الفهرس 
Anatomy of the conjunctivaOnly 14 pages are availabe for public view
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Abstract
The prevalence of ocular allergy clearly is underappreciated and has been under diagnosed and undertreated. The ocular symptoms associated with the most common ocular allergy conditions, such as SAC and PAC, are twice as likely to affect the allergy sufferer rather than nasal symptoms alone. The differential diagnosis of conjunctivitis is quite broad, with the most common forms associated with allergies, infections, and hormones. There are common features and some discerning features that, with a good history and examination, may provide a more focused and appropriate management.
Allergic conjunctivitis is common, especially during the allergy season. Ocular symptoms are usually accompanied by nasal symptoms, and there may be other allergic events in the patient’s history that support the diagnosis of ocular allergy. Diagnostic tests can be helpful, especially conjunctival scrapings, to look for eosinophils. Consultation with the allergist to perform skin tests or in vitro tests may be useful and confirmatory in the diagnosis of ocular allergy. Symptoms may be mild, and many patients do not require treatment. If treatment is necessary, several antiallergic drugs are available. The selection of an antiallergic drug is based on the patient’s need and a determination of which drug is well tolerated and most effective.
VKC is most often a self-limiting disease, usually resolving within 2 to 10 years. Permanent conjunctival scarring is rare unless surgery was performed or unless the disease transforms into AKC. Although corneal changes, such as pannus, subepithelial scarring, astigmatism, keratoconus, and marginal corneal degeneration may be permanent, VKC rarely results in diminished visual acuity that is not correctable by semi-rigid contact lenses or surgery. In their long-term follow-up of 195 VKC patients, Bonini and colleagues report that 6% of patients develop a visual impairment owing to corneal damage. Bonini and colleagues also report that the size of the giant papillae is directly related to the probability of the persistence or worsening of symptoms, and that the bulbar forms of VKC have a worse long-term prognosis than the tarsal forms.
If GPC is under control, patients are able to maintain a wearing schedule that is satisfactory to their lifestyle without the recurrence of the symptoms associated with this syndrome. The upper tarsal inflammation in the form of injection usually resolves; however, the papules either remain unchanged or over time may slowly decrease in diameter and height. In some patients, however, the tarsal conjunctiva remains thickened, with a significant papillary reaction but without inflammation, for years after the onset of GPC; yet, they are still be able comfortably to wear their contact lenses. Patients have to be instructed at the first onset of excessive mucus, coating of the contact lens, or increased contact lens awareness to contact their ophthalmologist. With proper lens care, frequent lens replacement, and continued follow-up care, over 90% of patients with GPC can continue in contact lenses.
Pharmacologic treatment of allergic conjunctivitis consists of agents designed to block various pathways in the IgE–mast cell mediated inflammatory cascade. Oral and topical antihistamines target histamine receptors, preventing histamine-mediated symptoms of allergic conjunctivitis, such as itching, watery eyes, chemosis, and periorbital swelling. Antihistamines may have a minimal effect on inflammatory mediators and tend to induce ocular drying, which may limit use. Although topical mast cell stabilizers block the release of histamine, prostaglandins, and leukotrienes through stabilizing mast cell membranes, they are more useful as prophylaxis because they have no effect on already-synthesized inflammatory mediators.
Topical multiple-action agents with mast-cell–stabilizing activity have more diverse inhibitory effects on the inflammatory cascade, and will inhibit preexisting inflammatory mediators and block synthesis of more inflammatory mediators. Because of their ability to block the generation of most inflammatory mediators through inhibition of mast cell phospholipase A2, topical corticosteroids are the most effective treatment for persistent and chronic forms of allergic conjunctivitis. However, corticosteroids are less likely to be prescribed because of their increased risk for cataract formation and elevated IOP, and their restriction to short-term use. According to current treatment recommendations, allergic conjunctivitis is managed in a stepwise approach. Lubricants are initially recommended for disease prevention. In patients who do not experience response, pharmacotherapy is prescribed in the following sequence until acceptable relief of symptoms is achieved: (1) topical antihistamines, alone or (2) in combination with nonsteroidal anti-inflammatory drugs; and (3) multiple-action agents with a short course of corticosteroids.