PHLYCTENULAR KERATOCONJUNCTIVITIS

Phlyctenular keratoconjunctivitis is a characteristic nodular affection occurring as an allergic response of the conjunctival and corneal epithelium to some endogenous allergens to which they have become sensitized. Phlyctenular conjunctivitis is of worldwide distribution. However, its incidence is higher in developing countries.
Etiology
It is believed to be a delayed hypersensitivity (Type IV-cell mediated) response to endogenous microbial proteins.
I. Causative allergens
1. Tuberculous proteins were considered, previously, as the most common cause.
2. Staphylococcus proteins are
now thought to account for most of the cases.
3. Other allergens may be proteins of Moraxella Axenfeld bacillius and certain parasites (worm infestation).
II. Predisposing factors
1. Age. Peak age group is 3-15 years.
2. Sex. Incidence is higher in girls than boys.
3. Undernourishment. Disease is more common in undernourished children.
4. Living conditions. Overcrowded and unhygienic.
5. Season. It occurs in all climates but incidence is high in spring and summer seasons.
Pathology
1. Stage of nodule formation. In this stage there occurs exudation and infiltration of leucocytes into the deeper layers of conjunctiva leading to
a nodule formation. The central cells are polymorphonuclear and peripheral cells are lymphocytes. The neighbouring blood vessels dilate and their endothelium proliferates.

2. Stage of ulceration. Later on necrosis occurs at the apex of the nodule and an ulcer is formed. Leucocytic infiltration increases with plasma cells and mast cells.

3. Stage of granulation. Eventually floor of the ulcer becomes covered by granulation tissue.

4. Stage of healing. Healing occurs usually with minimal scarring.

Clinical picture
Symptoms in simple phlyctenular conjunctivitis are few, like mild discomfort in the eye, irritation and reflex watering. However, usually there is associated
mucopurulent conjunctivitis due to secondary bacterial infection.
Signs. The phlyctenular conjunctivitis can present in three forms: simple, necrotizing and miliary.
1. Simple phylctenular conjunctivitis. It is the most commonly seen variety. It is characterised by the presence of a typical pinkish white nodule
surrounded by hyperaemia on the bulbar conjunctiva, usually near the limbus. Most of the times there is solitary nodule but at times there may be two nodules (Fig. 1). In a few days the nodule ulcerates at apex which later on gets epithelised. Rest of the conjunctiva is normal.

Fig. 1. Phylctenular conjunctivitis.

2. Necrotizing phlyctenular conjunctivitis is characterised by the presence of a very large phlycten with necrosis and ulceration leading to a severe pustular conjunctivitis.

3. Miliary phlyctenular conjunctivitis is characterized by the presence of multiple phlyctens which may be arranged haphazardly or in the form of a ring around the limbus and may even form a ring ulcer.