Tear supplements are a basic therapy for dry eye disease

Since dry eye disease typically has a deficiency of the tear film on the eye, the approach to substitute or to supplement water is certainly an immediate idea.

Such tear supplements have several different names that basically all mean the same: something that occurs naturally in the tears or that can at least mimic aspects of the function of tear components is added.

Tear supplements are a dog of many names

• “Artifical tears” is a frequently used but too optimistic term. Unluckily, it is impossible at present to fully replace all valuable ingredients of natural tears.

• “Tear substitutes” seems to point into the same direction. It seems to suggest that the tears are substituted with all their important functions - which is impossible as mentioned above.

• “Tear supplements” is probably a more suitable term. It describes that one or more factors are added to the deficient tear film in an attempt to replace or add the most urgently needed substances and functions to the deficient tears.

Tear supplements typically provide immediate but short-term relief of symptoms

Therapy with tear supplements typically improves the dryness and irritation of the eyes immediately. The duration of action is typically limited, however. This is because:

• the supplementation can not contain all the ingredients of the natural tears - therefore it has a limited functionality, that is rapidly lost.

• artificial supplements are constantly removed together with the natural ´used tears´ by the normal tear drainage into the nose.

• supplemented fluid - often mainly water - is drying out/ evaporating, just like the natural tear water. Thus the water in tear substitutes is bound by typically large molecules in order to limit evaporation … but it still needs frequent replacement. An addition of oil/ lipids can limit the water evaporation and provide longer relief.

Therefore, aqueous tear supplements have to be applied repeatedly during the day - about every two hours to every hour, depending on the severity of dry eyes and on the actual applied tear supplement.

Since tear supplements are typically only a symptomatic treatment it generally makes sense to aim at more causative therapy approaches, such as physical therapy of the often prevailing Meibomian oil gland obstruction and lid margin hygiene.

Tear supplements have seen great advancements

Tear supplementation is still the cornerstone of dry eye therapy. The pharmacological formulation of tear supplements has made considerable technical advancements over time. This is driven by continued intense research on dry eye disease.

Research has allowed better insight into the mechanisms of dry eye disease and the composition and action of the tear film and of tear components.

• Besides purely aqueous tear supplements there is increasing availability of tear supplements that include oil/lipids in order to improve the lack of oil with subsequent evaporative Dry Eye, that represents the main type of Dry Eyes.

• Some tear supplements aim to reconstruct all three phases of the tear film (mucin/slime, water, oil) and are thus on the way to achieve real “artificial tears”. However, this is unfortunately still a very distant goal, since tears contain an extreme multitude of different substances, that conceivably all have a function for the health of the ocular surface.

• Among the aqueous formulations the choice of water binding molecules has seen advancements. Novel water binding substances allow better binding to the ocular surface. Longer binding to the surface tissue translates into longer residence time on the surface and thus less frequent application of the artificial tears. This is a major relief for dry eye patients.

• Additional integrated substances in the tear supplements allow additional functions such as tissue protection, protection against hyperosmolarity or nutritive, healing and anti-inflammatory functions, => here is selection of tear supplements with additional functions

A general improvement in all kinds of tear supplements it the fact that they are increasingly available without preservatives that are harmful to the tissue.

Additional measures for prevention and therapy are useful

Additionally, it is of course useful to avoid or minimize desiccating risk factors (computer screen work, draft, dry indoor air, low humidity, contact lenses, etc.) and to care for sufficient fluid intake, diet and adequate sleep,

Simultaneous regular eyelid therapy (with warming, massage and cleaning of the eyelids) is important to improve the function of the eyelids and Meibomian oil glands, which are very important for the health of the eye.

Water is bound in aqueous tear supplements (“water drops”)

A disorder of the tear film, or one of its 3 layers is eventually related to a lack of water. Aqueous tear substitutes are used to supplement water deficiency in the tear film and are thus a basic therapy for dry eyes.

A lack of water occurs either when the lacrimal gland produces too little aqueous tears, or when the tear water evaporates too quickly from the ocular surface into the ambient air. A low production of watery tears as well as a lack of mucus production into the lowest tear film layer, that binds the aqueous tears to the eye, are both rare.

According to the current state of scientific knowledge, a lack of aqueous tears due to evaporation is the most common case (in about 4/5 of the patients) and mostly due to an oil deficiency in Meibomian gland dysfunction inside the eyelids.

Large Molecules bind Water in Tear Supplements

To increase the retention time of the supplemented water on the surface of the eye it has to be bound somehow to prevent evaporation or simply its running off the edge of the eyelids onto the cheeks.

Binding agents for water in tear supplements are different sorts of mostly large water-binding molecules, nowadays often hyaluronic acid.

Viscosity determines the residence time on the eye

The concentration of water binding molecules in tear supplements determines their fluidity/ viscosity. With increasing amount of such molecule the viscosity increases i.e. it the drop becomes ´thicker´ and less fluid - it behaves more like a gel.

• Low viscosity tear supplements are similar to normal tears but stay on the eye relatively short. On the other hand they cause only minimal or now blurred vision after application. Low viscosity tear supplements are typically used for mild dry eyes.

• With higher viscosity the retention time of the fluid on the eye increases, Such gels can protect the eye for a longer time but may cause temporary blurred vision which is, however, mostly short term. This is no problem at night which is the typical application for moderate dry eyes. In addition, low viscosity supplements are used during day time.

• In severe dry eyes it is often necessary to use a high viscosity gel also during day time to provide sufficient lubrication.

Hyaluronic acid is a common water-binding agent in eye drops

A commonly used water binding agent in eye drops nowadays is hyaluronic acid.

Hyaluronic acid is an important molecule in the body. It serves to bind water in all tissues. It also reduces friction, for example in joints. In the vitreous of the eye water is also bound by hyaluronic acid.

Other water-binding molecules include cellulose, an important plant building material, high-molecular alcohols, high-molecular sugars, plant mucilages etc. Some substances have been used in eye drops for decades, others are relatively new.

Different water-binding substances can also be combined in eye drops in order to achieve a higher retention time on the ocular surface or to combine other beneficial effects of such molecules.

Which tear substitute for which complaint ?

• If the lacrimal gland lacks water production

  • In the rare primary aqueous tear deficiency due to low production in the lacrimal gland, there is a reduced amount of aqueous tears. This can easily be determined by a Schirmer´s tear test.

  • Aqueous tear substitutes can temporarily improve the lack of water - however, only until the added drop has disappeared from the surface of the eye due to evaporation or removal into the nose.

  • In severe lack of tear water a temporary closure of the lacrimal drainage system by a tiny ´´punctum plug´ can be useful in order to reduce the application frequency of tear drops.

• If the Meibomian oil glands are blocked an oil replacement is necessary

  • A Deficiency of oil on the tear film due to dysfunction of the meibomian glands in the eyelids is far more common. A decreased oil layer on the tear film can be visualized and measured by a clinical test (interferometry). With a lack of oil, there is increased evaporation with a subsequent secondary lack of aqueous tears in addition to the original lack of oil.

  • A lack of oil often leads to an eye burning sensation, due to an increased osmolarity in places where the tear water evaporates and thus an increased concentration of salts and proteins in the tears remains.

  • In this case, both water and oil are effectively missing. A pure replacement of water can only be of short benefit because without a replacement of oil it always evaporates quickly. Nevertheless, water replacement is necessary to quickly improve the 'lubrication' between the eyelids and the eyeball and thus to reduce the harmful friction harmful friction that damages the eye surface.

• In case of wet eyes by increased tear flow due to eye irritation

  • Aqueous tear substitutes are also useful for eyes that are ´wet´ and have increased tearing due to an irritation and thus have episodes of wet eyes (epiphora). Such 'stress tears' consist mainly of pure water and have few protective and friction-reducing ingredients.

  • Tear supplements where the water is bound to hyaluronic acid or other substances provide a better 'lubricating effect' and a longer residence time on the eye. Therefore, aqueous tear supplements have their place also in a wet eye because they help to normalize the irritation of the tissue and will thus improve the excessive tear flow.

  • Attention: In the case of wet eyes and tearing an eye doctor should always be consulted to rule out a blockage of the draining tear ducts as well as a disturbance of the eyelid function due to changes in the shape of the eyelids !

Preservatives & stabilizers ... better not

Preservatives

• In principle, all tear substitutes, as well as eye drops in general, should be free of preservatives, as these can damage the sensitive cells of the ocular surface.

• Some individuals can have a pronounced intolerance to preservatives and then react with severe reddening of the eyes and eyelids. However, there is a large number of different preservatives that cause different levels of damage.

On the other hand, eye drops must of course be sterile and remain so during use to prevent dangerous infections of the eye

Preservative free eye drops are increasingly available

• As small single dose (Mono Dose) vials for the amount of drops needed during one day … or …

• As larger sterile dispenser bottles that are equipped with different kinds of filter mechanism.

Both systems can dispense sterile single eye drops without preservatives. This is certainly preferable as compared to preserved solutions.

Such systems are preferable as compared to conventional drop bottles that have to contain preservatives in order to avoid contamination with bacteria or viruses.

Sterile dispenser bottles use different technologies but all systems can

• provide sterile eye drops over periods of weeks to months, depending on the applied technique

  
  

But - attention - even today, not all eye drops that are offered in small bottles are indeed free of preservatives. Appropriate information should be included on the package or in the enclosed information sheet or may be detected by a more sophisticated construction of the bottle cover.

Preserved eye drops typically have the advantage that they are less expensive because the technology of the container is less advanced. At least if these drops have to be used frequently, as in the case of dry eyes, preservative-free preparations should be preferred.

Other additives

• Buffers are a normal component of basically all tear supplements and eye drops because they are necessary to adjust the acidity/ pH-value to a physiological level between acid and alkaline.

  • Phosphates are one of the substances that are used as buffers. Phosphate buffers actually also occur in the normal tear fluid. It has been shown that irreversible phosphate deposits can occur in the cornea, when respective eyedrops are used frequently on a cornea where the outside layer is already irritated and altered so that it can no longer completely protect against the entrance of substances into the tissue. In such cases eye drops that are free of phosphate are advantageous. However, the amount/ concentration of phosphate in the drops is also important.

  • Other salts (e.g. Citrate) are also used as buffers to adjust the acidity, either alone or in addition to phosphate. Citrate binds the phosphate and can reduce its deposition on the eye. For Citrate buffer pathological depositions in the cornea are not yet reported.

Tear supplements for different functions

Aqueous tear supplements

• Thin liquid / low viscosity drops

  • Low viscosity eye drops are given during day time, preferably with a mild dry eye.

    • Since they have low viscosity they typically do not cause blurred vision.

    • But they should be used frequently enough, since they typically have an immediate but limited period of action.

    • This means application at least every 2 hours, or even every hour for more severe symptoms.

  • => More information can be found HERE

• Thick liquid / high viscosity gels or ointments

  • Thick liquid gel is usually given overnight in case of a mild to moderate dry eye. A thick gel protects the surface of the eye better from friction and often lasts all night, when the water production of the lacrimal gland almost stops. In severe dry eye a viscous gel during the day is more appropriate than a thin liquid also during day-time, but some patients are uncomfortable because the vision is sometimes blurry for a little while.

  • => More information can be found HERE

Independent of the viscosity some aqueous eye drops contain additives with special effects, from which one can expect additional benefits compared to a sole improvement of moisturization and reduced friction on the surface of the eye. => More information can be found HERE

Oil / lipid supplementation

• A replacement of lipids/ oil makes sense in most patients, since a lack of oil on the tear film due to Meibomian gland dysfunction with subsequently increased water evaporation is the most common cause of a dry eye.

• In oil deficiency with increased evaporation of tear water the remaining tears are typically “hyperosmolar” - this is a stress factor for the tissue that can promote inflammation. In such cases hypo-osmolar/ hypotonic tear supplements can be of advantage because they can re-dilute the concentrated tears more efficiently.

Lipid supplementation is of course only the second best solution compared to regular physical eyelid therapy with the aim to restore the function of the Meibomian oil glands. While eyelid therapy must be carried out regularly 1-2 times a day for several weeks until improvement, an oil replacement usually brings an immediate improvement in the symptoms.

• Oil replacement / Oil supplementation can take various forms:

  • as aqueous tear supplementation with oil addition - two functions are achieved with one tear substitute!

  • as a pure oil / lipid, usually as a liposomal spray, which has the function to prevent premature evaporation if the patient's own aqueous tears are still sufficient and mainly oil is missing. A spray is easy to use because it is sprayed onto the closed eyelids - this is much easier, particularly for aged patients, than trying to target the opened eye with a bottle of eye drops.

  • oil substitutes are also available. They mimic characteristics of lipids and are thought to combine with the oil layer on the tear film in order to complement it.

Hypo-Osmolar Tear Supplements can be advantageous in Evaporative Dry Eyes

• In oil deficiency with subsequent increased evaporation of the tear water (evaporative Dry Eye) the remaining tear fluid is typically "hyper-osmolar" - with increased concentration of salts. This is a stress factor for the tissue that can induce inflammatory reactions.

• Therefore, a hypo-osmolar/ hypo-tonic Tear Supplement, that contains less salts, can be advantageous because it can re-dilute the concentrated tears more efficiently.

• Hypo-osmolar/ hypo-tonic tear supplements are available with or without oil addition. Due to the causative oil deficiency a replacement of oil is preferable.

• As always with tear supplements it is important to find a preparation that is individually comfortable.

Special additives

• If necessary, it can make sense to use a tear substitute with special additives in order to achieve improved effects if necessary. You can find more information on the relevant pages.

• Tear substitutes with special additives are available in various forms, both as thin drops and thick gels.

=> Further information on the use of tear substitutes can be found in the chapter on step therapy for dry eyes and in the selection of different tear substitutes.

How often should tear supplements be applied ?

Since Tear supplements/ artificial tears are a symptomatic therapy, they should be applied as needed and sufficiently frequent - 5-8 times a day, that is about every two hours, at most every hour in case of severe discomfort … but not “every 5 minutes” !

Even more frequent use of aqueous eye drops is usually not advisable, as this can reduce the effect of the (remaining) own tears, with their important active substances - this could make the irritation condition of the eye even worse.

It may then be necessary to apply additional therapy options:

• Regular daily hygiene and care of the eyelids and particularly the lid margin. In case of clogged Meibomian oil glands inside the eyelids “Physical Lidtherapy” is typically recommended as well as other options => please see an Overview of options for Eyelid- and Meibomian gland-Therapy.

• In case of severe tear deficiency, a temporary reduction of the natural tear outflow into the nose by small plastic plugs (punctum plugs) may be useful.

• In cases of severe irritation, the use of thick gel instead of thin drops may be useful (according to the staggered therapy scheme for dry eyes).

• as there is often a causative dysfunction of the Meibomian oil glands, a respective device -based therapy in the doctors office can provide improvement of the condition, e.g. by automated Warming and Expression of the glands (Thermopulsation by the Lipiflow device) or a Light Therapie (IPL oder LLLT).

• If necessary, the ophthalmologic diagnosis of a significant inflammatory condition in dry eye may also necessitate anti-inflammatory therapy, in addition to tear substitutes.

• In severe dry eye disease the application of Scleral Contact Lenses can omit annoying symptoms, restore vision and make largely independent of artificial tears.

Which tear substitute is the BEST for my eye ?

This is an understandable, obvious and frequently asked question ... but it is not so easy to answer because not every dry eye is the same - this can be seen by looking at the different disease factors in dry eye.

=> A thorough ophthalmological examination by your eye doctor can identify the individual disease factors and the most promising treatment options !

Generally:

• A good choice is first an aqueous tear replacement. For mild dry eyes, a thin tear drop is recommended, during day-time at least every 2 hours, and for more severe symptoms, a thick gel at night.

  • The different preparations in the available products on the market are tolerated differently by different people and therefore it can be useful to try some of them until something well tolerated and effective is found.

  • Since, however, aqueous tear substitutes mostly contain few special active ingredients apart from water, they can only provide improvement if they are used sufficiently frequent.

If there is a prevailing lack of oil

• In cases of a prevailing lipid deficiency and/or insufficient success of physical eyelid therapy (with warming, lid massage and lid margin hygiene), studies have shown that it is often a good choice to replace the missing oil on the tear film.

• For a beginning dry eye, particularly in younger individuals who do concentrated office computer screen work with rare eyelid blinks

  • it can be tried to get on with only a pure lipid replacement, e.g. a liposomal spray.

  • in addition, the improvement of desiccating risk factors and short breaks with eyelid blink exercise can certainly improve the condition - this should be tried first and continued during tear supplementation, it that becomes indeed necessary.

Staggered Therapy for the dry eye

The dry eye therapy is generally carried out as a staggered therapy approach. It is starts with information from the patient about his illness and the avoidance of risk factors. Then there is a basic therapy with eyelid therapy and tear substitution. With increasing severity, further therapy modules are added.

=> here is more information about the staggered therapy for dry eyes