Allergic conjunctivitis

DEFINITION/OVERVIEW

Allergic conjunctivitis can be divided into five common forms, two acute ( seasonal allergic conjunctivitis [SAC] and perennial allergic conjunctivitis [PAC]), and three chronic (vernal keratoconjunctivitis [VKC], atopic keratoconjunctivitis [AKC], and giant papillary conjunctivitis [GPC]) (Table 9).27 AKC is usually seen in late adolescents and adults, so will not be discussed here.

‘If it doesn’t itch, it’s probably not allergy’ is probably the best way to start thinking about allergy as the etiology of an inflamed eye.

ETIOLOGY

Allergic conjunctivitis is usually associated with type 1 hypersensitivity reactions. The main component of ocular allergy is the mast cell along with IgE. When an allergen comes in contact with the conjunctiva of a previously sensitized patient, the mast cell, which is filled with granules of histamine, will degranulate, spilling the contents into the surrounding tissue. The release of histamine causes a cascading release of chemical mediators, which causes vasodilatation, increased vascular permeability, and increased mucoid

production. The main mediators in mast cell degranulation are histamine, tryptase, kininogenase, and eosinophil chemotactic factor of anaphylaxis (ECF-A). If the allergic reaction has a long protracted course, a latephase response can occur. The main mediators of this late-phase response includes leukotriene B4, leukotriene C4, D4, prostaglandins D2, and platelet activation factor.28

Seasonal conjunctivitis is the most common form of ocular allergic disease.26 The ocular manifestations occur either seasonally (SAC) or perennially (PAC). Although the symptoms, including rhinitis and congestion, can be treated quickly by primary care providers, the ocular complaints may not be elucidated during the examination. The symptomatic patient is usually miserable and treatment of their systemic symptoms as well as their ocular symptoms is beneficial. SAC is associated with release of pollens in the early spring from grasses and trees, or in the late summer and early fall secondary to ragweed. PAC can occur at any time throughout the year. This is usually associated with allergens such as pet dander and dust mites. Once an individual is exposed to a sensitizing agent, the symptoms of the allergic response occur quickly. Although PAC sufferers have symptoms year round, they will usually experience seasonal exacerbations.29,30

CLINICAL PRESENTATION

Although acute allergic conjunctivitis is usually seen bilaterally, it is not uncommon for a patient to complain of unilateral symptoms, even when bilateral signs are present. Besides the itching, patients will often complain of a stringy or ropey mucoid discharge, lid edema, chemosis (edema of the conjunctiva), and red, hyperemic conjunctiva (81).31 Patients will often show other signs of atopy, with allergic rhinitis being extremely common. Patients with atopic disease will sometimes not have a primary complaint of itching eyes, but instead other symptoms of allergic reactions including wheezing, rhinoconjunctivitis, and eczema.32

MANAGEMENT/TREATMENT

The treatment of acute allergic conjunctivitis centers around symptomatic relief. By reducing the allergic response to the allergen and reducing the inflammatory response of the eye and periorbital region, the patient will be much more comfortable and less symptomatic.33 The most important goal is to reduce the amount of allergic load to the patient. If the child is suffering from PAC, then eliminating the allergen will be the most beneficial approach. Eliminating pet dander or laundry detergent, or reducing contact with dust mites can show significant relief of the patient’s symptoms. If the allergic response is caused by seasonal allergens, this is not an easy task. SAC will also benefit from any reduction in the allergen load, including keeping windows closed and using an air filtration system in the house. When the child is outside exposed to various pollens and other allergens, these allergens will collect in his or her hair, which can be transferred to the pillow at night, putting a significant allergen load in direct contact with the ocular adnexa. By simply washing the child’s hair before they go to bed, the allergen load will not be transferred to the pillow and thus the eyes. Cool or cold compresses are also beneficial for symptomatic relief. The use of topical ophthalmic drops can also help to lower the allergic response, and the patient’s symptoms. These medications are divided into five categories: antihistamines, mast cell stabilizers, antihistamine/mast cell stabilizer combinations, corticosteroids, and nonsteroidal anti-inflammatory drugs (NSAIDs).

PROGNOSIS

The treatment of SAC is often frustrating for both the physician and patient. Recurrences are common and complete resolution of symptoms without the use, and risk, of steroids is not always possible. However, many patients can be helped significantly. Patients will show a definite increase in the quality of life when their symptoms are controlled.34 Patients with chronic disease can show permanent changes and potential visual impairment.

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81 Conjunctival chemosis.(Courtesy of Casey Eye Institute,Oregon Health Sciences University.)

Vernal keratoconjunctivitis

ETIOLOGY

VKC is caused by the exuberant reaction of the body’s immune system towards an allergen. VKC is thought to be mainly a type I hypersensitivity reaction, with eosinophils, as well as mast cells the most involved cells. There has also been some speculation that a type IV hypersensitivity reaction may also play a role in this condition, with mononuclear cells, fibroblasts, and newly secreted collagen seen.35

VKC (82). The superior tarsal conjunctiva will often show large ‘cobblestone-like’ papillae (83). In severe and chronic cases of VKC, sterile corneal ulcers, known as corneal shield (Togby’s) ulcers, may be present (84). They are usually seen at the superior limbus, and can be painful, serious vision-threatening lesions. These ulcers need to be aggressively managed if they do not show rapid re-epithelialization.38 Other symptoms seen in VKC are foreign body sensation, epiphora or excess tearing, photophobia, and ocular burning and stinging (Table 10).

MANAGEMENT/TREATMENT

CLINICAL PRESENTATION

VKC is a chronic form of allergic conjunctivitis. It is bilateral and will usually be seen affecting the superior and limbal conjunctivae. There is a definite predilection for VKC affecting males more than females,36 and it is seen in warmer climates more often than cooler climates. It usually presents before age 10 years, and will often resolve following puberty. There is also a history of eczema or asthma in 75% of patients.37 Although this is a chronic condition, seasonal exacerbations are often seen. The symptoms that are reported are similar to those seen in acute allergic conjunctivitis but are usually more severe and chronic. The primary complaints are severe itching, and a thick, ropey discharge. The patient will usually have a history of allergies and atopy. Along with conjunctival injection, small whitish dots on the cornea at the superior limbus will often be visible with a direct ophthalmoscope. These dots, Trantas or Horner–Trantas dots, are pathognomonic for

Treatment is centered on reducing the patient’s symptoms, controlling the hypersensitivity reaction, and keeping the ocular structures well lubricated to prevent the serious vision-threatening sequelae that can be seen with VKC. The initiation of therapy as early as possible to prevent these sequelae is highly recommended once the diagnosis of VKC is made. The use of cool or cold compresses, artificial tears, as well as bland ophthalmic ointments can help reduce the early symptoms. Systemic as well as topical antihistamines, along with mast cell stabilizers can keep the symptoms under control, but play a less prominent role during an acute exacerbation. The use of NSAIDs as well as topical steroidal anti-inflammatory drops will usually be required during an acute exacerbation.

In patients that have corneal shield ulcers, aggressive therapy is indicated. Since these ulcers are painful, the use of a cycloplegic drop is indicated and will reduce the ciliary spasm and

pain that the child may experience. If the ulcer does not rapidly re-epithelialize, the use of topical antibiotics is also indicated. A physical barrier with a low water content hydrogel lens can be used to stop the cobblestone-like giant papillae from re-abrading the corneal epithelium. If a patient is showing these significant symptoms during an acute exacerbation, consultation with an ophthalmologist is highly recommended.

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PROGNOSIS

VKC is often a chronic and recurring problem. Mild cases can be effectively managed and patients can be made comfortable. More severe cases place the patient at significant risk for vision loss, usually as a result of the disease process itself. However, the overly aggressive use of topical corticosteroids to treat the disease may also cause problems.

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82 Horner–Trantas dots.(Courtesy of Casey Eye Institute,Oregon Health Sciences University.)

83 Tarsal cobblestone papillae.(Courtesy of Casey Eye Institute,Oregon Health Sciences University.)