the condition of being unable to perform as a consequence of physical or mental unfitness

partial or total loss of sight without pathology of the eye; caused by disease of optic nerve or retina or brain

visual impairment without apparent organic pathology

(ophthalmology) faulty refraction of light rays in the eye as in astigmatism or myopia

visual defect in which the shape and size of an ocular image differ in the two eyes

distorted vision in which straight lines appear curved