NeuroOptometric Evaluation and Rehabilitation
Low Vision Evaluation and Treatment
Padula Institute News Releases
Vision Resources:
- Learn to See Program
- for Patients
- for Educators
- for Clinicians
- for the Elderly
- for learning disabilities
- large print website
- other language versions available
How vision relates to Learning Disabilities
|
Low Vision Related to Function and Service Delivery for the Elderly Aging and Human Visual Function, pages 315-322 1982 Alan R. Lis Color s, Inc., 150 Fifth Avenue, New York, NY 10011 |
||
 |
W. V. PADULA |
|
| Demographic studies consistently show that age is the best predictor of blindness and visual impairment [Hatfield, 1973; Trovern-Trend, 1968]. Aging contributes to visual impairment through both normal deterioration of eye tissues and increased incidence of eye pathology. According to the National Center for Health Statistics (NCHS) Health Interview Survey of 1977, [Kirchner and Peterson, 1979], an estimated 1.4 million individuals in the United States have severe visual impairments (inability to read normal newspaper-size print with conventional glasses). Estimated as legally blind (20/200 visual acuity or less and/or less than a 20* visual field) are 500,000 individuals. The U.S. Bureau of the Census projects that by the year 2000, the population of the United States will increase by 20% to over 260 million people. The number of people aged 65 and over is expected to increase disproportionately, rising from 23 million in 1977 to 32 million by the year 2000 [Lowman and Kirchner, 1979]. Kirchner and Peterson [1979] have reported that the estimated prevalence of legal blindness for those over 65 is approximately 230,000 and that, according to the 1977 NCHS survey, there are 990,000 elderly individuals with severe visual impairment. These estimates may be undercounts (see Greenberg and Branch, this volume). The projection for the year 2000 is that there will be between 272,000 and 376,000 elderly individuals who are legally blind and 1,760,000 elderly individuals with severe visual impairment. These statistics indicate that while the overall legally blind population will increase by 14%, the population of persons over 65 with severe visual impairment is expected to approximately double. This increase in visual impairment is projected from a major increase expected in the population over 65. According to 1977 Bureau of Census projections, there will be a 20% increase of persons between 65 and 74, a 56% increase of persons between 75 and 84, and an 84% increase of persons aged 85 and over. It was assumed, in Lowman and Kirchner's [ 1979] projections, that the rates of visual impairments within those age categories would remain the same, as would the underlying causes. For example, the most common cause of blindness in the United States at present is glaucoma, which in 1962 accounted for 13.5% of all blindness, occurring predominantly in individuals over 40 years of age. Therefore, with the statistical projections for the year 2000, the over-65 age group is expected to increase considerably and the incidence of blindness or sight impairment caused by glaucoma may be assumed to rise proportionately. Also, the rates of sight impairment in older groups may increase, so these projections may be conservative. It is speculated that because of continued advances in medical and surgical technology and treatment regimens, sight loss will less often be total and the relative proportion of partial loss will be greater. Sight impairment can greatly interfere with the performance of aging individuals. For the purposes of this paper, sight impairment is loss of acuity and/ or restriction of field and may be analyzed by taking acuity and/or field measurements. However, these measurements alone do not indicate the severity of interference with performance and function. Visual impairment must be characterized by the degree to which behavior is affected. In other words, visual impairment is defined as interference with the processing of information received through the sense of sight that in turn impedes performance and function. Recent psychophysical research indicates that measurement of visual acuity gives only a very limited indication of overall visual functioning. For example, acuity, which refers to the ability to resolve minute objects or separations, is a function of the visual system's sensitivity to high spatial frequencies but not low and intermediate frequencies. Thus, measuring an individual's visual acuity can give an indication of his ability to distinguish small print but would not necessarily predict his ability to recognize faces and distinguish forms from background, tasks involving low and intermediate spatial frequency information-processing. Aging appears to produce a selective loss in sensitivity to lower spatial frequencies (Sekuler, this volume). For the aging person, the effects on life style of a visual impairment can be quite profound. Since vision is the dominant mode of processing information about the environment and leading motor movement [Gesell, 1949], impairment can cause a variety of problems such as inaccurate visual-motor coordination, reduced depth judgment, wide stance and gait, head tilt and/or turn, moving the head close to working material, and eccentric viewing. The frustration of having visual impairment may also lead to depression, irritability, disorientation, dizziness, lack of continuity of thought, memory loss, etc. Ultimately, these problems can result in a loss of independence. It must be realized that these behaviors are symptoms and that the cause lies in the inability to visually adapt to the impaired and relate visual information to deeper psychophysical processes. Sight impairments traditionally have been divided into four classes: (1) central acuity reduction, (2) central field loss, (3) peripheral field loss, and (4) combinations of these three. It has been a common clinical observation that not all people are affected the same by acuity and/or field losses [Genensky, 1976], and that performance and functional abilities can vary considerably. Elderly individuals with impaired sight may or may not experience interference with function and performance, depending on their habitual mode of visual operation. An individual who depends heavily on central acuity (e.g., a jeweler) may be expected to be more profoundly affected by a loss of foveal vision than by loss of peripheral function, whereas another person, perhaps an actor, might be more seriously affected by peripheral loss. The functional impact of losses in different parts of the visual field may be considered in terms of the concept of two fundamental modes of processing of visual information: focal and ambient [Leibowitz and Post, 1982; Trevarthen, 1973]. Focal vision subserves visual attention (conscious), object recognition, and identification. The ambient mode is a general awareness state of vision (conscious or unconscious). It is spatially oriented and involved with locomotion and posture. Focal vision primarily involves the central field, whereas the ambient system involves the entire visual field. Typically, the individual is well aware of the operation of focal functions but can process ambient information with little conscious awareness. The focal and ambient functions are mediated by eye and brain. Although the two systems can be distinguished on the basis of retinal location, effective visual functioning is dependent on the sharing of information between the two systems through higher-order perceptual processes - For example, stereopsis (a focal process) involves the fusion of the two visual fields, using such ' skills as differentiating figure from ground and maintaining strong object or perceptual constancies. The perception of depth involves the spatial projection from disparate retinal points (ambient function) in relation to central function. A full appreciation of visual space is made possible by the integration of information from these two systems. The relationship between vision and the individual's overall situation is complex. Arteriosclerosis and deterioration of neurons and muscle fibers gradually erode psychological, emotional, physical, and psychological functions; however, my own clinical experience has been that the effects of visual impairment are especially profound. Visual impairment has many ramifications. Loss of independence may result from interference with simple tasks such as reading labels on medicine bottles and walking to the store. Extreme frustration and failure can lead to social isolation and the development of a myriad of psychological defenses and neuroses [Gilbert, 1968]. The impaired person's loss of independence places burdens on his family's time and finances. An economical burden is also placed on community, state, and federal programs to deliver alternative support programs, varying from driving services to living care programs, to the elderly visually impaired individual. Historically, compensatory care services for the elderly visually impaired have been oriented toward compensating for their loss of independence. This approach is symptom-oriented and does not attempt to deal with the cause of the loss of independence by rehabilitating the person's functional abilities. Unfortunately, the majority of visually impaired individuals in the United States are served only through such alternative support means and are never referred for low-vision services, which are oriented around the individual's impairment and his/her rehabilitation. Kirchner and Phillips [1980] -estimated that in 1976 only 35,000 of the approximately 1,700,000 visually impaired people in this country received low-vision services. The elderly visually impaired are no exception to these general statistics. Return to top |
||
|
|
||
|
The Low-Vision Service Approach: | |
| Low-vision services are multidisciplinary and utilize special visual examination techniques and optical aids to improve the individual's vision, thereby rehabilitating functional abilities and skills. The primary objective of low-vision services is to increase independence. The low-vision examination is a specialized form of vision analysis, differing from routine eye examinations in that special methods of testing must be used to determine refractive status, acuities (near and far), visual field, and eye health of individuals with substantial impairment. On the basis of this analysis, lens prescriptions and special optical aids of various types are prescribed to improve acuity levels. Unlike the routine eye examination, the low-vision service ideally should begin with a functional assessment of the individual in his normal environment. Functional assessment is important because it allows the low-vision doctor to better evaluate the individual's abilities and needs: the extent to which the sight loss may be interfering with visual functioning, the areas with which testing should begin, and, in general, the type(s) of optical aids that may help the person meet his or her needs. Since the optometrist or ophthalmologist performing the low-vision examination is usually unable to go to the visually impaired individual's home or place of employment, other professionals such as social workers, orientation mobility specialists, or educators involved in the rehabilitative program should evaluate the patient's abilities and needs in the field. These professionals can provide the low-vision doctor with information regarding typical lighting conditions, architectural barriers, and educational activities, and with behavioral observations of visual functioning (i.e., how well the person negotiates stairways, travels, recognizes faces at distances; the lighting conditions he prefers; how the person interacts socially). The next phase of the service is the low-vision examination, which the doctor -begins by analyzing functional abilities the moment the person walks into the office. This continued behavioral analysis, in conjunction with assessment of function, adds meaning to the measurements of sight that the doctor will make during the examination. An in-depth history is taken, and social workers, educators, and other professionals may need to confer to further assess needs and abilities. When examining elderly visually impaired persons, the doctor should take special care to display a positive attitude and adapt the examination procedure to bring out the visual abilities the patient retains. I have found that elderly people have generally experienced greater frustration and failure from sight impairment than have younger patients. The examiner can stimulate motivation, interest, and cooperation by designing the examination so that the patient can perform successfully. For example, instead of taking acuities at 20 feet with the standard Snellen acuity chart, a special low-vision acuity chart with larger letters and numbers can be used at any distance that the patient can see. Lighting conditions should be adapted to maximize the patient's visual functioning. In general, the normal procedures for field testing, refractive analysis, eye health examination, etc., should be altered to emphasize the particular abilities the patient retains. (See Faye, this volume, for an in-depth description of the low vision examination.) After the examination, optical aids are chosen on the basis of both the functional assessment and the refractive analysis. These aids may include handheld or spectacle-mounted telescopes, microscopes, telemicroscopes, handheld magnifiers, stand magnifiers, etc., as well as special spectacle lenses. Optical aids improve visual acuity, thereby directly improving sight, but improvement of performance and function depends on how the patient utilizes his enhanced sight. The prescribed aids are often loaned to the patient on a trial basis, but before he takes them home he must be trained in their use. Training may be provided by either the prescribing doctor or other professionals within the office or clinic. The elderly individual with sight impairment may need only demonstration of the use of the aid; however, if he also has a visual (performance) impairment, training must be more involved. In the latter case training may require several office visits utilizing special techniques to improve the patient's ability to match and reinforce visual information with input from other sensory and motor channels. After the patient has demonstrated efficient use of the aid and the final prescription has been made, he or she may be referred to other professionals for continuation of the low vision service. For example, social workers may provide counseling on emotional, family, or financial difficulties; rehabilitation counselors can help develop useful work skills utilizing the optical aids prescribed; and orientation and mobility specialists may provide training in navigational skills using the optical aids. Communication between the doctor prescribing the optical aid and the professionals in the field is essential for successful rehabilitation of the elderly visually impaired. Follow-through by rehabilitation professionals can determine the degree of improvement of the patient's functional abilities and training in the field can further improve use of the optical aid. Return to top |
||
|
|
||
|
Economic Considerations: | |
| Delivering low-vision services is more economical than providing only compensatory care services. Hospital care costs for a person over 65 average $125.00 a day, not including special services (R. Jose, personal communication); nursing home care is $30-35 a day, not including special services. A year's nursing home care would cost approximately $11,000. Compensatory care services are designed to provide care for individuals who cannot function effectively in their normal environments; many elderly people end up in nursing homes because of the functional impairment resulting from their sight loss. The 1976 Survey of Institutionalized Persons (SIP) reported that 48% of the people in nursing homes (572,000) have trouble seeing and that 14% are "severely disabled" or "unable to see" [Peterson and Kirchner, 1980]. Of this population, one-quarter of those under 65 years of age have trouble seeing, and one-half of those over 65 have difficulty seeing. Many elderly visually impaired individuals in nursing homes could benefit from low-vision services and might be rehabilitated. The cost of delivering low vision services in a clinical setting would be between $800-1600 (R. Jose, personal communication) less the cost of optical aids. The costs of low-vision services vary widely because individual needs differ considerably. An elderly visually impaired individual who also has other handicaps may require additional professional services, such as physical and/or occupational therapy. The cost of optical aids also varies greatly depending on need. A handheld magnifier may cost as little as $10, whereas a closed circuit television may be $1,200. The average cost for optical aids per person at the Low Vision Clinic at the Lighthouse for the Blind in New York is $67 (C. Hood, personal communication), which includes optical aids such as handheld magnifiers, stand magnifiers, spectacle-mounted magnifiers, microscopes, and telescopes, but not closed circuit televisions and driving telescopes. Obviously, the cost of services and optical aids together is considerably less than that of providing compensatory care services. Follow-up services for the visually impaired cost considerably less than initial costs of low-vision services; in contrast, compensatory care programs usually require continuing care at an increasing yearly cost. |
||
|
|
||
|
Summary: | |
| For the elderly person, low-vision services are a means to redevelop effective visual functioning; the purpose of the service is to increase the independence and improve the self-concept of the aging person. Low-vision services enable federal, state, and individual costs to be reduced by actively dealing with the cause of the problem, vision loss, and not simply reacting to the symptom; loss of independence. Thus, these services both reduce the economic burden on society and help us fulfill our obligations to the elderly by assisting them to maintain their independence through rehabilitative health care. Return to top |
||
|
|
||