[A new test for evaluating functional vision and its application to "low vision"].
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Humans↗
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[Aids for low vision--strategic approach].
There are currently methods to rehabilitate the remaining visual function of visually impaired people. Treatment stages and tests are based on classical physiology of vision and still remain strictly experimental. Recent investigations showed that the visual system, as a whole, operates as a space frequency analyzer. There are reception to each spatial frequency. They have to be assessed with accuracy before any rehabilitation attempting to develop channels which are still functional by elective stimulation. This stimulation must have a maximum determined energetic efficiency. The study of the Fourier spectrum on two different images demonstrates this possibility and starts opening the way for specific research.
Contrast Sensitivity↗
Quebec model for low vision rehabilitation.
The increase in longevity (and secondary morbidity) in the Quebec population adds social and financial pressure to society, as it does elsewhere in Canada and in many western countries. This article gives a brief history of the evolution of vision rehabilitation services in Quebec and describes how services are provided for people with low vision throughout the province. Although numerous groups, associations, centres, and resources are available to assist people with vision impairments, such as the Canadian National Institute for the Blind-Québec, the majority of visual rehabilitation services are provided by government-sponsored rehabilitation centres, namely the Centres régionaux de réadaptation en déficience physique that are located strategically throughout the province. Low vision clinical evaluations in these centres are shared by 36 optometrists throughout the province. Between 5 and 7 ophthalmologists are involved in low vision care, half in university-affiliated hospitals, primarily in Montreal. There may be delays of up to 6 months to be seen in a funded low vision clinic. Statistics obtained from la Régie de l'assurance maladie du Québec show that there are approximately 8,000 requests for low vision aids every year, and that 80% of clients retain at least some level of visual function. Services are covered by Medicare and low vision aids are provided at no cost, although ophthalmologists cannot prescribe low vision aids through the Medicare-funded system. We must ensure that the capacity of our system continues to provide adequately for clientele in the future.
Health Resources↗
[An epidemiological survey of blindness and low vision in Shandong Province].
An epidemiological survey of blindness and low vision was carried out in a sample population of 115 167 in Shandong Province to find that the prevalence of binocular blindness was 0.34%, that of unilateral blindness 0.65%, that of binocular low vision 0.46%, and that of unilateral low vision 0.64%. The prevalence rates increased with age and the leading causes of blindness, in order of importance, were cataract, corneal diseases and glaucoma in urban areas, and cataract, corneal diseases and retinal diseases in rural areas.
Adolescent↗
Iowa's pediatric low-vision services.
BACKGROUND: Reports in the literature concerning best practice for the evaluation and management of children with visual impairments are limited, with a resulting lack of information concerning the potential for optimizing vision to enhance general development and assist with the educational needs of this population. METHOD: The development of a multidisciplinary approach to provide low-vision services for children with visual impairment has occurred over the past 18 years in Iowa. In that time, 1,348 children from around the state of Iowa have been evaluated through an itinerant low-vision service program, coordinated by the Iowa Braille School. RESULTS: A low-vision clinic model--designed to provide services (primarily) for academic students--was not meeting the needs of the pediatric low-vision population in the state. After a statewide review of the program, changes were made that have resulted in low-vision services being provided to a greater and more diverse number of students. The roles of the various members of the multidisciplinary team will be reviewed. Changes in large-print orders and use by special education teachers in the state as a direct result of the low-vision services will also be discussed. CONCLUSION: Ongoing, comprehensive multidisciplinary low-vision services--including optometric low-vision care as a key component--are necessary to help children with visual impairments meet their educational, vocational, and avocational needs. With ongoing low-vision services, unnecessary costs such as those associated with large-print materials can be reduced, thereby creating significant savings to local, state, and federal special educational services.
Child↗
Psychophysics of reading--II. Low vision.
Very little is known about the effects of visual impairment on reading. We used psychophysical methods to study reading by 16 low-vision observers. Reading rates were measured for text scanned across the face of a TV monitor while varying parameters that are likely to be important in low vision: angular character size, number of characters in the field, number of dots composing each character, contrast polarity (white-on-black vs black-on-white text), and character spacing. Despite diverse pathologies and degrees of vision loss in our sample, several major generalizations emerged. There is a wide variation in peak reading rates among low-vision observers, but 64% of the variance can be accounted for by two major distinctions: intact central fields vs central-field loss and cloudy vs clear ocular media. Peak reading rates for observers with central-field loss were very low (median 25 words/minute), while peak reading rates for observers with intact central fields were at least 90 words/minute (median 130 words/minute). Most low-vision readers require magnification to obtain characters of optimal size. Sloan M acuity was a better predictor of optimal character size than Snellen acuity, accounting for 72% of the variance. Low-vision reading is similar to normal reading in several respects. For example, both show the same dependence on the number of characters in the field. Our results provide estimates of the best reading performance to be expected from low-vision observers with characteristic forms of vision loss, and the stimulus parameters necessary for optimal performance. These results will be useful in the development of clinical tests of low vision, and in the design of low-vision reading aids.
Adolescent↗
Validation of physiologic predictors of successful telescopic spectacle use in low vision.
A group of 32 patients with low vision who were considered clinically appropriate candidates for visual rehabilitation with telescopic spectacles were prospectively studied before the first attempted use of these visual aids. Laboratory measurements were made of: (1) rotational head stability in pitch and yaw during quiet standing; (2) sensitivity of visual acuity with telescopic spectacles to imposed yaw head motion; and (3) ocular stabilization reflexes during passive, whole-body rotation in the horizontal plane. Predicted likelihood of successful use of telescopic spectacles was prospectively computed for each patient using the measurement of head stability in the pitch axis and the sensitivity of visual acuity with telescopic spectacles to head motion using a previously described statistical method. Patients were then given telescopic spectacles, and functional success was evaluated in the field at least 6 weeks later by independent masked observers. Although corrected visual acuities did not differ in the 24 patients in whom rehabilitation was successful or in the 8 patients in whom it was not, successful patients had statistically significantly less (P less than 0.05) angular head instability in pitch and yaw, as well as less impairment of visual acuity with telescopic spectacles during head motion. This finding was confirmed in a more clinically homogeneous subgroup of 16 patients who had low vision due to maculopathy. Gains of the 0.1 Hz horizontal vestibulo-ocular reflex (VOR) and visual-vestibulo-ocular reflex (VVOR) with 4X telescopic spectacles did not differ between patients in whom rehabilitation was successful and those in whom it was not.(ABSTRACT TRUNCATED AT 250 WORDS)
Adolescent↗
Luminance and chromatic contrast effects on reading and object recognition in low vision: a review of the literature.
This paper reviews the literature on the effects of luminance and chromatic contrast on reading and object recognition in low vision. The general consensus is that whereas luminance contrast can enhance reading and object recognition for some low vision subjects, chromatic contrast does not aid low vision reading but may be useful in low vision object recognition. Although providing useful theoretical results, the experimental designs have so far been remote from the conditions that low vision patients may experience in the home and work environment. Suggestions are made for an 'ideal' experimental design and details of current research, using conditions more likely to be experienced by low vision subjects in everyday life, are given. This research makes use of a recently developed instrument, the Intuitive Colorimeter.
Cognition↗
Outcomes of low-vision services using optometric and multidisciplinary approaches: a non-randomized comparison.
Consecutive patients (n = 215) who were referred to optometric (55%) or multidisciplinary (45%) low-vision services and above 50 years of age were recruited from four hospitals in the Netherlands. They completed two vision-related quality of life questionnaires, the Vision Quality of Life Core Measure (VCM1) and the Low Vision Quality of Life Questionnaire (LVQOL), before their first visit with low-vision services and 1 year later. At follow-up, patients referred to multidisciplinary low-vision services had lower scores on the mobility subscale of the LVQOL than patients referred to optometric low-vision services [5.3 points; 95% confidence interval (CI): 0.2-10.5]. Paired sample t-tests for the two groups of patients taken together show improvement for the VCM1 (3.1 points; 95% CI: 0.6-5.6) and deterioration for the basic aspects of vision (3.5 points; 95% CI: 1.1-5.9) and the mobility (6.6 points; 95% CI: 3.7-9.5) subscales of the LVQOL. In conclusion, people referred to optometric services showed less deterioration in mobility than those referred to multidisciplinary services. No differences were observed for any of the other subscales of the LVQOL and the VCM1. Future research in this field should include randomized controlled designs comparing low-vision services with no treatment or placebo.
Aged↗
Research needs in low vision.
Research needs are presented for several areas of low vision: (1) reading and learning, (2) new low-vision aids, (3) modifying the environment, (4) utilization of disciplines, (5) new technologies, and (6) integrating low-vision services.
Audiovisual Aids↗
Randomised controlled trial of an integrated versus an optometric low vision rehabilitation service for patients with age-related macular degeneration: study design and methodology.
A number of studies have measured the outcomes of low vision care but these have usually been longitudinal case series, thus constituting very low quality of evidence for effectiveness. To date, there have been no randomised controlled trials (RCTs) which have evaluated the effectiveness and cost effectiveness of different models of care in low vision. The size of the low vision population and the paucity of systematic evaluation have created a pressing need for evidence about cost-effectiveness in order to inform service developments for low vision rehabilitation. This paper describes the study design and methodology of a three-arm RCT currently under way in Manchester. The baseline population recruited is also described. A traditional hospital-based optometric service is being compared with an integrated service (comprising the addition of community-based rehabilitation officer input) and with more generic community input (which is non-integrated and is not vision specific). A wide range of outcome measures are being assessed at recruitment and 12 months post-intervention, including low vision specific and generic quality of life measures, patterns of low vision aid use, and task performance. The rationale for the trial is discussed and the main study outcomes are described.
Aged↗
National epidemiological survey of blindness and low vision in China.
According to the National Sample Survey of Blindness and Low Vision, the prevalence of blindness in China was 0.43%, resulting chiefly from cataract (41.06%), corneal diseases (15.38%), trachoma (10.87%), and glaucoma (8.80%); and the prevalence of low vision in China was 0.58%, of which the main causes were cataract (49.83%), ametropia/amblyopia (14.98%), trachoma (9.55%), corneal diseases (8.48%), chorioretinal diseases (6.27%), etc. Among children under 14 years of age, the leading cause of blindness and low vision was heredity (48.46%). Among elderly of 60 years and over, the leading cause of blindness and low vision was cataract (73.13%).
Aged↗
Psychophysics of reading. Clinical predictors of low-vision reading speed.
Clinicians need to estimate how well their low-vision patients will perform everyday visual tasks such as reading or driving. Typically, it is not practical to measure task performance directly or to administer a lengthy series of special tests. Recent laboratory research has suggested that some routine clinical data may be useful in predicting reading performance. The purpose of the present study was to determine whether a promising set of simple measures--Snellen acuity, status of the central fields and ocular media, diagnosis, and age--could be used in a clinical setting to predict reading speed. One hundred and forty one patients who entered the low-vision clinic of the Minneapolis Society for the Blind received thorough eye examinations and a test of reading speed. Snellen acuity accounted for only 10% of the variance in reading speeds overall, but played a more important role for subjects with central loss. Age was a better predictor than acuity. A diagnosis of age-related maculopathy predicted slower reading speed than other causes of central-field loss, but the difference was attributed to age. Media status (clear or cloudy) had no predictive value. Our set of clinical predictors accounted for only about 30% of the variance in low-vision reading speeds. While data from more detailed visual testing might improve prediction, nonvisual factors such as age probably also contribute to the variance. Rather than relying on predictions from visual testing, clinical assessment of low-vision reading may be accomplished most easily with a suitably designed reading test.
Adolescent↗
[A cross-sectional survey of blindness and low vision among adults aged 60 years and above in Xinchengqiao Blocks, Nantong].
OBJECTIVE: To investigate the prevalence and causes of blindness and low vision among adults aged > or = 60 years in the urban population of Nantong. METHODS: Cluster sampling was used to select 8 from 14 communities in Xinchengqiao Blocks, in which all individuals aged > or = 60 years were visited. The visual acuity without correction and the presenting acuity with the participants' habitual distance correction were measured separately for each eye. In individuals with visual acuity less than 0.6, pinhole visual acuity was tested with pinhole spectacle. External eye, anterior segment and ocular fundus were examined by the ophthalmologist using a slit lamp-microscope and direct ophthalmoscopy. The survey was preceded by a pilot study. RESULTS: Of 3352 enumerated subjects, 3040 individuals participated in this survey (90.69% response rate). According to pinhole visual acuity and World Health Organization (WHO) visual impairment criterion (blindness: less than 0.05 in the better eye; low vision: less than 0.3 to 0.05 in the better eye), the prevalence of blindness and low vision was 1.35% and 1.84% respectively. The prevalence of blindness and low vision for females were 1.92% and 2.33%, respectively, which were differenced from that in males (0.66% and 1.24%, respectively). The prevalence of blindness and low vision increased with age. The survey showed that the most important cause leading to blindness and low vision was cataract. According to the presenting visual acuity and visual impairment criterion (blindness: less than 0.1 in both eyes), the prevalence of blindness and visual impairment was 1.58% and 13.59%, respectively, 2.10% and 15.98% in females and 0.95% and 10.66% in males, respectively. The prevalence of blindness and visual impairment was raised with increasing age. Cataract was also the leading cause for blindness. CONCLUSIONS: The prevalence of blindness in the Nantong area was lower than that in northern, southern and western China. Females and illiteracy were more likely to have blindness and low vision than that of males and literate. The leading causes of blindness in Nantong are, in descending sequence, cataract, ocular fundus diseases, ametropia and corneal scar/opacity.
Aged↗
A training sequence for low vision patients.
A structured training program for teaching low vision patients to efficiently use their optical aids for reading tasks is presented. The arguments for the use of this particular training sequence is supported through the sample patient histories. The training sequences can be developed in any low vision practice and the materials are readily available. The importance of training in a low vision program is emphasized.
Adolescent↗
Multi-disciplinary low vision care.
Case reports for three patients with low vision due to different ocular diseases are presented. In each case, a different rehabilitation professional was the main provider of the low vision care needed to meet the patient's goals. However, in all cases the patients benefited from the services of a range of professionals, agencies or groups for visually impaired people. The importance of defining patients' specific goals, referral to multi-disciplinary low vision services and regular reviews of vision and visual tasks is highlighted.
Journal Article↗
Causes of low vision and use of optical aids in the elderly.
PURPOSE: To determine the causes of low vision in an elderly population attended by a university visual rehabilitation service and to check for the use of prescribed optical aids. METHOD: A cross-sectional study was carried out on patients aged 60 years or over attending for the first time a university low vision service in 2001. Ophthalmic reevaluation and interview were performed by means of a structured questionnaire in 2002. RESULTS: The sample comprised 50 subjects aged between 60 and 90 years. Severe low vision (< or =20/200) was present in 68.0% of patients. The main cause of low vision was age-related macular degeneration (44.0%). Regarding literacy, 16.0% were illiterate and 72.0% had completed fundamental schooling. Thirty-one patients (62.0%) had been prescribed optical aids; 54.8% of these patients stated that they use them. A majority (70.6%) held a favorable opinion of these aids. CONCLUSIONS: The main cause of low vision was age-related macular degeneration. Approximately half of those receiving prescriptions reported actually using the aids in their daily activities. Making best use of residual vision in the elderly population with visual impairment is a priority, given the social context, if the independence necessary for enhanced quality of life is to be achieved.
Activities of Daily Living↗
Incidence of blindness and low vision in a sample population: the Priverno Eye Study, Italy.
PURPOSE: To study the incidence of blindness and low vision over a 7-year period. DESIGN: Population-based cohort study. PARTICIPANTS: The survivors of the original cohort of 860 persons from Priverno, Italy, aged 45 to 69 years, were reexamined. Of the 760 eligible survivors, 619 (81.4%) had a 7-year follow-up visit. METHODS: Baseline and follow-up examinations included the collection of anamnestic and ophthalmologic data by the same observers using the same methods and classification criteria to minimize sources of variability. MAIN OUTCOME MEASURES: Best-corrected visual acuity (VA) measured at 4 m by standardized logarithmic chart was expressed as the logarithm of the minimum angle of resolution (logMAR). World Health Organization definitions of blindness and low vision were adopted (respectively, VA > 1.3 logMar and VA > 0.6 to 1.3 logMar in the better eye or in either eye). Participants at risk for visual impairment were those without blindness or low vision in one or both eyes at baseline; participants at risk for one-eye visual impairment were those without blindness or low vision in both eyes at baseline. RESULTS: A total of 33 participants were defined as incident cases of visual impairment. The overall incidence figures for blindness, low vision, one-eye blindness, and one-eye low vision were respectively 0.2% (95% confidence interval [CI], 0.0-0.9), 1.3% (95% CI, 0.7-2.6), 1.2% (95% CI, 0.6-2.4), and 2.9% (95% CI, 1.8-4.6). CONCLUSIONS: This study provides population-based estimates of the incidence of visual impairment in an adult, free-living European population. With respect to the younger participants, older subjects at baseline were at higher risk for incident visual impairment, the main causes of which were cataract, myopia, and diabetic retinopathy. The incidence of visual impairment in the subgroup aged 55 to 64 years at baseline was significantly higher than that found in Beaver Dam 5-year study and similar to that found in Beaver Dam 10-year Study, when the same definitions were adopted. This difference may be partially explained by social and cultural habits of the female samples, but many other factors may play a role.
Aged↗