VERNAL KERATOCONJUNCTIVITIS

vernal keratoconjunctivitis (vkc) or spring catarrh
It is a recurrent, bilateral, interstitial, self-limiting, allergic inflammation of the conjunctiva having a periodic seasonal incidence.

Etiology
It is considered a hypersensitivity reaction to some exogenous allergen, such as grass pollens. VKC is thought to be an atopic allergic disorder in many
cases, in which IgE-mediated mechanisms play an important role. Such patients may give personal or family history of
  other atopic diseases such as hay fever, asthma, or eczema and their peripheral blood shows eosinophilia and inceased serum IgE levels.

Predisposing factors
1. Age and sex. 4-20 years; more common in boys than girls.

2. Season. More common in summer; hence the name spring catarrh looks a misnomer. Recently it is being labelled as 'Warm weather conjunctivitis'.

3. Climate. More prevalent in tropics, less in temperate zones and almost non-existent in cold climate.

Pathology
1. Conjunctival epithelium undergoes hyperplasia and sends downward projections into the subepithelial tissue.

2. Adenoid layer shows marked cellular infiltration by eosinophils, plasma cells, lymphocytes and histiocytes.

3. Fibrous layer shows proliferation which later on undergoes hyaline changes.

4. Conjunctival vessels also show proliferation, increased permeability and vasodilation. All these pathological changes lead to formation of multiple papillae in the upper tarsal conjunctiva.

Clinical picture
Symptoms. Spring catarrh is characterised by marked burning and itching sensation which is usually intolerable and accentuated when patient comes in a warm humid atmosphere. Itching is more marked with palpebral form of disease. Other associated symptoms include: mild photophobia, lacrimation, stringy (ropy) discharge and heaviness of lids.

Signs of vernal keratoconjunctivitis can be described
in following three clinical forms:

1. Palpebral form. Usually upper tarsal conjunctiva of both eyes is involved. The typical lesion is characterized by the presence of hard, flat topped,
papillae arranged in a 'cobble-stone' or 'pavement stone', fashion (Fig. 1). In severe cases, papillae may hypertrophy to produce cauliflower like excrescences of 'giant papillae'. Conjunctival changes are associated with white ropy discharge.
                                                

Fig. 1 . Palpebral form of vernal keratoconjunctivitis

2. Bulbar form. It is characterised by: (i) dusky red triangular congestion of bulbar conjunctiva in palpebral area; (ii) gelatinous thickened accumulation of tissue around the limbus; and (iii) presence of discrete whitish raised dots along the limbus (Tranta's spots) (Fig. 2).
                                                           

Fig. 2. Bulbar form of vernal keratoconjunctivitis.

3. Mixed form. It shows combined features of both palpebral and bulbar forms (Fig. 3).

Fig. 3. Artist's diagram of mixed form of vernal
keratoconjunctivitis.c

                                                           

Vernal keratopathy. Corneal involvement in VKC may be primary or secondary due to extension of limbal lesions. Vernal keratopathy includes following 5 types of lesions:

1. Punctate epithelial keratitis involving upper cornea is usually associated with palpebral form of disease. The lesions always stain with rose bengal and invariably with fluorescein dye.

2. Ulcerative vernal keratitis (shield ulceration) presents as a shallow transverse ulcer in upper part of cornea. The ulceration results due to
epithelial macroerosions. It is a serious problem which may be complicated by bacterial keratitis.

3. Vernal corneal plaques result due to coating of bare areas of epithelial macroerosions with a layer of altered exudates (Fig. 4).

Fig. 4.23. Vernal corneal plaque.

4. Subepithelial scarring occurs in the form of a ring scar.

5. Pseudogerontoxon is characterised by a classical ‘cupid’s bow’ outline.

Clinical course of disease is often self-limiting and usually burns out spontaneously after 5-10 years.
Differential diagnosis. Palpebral form of VKC needs
to be differentiated from trachoma with pre-dominant
papillary hypertrophy