Trachoma is the world’s leading cause of preventable blindness of infectious origin. Caused by the bacterium Chlamydia trachomatis, trachoma is easily spread through direct personal contact, shared towels and cloths, and flies that have come in contact with the eyes or nose of an infected person. If left untreated, repeated trachoma infections can cause severe scarring of the inside of the eyelid and can cause the eyelashes to scratch the cornea (trichiasis). In addition to causing pain, trichiasis permanently damages the cornea and can lead to irreversible blindness.
Trachoma is caused by repeated conjunctival infection with C trachomatis. Important individual-level risk factors for active trachoma include
1. having siblings with active disease,
2. having a dirty face, and
3. crowded sleeping arrangements.
At the community level, adequate water access for personal hygiene, sanitation, and fly control determine the risk of endemic trachoma.
The World Health Organization recommends a simplified grading system for trachoma. The Simplified WHO Grading System is summarized below:
- Trachomatous inflammation, follicular (TF)—Five or more follicles of >0.5 mm on the upper tarsal conjunctiva
- Trachomatous inflammation, intense (TI)—Papillary hypertrophy and inflammatory thickening of the upper tarsal conjunctiva obscuring more than half the deep tarsal vessels
- Trachomatous scarring (TS)—Presence of scarring in tarsal conjunctiva.
- Trachomatous trichiasis (TT)—At least one ingrown eyelash touching the globe, or evidence of epilation (eyelash removal)
- Corneal opacity (CO)—Corneal opacity blurring part of the pupil margin
Active trachoma is characterized by a mucopurulent keratoconjunctivitis. The conjunctival surface of the upper eyelid shows a follicular and inflammatory response. The cornea may have limbal follicles, superior neovascularization (pannus), and punctate keratitis. Infection with C trachomatis concurrently occurs in other extraocular mucous membranes, commonly the nasopharynx, leading to a nasal discharge.
Trachomatous inflammation, follicular (TF), is the Trachomatous inflammation, follicular (TF), is the presence of 5 or more follicles (each at least 0.5 mm in diameter) on the central part of the upper tarsal conjunctiva.Follicular trachoma indicates active disease.This form is most commonly found in children, with a peak prevalence in those aged 3-5 years. The prevalence rapidly decreases in school-aged children as they leave the pool of re-infection (i.e. their family childcare group).
Follicles are germinal centers that primarily consist of lymphocytes and monocytes.The presence and involution of follicles at the limbus (corneoscleral border) give rise to the pathognomonic lesion of past active trachoma.
Intense inflammatory trachoma
Trachomatous inflammation, intense (TI) is pronoun Trachomatous inflammation, intense (TI) is pronounced inflammatory thickening of the upper tarsal conjunctiva that obscures more than one half the normal deep tarsal vessels.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.The cause is an intense inflammatory response. Like follicular trachoma, intense inflammatory trachoma indicates active disease.The normally thin tarsal conjunctiva develops a velvety thickening.Papillae are visible under slit lamp examination.Intense inflammatory trachoma indicates an increased potential for significant conjunctival scarring and, hence, a higher ultimate risk of blinding disease.Surveying the prevalence of intense inflammatory trachoma in children can help in predicting the risk of future blinding trachoma in that cohort of children.
Trachomatous conjunctival scarring (TS) is the pre Trachomatous conjunctival scarring (TS) is the presence of easily visible scars in the tarsal conjunctiva.Trachomatous scarring indicates past inflammatory disease and a risk of future trichiasis. The more severe the scarring, the higher 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 may also lead to a weeping eye.
Trichiasis is defined as at least 1 eyelash rubs on the eyeball or 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 that leads to lid distortion.Some vision can be restored with the successful correction of trichiasis.
Corneal opacity is defined as easily visible corneal opacity over the pupil that is so dense that it blurs at least part of the pupillary margin when it is viewed through the opacity.Corneal opacity or scarring reflects the prevalence of vision loss and blindness resulting from trachoma.This condition includes pannus, epithelial vascularization, and infiltration only if it involves the central cornea.
The key to the treatment of trachoma is the SAFE strategy developed by the WHO. The surgical ("S") component of this strategy is described in Surgical Care . Antibiotics ("A"), facial cleanliness ("F"), and environmental improvement ("E") are described in this section.
The WHO recommends 2 antibiotics for trachoma control: oral azithromycin and tetracycline eye ointment. Azithromycin eye drops have also been shown to be very effective.Azithromycin is better than tetracycline, but it is more expensive.National trachoma control programs in a number of countries are fortunate to be beneficiaries of a philanthropic donation of azithromycin.
Azithromycin is the drug of choice because it is easy to administer as a single oral dose. Its administration can be directly observed. Therefore, compliance is higher than with tetracycline and can actually be measured, whereas, with the home administration of tetracycline, the level of compliance is unknown.Azithromycin has high efficacy and a low incidence of adverse effects. When adverse effects occur, they are usually mild; gastrointestinal upset and rash are the most common adverse events.Infection with C trachomatis occurs in the nasopharynx; therefore, patients may reinfect themselves if only topical antibiotics are used.Beneficial secondary effects of azithromycin include its treatment of genital, respiratory, and skin infections.
Epidemiologic studies and community-randomized trials have shown that facial cleanliness in children reduces both the risk and the severity of active trachoma.To be successful, health education and promotion activities must be community based and require considerable effort.
General improvements in personal and community hygiene are almost universally associated with a reduction in the prevalence—and eventually the disappearance—of trachoma. This is true not only in Europe, the Americas, and Australia but also in Africa and Asia.Environmental improvement activities are the promotion of improved water supplies and improved household sanitation, particularly methods for safe disposal of human feces.These activities should be prioritized.The flies that transmit trachoma preferentially lay their eggs on human feces lying exposed on the soil. Controlling fly populations by spraying insecticide is difficult. Studies on the impact of fly control on trachoma have had variable results. Trials undertaken to evaluate the installation of pit latrines suggested that the prevalence of trachoma was reduced but failed to demonstrate a statistically significant effect.
Eyelid surgery to correct trichiasis is important in people with trichiasis, who are at high-risk for trachomatous visual impairment and blindness. Eyelid surgery to correct entropion and/or trichiasis may prevent blindness in individuals at immediate risk.Eyelid rotation limits the progression of corneal scarring. In some cases, it can result in a slight improvement in visual acuity, probably due to restoration of the visual surface and reductions in ocular secretions and blepharospasm.The W.H.O. has produced a training manual on the bilamellar tarsal rotation procedure.Details are as follows:
This procedure involves a full-thickness incision of the scarred lid and external rotation of the distal margin by using 3 sutures.
In regions where access to ophthalmologists is limited, well-trained and well-supported health workers can perform bilamellar tarsal rotation.
Results of randomized clinical trials have confirmed the superiority of this method over other techniques.
Even after successful surgery, patients remain at risk for recurrence. Therefore, long-term follow-up care and intermittent screening are important after surgery.
Recurrence rates vary greatly between surgeons. Ongoing audit is an essential element of trichiasis surgery programs.
PREVENTIONThe World Health Organization has targeted trachoma for elimination by 2020 through an innovative, multi-faceted public health strategy known as S.A.F.E.Surgery to correct the advanced, blinding stage of the disease (trichiasis),Antibiotics to treat active infection,Facial cleanliness and,
Environmental improvements in the areas of water and sanitation to reduce disease transmission.Facial cleanliness and environmental improvement are major components of the SAFE strategy.Many regard the lack of facial cleanliness in children as the key factor for the persistence of trachoma.
The prognosis depends on the severity of the disease at the time of treatment, the appropriateness of the treatment, and the risk of reinfection.Patients in whom early disease is treated appropriately have an excellent prognosis.Severe disease may be stabilized, but the patient's vision may not improve once corneal scarring has developed.Reinfection worsens the prognosis.