Commonest cause of posterior staphyloma is:
**Core Concept**
Posterior staphyloma is a condition characterized by a protrusion of the sclera and choroid into the vitreous space, resulting from chronic inflammation, trauma, or other causes of scleral thinning. The posterior segment of the eye is particularly susceptible to damage due to its delicate anatomy and the presence of the retina and choroid.
**Why the Correct Answer is Right**
The correct answer is **A. High Myopia**. High myopia is associated with thinning of the sclera, which can lead to posterior staphyloma. This is because the increased axial length of the eye in high myopia puts additional stress on the posterior segment, causing the sclera to stretch and weaken. The resulting thinning of the sclera can lead to a posterior staphyloma, which can be a complication of high myopia.
**Why Each Wrong Option is Incorrect**
* **Option B:** **Glaucoma** is not directly associated with posterior staphyloma. While glaucoma can cause damage to the optic nerve and retina, it is not a common cause of scleral thinning or posterior staphyloma.
* **Option C:** **Diabetic Retinopathy** can cause a range of complications, including vitreous hemorrhage and retinal detachment, but it is not typically associated with posterior staphyloma.
**Clinical Pearl / High-Yield Fact**
High myopia is a significant risk factor for posterior staphyloma, and patients with high myopia should be monitored closely for signs of scleral thinning or other complications.
**Correct Answer: A. High Myopia**