This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Inflammations of the Cornea, Subject name: Ophthalmology
Corneal sensation is decreased in - 
Select and explain. 
A. Viral infection, B. Fungal infection, C. TB, D. None
A: Viral infection
Answer: A: Viral infection 
Explanation: Ans. is 'a' i.e.. Viral infection o There is marked diminution of corneal sensations in herpetic dendritic ulcer (Viral infection).Decreased corneal sensationso Alterations in corneal sensitivity occur normally with variations in physiological and environmental factors. Corneal sensitivity decreases steadily with age. In addition, the corneas of brown eyed individuals are generally less sensitive than those in blue -eyed individuals. Important causes of reduced corneal sensitivity' are : -IatroginicTopical drugs : - Cocaine, proparacaine, NSAIDs (Diclofenac, ketorolac), Timolal, Betaxoiol.Surgery : - Corneal and cataract operations.Contact lens useCongenital & acquired diseasesCorneal dystrophiesScieritis, acute angle closure glaucoma.Infections : - Herpes simplex keratitis Idendritic ulcer). Leprosy, Herpes zoster, Syphilic (luetic neuropathy).Cerebello-pontile angle tumor : - Acoustic neuroma.Sensory neuropathies : - Diabetes, Leprosy, Amyloidosis, Vitamin 'A' deficiency.Toxins : - Carbon disulfide and Hydrogen sulfide.Syndromes : - Goidenhaf s syndrome, VACTERAL anomalies, Abetalipoproteinemia, Refsum's syndrome, Parry-Romberg syndrome and nephropathic cystinosis, congenital insensitivity to pain, Familial dysautonomia (Riley-Day syndrome).