Ocular Allergies

 

Allergy & Dry Eye

Allergies are often associated with ocular surface disease and in particular with dry eye syndromes. For the least, it is likely that the reduced quantity or quality of tears increases the quantity of allergens, limits their evacuation through the canaculi and increses inflammation which is a known aggravating factor for allergies. The prevalence of allergic persons among dry eye sufferers and particularly with blepharitis, rosacea and meibomitis seems to indicate that there is some connection in many cases. Some authors suggest that severe allergies may cause a permanent dry eye state and sometimes; the exact frontier between the 2 pathologies is unknown. But it's obvious that both cause inflammation and both aggravate each other.  In any case, we may say that allergy further complicates diagnostic and care of ocular surface diseases.

Ocular Allergy as such

Ocular Allergy in its mildest forms is more and more prevalent and surely one of the most common conditions. It's probably the result of the increase of allergy sufferers altogether but surely other factors such as internal (in-house) and external pollution, the catastrophic management of human environnement, etc. The causative agents are pollens, acarians, some chemical substances provoking intolerances, cosmetics, furs and animal hair, etc. Let's mention two examples of catastrophic management of our new environnement: It is obvious that if some many persons are allergic to plane trees in European cities it's probably because of the omnipresence of that tree in our polluted cities and bordering our roads. Another example is new species, such as rag weed (ambrosias), which colonize new territories and become omnipresent, or excessive planting of cyprus trees by man for ornamentation. For the first time, a babyborn was granted the righ to uproot trees that were threatenning his life in Connecticut. A better management and planting various/different breeds, as much as possible non-allergenic trees, will surely be part of the solution if when want to avoid the increased incidence of allergy in our modern cities.  On the left, a picture of an eyelid presenting allergic sign including papillary reaction by Dr Edouard Benois.

In any case, ocular allergy, as all allergies are immunitary reactions to the excessive production of IgE and liberation of histamine, prostaglandins, leucotriens and kinins.  The body (and in this case) the eye will interpret the presence of the allergen as an aggression.  

Two types of allergy are predominant (more that half of all cases) and are associated with high IgE levels in tears:

Allergic conjunctivitis, is an inflammatory reaction or the conjonctiva (the slim transparent membrane covering the eye and the interior of the lids. It is similar to allergic rhinitis, with which it shares many features and sometimes even a link. The main symptoms are: red eyes, stinging, grittiness, irritation, photophobia and tearing. The lids are also often swollen and red and sometimes chemosis (conjonctival swelling), dark circles around the eyes. In some cases, mucus secreation may be very important. it usually doens't affect the cornea.  It's less serious and surely the most frequent types of ocular allergy. This type of allergic reaction is often the result of the presence of pollens in the spring and summer (tree pollens and grasses).

Perannual conjonctivitis last all year long and is often due to the presence of allergens such as acarians or animals in the house of the patient. It's frequently a mild form of allergy and an annual variant of the allergic conjonctivitis. The symptoms are the same.

But there are rarer and surely more serious forms of ocular allergy. These are usually totally unknown by the general population. These are allergies seem to combine both a Type I and Type II sensitivity.

Vernal (kerato)conjonctivitis is essentially a male and infantale form of ocular allergy (it usually disappears after adolescence). It's a serious form of allergy, since it sometimes causes ulcerations leading to extensive and definitive loss of sight. The ulcerations will usually appear in the upper part of the cornea and papillary  hypertrophy of the upper lid.

Atopic (kerato)conjonctivitis is found in patients having an atopic tendency (eczema, asthma and other allergic sylptoms, at least 40% of the patients have allergic dermatitis), it's usually a male subject of 30 to 50 years. it's a very serious form of allergy that leads to ulcerations and possibly extensive and definitive visual loss.

Giant-papillary conjonctivitis is often seen in contact lens wearers (or due the presence of a foreign body in the eye). Preservatives in eye drops or contact lens solutions may cause these severe allergic reactions. It provokes serious papillary hypertrophy of the lids (mainly the upper ones).

Allergic palpebral pathologies

These may also have  an impact on the eye surface.

Palpebral Eczema: is an allergic reaction caused by many allergens including preservatives in eye drops or make up.

Allergic Blepharitis: is an inflammation of lids caused by allergies (pollens, drugs, creams and make-up), which ocular consequences are often disregarded. As with any blepharitis, it may cause meibomitis and further disturb the lipid layer of tears and further disrupt stability of tears altogether. On the left, a picture of an eyelid presenting eczema by Dr Edouard Benois.

The negative impact of preservatives in eye drops

Allergic and toxic, preservatives may alter the eye's epithelium, in particular benzalkonium and thiormersal. This allergenic activity particularly concerns  all ocular surface sufferers who have to use many drops. Preservatives may cause severe allergic reactions. A similar problem is sometimes noticed in contact lens wearers where preservatives in decontamination solutions are usually the culprits. Beyond allergy many studies show that cytotoxicity (a different and delayed type of immunitary reaction that occurs without any obvious short term signs) and tear film disruption caused by preservatives are likely to inscrease corneal erosions.

This situation is particularly absurd when so many drops for ocular allergies containt preservatives (notably benzalkonium) which are allergenic, inflammatory and irritant for eye surface. The limited choice of unpreserved antihistaminic eye drops is obvious challenge for dry eye sufferers.

Please visit our site dedicated to preservatives in eye drops: Preserve our Eyes, not our Drops!

See our following pages on ocular allergy testimonials and contacts on allergy and air quality

How is it possible to explain the exponantial rise and incidence of ocular allergies?

As with dry eyes, probably a better diagnostic, improved screening of patients and attentive doctors to patients complaints has permitted to unravel more cases of allergies and probably milder cases that would have remain disregarded until they became very disabling.  But this does not explain such a rise and one must look for additional environmental causes, changes in our way of life and food habits to justify this.

The role of pollution

The main cause of allergy is the allergen itself of course, but since it has existed all along, there are surely other aggravating factors to justify this current prevalence. Certain authors point out in-house and air pollution, which could trigger, amplify and catalyse allergic reactions.

The exact mechanism is unknown but three leads are usually suggested:

• Immunotoxicity - the pollution in this configuration, would be a co-factor of allergie by inter-acting with the allergen inscreasing the immune reaction.

• Pro-inflammatory effect - pollution creates an inflammatory reaction which could serve has mediator for allergy facilitating and inscreasing it.

• By inscreasing the allergen's allergenicity - pollution is then accused of modifiying the allergen itself and amplifying their release in the case of pollens.

This could explain the importance of allergies in urban areas whereas pollens are more present in rural areas. As such, quantity alone may not explain the inscrease of allergies in urban areas. Another immunitary reaction beyond allergy may be involved in the process: the complement system which has a key role in inflammatories processes and immunitary responses.

Useful Reading: Pollution et Allergies Oculaires - Volume2, Système du complément et allergies, Collection Librairie Médicale Théa.

 

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