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Allergic Conjunctivitis

 

C. ALLERGIC CONJUNCTIVITIS

This group includes 2 major diseases:

1. Phlyctenular kerato-conjunctivitis (type 4 hypersensitivity).

2. Spring catarrhal (type 1 hypersensitivity).

1. PHLYCTENULAR  KERATO-CONJUNCTIVITIS

Definition:-

It is acute conjunctivitis caused by type IV hypersensitivity reaction due to an endogenous antigen.

Etiology:-

It is a cell mediated immune response (type IV hypersensitivity). It may occur in cases of:

- TB (the most important).

- Intestinal parasites.

- Tonsillitis.

- Ulcerative blepharitis.

Clinical picture:-

It is more common in children. It is usually recurrent. It may be unilateral or bilateral, single or multiple.

Symptoms:

- Pure conjunctival phlycten is painless and the patient complains only of redness.

- If the corneal is affected there will be pricky pain with reflex lacrimation, photophobia and blepharospasm.

- Mucopurulent discharge occurs if there is secondary infection.

Signs:

A. Conjunctival phlycten:

There is a greyish nodule about 1 - 3 mm in the exposed part of bulbar conjunctiva with a triangular leash of blood vessels. Later on the epithelium is ulcerated leading to MPC due to Staph. infection.

B. Corneal phlycten (phlyctenular kerato-conjunctivitis):

1. Limbal phlycten:

- Single or multiple phlyctenular nodules present at the limbus.

- Each nodule is greyish measuring 1 - 3 mm in diameter.

- They may surround the whole limbus.

2. Phlyctenular pannus:

There are superficial corneal vascularization and infiltration with inflammatory cells. It differs from trachomatous pannus in that:

- Can occur in any site, not necessarily in the upper half.

- Vessels lie deep to Bowman's membrane.

- Infiltration does not end in a straight line.

3. Phlyctenular ulcers:

a. Limbal ulcer (ulcerated limbal phlycten):- The ulcers may surround the whole limbus forming a ring ulcer.

b. Fascicular ulcer (ulcerated pannus):-

- It is a superficial secondary corneal ulcer with no tendency to perforate.

- It has a crescentic undermined progressive edge toward the centre of the cornea. It creeps towards the centre of the cornea (it is a serpeginous ulcer).

- The healing edge is present toward the limbus from which it is supplied by a leash of blood vessels, so that the healing edge is thin, scarred and vascular.

Histopathology:-

There is focal lymphocytic infiltration. If ulceration occur, PNL reaction occur.

Complications:-

1. MPC due to secondary infection by staph.

2. Recurrence of the cause is not treated.

Differential diagnosis:-

1. Conjunctival phlycten should be differentiated form:-

- Pinguicula (yellowish non ulcerating nodule in old age).

- Episcleritis (purple non ulcerating nodule in middle age females with collagen diseases).

2. Limbal phlycten should be differentiated from:

- Limbal spring catarrhal (non ulcerating gelatinous masses with Tranta spots and papillae in tarsal conjunctiva).

3. Phlyctenular pannus should be differentiated from trachomatous pannus (present in the upper part of cornea with other signs of trachoma).

Treatment:-

1. Local steroids and antibiotics eye drops 4 times by day and ointment at bed time. Treatment is needed only for few days.

2. Atropine eye drops may be added if there is corneal ulceration, but never bandage.

3. In severe and resistant cases of fascicular ulcer we interrupt the feeding vessels by perilimbal cautery.

4. Treatment of the systemic disease to prevent recurrence.

 

2. SPRING CATARRHAL (VERNAL CONJUNCTIVITIS)

Definition:-

It is a bilateral, seasonally recurrent, chronic conjunctivitis due to type I hypersensitivity allergic reaction to an external antigen.

Etiology & pathology:-

The antigen reacts with IgE that will stimulate mast cell leading to release of histamine and other mediators of the allergic response. The antigen is usually unknown, but the ultraviolet rays, heat and dust are contributing factors.

Epidemiology:-

- It starts in childhood and usually disappears spontaneously by the age of 25 years.

- It is more common in boys than in girls.

- Exacerbations occur in summer (not in spring).

Clinical picture:-

Symptoms: Bilateral recurrent seasonal attacks of:

Marked itching, lacrimation, photophobia and ropy discharge.

N.B. The discharge is formed of mucus, eosinophils and epithelial debris, so that it is scanty, white and elastic.

Signs:

There are 3 types:

1. The palpebral:-

It is the commonest type. The upper palpebral conjunctiva shows papillae with their characteristic appearance:-

- Large & flat topped.

- Cobble stone arrangement.

These papillae heal by remission without scarring.

NB. Sometimes fine papillae are formed in the lower tarsal conjunctiva.

NB. If the upper lid is everted for a short time, a white discharge rich in eosinophils will accumulate on the surface of conjunctiva.

2. The bulbar type:-

At first there  is thickening and broadening of the limbus formed by formation of gelatinous masses and ciliary injection around the limbus. White spots (called Tranta spots) may occur on these gelatinous masses due to aggregation of eosinophils, epithelial debris and calcium deposition.

3. The mixed type:-

Both bulbar and palpebral manifestations occur together.

Differential diagnosis:-

1. The bulbar type should be differentiated from limbal phlycten (ulcerating nodules with non seasonal recurrences).

2. The papillae should be differentiated from the papillae of trachoma which are small and finger like with rounded top.

Complications:-

They are mainly corneal in the form of:-

1. Complications of steroid treatment (mention).

2. Keratitis superficialis vernalis of Tobgy, where the cornea is dusted with many punctate superficial ulcers.

3. Corneal plaques: Large epithelial defects covered by mucus plaques that should by scrapped.

4. Arc like opacity in the periphery of the cornea (Cupid's bow).

5. Weakness of the cornea with higher incidence of keratoconus and keratectasia.

Treatment:-

1. Dark glasses and cold compresses are important to decrease the condition.

2. Local antihistaminic (as antistine) + vasoconstrictors (as previne) eye drops.

3. Local steroid are used only in severe cases. Their local side effects include glaucoma, cataract and they invite fungal and viral corneal ulcers.

4. Local disodium cromoglycate eye drops to stabilize the mast cells.

5. In resistant cases of palpebral type we do either:-

- Beta irradiation to close the vascular bed of the papillae.

- Cryo application to the papillae.

6. Systemic treatment:

- Skin desensitization.

- Antihistaminics.

 

3. CHRONIC FOLLICULAR CONJUNCTIVITIS

Etiology: Hypersensitivity to chronic exposure to chemical fumes, cigarette smokes, make-up preparations, atropine, miotics and neomycin.

Clinical picture: Redness, burning sensation and follicles in the lower fornix.

Treatment: Eliminate the cause plus antihistaminic decongestant drops.

GIANT PAPILLARY CONJUNCTIVITIS

It is conjunctivitis characterized by the formation of giant papillae. It occurs most probably due to mechanical irritation of the palpebral conjunctiva in cases of:-

- Contact lenses.

- Artificial eyes.

- Prominent suture following surgery.