Ocular allergy is an inflammatory reaction of the surface of the eye to particles (allergens) in the environment. It is quite common and affects people of all ages. Inflammation can be asymptomatic, or cause dramatic symptoms, and in severe cases, severe loss of vision.
There are five types of ocular allergy.
Exposure of susceptible individuals to allergens such as pollen, ragweed, or pet dander may allow these particles to bind to special antibody receptors that then trigger a cascade of inflammatory events involving the release of histamine and the activation of inflammatory cells called mast cells, and at times eosinophils.
Particles which adhere to contact lenses or even some topical eye drops can also be triggers. Histamine causes blood vessels to leak fluid, protein, and inflammatory cells into the area of exposure, causing many of the symptoms of allergy.
Inflammatory cells can further propagate the response, and in severe ocular allergy such as VKC or AKC, can release enzymes that damage the cornea leading to growth of new blood vessels, scarring, and permanent loss of vision.
As above, sometimes ocular allergy can be asymptomatic, or more likely unrealized, finally seen on examination by the ophthalmologist.
Ocular allergy can occur on its own, but typically occurs in conjunction with allergic rhinitis or sinusitis. It is not uncommon to see those who suffer from allergy to have other systemic diseases such as eczema or asthma, especially in AKC.
Redness and other symptoms which occur along with seasonal allergies or at certain times of year also suggest allergy.
Review of medical history for eczema and asthma, and a family history for allergic disease, are also important.
Response of symptoms to anti-allergy medication may help indicate whether allergy is involved.
Allergy testing and review of the patient’s life from top to bottom may reveal possible sources, some which have been around for years and unknown to the patient to be driving inflammation.
Slit lamp examination often reveals characteristic bumps on conjunctiva, especially underneath the upper and lower eyelids, which correspond to swelling and collections of inflammatory cells.
Rarely, severe cases may show spread of new blood vessels toward the middle of the cornea, usually irreversible, or worse still, scarring and growth of conjunctiva over the entire cornea leading to near complete loss of vision.
Analysis of conjunctival biopsy can sometimes suggest allergy in patients with chronic conjunctivitis.
Complications of ocular allergy, aside from debilitating aggravation, are not common. Chronis rubbing of the eyes may eventually result in a change in its curvature, making it more like a cone than a sphere, a condition called keratoconus. Poor corneal health may make it more susceptible to infection.
When disease is severe, new blood vessels and scarring that occurs across the cornea can cause large decreases in vision, and may only be reparable by surgery.
Avoidance of triggering allergens is the number one way of treating allergy. Other conservative measures are often successful in treating mild allergy, and include frequent use of lubricating eye drops, chilled if possible, and preferably without preservatives.
Cool compresses help relieve symptoms and may lessen inflammation.
Topical therapy with drops that fight both histamine and mast cells, such as Patanol, has become an important weapon against allergy, and can be used daily.
Topical corticosteroids are useful for controlling active inflammation, but all efforts to treat without dependence on steroids should be made to avoid other complications of these medications; a mild topical corticosteroid is sometimes necessary.
Oral anti-allergy medications can be used to treat seasonal allergies, along with the component driving eye symptoms.
It is also important to treat any coexisting conditions that may affect the surface of the eye. Immunomodulatory therapy with oral cyclosporine can also be used for severe and unresponsive cases of AKC with success.
Refraining from use of contact lenses, either temporarily or permanently, may be the only solution to those patients with GPC. Those with developing GPC can be counseled on limiting contact lens use so they do not develop complete intolerance of lenses.
Anyone with chronic or severe allergies should consult an allergist, who can perform diagnostic allergy testing, make recommendations to treat systemic allergy, and, if needed, provide regular injections to help limit reactions.
Corneal surgery can be attempted for those with scarring of central cornea, or in cases where chronic rubbing of the eyes has resulted in severe irregular astigmatism or keratoconus.