Follicles of 0.5 mm size are typically seen in

Ans. B. Trachoma. (Ref: Khurana 3rd Edition page 92.).To diagnose active trachoma (esp Trachomatous inflammation-follicular stage), at least >5 follicles each of >0.5 mm diameter must be present on the upper tarsal conjunctiva.TRACHOMA WHO CLASSIFICATIONTrachoma has always been an important blinding disease under consideration of WHOand thus many attempts have been made to streamline is clinical profile. The latest classification suggested by WHO in 1987 (to replace all the previous ones) is as follows:1. Trachomatous inflammation-follicular (TF). 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 indimeter) must be present on the upper tarsal conjunctiva (PL. 1.2). Further, the deep trasal vessels should be visible through the follicles and papillae.2. Trachomatous inflammation-intense (TI). This stage is diagnosed when pronounced inflammatory thickening of more upper tarsal conjunctiva obscures more than half of the normal deep tarsal vessels (PL. 1.3).3. Trachomatous scarring (TS). This stage is diagnosed by the presence of scarring in the tarsal conjuctiva. These scars are easily visible as white, banks or sheets (fibrosis) in the tarsal conjunctiva (PL. 1.4).4. Trachomatous trichiasis(TT). It is labelled when at least one eyelash rubs the eyeball. Evidence of recent removal of inturned eyelashes should also be graded as trachomatous trichiasis (PL. 1.5)/5. Corneal opacity (CO). This stage is labelled when early visible corneal opacity is present over the pupil. This sign ferers to corneal scarring that is do 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).