what is trachoma ?

Trachoma (previously known as Egyptian ophthalmia) is a chronic keratoconjunctivitis, primarily affecting the superficial epithelium of
conjunctiva and cornea simultaneously. It is characterised by a mixed follicular and papillary response of conjunctival tissue. It is still one of the
leading causes of 
preventable blindness in the world.

The word 'trachoma' comes from the Greek word for
'rough' which describes the surface appearance of
the conjunctiva in chronic trachoma.

Etiology
A. Causative organism. Trachoma is caused by a
Bedsonian organism, the Chlamydia trachomatis
belonging to the Psittacosis-lymphogranulomatrachoma
(PLT) group. The organism is epitheliotropic
and produces intracytoplasmic inclusion bodies
called H.P. bodies (Halberstaedter Prowazeke
bodies). Presently, 11 serotypes of chlamydia, (A, B,
Ba, C, D, E, F, G, H, J and K) have been identified
using microimmunofluorescence techniques.
Serotypes A, B, Ba and C are associated with
hyperendemic (blinding) trachoma, while serotypes
D-K are associated with paratrachoma (oculogenital
chlamydial disease).

B. Predisposing factors. These include age, sex, race,
climate, socioeconomic status and environmental
factors.
1. Age. The infection is usually contracted during
infancy and early childhood. Otherwise, there is
no age bar.

2. Sex. As far as sex is concerned, there is general
agreement that preponderance exists in the
females both in number and in severity of disease.

3. Race. No race is immune to trachoma, but the
disease is very common in Jews and comparatively
less common among Negroes.

4. Climate. Trachoma is more common in areas with
dry and dusty weather.

5. Socioeconomic status. The disease is more
common in poor classes owing to unhygienic
living conditions, overcrowding, unsanitary
conditions, abundant fly population, paucity of
water, lack of materials like separate towels and
handkerchiefs, and lack of education and
understanding about spread of contagious
diseases.

6. Environmental factors like exposure to dust,
smoke, irritants, sunlight etc. increase the risk of
contracting disease. Therefore, outdoor workers
are more affected in comparison to office workers.

C. Source of infection. In trachoma endemic zones
the main source of infection is the conjunctival
discharge of the affected person. Therefore,
superimposed bacterial infections help in
transmission of the disease by increasing the
conjunctival secretions.

D. Modes of infection. Infection may spread from
eye to eye by any of the following modes:
1. Direct spread of infection may occur through
contact by air-borne or water-borne modes.

2. Vector transmission of trachoma is common
through flies.

3. Material transfer plays an important role in the
spread of trachoma. Material transfer can occur
through contaminated fingers of doctors, nurses
and contaminated tonometers. Other sources of
material transfer of infection are use of common
towel, handkerchief, bedding and surma-rods.

Prevalence
Trachoma is a worldwide disease but it is highly
prevalent in North Africa, Middle East and certain
regions of Sourth-East Asia. It is believed to affect
some 500 million people in the world. There are about
150 million cases with active trachoma and about 30
million having trichiasis, needing lid surgery.
Trachoma is responsible for 15-20 percent of the
world's blindness, being second only to cataract.

Clinical profile of trachoma
Incubation period of trachoma varies from 5-21 days.
Onset of disease is usually insidious (subacute),
however, rarely it may present in acute form.

Clinical course of trachoma is determined by the
presence or absence of secondary infection. In the absence of such an infection, a pure trachoma is so mild and symptomless that the disease is usually neglected. But, mostly the picture is complicated by secondary infection and may start with typical symptoms of acute conjunctivitis. In the early stages it is clinically indistinguishable from the
bacterial conjunctivitis and the term 'trachomadubium' (doubtful trachoma) is sometimes used for this stage.

Natural history. In an endemic area natural history of trachoma is characterized by the development of acute disease in the first decade of life which continues with slow progression, until the disease becomes inactive in the second decade of life. The sequelae occur at least after 20 years of the disease. Thus, the peak incidence of blinding sequelae is seen in the fourth and fifth decade of life