Vision Impairment Assessment and Assistive Technologies

Low vision refers to a condition of irreversible vision loss that is not correctable by conventional spectacles, contact lenses, surgery, or medicine. The ocular disease leads to a visual impairment that results in a functional limitation of the eye or visual system. This may include a reduction in detail vision (visual acuity), side vision (peripheral visual field), distorted or double vision, or a combination thereof. The consequence of this impairment may lead to a visual disability that prevents the person from performing specific tasks such as reading, driving, cooking, or watching television. Depending on the severity of the disability, the result may be a visual handicap that may lead to a loss of personal and/or socioeconomic independence. Much work has been done in an attempt to classify the interaction of visual impairment, disability, and handicap in an effort to characterize the impact of low-vision rehabilitation (LVR) as a treatment modality [1, 2]. LVR embraces an inter-disciplinary approach to ameliorating the handicap and maximizing quality of life for the partially sighted [3]. Eligibility for services for the elderly for LVR often depends on categorizing the level of visual impairment, specifically whether a person is “legally blind” or “visually impaired.” The Social Security Administration defines “legal blindness” as best corrected visual acuity in the better seeing eye that is 20/200 or worse. Alternatively, it may be characterized by a visual field less than 20◦ in diameter in the eye with the larger remaining field [4]. Visual impairment describes vision that does not meet the criteria for legal blindness but may still result in a visual disability or handicap. These are codified in the “International Classification of Diseases, 9th Revision, Clinical Modification” (ICD-9-CM), Sixth Edition, based on the combination of vision (visual acuity and/or visual field) in each eye. The ICD-9 codes are essential for documentation and billing for rehabilitative services (Table 6.1).