November 8, 2010
Treating Low Vision
By Eleanor E. Faye, MD, FACS
For The Record
Vol. 22 No. 20 P. 24
Vision loss threatens older adults’ independence and quality of life, but practitioners can be proactive in helping elders cope.
The vision-loss epidemic occurring in the United States affects virtually every aspect of older adults’ lives, from medical care to the books they read, the restaurants they visit, and their ability to navigate the Internet. Approximately 61 million Americans are at risk for vision loss due to factors such as diabetes and macular degeneration.
Diabetes itself affects about 24 million Americans. Left uncontrolled, it can lead to diabetic retinopathy that can result in vision loss and blindness. In fact, diabetes is the leading cause of new cases of blindness in adults aged 20 to 74. Age-related macular degeneration (AMD) affects about 13 million Americans and is the leading cause of vision impairment among those aged 65 and older. Other age-related causes of low vision include complicated cataracts, corneal dystrophy, glaucoma, optic atrophy, stroke, degenerative myopia, and retinitis pigmentosa.
Despite this evidence, little attention has been paid to the impact low vision will exert on healthcare professionals and medical facilities. The current need for more ophthalmologists and optometrists, particularly those trained in low vision, will be exacerbated. Hospitals in the United States need to be equipped with vision rehabilitation clinics while integrating the concept of low vision into their system of care, as is being done in most facilities in England, Scandinavia, and Germany.
Nurses, physical therapists, and other healthcare professionals must be trained to recognize the signs and symptoms of older adults’ vision loss. For instance, vision impairment is the cause of 18% of hip fractures among older adults; proactive treatment of elders’ vision problems could likely prevent some falls and accidents.
Defining the Problem
Low vision is defined as vision that cannot be corrected by medication, surgery, standard glasses, or contact lenses. It is important to note that while the number of visually impaired older adults is increasing, various devices, therapies, and a wide range of technologies enable them to live productive and independent lives.
Medical intervention to treat low vision should occur as soon as a patient exhibits symptoms or has difficulty performing routine tasks. A treatment plan should consider the level of function, realistic goals for intervention, and devices that could be helpful. Patients must understand that impaired vision is usually progressive. The sooner patients adapt to the everyday use of low-vision devices, the sooner they can adjust to the new techniques required to use their vision. Evaluating an elder’s vision impairment should never be delayed unless he or she is actively receiving medical or surgical treatment.
In every area of ophthalmology, patients with low vision represent unique challenges in care. Whether impaired vision is temporary or permanent, low-vision patients may have a variety of symptoms, including cloudy vision, constricted fields of vision, or large scotomas. They may complain of functional issues such as glare sensitivity, abnormal color perception, or difficulty with diminished contrast. Some patients have diplopia (double vision) and frequently complain of confusion due to overlapping but dissimilar images from each eye.
Low vision may mean a wide range of visual impairment. Some older adults in the earlier stages of an eye disorder may retain near-normal vision while others may experience moderate to severe loss. It’s important to understand that all low-vision patients have some degree of useful vision even when the vision loss is significant. Whether a patient’s reduced vision is temporary or permanent, it results from an eye disorder and therefore requires treatment by an ophthalmologist and/or optometrist.
If the result of proper medical and surgical attention is a diminished range of functional vision, then the patient needs rehabilitation. Patients should not be considered blind unless their level of functioning vision is near blind. While performance varies with each patient, the most important aspect of regaining functional vision is the rehabilitation process, which is the responsibility of healthcare professionals.
It is important to note that older adults with low vision can improve their visual performance by using various optical and nonoptical devices. There are a number of steps involved in a comprehensive management plan.
Practitioners should take a history of the symptoms’ onset and determine the effect of eye disorders on elders’ daily lives and activities. It’s important to document the specific details of the onset, treatment provided, and current medications. The patients’ response indicate their understanding of their conditions. It is important to determine patients’ attitudes toward recovery to ensure they have a realistic understanding of what can be achieved through low-vision rehabilitation.
There are several types of low-vision aids: convex lens aids such as glasses; hand-held and stand-mounted magnifiers; telescopic systems, either spectacle mounted or hand held; nonoptical (adaptive) devices such as large print, lighting, reading stands, marking devices, talking clocks, timers, and scales; tints and filters, including antireflective lenses; and electronic reading systems such as CCTV reading machines, optical print scanners, computers with large-print programs, and computers equipped with voice commands to access programs.
More than 90% of low-vision patients are prescribed glasses and hand and stand magnifiers. The various types of mounting have inherent advantages and disadvantages. The stronger the lens, the shorter the reading distance, which tends to obstruct light. The advantage of glasses is that a patient’s hands remain free to hold the reading material. There are glasses, hand-held magnifiers, and stand magnifiers all with various advantages depending on a patient’s needs.
Patients with binocular potential may use glasses in the 4- to 14-diopter range with a base-in prism to aid convergence. Above 14 diopters, a monocular sphere must be used for the better eye. To enlarge print, older patients often use hand-held magnifiers in conjunction with reading glasses. The advantage of these magnifiers is a larger working space between the eye and lens.
However, hand-held magnifiers may pose problems for patients with trembling hands or stiff joints. Hand magnifiers are available from 4 to 68 diopters. Stand magnifiers are convex lenses mounted on bases whose heights relate to the power of the lenses. In some cases, the lens mounting may block light, so a lens with a battery-powered light source may be the best choice. However, patients with corneal and lens pathology may be unable to tolerate the glare generated by an illuminated device.
Telescopic systems are the only devices that can be focused from far or near. For low vision, the simplest device is the hand-held monocular for short-term viewing, particularly of signs. For patients with vocational interests, Galilean or Keplerian telescopes (internal prism systems) in a spectacle frame are practical. There is even a monocular auto-focus telescope. The practical limit of power for hand-held units is 2X to 8X. Spectacle telescopes are difficult to use above 6X. All telescopes share the disadvantage of a small field diameter and shallow depth of field.
Low-vision patients often complain of poor contrast and glare that hamper independent travel. A basic approach is to consider the effect of short-wave light on cloudy media and to remember that contrast is also affected by time of day, weather, and textures and colors in the surroundings. As a rule, prescribing light- or medium-gray lenses reduces light intensity. To improve contrast and reduce the effect of short-wave light rays, amber or yellow lenses are suggested. An additional antireflective coating should be considered for patients who are mildly glare sensitive.
Electronic devices are the only visual aids that encourage a natural reading posture. A CCTV reading machine consists of a high-resolution television monitor and a built-in camera with a zoom lens, a lamp, and an X-Y reading platform. The patient sits in front of the screen, moving the print with a scanning device. Magnification from 1.5X to 45X is possible with adjustable font sizes and the background can be reversed from white to dark gray.
Some units offer a choice of print colors. Some also include a hand-held camera, the Mouse-cam, a portable device that can be carried around and plugged into any TV; computers with voice output and text scrolling; and optical scanners that can read text aloud. Standard personal computers can be easily modified for large-print programs. A computer designed to present a variety of programs is the most practical low-vision aid to provide a full range of font types, sizes, and colors.
Knowing treatment options is important but the type and strength of a visual aid is influenced by the type and extent of the vision deficit. Treatment plans should take into account the effect of the eye disorder on both visual acuity and visual field.
Healthcare professionals need to be aware of the need for elders with low vision to access devices, therapy, and counseling, as well as some of the key organizations that help rehabilitate elders with vision loss. These organizations include Lighthouse International, Vision AWARE, VISIONS Services for the Blind and Visually Impaired, and AMD Alliance International.
— Eleanor E. Faye, MD, FACS, has been affiliated with Lighthouse International since 1956, serving as medical director since 2006. She is recognized as an expert in low vision.