Trachoma is a chronic keratoconjunctivitis caused by four ocular serotypes A, B, Ba and C of organism Chlamydia trachomatis. It is a disease of underprivileged populations living in poor conditions of hygiene.
Active trachoma is most common in young children with the prevalence decreasing with age. Trachoma is a common infectious cause of blindness and is due to recurrent eye infection with Chlamydia trachomatis. The common house-fly is the major vector in perpetuating infection-reinfection cycle. Long-term sequlae of trachoma in adults relate to their exposure to active trachoma when they were young. Repeat infection by this organism leads to conjunctival inflammation, scarring, trichiasis and blinding corneal opacification.
Basak Samar K, Atlas of Clinical Ophthalmology, 2nd ed. Jaypee Brothers Medical Publishers (P) Ltd, 2013, New Delhi, P. 52.
Kanski,Jack J. Clinical Ophthalmology, A Systematic Approach .Third Edition.UK. Butterworth Heinemann, 1994. P 81-82.
Most of the individuals with trachoma are asymptomatic or have mild symptoms depending on the severity of inflammation. Symptoms in eye are similar to those seen in any chronic conjunctivitis and may include:-
- Foreign body sensation.
- Eye discharge.
- Dryness of eyes due to scarring.
- Diminution of vision.
Trachoma is caused by repeated conjunctival infection with serotypes A, B, Ba and C of organism Chlamydia trachomatis. Chlamydiae are gram-negative obligate intracellular bacteria. The incubation period for trachoma is 5-12 days.
Chlamydia trachomatis causes trachoma and also genital infections (serotypes D to K) and disease Lymphogranuloma venereum (serotypes L1 to L3). Infection with genital serotypes D to K can cause isolated episodes of Ophthalmia neonatorum in infants or inclusion conjunctivitis in adults. Genital serotypes do not cause trachoma blindness since they do not enter stable transmission cycles within communities. Serotypes D to K occasionally cause sub-acute follicular conjunctivitis but conjunctival scarring is rare.
Two phases, active and cicatricial (scarring) exists for the disease process.
Active trachoma occurs most commonly in preschool children, with the highest prevalence in children aged 3-5 years.
Cicatricial trachoma is most common in middle-aged people. The age group in which cicatricial disease begins to appear depends on the intensity of its transmission in the community.
Risk factors for active trachoma:
Individual-level risk factors:-
- Having siblings with active disease.
- Dirty face which attract flies.
- Crowded sleeping arrangement enables exchange of secretions.
Community-level risk factors:-
- Inadequate water access for personal hygiene.
- Limited toilet facilities and poor sanitation leads to increased faecal contamination of the environment which provides a breeding ground for flies.
- Control of flies.
Recurrent episode of active trachoma infection leads to blindness. Initial infection is confined to conjunctival epithelium and triggers an immune response. Repeat infection with subsequent inflammatory response results in tissue destruction, scarring, contraction and buckling of tarsal plate of upper lid, leading to cicatricial entropion and trichiasis, and corneal opacification by lashes rubbing against it.
Diagnosis of trachoma mainly depends upon clinical presentation.
Most patients with active trachoma are relatively asymptomatic. Active phase resembles many other diseases in which follicular conjunctivitis is a feature.
The cicatricial phase has unique clinical features, which helps in diagnosing trachoma. Conjunctival scarring alone tends to be asymptomatic, though the associated disturbance of tear film (produced by scarring of mucous and serous glands) often leads to dry eye. Trichiasis causes foreign body sensation as well as blepharospasm. Constant rubbing of eyelashes may lead to corneal opacification and impairment of vision.
WHO grading and clinical features of trachoma:
Slit-lamp examination by an eye-specialist is required for grading.
Active trachoma is characterised by muco-purulent keratoconjunctivitis. Conjunctival surface of upper eyelid develops follicular and inflammatory response. Cornea may have limbal follicles, pannus (superior neovascularisation of cornea) formation and punctate keratitis. Other extra-ocular mucous membranes like nasopharynx may be involved leading to nasal discharge.
Follicular Trachoma (TF):
Follicular trachoma is defined as the presence of 5 or more follicles at least 0.5 mm in diameter in the central part of upper tarsal conjunctiva.
Follicular trachoma indicates active disease. This form is most commonly found in children, with peak prevalence in those aged 3-5 years of age.
Follicles are germinal centers that primarily consist of lymphocytes and monocytes. Involution of follicles at limbus (corneoscleral junction) gives rise to pathognomonic lesion of past trachoma in the form of Herbert pits.
Intense inflammatory trachoma (TI):
Intense inflammatory trachoma is defined as pronounced inflammatory thickening of the upper tarsal conjunctiva that obscures more than one half of the normal deep tarsal vessels.
Intense inflammatory trachoma also indicates active disease. Thin tarsal conjunctiva develops a velvety thickening. Papillae may also be visible. Intense inflammatory trachoma indicates increased potential for significant conjunctival scarring and corneal opacification.
Trachomatous scarring (TS):
Trachomatous scarring is defined as the presence of easily visible scars in tarsal conjunctiva. Upper tarsal conjunctiva may show scarring as Arlt’s line.
Trachomatous scarring indicates past inflammatory disease and a risk of trichiasis. Severe the scarring, higher is the risk of subsequent trichiasis.
This form may be associated with the development of dry eye syndrome, but chronic low-grade bacterial conjunctivitis and dacryocystitis (inflammation of lacrimal sac) may lead to watering of eyes.
Trachomatous trichiasis is defined as the presence of at least one eyelash rubbing on the eyeball or there is evidence of recent removal of in-turned eyelashes.
This is a potentially blinding lesion that can lead to corneal opacification.
Trichiasis is due to subconjunctival fibrosis over the tarsal plate which leads to distortion of lid.
Successful correction of trichiasis may help in restoring some vision.
Corneal Opacity (CO):
Corneal opacity is defined as easily visible corneal opacity over the pupil that is so dense that at least part of the pupillary margin is blurred, when viewed through the opacity.
Corneal opacity reflects the prevalence of visual loss and blindness resulting from trachoma.
This condition includes pannus, epithelial vascularisation and infiltration only if it involves central cornea.
In endemic regions, diagnosis is almost always based on clinical features.
Laboratory investigations are mainly used in research.
- Nucleic acid amplification tests (NAATs): Nucleic acid amplification test is the best laboratory technique, of which polymerase chain reaction is an example.
NAATs have high sensitivity and specificity but are expensive and not widely available.
- Direct fluorescent antibody (DFA) assay: Direct fluorescent antibody assay of conjunctival smears is less sensitive than NAATs.
- Enzyme immunoassay (EIA): Enzyme immunoassay of conjunctival smears is also less sensitive than NAATs.
- Cell culture: Cell culture has high specificity but only moderate sensitivity. Cell culture requires a highly specialised laboratory and is expensive. Newer diagnostic methods have superseded cell culture.
- Giemsa cytology: Giemsa cytology is microscopic examination of stained conjunctival scrapings for intracytoplasmic inclusions. This test is highly specific but has low sensitivity.
Trachomatous inflammation is characterised predominantly by lymphocytic and monocytic infiltrate with plasma cells and macrophages in follicles. Follicles have typical germinal centers with islands of B-cells proliferation, surrounded by number of T-cells.
With inflammation, there may be formation of papillae. Recurrent conjunctival re-infection causes prolonged inflammation and conjunctival scarring. Scarring is associated with atrophy of conjunctival epithelium, loss of goblet cells and replacement of normal loose vascular sub-epithelial stroma with bands of collagen.
Trachoma should be differentiated from:-
- Acute inclusion conjunctivitis.
- Neonatal conjunctivitis.
- Toxic follicular conjunctivitis caused by topical medications or other compounds.
- Allergic conjunctivitis which shows typical cobblestone papillae.
- Bacterial conjunctivitis.
- Viral conjunctivitis.
- Trichiasis due to other causes such as entropion.
Management should be carried out under medical supervision.
World Health Organisation (WHO) recommends the ‘SAFE’ strategy for the management of trachoma. The strategy was developed by WHO Alliance for the Global Elimination of Blinding Trachoma by the year 2020 (GET 2020) and utilises a four step approach:-
- S (Surgery for Trichiasis): Eyelid surgery to correct entropion and/or trichiasis may prevent trachomatous visual impairment and blindness in individuals at immediate risk. Eyelid bi-lamellar tarsal rotation surgery limits the progression of corneal scarring. In some cases, it can result in slight improvement in visual acuity. Adjuvant single dose azithromycin is given at the time of surgery.
- A (Antibiotics for Chlamydia trachomatis infection): WHO recommends oral azithromycin and tetracycline eye ointment for trachoma control. Azithromycin eye drops have also been shown to be very effective. Beneficial secondary effects of azithromycin include its treatment of genital, respiratory and skin infections.
Aim in treatment is to reduce the reservoir of Chlamydia trachomatis infection in the family. All family members, including infants, should be treated for trachoma. In hyper-endemic areas, whole community should be treated with antibiotics.
Sulphacetamide (topical sulphonamide) eye drops are also being used.
- F (Facial cleanliness): Facial cleanliness in children reduces both the risk and the severity of active trachoma.
- E (Environmental change to improve sanitation and increase access to clean water): General improvements in personal and community hygiene are associated with a reduction in prevalence and eventually the disappearance of trachoma. Environmental improvement activities are the promotion of improved water supplies and improved household sanitation, particularly methods for safe disposal of human faeces. The flies that transmit trachoma preferentially lay their eggs on human faeces lying exposed on soil.
Prognosis of trachoma depends on the severity of disease at the time of treatment, institution of appropriate treatment and the risk of re-infection.
Patients with early and appropriate treatment have excellent prognosis.
Severe disease may be stabilised, but vision may not improve once corneal scarring develops.
Re-infection worsens the prognosis in a patient.
Trachoma may lead to complications and sequlae like:
- Scarring of upper palpebral conjunctiva.
- Trchiasis (inward turning of eyelash) due to contraction of scar tissue at lid margin.
- Entropion (lid margin rolls inside).
- Tylosis (Thickening of lid margin).
- Trachomatous Ptosis may develop due to dense infiltration and cicatrisation of tarsal plate.
- Xerosis/xerophthalmia (dryness of eyes).
- Symblepharon (adhesion of palpebral and bulbar conjunctiva).
- Corneal ulceration.
- Corneal opacity.
- Visual impairment.
- Iritis (occasionally).
Facial cleanliness and improvement of environment are major components of ‘SAFE’ strategy.
Lack of facial cleanliness is regarded by many as the key factor for the persistence of trachoma.