Trachoma

What is trachoma

Trachoma: world’s major infectious cause of blindness

Trachoma is the leading infectious cause of blindness in the world. Infection spreads from person to person, particularly from child to child and from child to mother to child. The disease thrives especially in crowded living conditions where there are shortages of water, inadequate sanitation and where numerous eye-seeking flies are present. In affected communities, infection is often first encountered in infancy or childhood.

In affected communities, infection is often first encountered in infancy or childhood. With repeated infection over many years, the cumulative effect of many inflammatory episodes may cause the upper eyelid to turn inwards, so that the eyelashes rub on the eyeball, resulting in intense pain and scarring of the front of the eye. This is called trachomatous trichiasis, and ultimately leads to irreversible blindness.

The age at which people in a community start going blind from trachoma is related to the intensity of transmission of infection in the community.

Diagnosis

Trachoma disease is usually clinically diagnosed. People are examined for clinical signs through the use of magnifiers (loupes). In most early stages, infection does not present visible signs of the disease. However, repeated infections cause scarring of the conjunctiva and it is during this phase that infected individuals get the feeling of irritation.

The WHO grading system for trachoma classifies the disease in 5 grades:

  • Trachomatous Inflammation – Follicular (TF) - which mostly requires topical treatment.
  • Trachomatous Inflammation – Intense (TI) - during which topical and systemic treatments are considered.
  • Trachomatous Scarring (TS) - when scars are visible as in the tarsal conjunctiva and which may obscure tarsal blood vessels.
  • Trachomatous Trichiasis (TT) - when an individual is referred for eyelid surgery; and
  • Corneal Opacity - a stage during which a person is irreversibly blind.

Clinical characteristics

In areas where trachoma is endemic, active (inflammatory) trachoma is common among preschool-aged children, with prevalence rates which can be as high as 60-90%. Infection becomes less frequent and shorter in duration with increasing age.

Infection is usually acquired through living in close proximity to others with active disease, and the family is the principal unit for transmission. An individual’s immune system can clear a single episode of infection, but in endemic communities, re-acquisition of the organism occurs frequently.

After years of repeated infection, the inside of the eyelid can become so severely scarred (trachomatous conjunctival scarring) that it turns inwards and causes the eye-lashes to rub against the eyeball (trachomatous trichiasis) resulting in constant pain and light intolerance; this and other alterations of the eye can lead to the scarring of the cornea. Left untreated, this condition leads to the formation of irreversible opacities, with resulting visual impairment or blindness. The age at which this occurs depends on several factors including local transmission intensity. In very highly endemic communities, it can occur in childhood, though onset between the ages of 30 and 40 years is more typical.

Morbidity

Visual impairment or blindness results in a worsening of the life experience of affected individuals and their families, who are normally already amongst the poorest of the poor. Women are blinded 2 to 3 times more often than men, probably due to their close contact with infected children and their resulting greater frequency of infection episodes themselves.

Environmental risk factors influencing the transmission of the disease include:

  • poor hygiene;
  • crowded households;
  • water shortage; and
  • inadequate latrines and sanitation facilities.