Grading of trachoma

McCallan's classification
McCallan in 1908, divided the clinical course of the
trachoma into following four stages:

• Stage I (Incipient trachoma or stage of infiltration). It is characterized by hyperaemia of palpebral conjunctiva and immature follicles.
• Stage II (Established trachoma or stage of florid infiltration). It is characterized by appearance of mature   follicles, papillae and progressive corneal pannus.
• Stage III (Cicatrising trachoma or stage of scarring). It includes obvious scarring of palpebral conjunctiva.
• Stage IV (Healed trachoma or stage of sequelae). The disease is quite and cured but sequelae due to cicatrisation give rise to symptoms.

WHO classification
Trachoma has always been an important blinding
disease under consideration of WHO and thus many
attempts have been made to streamline its clinical
profile. The latest classification suggested by WHO
in 1987 (to replace all the previous ones) is as follows
(FISTO):
1. TF: Trachomatous inflammation-follicular. It is
the stage of active trachoma with predominantly
follicular inflammation. To diagnose this stage at
least five or more follicles (each 0.5 mm or more
in diameter) must be present on the upper tarsal
conjunctiva (Fig. 1). Further, the deep tarsal
vessels should be visible through the follicles
and papillae.
2. TI : Trachomatous inflammation intense. This
stage is diagnosed when pronounced
inflammatory thickening of the upper tarsal
conjunctiva obscures more than half of the normal
deep tarsal vessels (Fig. 2).

(Fig. 2).

3. TS: Trachomatous scarring. This stage is
diagnosed by the presence of scarring in the
tarsal conjunctiva. These scars are easily visible
as white, bands or sheets (fibrosis) in the tarsal
conjunctiva (Fig. 3).

(Fig. 3)

4. TT: Trachomatous trichiasis. TT is labelled when
at least one eyelash rubs the eyeball. Evidence of
recent removal of inturned eyelashes should also
be graded as trachomatous trichiasis (Fig. 4).

Fig. 4.. Trachomatous trichiasis (TT).

5. CO: Corneal opacity. This stage is labelled when
easily visible corneal opacity is present over the
pupil. This sign refers to corneal scarring that is
so dense that at least part of pupil margin is
blurred when seen through the opacity. The
definition is intended to detect corneal opacities
that cause significant visual impairment (less than
6/18).

 Sequelae of trachoma
1. Sequelae in the lids may be trichiasis (Fig. 4),
entropion, tylosis (thickening of lid margin), ptosis,
madarosis and ankyloblepharon.
2. Conjunctival sequelae include concretions,
pseudocyst, xerosis and symblepharon.
3. Corneal sequelae may be corneal opacity, ectasia,
corneal xerosis and total corneal pannus (blinding
sequelae).
4. Other sequelae may be chronic dacryocystitis,
and chronic dacryoadenitis.