Head mounted video magnification devices for low vision rehabilitation: a comparison with existing technology

Patients with low vision typically have reduced visual acuity and a significant loss of contrast sensitivity, often in combination with visual field loss. These impairments cause a number of disabilities including difficulty with reading, writing, recognising faces, watching television, orientation and mobility, and completing activities of daily living. In a recent large scale survey of providers of low vision services, Elliott et al  1found that for elderly patients with low vision, the primary objectives identified at low vision assessment were to obtain help with reading and with vision oriented performance of daily living activities. Secondary objectives commonly include obtaining help with watching television, mobility and independent travel, and hobbies. In many cases, these objectives can be met by the prescription and use of conventional low vision aids (LVAs)—that is, optical devices providing magnification in order to compensate for reduced visual acuity, while contrast is maximised with local task lighting. LVAs are, unfortunately, highly task specific, and the patient may need several different aids to deal with a variety of identified requirements. Recently, however, alternative devices have been introduced which offer a number of distinct advantages over conventional LVAs in low vision rehabilitation. The purpose of this review is to describe these devices and to discuss both their current and future potential in comparison with existing technology. Contrary to early work suggesting that LVAs are often limited in their effectiveness,2 3 more recent studies indicate that low vision rehabilitation and the prescription of LVAs can offer considerable benefit to the visually impaired, with at least one device being used by between 80% and 91% of patients provided with an LVA.4-8 It is recognised, however, that some patients do not continue to use LVAs following their dispensing. While some users discontinue with an LVA because of a change …

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