Low Vision Evaluation
A low vision rehabilitative evaluation falls along the continuum of eye care.
It is a comprehensive eye examination (by an optometrist or ophthalmologist)
that is directed toward achieving a specific task like reading, television
viewing, etc. Unlike a general eye examination, it is not designed to make an
individual “just see more clearly,” or to purely determine eye health status.
Typically the patient is visually impaired and cannot accomplish a task (s) with
conventional eyeglasses, contact lenses, medication, or through surgical
intervention. As a result, this examination necessarily goes beyond a
conventional eye examination; the overarching goal is to help an individual
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
(for regular eyeglasses), and prescription of non refractive sight enhancement
(magnification, environmental modifications, etc).
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), and 2) to 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, the eye health evaluation can also 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 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 is typically done using a special frame in which to place lenses, and then using a retinoscope, an instrument that uses a special light to objectively determine the lens which might maximize visual acuity while the patient looks straight ahead or eccentrically (and being observed by the doctor), and then modifying the lenses based on patient response to get the best eye position for seeing most clearly.
The third component is to determine what type of optical, non optical, or electro optical enhancement is necessary to meet the goal (s) of the patient. This must be 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, enhancing contrast, minimizing distortion, and enhancing field awareness. These components can then be systematically evaluated for the maximum benefit of the best device (s) or technique necessary to achieve the stated goal (s) of the patient before being prescribed. Once the eye doctor has determined a treatment plan, vision rehabilitative training can help maximize the successful implementation of what has been recommended.
Paul B. Freeman, OD, FAAO,
FCOVD, Diplomate Low Vision
Kathleen F. Freeman, OD, FAAO, Diplomate Low Vision
As published in: Insights Into Low Vision (cclvi.org)