This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Ophthalmology
Intractable secondary glaucoma is seen in – 
Select and explain. 
A. Diffuse iris melanoma, B. Nodular iris melanoma, C. Melanocytic deposits in anterior part of iris, D. Melanocyte proliferation in posterior uveal tissue
A: Diffuse iris melanoma
Answer: A: Diffuse iris melanoma 
Explanation: Iris melanomas may be of two types :-

Circumscribed/ Nodular: - It is the most common type which presents as a pigmented spot on the iris. Glaucoma is less common and usually treatable.
Diffuse iris melanoma: - Present as a unilateral dark iris (hyperchromic hetrochromia). The tumor has diffusely infiltration pattern of growth and invades the intertrabecular spaces, and plugs the drainage mechanism. This results in intractable secondary glaucoma.