Trachoma

Trachoma is the leading infectious cause of blindness in the world.

Trachoma is a contagious bacterial infection that affects the surface of the eyes. Over time, scar tissue or ulcers can form that lead to blindness.

Around 1.9 million people worldwide are blind or visually impaired by trachoma, and it remains a public health problem in 44 countries. It spreads when bacteria in the secretions from the eyes of an affected individual extend to others either by person-to-person contact or by eye-seeking flies, particularly the Musca sorbens fly. It occurs most commonly in endemic communities with poor hygiene and a lack of access to clean water. It is the leading infectious cause of preventable blindness in the world.

Approximately 21 million people in the world have active trachoma. The majority of these are children between 3-6 years of age. The disease is found predominantly in dry, arid lands near the equator, with the largest number of cases in sub-Saharan Africa.

The bacteria responsible for trachoma is Chlamydia trachomatis. There are different types of Chlamydia trachomatis. Types A, B, Ba, and C cause blinding trachoma. Other types (D to K) are associated with sexually transmitted chlamydia infection.

Living conditions with poor sanitation, unclean water supply, and lack of regular face washing allow the bacteria to infect and re-infect the eyes of individuals living in trachoma-endemic areas.

The active form is most common in young children who spread it to those closest to them such as siblings, playmates, and caregivers. Among adults, women who care for children have a higher incidence of active disease.

The symptoms include irritation of the eyes with tearing, pain, light sensitivity, and vision loss. The signs include the presence of follicles, redness, scarring, and corneal opacity as described in the five stages listed above.

Although there are tests to identify the bacteria, doctors primarily diagnose trachoma by examining the eyes and eyelids of the patient. Healthcare workers are trained in basic eye health examination techniques and can make the diagnosis by identifying the five stages of blinding trachoma with the aid of light and simple magnifiers.

The World Health Organization created a grading system to classify the five stages of blinding trachoma, based on the clinical signs that are seen as the disease progresses.

1. Trachomatous inflammation—follicular (TF): The first sign is the presence of follicles, which are small bumps formed by swollen lymph tissue on the back of the upper eyelid and sometimes extending to the top part of the eye. The presence of five or more follicles greater than 0.5 mm in size on the conjunctiva lining the back of the upper eyelid is considered grade TF.
2. Trachomatous inflammation—intense (TI): The next phase is swelling (inflammation) of the conjunctiva that obscures the view of the normal deeper blood vessels of the conjunctiva.
3. Trachomatous scarring (TS): Bands of scar tissue form within the conjunctiva lining the inside of the upper eyelid.
4. Trachomatous trichiasis (TT): The bands of scar tissue tighten, causing the lid margins to turn inward (entropion) and the eyelashes to rub against the eye (trichiasis). Over time, this rubbing results in abrasions of the cornea, the clear central covering of the front of the eye.
5. Corneal opacity: Corneal abrasions can lead to infectious ulcers and ultimately opaque scarring that blocks light from entering the eye, leading to blindness.

The World Health Organization reported that the number of people at risk for trachoma has fallen from 1.5 billion in 2002 to just over 142 million in 2019.

The WHO Alliance for the Global Elimination of Trachoma by 2020 (GET2020) aims to completely eradicate the disease through the implementation of the multifaceted SAFE strategy to prevent and treat trachoma:

• S = surgery to correct in-turned eyelids and trichiasis
• A = antibiotics (azithromycin) to treat an active infection
• F = facial cleanliness to reduce human transmission
• E = environmental improvement (such as access to clean water and hygiene measures to reduce the fly population) to reduce human transmission

The antibiotic treatment for the active disease is a one-time use of azithromycin (Zithromax) pills. However, reinfection is common if a person doesn't make improvements in hygiene and access to clean water.

When trachoma has progressed to inward-turning of the lashes, surgery is necessary to correct the lid position.

If significant corneal scarring develops, a corneal transplantation surgery is required to restore sight.

Various government agencies and international nongovernmental development organizations (INGDOs), such as the Carter Center Trachoma Control Program, work together to implement the SAFE strategy.

Community-based implementation of the SAFE strategy improved the prognosis for millions of at-risk individuals. If a doctor diagnoses trachoma and treats it early, before scarring of the eyelids and cornea, the prognosis for the preservation of vision is excellent.

Some individuals who have trachoma infection of the eyes will have it only once and scarring will not necessarily occur. However, reinfections are common, and over many years, the untreated disease can progress through the five stages of blindness.