Low vision aids: A boon

Abstract

Dear Friends, It gives me great pleasure to write the last summer editorial of this Diamond Jubilee year of Indian Journal of Ophthalmology (IJO). We live in an era when technology in every field is growing exponentially. High tech gadgets have given us innumerable ways to improve our quality of life. Here, I write to you about an important but underutilized modality of vision rehabilitation using currently available options. A person with low vision is one who has permanent visual impairment with best corrected visual acuity (BCVA) less than 6/18 to perception of light or central visual field <10° because of an untreatable cause in both eyes, but who uses, or is potentially able to use, vision for the planning and/or execution of a task.[1] As it does not include patients with treatable causes (refractive errors, cataract, posterior capsular opacification, and corneal scars, clinically judged to be treatable by penetrating keratoplasty), it identifies patients who will benefit from low vision services. The leading causes of noncurable visual impairment include retinal disease (age-related macular degeneration, diabetic retinopathy, hereditary dystrophies, myopic degeneration, etc.), glaucoma, other forms of optic atrophy, amblyopia, corneal disease, endophthalmitis, congenital eye anomalies, and higher visual pathway defects. As noted above, most causes are related to the aging process; hence, the numbers with visual impairment will only rise, as the trend is toward increasing life expectancy. This brings us to focus on the need to rehabilitate the ‘rehabilitative services’. According to a study, percentage of patients regaining near vision to N8 were from the age related macular degeneration (ARMD) group, followed by glaucoma, diabetic retinopathy, and myopic degeneration.[2] There are numerous ways to help the patient with low vision remain independent, including making things brighter (by improving illumination, controlling glare, and increasing contrast), bigger, and bolder. Using audio books, e-book reader, and text-to-speech computer software are few available technologies. Various products are available to magnify reading fonts, which includes optical (telescopes and magnifiers) and electronic devices. Optical devices, like telescopes, are used for refining distant tasks like reading blackboard, street signs, bus numbers, recognizing faces. These are available as refractive devices to be fitted on to glasses, and as hand held for monocular magnification, which, however, severely restricts the field of view. Telescopes may be rejected by many patients for cosmetic purposes and problems with spatial judgment as it makes the objects appear nearer. While others may be very happy for the clarity it offers. Magnifiers are another form of optical devices (hand held, bar, dome, fixed or variable focus stand, spectacle binoculars). These may have inbuilt illumination function. Its prime use is for near tasks like reading newspapers or books, writing and signing, viewing mobile texts, checking price tags, and much more. Spectacle magnifiers in particular provide widest field of view. Hand held magnifiers are cumbersome, as they are not hands free like their counterparts, making it difficult for patients with tremors and while doing tasks that require use of hands, like writing, etc. Electronic video magnifiers like closed-circuit TVs (CCTVs) provide distortion free viewing, a large field of view, and a very large range of magnification levels (from 2 to 70 times). Video magnifiers have an advantage over the conventional optical magnifier in being flexible in its larger field of view and greater magnification. However, it may be limited by its display size and power requirements.