Trachoma Grading

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Ocular infections

Trachoma in Pictures

Clinical grading.

Trachoma is a clinical diagnosis, made by examining the conjunctivae of the eye in good light using a 2.5x magnification lens.

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Fig 1. The upper eye-lid has been turned over to examine the conjunctiva over the stiffer part of the upper lid, as dotted in. The normal conjunctiva shown here is pink, smooth and transparent. Large, deep-lying blood vessels normally run vertically over the whole area of the conjunctiva. From the World Health Organisation Prevention of blindness web site. Fig 2. Trachomatous inflammation TF. There must be 5 or more follicles on the upper conjunctiva. Follicles must be at least 0.5 mm in diameter and are round, whitish, paler than the surrounding conjunctiva.

The initial response to eye infection with trachoma agents is conjunctivitis involving the palpebral and bulbar conjunctivae. The conjunctiva is inflamed, slightly swollen and congested, with papillary hypertrophy prominent in the palpebral conjunctiva. This is followed by lymphoid follicle formation, most commonly on the palpebral conjunctiva (Fig 2). However follicles may also be found on the bulbar conjunctiva. Trachomatous inflammation grade TF involves the presence of at least five lymphoid follicles on the upper conjunctiva. Pannus may also be present.

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Fig 3. Shallow pits at the limbal margin of the bulbar conjunctiva, caused by the rupture of lymphoid follicles leaving small scarred depressions termed Herbert’s pits. These are considered, together with lymphoid follicles or vascular pannus, as one of the characteristic diagnostic signs of trachoma. Fig 4. Intense trachomatous inflammation, TI. The tarsal conjunctiva appears red, rough and thickened, obscuring more than half of the normal, deep, tarsal vessels. There are numerous follicles which are partially covered by the thickened conjunctiva. Figure kindly provided by the World Health Organisation.

Conjunctival follicles, after rupture, may leave shallow pits, termed Herbert’s pits (Fig 3). [Herbert was an English ophthalmic surgeon, 1865 – 1942]. In some areas of the world secondary bacterial infection with Moraxella or other species is common giving rise to the discharge of pus from the eyes [Wood & Dawson, 1967].

Cicatricial trachoma.

Severe initial infection, but more commonly repeated re-infection in an endemic area, leads to the development of conjunctival scarring ( Fig 5).

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Fig 5. Grade TS. Scarring and fibrosis of the tarsal conjunctiva in response to severe or chronic trachoma. This is sometimes called cicatricial trachoma. The scars, glistening and fibrous in appearance, are easily visible as white lines, bands, or even sheets. Scarring and, particularly, diffuse fibrosis may obscure the deep conjunctival blood vessels. Scarring is important because it gives rise to the blinding sequelae of trachoma. Fig 6. Grade TS. An example of more sheet-like fibrosis of the conjunctiva as a result of trachoma. The conjunctival blood vessels are almost entirely obscured. Severe trachomatous scarring such as this is usually seen in older adults, and in women more commonly than men.

Severe scarring of the tarsal conjunctiva distorts the eyelid, a condition called entropion ( Fig 7). This re-directs the eyelashes inwards so that they lash the orb of the eye, ( trichiasis) leading to corneal damage and visual loss ( Fig 8).

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Fig 7. Grade TT. Trichiasis is defined as occurring when at least one eye-lash rubs on the eye-ball as a result of entropion of the lid. The inturned eye-lashes are irritating, leading to attempts to remove them. Evidence of recent attempts to remove inturned eye lashes in a trachoma endemic community should also be graded TT. Fig 8. Grade TT & CO. The eyelashes have abraded the cornea, damaging it, leading to corneal opacity and undoubted visual loss. The tragedy is that this loss could have been prevented at the right time by surgical correction of the eye lid deformity, a procedure which can be performed in rural villages, takes about 15 minutes and costs roughly US$ 20.

NEXT: Trachoma prevalence

[MEW] March 2002

Web resource

WHO Prevention of Blindness Program web site

References

Thylefors, B., Dawson, C. R., Jones, B. R., West, S. K. & Taylor, H. R. (1987). A simple system for the assessment of trachoma and its complications. Bulletin of the World Health Organisation 65, 477 – 483.

West, S. K. & Taylor, H. R. (1990). Reliability of photographs for grading trachoma in field studies. British Journal of Ophthalmology 74, 12 – 13.

Wood, T. R. & Dawson, C. R. (1967). Bacteriologic studies of a trachomatous population. American Journal of Ophthalmology 63, Suppl:1298-301.