True about corneal opacity are all except: March 2008
Ans. C: A strictly localized dense leucoma interferes more than a thin,diffuse nebula covering the papillary area Nebular corneal opacity-If the details of the iris can be seen through the opacity. Macular corneal opacity-Details of the iris cannot be seen but the margins of the iris and the pupil can be marked out Leucomatous corneal opacity-if the opacity is very dense and totally opaque obscuring the view of pupil. Anterior staphyloma has iris tissue incorporated and incarcerated within the scar tissue, as seen in healing of a large sloughed corneal ulcer. Healing of a perforated corneal ulcer, so that iris is adherent to the back of the leucoma may lead to formation of adherent leucoma. A strictly localized dense leucoma interferes more less than a thin, diffuse nebula covering the papillary area because leucoma stops all the light falling on it, whereas nebula refracts it irregularly, allowing many of the rays to fall upon retina where they blur the image formed by the regularly refracted rays. Some opacities may persists despite destruction of Bowman's membrane but many clears considerably paicularly in younger patients.
Anterior staphyloma has iris tissue incorporated within the scar tissue
Healing of a perforated corneal ulcer may lead to formation of adherent leucoma
A strictly localized dense leucoma interferes more than a thin,diffuse nebula covering the papillary area.
Some opacities may persists despite destruction of Bowman's membrane