What is low vision?

Typically someone who has “low vision” is visually impaired and cannot accomplish a visual task(s) with conventional eyeglasses, contact lenses, medication, or through surgical intervention.As a result, a low vision rehabilitation examination is crucial ( with the overarching goal: to help someone who is visually impaired to be able to achieve specific desired visual tasks such as reading, identifying medications, watching television, seeing faces, etc., and as much as possible, to maintain independence.

What is a Low Vision Rehabilitation examination?

A low vision rehabilitative examination falls along the continuum of eye care. It is a comprehensive eye examination directed toward achieving a specific task like reading, writing, television viewing, etc. Unlike a general eye examination, it is not intended to make someone “just see more clearly,” or to purely determine eye health status. The initial low vision rehabilitation examination can be viewed as three separate yet integral parts. These parts, not necessarily in a specific order, are eye health evaluation (including investigating systemic conditions that can influence eye health), determination of refractive status (the need for regular eyeglasses to provide the best focus), and prescription of non refractive sight enhancement (magnification, environmental modifications, etc.).

Eye health evaluation

Even though a patient may be under the care of another eye doctor, the eye health evaluation is necessary to
1) confirm the basis for the visual impairment and to determine whether or not that specific condition is active (requiring immediate or ongoing attention)
2) determine if there are other eye conditions that are influencing, or can influence, the outcome of vision rehabilitation. An example might be a cataract for which it may have been determined that removal is not likely to improve visual acuity; however, its removal could enhance contrast sensitivity and decrease glare, thereby improving the ultimate outcome of the vision rehabilitative process. Additionally, an eye health evaluation can assess visual functions such as eye movements, peripheral vision, contrast sensitivity function, and color vision. It is, however, important to note that each eye health evaluation may be slightly different, depending on a number of factors.

Determination of refractive status

Determination of refractive status is necessary to establish how much of the decrease in vision is actually due to a refractive condition like nearsightedness, farsightedness, astigmatism, or the need for a bifocal. This procedure can be done by an automated instrument or by the doctor using a retinoscope and lenses placed in a special frame to objectively determine the lens which might maximize visual acuity while the patient looks straight ahead or eccentrically (looking off to the side). In either case, the doctor will carefully modify the lenses, based on patient response, to determine the best lenses and eye position for seeing most clearly.

Prescription of non refractive sight enhancement

The third component of a low vision rehabilitation examination is to determine what type of optical, non optical, or electro optical enhancement is necessary to meet the goal (s) of the patient. This is done using the refractive lens (where appropriate) as a platform, then determining magnification based on what can presently be seen vs. what the patient wants to see, by enhancing contrast, by minimizing distortion, or by enhancing field awareness. These components can then be systematically evaluated for the maximum benefit of the optimum device (s) or technique necessary to achieve the stated goal (s) of the patient before being prescribed. Once a treatment plan has determined, vision rehabilitative training can help maximize the successful implementation of what has been recommended.

Motivation is key to the rehabilitation process, as in most cases the treatment plan involves learning new techniques and strategies for optimizing remaining vision.

Paul B. Freeman, OD, FAAO, FCOVD, Diplomate Low Vision
Kathleen F. Freeman, OD, FAAO, Diplomate Low Vision