This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Sclera, Subject name: Ophthalmology
Commonest cause of posterior staphyloma is: 
Select and explain. 
A. Glaucoma, B. Retinal detachment, C. iridocyclitis, D. High myopia
D: High myopia
Answer: D: High myopia 
Explanation: Ans. d (High myopia). (Ref: Ophthalmology by AK Khurana 2nd ed. 151)POSTERIOR STAPHYLOMA# It refers to bulge of weak sclera lined by the choroid behind the equator.# Common causes are:- Pathological myopia,- Posterior scleritis and- Perforating injuries.# Diagnosed best on ophthalmoscopy# It is seen as an excavated area with retinal vessels dipping in it.Excessively progressive degenerative myopia leads to sclerectasia circumscribed behind or posterior staphyloma. This is a sharply demarcated bulging of the entire posterior pole, which is associated with massive chorioretinal atrophy.