Vernal Keratoconjunctivitis (VKC) / Spring Catarrh

Definition: VKC is a recurrent, bilateral, interstitial, self-limiting, allergic inflammation of the conjunctiva having a periodic seasonal incidence.

Etiopathogenesis

Found in individuals with a predisposed atopic background. Previously considered a type-I IgE-mediated hypersensitivity reaction to pollen. Now believed that pathogenesis is characterized by Th2 lymphocyte alteration and that the exaggerated IgE response to common allergens is a secondary event.

Predisposing factors

• Age and sex: 4-20 years; more common in boys than girls.
• Season: More common in summer; hence the name "spring catarrh" seems to be a misnomer. Recently labelled as 'Warm weather conjunctivitis'. Seasonal exacerbation is common, but symptoms can be year-round.
• Climate: More prevalent in tropics, less in temperate zones, almost non-existent in cold climates.
• Other atopic manifestations: Eczema or asthma associated in 40-75% of patients.
• Family history: Atopy found in 40-60% of patients.

Pathology

• Conjunctival epithelium in the papillary region contains large numbers of mast cells & eosinophils, undergoes hyperplasia, and sends downward projections into subepithelial tissue.
• Adenoid layer shows marked cellular infiltration (mast cells, eosinophils, plasma cells, lymphocytes, histiocytes).
• Fibrous layer shows proliferation which later undergoes hyaline changes.
• Conjunctival vessels show proliferation, increased permeability, and vasodilation.

Note: All these changes lead to the formation of multiple papillae in the upper tarsal conjunctiva.

Clinical Features

Signs & Clinical Forms

1. Palpebral VKC: Usually upper tarsal conjunctiva of both eyes. Characterized by hard, flat-topped papillae arranged in a 'cobble-stone' or 'pavement stone' fashion with hyperemia. In severe cases, giant papillae (cauliflower-like) form. Associated with white ropy discharge.

Palpebral form of vernal keratoconjunctivitis

2. Bulbar limbal VKC:

• Dusky red triangular congestion of bulbar conjunctiva in palpebral area.
• Limbal papillae (gelatinous, thickened confluent accumulation around limbus).
• Presence of discrete whitish raised dots along the limbus called Horner-Tranta's spots.

3. Mixed VKC: Combined features of both palpebral and bulbar forms.

Vernal Keratopathy

Corneal involvement is more frequent with palpebral form and includes:

• Superior punctate epithelial keratitis: Upper cornea, caused by friction from inflamed tarsal conjunctiva. Stains with rose bengal and fluorescein.
• Epithelial macro erosions: Coalescence of punctate lesions (Bowman's membrane intact).
• Vernal corneal plaques: Coating of bare areas with altered exudates.
• Ulcerative vernal keratitis (Shield ulceration): Shallow transverse ulcer in upper cornea. A serious problem prone to bacterial keratitis.
• Subepithelial scarring: Ring scar formation.
• Pseudogerontoxon: Develops in recurrent limbal disease (classical 'cupid's bow' outline).

Treatment

A. Topical anti-allergic & anti-inflammatory

• Dual action antihistamines/mast cell stabilizers: First-line for mild/moderate cases (olopatadine 0.1%, azelastine, bepotastine 1.5%).
• Mast cell stabilizers: Sodium cromoglycate 2% drops (3-4 times/day).
• Topical steroids: Effective in all forms but reserved for moderate/severe/recalcitrant cases due to steroid-induced glaucoma risk. Monitor IOP. Intensive short tapering course. (Safest: loteprednol, fluorometholone).
• Topical Immunomodulators: When steroids are ineffective or as steroid-sparing agents (Cyclosporine 0.5-1%, Tacrolimus 0.03% ointment).

B. Topical lubricating and mucolytics

• Artificial tears: Carboxymethyl cellulose for soothing effect.
• Acetyl cysteine (0.5%): Mucolytic properties, useful for early plaque formation.

C. Systemic therapy (Severe cases only)

• Oral antihistaminics (for severe itching).
• Oral steroids (short duration for advanced/non-responsive cases).

D. Treatment of large papillae

E. Supportive measures

• Dark goggles to prevent photophobia.
• Cold compresses and ice packs.
• Avoid eye rubbing (causes mast cell degranulation).
• Change of place from hot to cold area for recalcitrant cases.

F. Treatment of Vernal Keratopathy

• Punctate epithelial keratitis: Increase steroid instillation.
• Large vernal plaque: Superficial keratectomy excision.
• Severe shield ulcer: Debridement, superficial keratectomy, excimer laser therapeutic keratectomy, or amniotic membrane transplantation to enhance re-epithelialization.