Allergic diseases of the eye
Allergic eye disease is typically divided into four distinct types: allergic conjunctivitis, subdivided into seasonal and perennial allergic conjunctivitis (SAC and PAC, respectively), atopic keratoconjunctivitis (AKC), and vernal keratoconjunctivitis (VKC). Giant papillary conjunctivitis (GPC) is increasingly considered a result of microtrauma rather than an immunologically driven disease entity. In the discussion that follows, clinical, pathophysiological, and diagnostic aspects of each ocular process will be discussed in detail.
Allergic conjunctivitis – seasonal/perennial ( Box 13.1 )
Allergic conjunctivitis is a bilateral, self-limiting conjunctival inflammatory process. It occurs in sensitized individuals (no gender difference) and is initiated by allergen binding to immunoglobulin E (IgE) antibody on resident mast cells. The importance of this process is related more to its frequency rather than its severity of symptoms. The two forms of allergic conjunctivitis are defined by whether the inflammation occurs seasonally, SAC (spring, fall) or perennially, PAC. Both SAC and PAC must be differentiated from the sight-threatening allergic diseases of the eye, namely AKC and VKC.
- •
Seasonal allergic conjunctivitis is the commonest form of ocular allergy and is a self-limiting allergic process
- •
No conjunctiva scar formation is noted
- •
Treatment with topical combination mast cell stabilizer/antihistamine drops is usually sufficient for relief of symptoms
- •
Allergic disease of the eye is underreported by patients and often self-medicated with over-the-counter preparations
- •
Patients may not report the use of over-the-counter medication
Clinical background
The key symptom reported in allergic conjunctivitis is ocular itching. Symptoms, signs, and differential diagnosis are listed in Table 13.1 . A survey conducted by the American College of Allergy, Asthma, and Immunology (ACAAI) found that 35% of families interviewed experience allergies, and at least 50% of these individuals describe associated eye symptoms. Most reports agree that allergic conjunctivitis affects up to 20% of the population. Importantly, 60% of all allergic rhinitis sufferers have associated allergic conjunctivitis. The distribution of SAC depends largely on the climate. There are no racial or gender difference noted for allergic conjunctivitis. Onset of disease tends to be during infancy and is typically accompanied by the development of other allergic diseases such as atopic dermatitis or asthma.
| Disease | Clinical parameters | Signs/symptoms | Differential diagnosis |
|---|---|---|---|
| Seasonal allergic conjunctivitis (SAC) |
|
|
|
| Perennial allergic conjunctivitis (PAC) |
|
|
|
| Atopic keratoconjunctivitis (AKC) |
|
|
|
| Vernal keratoconjunctivitis (VKC) |
|
|
|
| Giant papillary conjunctivitis (GPC) |
|
|
|
There is little reason beyond the history and examination to investigate further the patient with allergic conjunctivitis. The commonest treatment for allergic conjunctivitis is once- or twice-daily topical administration of a dual-acting drop with mast cell-stabilizing and antihistamine activity. The self-limiting nature of the disease means there is quite a good prognosis for retention of good vision and no ocular surface scar formation.
Pathology
Histopathologic and laboratory manifestation of allergic ocular diseases is shown in Table 13.2 . Granule-associated neutral proteases (tryptase and chymase) unique to mast cells are generally accepted as the most appropriate phenotypic markers to categorize human mast cells into subsets. Mast cells on this basis have been divided into MC T (tryptase) and MC TC (tryptase/chymase) phenotypes. The phenotype of normal human conjunctival mast cells has been well documented using immunostaining of conjunctival biopsy specimens. Mast cells are rarely present in the normal human conjunctival epithelium, but when they are found, they appear to be limited to the MC T phenotype. Mast cells (MC T phenotype) and eosinophils are increased in the conjunctival epithelium of individuals with SAC and PAC ( Table 13.2 ). In the substantia propria of the normal human conjunctiva, mast cells are found and 95% are of the MC TC phenotype. The total number of mast cells (MC TC phenotype) is also increased in the substantia propria of individuals with allergic conjunctivitis.
| Disease | Histopathology | Laboratory manifestations |
|---|---|---|
| Seasonal/perennial allergic conjunctivitis |
|
|
| Atopic keratoconjunctivitis |
|
|
| Vernal keratoconjunctivitis |
|
|
| Giant papillary conjunctivitis |
|
|
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
