This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Anatomy, Development and clinical examination, Subject name: Ophthalmology
Following are the causes of sudden loss of vision except 
Select and explain. 
A. Angle closure glaucoma, B. Endophthalmitis, C. Central serous retinopathy, D. Corneal ulceration
D: Corneal ulceration
Answer: D: Corneal ulceration 
Explanation: Sudden painless loss of vision  Central retinal aery occlusion  Massive vitreous hemorrhage  Retinal detachment involving macular area  Ischaemic central retinal vein occlusion The sudden painless onset of defective vision  Central serous retinopathy  Optic neuritis  Methyl alcohol amblyopia  Non-ischemic central retinal vein occlusion Sudden painful loss of vision  Acute congestive glaucoma  Acute iridocyclitis  Chemical injuries to the eyeball  Mechanical injuries to the eyeball Corneal ulceration causes Gradual painful defective vision Reference : AK KHURANA COMPREHENSIVE OPHTHALMOLOGY, Edi4, Page-462