower and upper eyelids.

  • The eyelid blink spreads out the tear film

A sufficiently frequent and complete eyelid blink is necessary for an even and stable tear film which allows permanent moistening of the eye and sharp vision.

  • it mainly moves the upper eyelid downwards, wiping the cornea and conjunctiva

  • during the downstroke of the eyelid the 'used' tear film 'removed' and compressed into the tear lake

  • the tears are sucked up into the lacrimal puncta and transported into the nose.

  • during the upstroke of the eyelid a new tear film is spread

  • during the eyelid blink the eyelid muscles also squeeze out oil from the meibomian glands onto the eyelid margin and the tear film

The eyelid margin with the eyelashes is of particular importance for the homogeneous spreading of the tear film and for ocular health.

Disturbances of the eyelids and of the regular and complete eyelid blink can lead to disturbances of the tear film with tissue damage and thus to the typical symptoms of dry eye.

The force of muscle contraction during the eyelid blink helps to squeeze out oil from the meibomian glands inside the eyelids.

Rare eyelid blinking (often during concentrated visual tasks) is therefore an important cause of oil deficiency on the tear film and is possibly a co-factor for the onset of Meibomian gland dysfunction (MGD). 

Studies have shown that deliberate, powerful eyelid blinking (eyelid link exercise) is a simple way of increasing the oil layer on the tear film (see animated image). This increases the stability of the tear film and prevents or improves dry eye.

In Meibomian gland dysfunction (MGD), the oil in the passages of the gland thickens and eventually it comes to a blockage of the gland. This is considered the most common cause of dry eye.

Cross-section of the eyelid (schematic): The eyelid blink ensures that the meibomian glands are expressed: The Meibomian glands produce the oil through clusters of gland cells in rounded end pieces ("Secretion", bottom left in the figure). The gland cells lie deep in the eyelid and fill the duct system of the glands with oily secretions (arrows). The slight pressure of the eyelid musculature during the eyelid blink pushes oil droplets out of the gland opening on the edge of the eyelid (“Delivery”).

=> Another animated figure shows what happens when the glands are blocked in Meibomian gland dysfunction.

The TEAR FILM

A Look into the tear film - it provides the moisture of the tissue surface

The ocular surface is covered by a thin, even film of tear fluid - the tear film consists of different layers.

Water-binding mucous substances (mucins, in the picture as pink colored fibers) ensure the adhesion of the watery tears to the cell surface and thus the constant wetting, humidification and lubrication. Some are attached to the cells and others are dissolved as a gel with the water of the tears.

Numerous finger-like extensions of the cells enlarge the surface and thereby improve the adhesion of the tear water. When the normal cell surface is damaged, the adhesion of the tear film is reduced and it breaks up quickly ... which then leads to surface dryness and further tissue damage. Tear film disorders and tissue damage reinforce each other.

The tear film is arranged in layers on the surface of the eye

=> here you can find an animated figure of the distribution of tears into the tear film by the eyelid blink

The tear film is spread into layers by the eyelid blink. However, these layers are not sharply separated, but rather mixed to a certain extent. They each consist predominantly of the secretions of one type of gland.

The break-up of the thin tear film becomes visible when the tears are stained with the fluorescein dye that is observed in blue light. A break-up occurs as a dark area (seen here in the middle of the faint “C” of the OSCB overlay). The break-up of the tear film is the stimulus that triggers an eyelid blink in order to distribute a new tear film.

As long as the intact layering of the tear film is preserved and the tissue is still intact, the tear film remains stable and can keep the tissue moist.

The tear film

  • is only stable for a short time (about 10-20 seconds)

  • then becomes thinner due to the normal evaporation of tear water into the surrounding air

  • eventually breaks-up completely (see image)

  • ... thus the tear film has to be renewed again and again by an eyelid blink or the tissue dries out and is damaged, which leads to symptoms of eye irritation.

… and thus … the intact tear film is the ´ tip on the scale´ of ocular surface health and function.

The short time in which the tear film remains stable shows how sensitive the system is and how easily dry eyes can occur. Therefore, the desiccating irritation of the tissue by the break-up is the signal that triggers a new eyelid blink.

The stability of the tear film depends on sufficient tear production by the glands and the even, thin spreading by the regular eyelid blink. Tear film stability can be assessed by a simple clinical test.

If one of the layers or the substances it is made of is deficient, diminished and has gaps ... then the tear film becomes unstable and breaks up.

Tear film instability in tear film disorders leads to drying of the tissue, irritation, irritation and other symptoms of dry eye . The determination of the tear film stability by measuring the tear film break-up time (BUT) is therefore one of the most important functional parameters in the diagnosis of dry eye.

The oil layer of the tear film consists of two different lipid layers

Since oil typically cannot mix with water, the important oil layer on the aqueous tear film must consist of 2 different layers ( see illustration):

  • on the outside is a thicker layer of ´typical´ ( non- polar) lipids, that cannot mix with water.

    • these include, for example, so-called triglycerides. This thicker layer is the actual “ lid on the pot” ´… of the warm water in the tear film.

  • on the inside the lipids are connected by a very thin layer with the aqueous tear film - so that the " lid on the pot remains in place" in order to keep the above comparison.

    • this inner layer consists of ´atypical´ (polar) lipids, that are partially miscible with water. Important molecules that can combine oil with water are phospholipids, for example. Conceivably proteins also contribute to this function.

Since the very important connection layer between oil and water is extremely thin, it is also very sensitive. This can easily lead to a disruption of the molecular balance that ensures the stability of the tear film ...

... and the stability of the tear film is the most important factor that keeps the surface permanently moist and prevents dry eyes.

The fact that a stable tear film is of crucial importance for the health of the eye also explains why dysfunction of the lipid layer due to oil deficiency is the main cause of dry eye .

The tear film has many functions

Ocular glands produce the tear fluid and the eyelids spread it into the tear film.

What is the function of the tear film on the ocular surface ?

The tears can perform many of their important functions only if they are spread out into an even, thin film of tears.

These functions include, for example:

  • Moisturizing of the tissue between the opened eyelids while seeing

  • Lubrication of the gliding movements of the eyelids over the eyeball during eyelid blinks and movements of the eyeball

  • homogeneous light Refraction - which makes the tear film also very important for visual acuity

    • even minor inhomogeneities of the tear film, as occur in dry eyes, can result in blurred vision.

Only a thin even film of tears allows perfect visual acuity

Only the thin homogeneous tear film guarantees health and clear vision

An intact thin and even tear film, with a certain layer structure, is not only necessary for moistening of the eye.

It is also the prerequisite for uniform light refraction and thus perfect visual acuity.

Disturbances of the tear film typically lead to reduced or fluctuating, i.e. unstable, visual acuity. This is often described as 'blurred vision', 'foggy vision' or 'veil vision'.

After one or more strong eyelid blinks of the eye (eyelid blink exercise ), the visual acuity improves again ... but mostly only temporarily.

If the visual acuity does not improve after eyelid blink exercise, at least temporarily, an eye doctor should be contacted in order to exclude more serious reasons !

Basic requirements for eye health

Basic functional complexes provide an intact stable tear film for permanent moisture and clear vision.

In summary, the basic functional complexes for ocular surface health are those that guarantee the permanent moisture of the tissue surface by an intact tear film*:

*this applies provided that the ocular surface tissue itself is not impaired by any other negative impact, typically a systemic disease.

How does drought come about?

Dry eyes are typically caused by a tear film disorder

A tear film disorder leads to dryness of the eye. This can be caused by any disturbance of the factors, that keep the ocular surface healthy and moist.

Basic causative factors typically result in Dry Eye Disease and this can lead to a degenerative remodelling of the tissue it becomes chronic

These are the two typical basic causal factors in the development of dry eye disease.

Disturbance of the tear film leads to damage to the sensitive tissue on the surface of the eye. Therefore, both are closely interrelated in the pathology of dry eyes. Tear film deficiency is the main mechanism for the onset and aggravation of dry eye disease.

Only rarely is the tissue surface damage first and interferes with the adhesion (wettability) by the aqueous tear film. In turn, impaired wettability of the surface leads to an unstable tear film - so that tissue damage and tear film disruption mutually reinforce one another.

Tissue damage can result from internal risk factors such as systemic, often inflammatory, diseases in the body, very strong vitamin A malnutrition or from external influences, such as aggressive preservatives in eye drops or from wearing contact lenses.

Different types of dry eye

Water deficiency in the tear film ... can have various causes

Every dry eye sooner or later has a lack of water.

This creates a feeling of dryness that gives the condition its name - although some patients may occasionally have episodes of wet watery eyes.

Water shortage can result from different conditions - please see below

  • Water deficiency

  • Insufficient water production - termed as “Hyposecretory dry eye” / “Tear deficient dry eye”/ “Aqueous deficient dry eye”

  • a primary lack of water is not very frequent only about 15% of dry eye patients (please see image) suffer from it according to studies - but when it occurs the aqueous deficiency is typically more severe

  • it is typically caused by disorders of the lacrimal gland, mostly by chronic inflammatory conditions such as e.g. Sjogren´s syndrome (which is quite rare).

  • In such cases there is a reduced production of watery tears by the lacrimal gland - or in extreme cases even no more watery tear production at all.

  • In advanced stages of chronic dry eye disease, however, when the regulation systems of the ocular surface are increasingly damaged, the different types of dry eyes tend to mix. An aqueous deficiency due to a reduced tear production can then go along with a primary lack of oil.

  1. a primary lack of oil is much more common with about 4/5 of dry eye patients (please see image), as compared to an initial lack of water

  2. a lack of oil leads to a subsequent increased evaporation of the sufficiently produced tear water on the surface of the eye - this is termed as “Evaporative Dry Eye”.

  3. A primary lack of oil thus also results in a lack of tear water - but this is secondary to the lack of oil … and typically less severe than in primary lacrimal gland failure

    Evaporative dry eye mainly usually occurs due to Meibomian gland dysfunction (MGD), typically by blocked of the glands, and with drying environmental influences.

  • Wetting disorder due to Mucin deficiency

    • A lack of the water-binding mucins on the tissue surface and in the lower area of ​​the tear film can also lead to impaired wetting of the ocular surface and thus to dry eyes. However, according to studies, this is rarely a primary cause.

    • In advanced chronic dry eyes with increased surface damage also the production of mucins and thus the wetting of the ocular surface, i.e. the binding of water to the tissue surface (please see this figure), tends to decrease.

THERAPY => Aqueous eye drops, with or without oil addition, are a useful therapy to compensate for the lack of water and conceivably also for the oil deficiency that is usually present.

... Tear supplements should be used as needed and often enough, up to once an hour. An even more frequent use of aqueous eye drops may not be useful, as this can reduce the effect of the (remaining) own tears with their important ingredients - thus the irritation of the eye could become even worse.

As always, for all eye problems, you should consult an ophthalmologist for a thorough diagnosis and appropriate therapy recommendations !

Evaporation of the tear water in the case of an oil deficiency leads to hyperosmolarity of the tear film

Even with normal production of watery tears by the lacrimal gland (upper left in the image), a lack of oil can lead to a secondary lack of water in the tear film due to dysfunction of the meibomian oil glands (upper right in the image) inside the eyelids. A lack of oil increases the evaporation of the tear water and thus the concentration of the remaining salts and proteins (gray circles in the image). This is known as hyperosmolarity and it can cause irritation and damage to cells that trigger inflammation. (The epithelium of the conjunctiva with a goblet cell is shown schematically here in the image). Hypo-osmolar aqueous tear supplements can be useful to dilute a hyper-osmolar tear film in evaporative dry eyes.

Evaporation of the tear water reduces the amount of aqueous tears on the eye and increases the salt concentration in the remaining tears. This is termed as “Increased osmolarity”/ “hyperosmolarity”/ “hyper-tonic tear film”). The osmolarity of the tear film is now relatively easy to measure with a clinical test.

Attention: even normal tears always taste salty ... so this is no sign of illness ! In the case of hyperosmolar harmful tears, the salt content is greatly increased by the evaporation of water.

  • A reduced amount of tears leads to reduced lubrication and thus to increased friction during eye movements and eyelid blinks. with damage to the cells.

  • Increased salt concentration (hyperosmolarity) can also damage the cells with shrinkage due to dehydration ( see animated figure ).

=> As a consequence, both, increased mechanical friction as well as increased concentration of the tears (hyperosmolarity) can put the cells in an ´alarm state´.

Therapy : Hyperosmolar tears can benefit from hypo-tonic tear supplements

In addition to therapy for the blocked meibomian oil glands (with warming and massage of the eyelids), eye drops can be useful for aqueous dilution of a ´hyperosmolar´ tear film.

Conceivably, can hypo-tonic / hypo-osmolar eye drops be beneficial and more effective because they contain less salts than the normal tear film and can thus allow for a reinforced dilution.

The tissue of the ocular surface can rarely be damaged first, and this can also lead to a dry eye condition.

Disturbances of the tear film lead to damage to the tissue surface

Disturbances of the thin tear film lead to damage to the tissue surface with a reduction in wettability. Chronic tissue damage can induce a degenerative tissue remodelling => as shown in a more detailed animation.

All disorders of the tear film in dry eyes lead to damage to the tissue on the ocular surface.

The most common tear film disorder is an oil deficiency on the surface of the tear film. Since the oil layer forms a barrier against rapid evaporation of the tear water, the result typically is:

The tear film disorder leads to subsequent damage of the sensitive surface of the cells (see animated figure):

Primary water shortage ... arises in Sjögren's Syndrome directly through disruption of the lacrimal gland ... and leads to the "tear-deficient dry eye"

Henrik SJÖGREN, Swedish ophthalmologist, who was the first to describe the inflammatory disease of the tear and salivary glands named after him, which leads to the sicca syndrome of the eyes and mouth.

The so-called Sjogren's Syndrome is a special form of watery lack of tears that is relatively rare.

It is caused by a chronic auto-immunological inflammation of the lacrimal glands in the eye and also of the salivary glands in the mouth. This was first described by Henrik Sjögren in 1933.

The chronic inflammation of the glands leads to dryness of the eyes and mouth - often with inflammatory glandular swelling. It can occur alone (primary Sjogren's Syndrome) or together with auto-immunological rheumatic disease and skin disease (secondary Sjogren's Syndrome). Even in primary Sjogren's Syndrome a dryness of the eyes may occur as a first sign.

To verify Sjögren´s Syndrome it is necessary to show the presence of anti-nuclear auto-antibodies (Anti-Ro/SSA und Anti-La/SSB), rheumatoid factor, and histologic evidence for the typical glandular inflammation in a small biopsy of the salivary glands.

The frequency of Sjogren´s syndrome is relatively low with an incidence of about 0,5 % of the population, and occurs mainly in females.

Sjögren´s Syndrome typically leads to a severe lack of tears, occasionally to complete absence of aqueous tears. The volume of tears in Schirmer-1 Test is at least below 5mm (in 5 minutes).

Therefore, not every lack of water on the eye is caused by Sjögren's syndrome and a presumptive diagnosis must be confirmed accordingly, e.g. by detecting autoantibodies.

Oil deficiency ... in the tear film is mostly caused by Meibomian Gland Dysfunction (MGD) in the eyelids ... and leads to "evaporative dry eye"

The meibomian oil glands in the eyelids normally (left side of the image) produce oil for the tear film, which retards the evaporation of the tear water. When the oil glands are blocked (middle part of the image) no oil comes out and thus the tear water evaporates faster. The oil however, is stuck inside the glands and dilates the ductal system causing gland tissue damage. When the gland obstruction persists for a prolonged time (on the right side in the image), the glands are damaged by the increased pressure and appear shortened or lost. This can be analysed with the diagnostic technique of meibography.

Usually it is not the water in the tears that is missing first, but the superficial oil layer on the tear film, that reduces the evaporation of the tear water.

The oil ( lipid ) comes from the meibomian oil glands in the eyelids:

  • the amount of oil is quite small compared to the aqueous tears from the lacrimal gland.

  • therefore the amount of tear fluid is not immediately changed by a lack of oil, only its quality - but this is already sufficient for a disruption of the tear film.

Oil deficiency is caused by disorders of the meibomian glands (Meibomian gland dysfunction, MGD) in the eyelids.

Usually the glands become blocked, and the lack of oil causes the aqueous tears to evaporate more quickly. This makes the eye dry and creates an " evaporative dry eye ".

Meibomian disorders are very common and increase with age .

Blockade of the Meibomian glands from thickened oil and flakes of skin

Blocked Meibomian oil glands with inspissated secretum.

Oil deficiency with subsequent dry eye usually results from clogging of the meibomian oil glands in the eyelids.

The meibomian glands clog up due to altered, inspissated oil together with skin flakes from increased cornification in the gland ducts. This often creates a plug in the opening of the gland.

Often with meibomian gland dysfunction (MDD), thickened or white discolored secretion can be pressed out of the small gland openings on the edge of the eyelid (see illustration).

By meibomian gland obstruction not only an oil shortage develops dry eye but also an unnoticed damage to the glandular tissue inside the eyelid by the increased pressure in the obstructed glands.

=> Here you can find more information about Meibomian gland dysfunction (MGD) - according to current knowledge from the TFOS MGD Workshop Report 2011, this is the most important primary cause of dry eye

Obstruction of the Meibomian glands leads first to tear film deficiency at the surface and later to dilatation and destruction of the gland tissue inside the eyelids. (For orientation, please compare with this figure of the eyelid margin) - For the secretory mechanism of the Meibomian glands please see this image)

2 causes for MGD

Meibomian gland dysfunction (MGD) with obstruction of the glands typically has 2 causes :

  • Thickening of the oil in the duct system in the glands

  • Cornification of the glandular opening

=> Both together lead to blockade of the gland opening (see image).

2 consequences of MGD

The clogging of the meibomian glands has 2 main consequences:

THERAPY → Eye drops that contain oil or a lipid spray can usually provide immediate (but temporary) relief from the symptoms of dry eye ... but ...

... above all, it is important to improve the function of the oil-producing meibomian glands in the eyelids !

This is done using a so-called physical lid therapy (with warming, massage, cleaning), which the patient himself regularly carries out at home in order to relieve the clogging and damage to the glands.

=> Here is more information about further therapy options for Meibomian gland dysfunction (MGD) and chronic blepharitis/ eyelid inflammation that is often associated with it.

The eyelids and eyelid blinks are important to the health of the eye

Regular eyelid blinking is necessary:

Disorders of the eyelids and of eyelid blinking contribute to dry eye

Protruding or outward rolling (ectropion) of the eyelid margin can lead to moist eyes with tears

  • more often with increasing age, e.g. eyelid laxity, without being noticed.

  • can also occur due to scarring after injuries and accidents or with chronic eyelid inflammation (blepharitis).

  • Typical alterations in shape are as rolling of the eyelid margin

    • outward (ectropion - see animated image)

    • inward (entropion) - this often causes rubbing of the eyelashes on the cornea with wounding

  • => here is more information about deformations of the eyelids.

  • Excessive population with bacteria and demodex and inflammation promoting depositions on the eyelid margin

The lid margin is populated by low numbers of harmless normal bacteria and Demodex hair mites. Demodex reside in the hair follicles and are mobile along the lashes. In case of chronic eyelid inflammation (chronic blepharitis), often associated with …

The lid margin is populated by low numbers of harmless normal bacteria and Demodex hair mites. Demodex reside in the hair follicles and are mobile along the lashes. In case of chronic eyelid inflammation (chronic blepharitis), often associated with chronic dry eye disease, the number of demodex and bacteria is increased.=> here is a microscope image of Demodex mites

Alterations at the eyelid margin play a role as disease factors in chronic dry eyes.

This concerns e.g.

Depositions of debris materials tend to build up in chronic ocular surface disease and provide a nourishing microenvironment for microbes and parasites. These multiply and in return promote the further deposition of pro-inflammatory depositions in a vicious circle.

Chronic blepharitis can eventually result in alterations of the posterior lid border such as

  • scarring

  • irregularities

  • rounding

These lid margin alterations impair the regular tear film formation and may eventually favor the development of changes in the shape and position of the eyelid such as entropion or ectropion.

=> Hygiene and Care of the eyelids and the eyelid margin is thus an important component in the therapy of dry eyes, Meibomian gland dysfunction and chronic blepharitis.

( 2 ) Disorders of the nerve regulation of eyelid blinking

If the eyelid blink is incomplete , the lower part of the tear film is not renewed and the tissue in this area is not sufficiently moistened.

  • Rare and incomplete eyelid blinks can be causes of a tear film disorder. 

    • In Rare eyelid blinks, the tear film is not renewed sufficiently often - it breaks up and the eye becomes dry. This can lead to irritation and blurred vision.

    • The normal frequency is around 10-12 eyelid blinks per minute, but it depends on the current visual task.

  • In the case of incomplete eyelid blinking (" nervous eyelid blinking ") the eye is not completely closed.

  • => Here you will find more information about disorders of the nerve regulation of the eyelid blinking

"Office Eye" combines many risk factors

The so-called office eye is a rapidly increasing type of dry eyes in "modern" office working environments .

In this condition, several harmful factors (risk factors) come together and and lead quickly to dry eyes.

This type of dry eye not only affects the elderly but is also increasingly common in younger people .

Concentrated visual work (e.g. with computer, screen (VDT), watching TV, driving a car) is associated with rare eyelid blinking and therefore easily leads to dry eyes.

The same is of course also true for private, concentrated screen activity, e.g. in computer games - this is known as the “gamer's eye”.

The risk of dry eyes increases: 

  • in a dry environment (air conditioning) and /or

  • with drafts (fans, blowers) and /or

  • dust particles or smoke in the air as well as smoking

  • mental stress and maybe in addition

  • too little drinking volume

In addition to an unstable tear film, there are also drying environmental factors and perhaps negative internal influences on tear production.

THERAPY → Your own observation and, if necessary, changing your eyelid blinks is important for a sufficiently frequent and complete eyelid closure. Furthermore, conscious eyelid blink exercises can be useful at work - there are even computer apps as a reminder.

Avoiding excessively dry work environments, taking sufficient breaks and drinking enough fluids are also helpful - please consider 7 golden rules for improving eye health .

What damage does drought cause ?

A disruption of the tear film damages the tissue of the surface of the eye => here you will find a more detailed description

Every tear film disorder leads to damage to the tissue at the ocular surface - regardless of whether it is caused by increased evaporation due to lack of oil in meibomian gland dysfunction (MDD) or by primary lack of water production by the lacrimal gland or by a potential mucus deficiency.

Tissue damage leads to poor wettability of the cells on the surface of the eye and thus intensifies the original tear film disorder.

Tissue damage also causes irritation to the sensitive nerve fibers and thus irritation and a feeling of pain.

=> Tear film disturbance and tissue damage worsen each other and form a central ´devil circle´ of self-aggravation in dry eye. - In addition, there are many more of these negative mechanisms.

Furthermore, the tissue damage leads to the development of inflammatory processes.

These are a defense reactions of the body. In the case of chronic disorder, as occurs in dry eye, however, chronic inflammation leads to an intensification of the disease process.

Stimulus, Irritation, Pain, and Chronic Pain Syndromes

  • The constant irritation to the eye can lead to pain, and chronic pain can turn into a disorder of the pain system. Then chronic pain syndromes can develop. They are an independent disease factor in dry eye disease and are often difficult to treat.

  • A collaboration with the pain medicine, psychosomatic medicine and neurology, can be helpful when strong subjective symptoms occur in an eye without significant clinically apparent damage. At the same time, these patients sometimes can have other functional disorders of the psychosomatic form (such as irritable bowel syndrome, unclear spinal column syndromes, tinnitus, unclear dizziness, etc.).

What causes worsening of dry eye?

"Dry eye" tends to get worse without adequate treatment

When does a dry eye become dry eye disease ?

A 'Dry' eye can certainly happen every once in a healthy person.

Dryness of the eyes can certainly occur occasionally - even in healthy people - and usually improves quickly after a few strong eyelid blinks and if risk factors are avoided. Only when this condition occurs chronically can an occasional " dry eye " develop into a "dry eye disease ".

´ vicious circles ´ of disease aggravation

The epithelium of the cornea is shown schematically here

Tear disorder

A tear film disorder creates or exacerbates a certain alteration of the ocular surface.

Tissue alteration

An altered tissue surface with a disturbance of the delicate microstructure in turn worsens the wettability of the tissue and thus the stability of the tear film on the altered ocular surface.

´Vicious circles´

Hence, dry eye has a tendency to worsen itself if not properly treated.

Such self-reinforcing reactions are referred to as ´vicious circles´ of disease aggravation.

Inflammatory reactions accelerate the self-aggravation of dry eyes.

=> HERE is a detailed description of the pathophysiology of dry eye disease.

If the surface of the eye is permanently irritated, as is typical with dry eyes, this can trigger an inflammatory reaction.

The inflammation is actually meant to defend the eye. If it becomes chronic, however, it can become deregulated into an immune-modulated inflammation.

Then inflammation can become an independent disease factor that represents a target for an effective anti-inflammatory therapy.

Therapy : an anti-inflammatory therapy by the ophthalmologist can be useful here.

There are even more therapy options available at your trusted ophthalmologist and, for severe cases, or in specialized Sicca centers.

With severe dry eye , the functional circuits of an intact surface are increasingly damaged .

It comes to increasing tissue disorder . This reduces the wettability of the surface and the production of tear fluid, which is required for wetting, by the glands.

The constant irritation of the nervous system not only triggers chronic irritation and pain, but also reduces the regulation of glandular activity.

Furthermore, the increased friction and irritation on the edge of the eyelid increases the disruption of the meibomian glands and the development of chronic eyelid inflammation (blepharitis).

Increased friction, reduced wetting and inflammation of the cornea can damage the constant regeneration of the uppermost corneal layer (epithelium). This can trigger the ingrowth of blood vessels and clouding of the cornea.

Therapy - many options

Treatment options for dry eye => Attention: Please note the following disclaimer

What really helps against dry eyes ... cannot be said that simply, as many disease factors act together to develop dry eyes. In addition, the various factors are not equally important for everyone's dry eye.

Prevention:

Therapy - Important options:

Only when the eye doctor has diagnosed a dry eye and excluded other diseases can therapy measures be selected. These are, e.g.:

Therapy for Dry Eye Disease is typically carried out after a detailed survey of your medical history and a thorough diagnosis of the causes.

The typical therapy approach is a staggered therapy. The respective treatment is intensified stepwise depending on the severity of the disease until sufficient improvement occurs.

=> here is more information on different therapy options

=> here is more information on staggered therapy

Disclaimer

The information about eye health given on this website is in no way a substitute for professional advice or treatment by doctors !

The content cannot and must not be used for making independent diagnoses or for the selection and application of treatment methods.

It is always advised to visit an ophthalmologist for a detailed individual diagnosis and treatment recommendations !