Corneal sensation is decreased in -

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).