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Diagnosing trachoma

Trachoma has a simple and clear definition for use by trained health personnel. Watch Allen Foster explain the WHO trachoma grading system.
By the end of this presentation, you should be able to: - Understand the importance of trachoma grading in public health. - Describe the features of the simplified WHO trachoma grading scheme. - Apply the grading scheme to assess the endemicity of trachoma in a community. Public or community health aims to prevent morbidity from diseases which affect populations. Trachoma is transmitted within families and communities. Over the course of many years, it can result in pain and loss of vision in affected individuals. An effective approach to control of diseases requires that we define and understand the disease at a population level. Grading for trachoma defines each of the stages of the disease process. The simplified trachoma grading scheme consists of five grades [signs].
Two of the grades document active disease called TF and TI and three grades document cicatricial disease that results from scarring, TS, TT, and CO. The examination for signs of trachoma should be performed with a good light and 2.5x magnification. First, the external eye, the eyelids, and the cornea are examined, followed by eversion of the upper eyelid and examination of the tarsal conjunctiva. Here is a normal eyelid and cornea. The eyelashes all turn out and the cornea is clear.
Here, we see trichiasis, or in-turned eyelashes due to trachoma. This is called trachomatous trichiasis, or TT. The definition of TT is when at least one eyelash from the upper eyelid is touching the eyeball or there is evidence of recent removal of in-turned eyelashes from the upper eyelid. If there is evidence of previous trichiasis surgery, this should not be graded as TT unless there is recurrence of in-turned lashes touching the eyeball. Please note that trachoma is not the only disease that can cause in-turned eyelashes. For the trichiasis to be attributed to trachoma, there must also be evidence of trachoma scarring, TS, which we will describe later.
The next stage shown here shows an opacity of the cornea due to trachoma, called CO. The definition is easily visible, corneal opacity over the pupil. The opacity is so dense that at least part of the pupil, the margin, is blurred when viewed through the opacity. Therefore, the opacity is sufficiently dense and sufficiently central to cause a decrease in visual acuity. CO is usually associated with trichiasis due to trachoma.
Having examined the eye externally with a light and magnification, one can now evert the upper eyelid to examine the tarsal conjunctiva on the inside of the upper eyelid for any signs of trachoma. Here, we see a normal, everted upper eyelid. Only the central area is examined for signs of trachoma, as shown on the slide. Any sign must be clearly seen to be considered present. In a trachoma patient, TF is a sign of moderately active disease. TF stands for trachomatous inflammation–follicular. The definition is five or more follicles in the central part of the upper tarsal conjunctiva.
The follicles are round swellings that are pale compared to the rest of the conjunctiva They must be at least 0.5 millimetres in diameter to be counted. If there are less than five follicles, then this is not TF and should not be graded as TF. Active disease is also seen as TI, which stands for trachomatous inflammation–intense. There is pronounced inflammatory swelling of the tarsal conjunctiva so that more than half of the deep, normal tarsal vessels are obscured by the inflammatory swelling. Often, there are follicles present, but they may be obscured by the inflammation. TF should also be diagnosed as well as TI if five or more follicles are seen. Repeated episodes of inflammation results in TS, which stands for trachomatous scarring.
The definition is easily visible scarring seen as white lines, sheets, or bands in the tarsal conjunctiva. Sometimes, the scarring obscures the deep tarsal blood vessels. However, this should not be graded as TI, only as TS. [TI is only diagnosed when it is pronounced inflammatory thickening that obscures the normal deep tarsal blood vessels.]
So to summarise: -The grades of active disease are TF and TI. -TF is trachomatous inflammation–follicular and is evidence of moderately active disease. -TI is trachoma inflammation–intense, and is evidence of severe, active disease. -TS is the sign of scarring of the conjunctiva resulting from past trachoma inflammation. -If the TS is severe, then it may result in trichiasis, TT. -If the trichiasis [TT] is not treated, it can cause corneal opacity (CO) and loss of vision. -In the same eye, a mixture of signs can be present. For example, TF with TI. Or TS with TT and CO.
-Active disease, TF and TI, are often seen in children in trachoma endemic regions, whereas cicatricial disease, TS, TT, and CO, are found more commonly in adults who have had repeated episodes of active disease over many years. -Active disease requires antibiotic treatment and trichiasis [TT] - requires surgery to prevent loss of vision.
In public health, there are three essential questions: What is the condition? Who in the population has it? What effective intervention do we have?

Using this information, a health programme can be planned and implemented.

In order to identify what a condition is, we need a clear and agreed definition that is simple enough for trained health personnel to use.

Grading trachoma

Throughout the long history of trachoma, clinicians have tried to describe and define the disease as seen in individuals. Early attempts to define the disease stages were mainly based on observations made on the clinical severity of disease – suspicion, mild, moderate, severe.

However, this subjective definition was problematic when used to describe trachoma in a population and to establish health programmes. In 1913, the MacCallan classification of trachoma with 4 ‘simple’ disease stages was published. It was widely accepted and used as a standard for over 60 years. It was also adopted and further adapted by the first WHO expert committee in 1952.

In 1966, the fourth WHO expert committee introduced a new trachoma grading scheme. This was based on up to 22 clinical signs and, although useful for researchers, it was too complicated to be used in health programmes. Further refinements and modifications focused on identifying five fundamental signs of trachoma and in 1987, the WHO published a simplified grading system that is used to assess communities for trachoma and monitor the impact of trachoma elimination activities.

This simplified grading scheme was used by teams during the Global Trachoma Mapping Project, and is now used by teams undertaking surveys supported by Tropical Data. It is also used in many countries by a wide range of trained health personnel at the hospital and community level.

WHO simplified trachoma grading system

  • TF = Trachomatous inflammation—follicular: the presence of five or more follicles, each at least 0.5mm in diameter, in the central part of the upper tarsal conjunctiva.
  • TI = Trachomatous inflammation—intense: pronounced inflammatory thickening of the upper tarsal conjunctiva that obscures more than half of the normal deep tarsal vessels.
  • TS = Trachomatous scarring: scarring of the tarsal conjunctiva (fibrosis).
  • TT = Trachomatous trichiasis: at least one eyelash from the upper eyelid rubbing on the eyeball or evidence of recent removal of in-turned eyelashes from the upper eyelid.
  • CO = Corneal opacity: corneal scarring so dense that at least part of the pupil margin is blurred when viewed through the opacity.

As you watch this video, consider why it is that the TF and TT grades are used at a programme level and not all five signs?

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Eliminating Trachoma

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