The present paper reviews studies on the prevalence of visual impairment (VI) in adults with intellectual disability (ID). Every publication describes an alarming prevalence of blindness and VI. Cataract and keratoconus were common. Many cases of poor distance vision were treatable by ordinary spherical or astigmatic glasses, but few people had had such prescriptions. Elderly residents in community and institutional care often did not receive glasses for near vision. Professional assessments disclosed higher prevalences of VI than questionnaires mailed to the care personnel. The prevalence of VI increased dramatically with the severity of ID and with age. Regular professional assessment of eye disorders, visual acuity and refraction are warranted in residents in both hospital and community care.