Ocular Allergic Responses

The eye is a common location of inflammation and a primary response sight for allergic responses. Because the majority of  allergic ocular responses involve the conjunctiva, the terms "ocular allergy", and "allergic conjunctivitis" are used interchangeably. The degree of allergic response can vary greatly, from mild symptoms, to severe responses with the potential for vision-threatening complications.

There are 4 main types of allergic eye rsponses: allergic conjunctivitis, vernal keratoconjunctivitis, atopic keratoconjunctivitis, and giant papillary conjunctivitis.

ALLERGIC CONJUNCTIVITIS
Seasonal allergic conjunctivitis is the most common forms of allergic conjunctivitis resulting in nearly half of all cases of ocular allergy. Symptoms of seasonal allergic conjunctivitis include itching, burning, watery or sometimes mild mucoid discharge and usually bilateral. The conjunctivae are usually mildly injected and edematous leading to a "milky" appearance. Fine papillary hypertrophy of the upper tarsal conjunctiva may occur. Additionally the venous congestion can cause the appearance of dark circles around the eyes called "allergic shiner". Many individuals also have concurrent nasal symptoms and because of the itchy nose they present a special habitus called "allergic salute". Corneal involvement is not among the findings. The primary cause of these allergens are the pollens,  dust, mite feces, animal dander and feathers.
  
VERNAL KERATOCONJUNCTIVITISVernal keratoconjunctivitis is a chronic bilateral conjunctival inflammatory reaction primarily affecting young males. The onset of the disease is generally before age 10; it lasts 2 to 10 years and usually resolves after puberty. The Mediterranean area and West Africa are the areas of the greatest numbers of patients. There is a history of eczema or asthma in 75 % of the patients. As the name implies, seasonal flare-ups are common, but patients usually have a year-round underlying condition. The main symptoms are itching, excessive tearing, ropy mucus production, light sensitivity, burning, foreign body sensation, and eye pain. The symptoms are generally confined to the conjunctiva and cornea. Eyelid skin and margins are relatively uninvolved compared to atopic keratoconjunctivitis. The identifying symptom is a cobblestone-like giant papillae of the upper tarsal conjunctiva. Bulbar conjunctiva is usually injected and edematous. Especially in heavily pigmented patients limbal changes are prominent. The limbus and perilimbal conjunctiva may be thickened and edematous forming a gelatinous-like hypertrophy. Limbal nodules and Trantas’ dots composed of eosinophils and dead epithelial cells may be observed.The cause has not been well defined - hyper-sensitivity to an allergen but what that allergen is has not been categorically determined.

ATOPIC KERATOCONJUNCTIVITIS
Atopic keratoconjunctivitis is an allergic ocular response associated with allergic dermatitis.Symptoms include extreme itching, burning, and redness. There is usually copious mucous discharge gluing the eyes together upon awakening. Lids are often red, macerated with crusting and scaling which may be related to suppressed t cell productions. 

GIANT PAPILLARY CONJUNCTIVITIS
 Giant papillary conjunctivitis  is a  complication resulting from the use of contact lenses, but may also be present as a result of cataract surgery. Symptoms include lens intolerance, excessive mucous secretion, blurred vision, itching, and ocular irritation. Giant papillary conjunctivitis is somewhat less of a problem as it is non-vision-threatening. When the underlying condition is a suture or a foreign body, removal will be enough to improve patients’ symptoms and signs. In contact lens wearers, treatment should be directed firstly to modify the patients’ routine behavior, and often the lens itself. Improving the lens hygiene, finding a better tolerated lens design and material may be useful.