摘要
In the United States,a patient is‘legally blind’if the best corrected vision in‘both eyes’is 20/200(0.1)or less or the peripheral visual field is less than 20°from the central fixation(1).It could be from advanced glaucoma,opaque cornea,amblyopia,cataract,macular degeneration,severe retinitis pigmentosa,retinal detachment,optic neuritis,conerod dystrophies,and/or chorio-retinal degenerations,etc.Legally blind are considered‘visually handicapped’.While some of these patients are‘functional’in their familiar surroundings,but most lose their‘independence’even in daily life activities.That has detrimental effect on their psychological wellbeing.They feel helpless and burden on their families and the society.
