This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Miscellaneous, Subject name: Ophthalmology
A 35-year-old Insulin Dependent Diabetes Mellitus (IDDM) patient on Insulin for the past 10 years com- plains of gradually progressive painless loss of vision. Most likely he has 
Select and explain. 
A. Cataract, B. Vitreous haemorrhage, C. Total rhegmatogenous retinal detachment, D. Tractional retinal detachment not involving the macula
A: Cataract
Answer: A: Cataract 
Explanation: (A) Cataract> Patients present with chronic, slowly progressive and generally painless visual loss. The reduction in vision is usually bilateral, though frequently asymmetrical, and occurs over weeks to years.> More common conditions that cause gradual loss of vision can be divided into two groups based on the reversibility of the visual loss.> Cataracts, refractive error, corneal blindness and early diabetic macular edema are generally reversible.> Optic atrophy, glaucoma, retinal degeneration and age-related macular degeneration usually cause permanent loss of vision.> Senile cataract occurs early and more frequently in diabetics.