Allergic conjunctivitis is a broad group of allergic conditions involving inflammation of the conjunctiva, the thin membrane that covers the inside of the eyelids and the eye, up to the cornea. The commoner conditions are mild and do not affect the cornea, but the rarer diseases do involve the cornea and can be sight-threatening.
Seasonal intermittent allergic conjunctivitis (SAC)
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Persistent allergic conjunctivitis (PAC)
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These common eye diseases are caused by the interaction of allergens with the IgE antibody. The symptoms are itching, watering and redness of the eye, and the eye symptoms commonly accompany allergic rhinitis. SAC occurs intermittently and often follows exposure to pollen allergens. PAC is a mild, persistent form of allergic conjunctivitis which results from continual exposure, for example, to year-round allergens such as house dust mites.
Vernal keratoconjunctivitis (VKC)
This is a severe inflammatory disease which may be intermittent or, less frequently, persistent. The symptoms are watering of the eyes, stickiness, itching and difficulty with opening the eyes on awaking. Large "cobbles" occur inside the upper eyelid (click for photograph). If the cornea is involved, pain, blurred vision and sensitivity to light are experienced. Bacterial infection may also occur.
Atopic keratoconjunctivitis (AKC)
This is a severe disease of the eye that is sometimes due to "true" IgE-related allergy and sometimes to other mechanisms. It is a lifelong disease starting in young adulthood. AKC is associated with atopic eczema of the face and eyelids, eye infection, damage to the cornea, cataract, and contact with airborne allergens (click for photograph). The symptoms are perpetual itching of the eye, soreness, impaired vision and a sensation of dryness.
Giant papillary conjunctivitis (GPC)
This disease results from damage caused by contact lens edges, false eyes or post-operative stitches, which may be aggravated by allergy. The symptoms are large "cobbles" inside the upper eyelid (click for photograph). This disease is not sight-threatening.
Seasonal allergic conjunctivitis
Seasonal allergic conjunctivitis is triggered by the same allergens responsible for seasonal allergic rhinitis. In the Northern Hemisphere these are tree pollens in April/May, grass pollens in June/July, and mold spores and weed pollens in July/August. In more northerly regions of the Northern Hemisphere the pollen seasons will occur slightly later, and in the southerly regions of the Northern Hemisphere the pollen seasons will occur slightly earlier.
Persistent allergic conjunctivitis
Persistent allergic conjunctivitis is triggered by house dust mites, molds and animal allergens, which may be present year-round, although the symptoms do show some seasonal variation. In the Southern Hemisphere the pollen season can last all year round, depending on the latitude.
The majority of cases of VKC are seasonal, and occur during the high pollen season, although persistent cases do occur in warm subtropical or desert climates. It is widely accepted that the disease is caused by a sensitivity to allergens in the environment.
AKC occurs all year, but may be worsened by contact with allergens such as house dust mites, mold spores, animal allergens, and rarely foods.
Giant papillary conjunctivitis
Giant papillary conjunctivitis occurs in the presence of foreign bodies in the eye, such as contact lenses or false eyes. "Cobbles" develop on the inside of the upper eyelid, along the line of contact with the source of mechanical trauma, for example, the edge of a contact lens. The upper eyelid is damaged with each blink of the eye, which occurs between 10,000 to 12,000 times daily, and the area of damage allows allergens to enter the eyelid. The immune response leading to the development of the cobbles may be triggered by an airborne allergen. It may also be an immune reaction to a combination of the mucus, protein and chemicals from contact lens solutions, bacteria, and cells which coat a contact lens after continued wear.
To diagnose allergic eye disease, the following examination and investigations may be performed:
- Appearance of the "flipped" eyelid. This may be performed by using a long thin object, such as a cotton bud, to turn the inside of the eyelid upwards for examination.
- Skin prick/puncture tests or blood tests for the presence of specific IgE antibodies may be performed to identify the allergens that may be causing the symptoms
- A few cells may be taken from inside the eyelid to be analysed for the presence of inflammation (eosinophils)
A diagnosis will be made based on the following:
- Typical symptoms, and whether they are intermittent or persistent
- Age - 80% of patients are under 30 years of age
- Strong personal or family history of IgE-mediated allergic diseases
What other diagnoses are possible?
- Blepharitis or inflammation of the eyelids
- Conjunctivitis caused by bacteria, viruses or Chlamydia
- Corneal abrasion or ulceration
- Dry eye syndrome
Itching is a key symptom of allergic eye disease and in the absence of itching an alternative diagnosis should be suspected.
SAC and PAC
SAC may occur alone or associated with seasonal allergic rhinitis (hay fever). Both SAC and PAC are primarily diseases of young adults and are slightly more common in males than in females.
AKC first occurs in the late teens or early twenties and peaks between the ages of 30–50 years. It occurs in up to 25% of patients with atopic eczema. There is usually a personal or family history of atopic diseases – for example, allergic rhinitis, asthma or eczema.
VKC is a disease of childhood and early adolescence. Genetic factors and atopic status – the enhanced ability to react to allergens - may be involved in the development of the disease, although many patients have no family or personal history of atopy and may have negative allergy skin tests. Environmental allergens may also contribute to the development of the disease. Males are more frequently affected than females, with a ratio of 3:1. The disease usually begins before the age of 10 years and improves at the time of puberty, although the age of affected individuals ranges from 3 to 25 years of age. VKC occurs more frequently in warm climates.
GPC occurring with contact lens use reflects the age of contact lens wearers and so rarely occurs in children or the elderly. However, when it is associated with post-surgical mechanical trauma, such as exposed stitches, it is more prevalent in older age groups.
Allergen avoidance can lead to significant improvement in symptoms of SAC and PAC. In GPC, the use of disposable contact lenses may be helpful, and changing to daily use of disposable lenses can eliminate the condition entirely.
Treatment of the rarer, more severe forms of allergic conjunctivitis requires the use of topical corticosteroids and should be managed with the assistance of an ophthamologist. Prolonged use of topical corticosteroids in the eye can lead to secondary bacterial infection, glaucoma and cataract, and so regular monitoring by a doctor specializing in eye disease (an ophthalmologist) is essential.
American Academy of Allergy, Asthma and Immunology (AAAAI)
Atopy: the personal and family tendency to make IgE antibody and develop allergic diseases
Blepharitis: inflammation of the outside of the eyelid
Conjunctiva: the thin membrane covering the inside of the eyelids and the eye
Cornea: the transparent tissue in front of the iris
Genetic disease: disease which results from inherited characteristics
IgE: the "allergy" antibody in the blood, which reacts when the body encounters an allergen to which it is sensitive
IgE-mediated: diseases/symptoms that occur as a result of IgE antibody reacting to allergens to which the body is sensitive
Iris: the colored part of the eye
Keratoconjunctivitis: eye disease involving the eyelid and the cornea
Intermittent symptoms: symptoms occurring at certain, restricted times of the year
Seasonal symptoms: symptoms occurring during a pollen season
Perennial symptoms: symptoms occurring during long periods at any time of the year
Topical treatment: Applied directly to the affected area of the body