blur vision chronic blur vision glaucoma cataract anatomy physiology neuro-Ophthalmology visual pathway and visual field defect optic disc swelling ptosis abnormal pupil Ophthalmic surgery ocular trauma eye emergency ocular manifestation in systemic disease 1 ocular manifestation in systemic disease 2 eye examination strabismus ocular pharmacology public health ophthalmology visual rehabilitation eye in occupational medicine preventable eye disease red eye