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
Sudden painful diminition of vision in
Anterior Uveitis is due to 
Select and explain. 
A. Blood in Anterior chamber, B. Cells in Anterior chamber, C. Edema of Cornea, D. Ciliary muscle spasm
D: Ciliary muscle spasm
Answer: D: Ciliary muscle spasm 
Explanation: Due to ciliary muscle spasm, convexity of lens increases leading to blurred vision and pain due to spasm.