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At least 19 recordsLinked to original sources

Visual perception in 'low vision'.

'Low vision' has an international classification as an impairment of vision that is defined by loss of visual acuity and the size of the visual field. Functional classification that would depict capability to use vision in different activities has not yet been agreed upon. Abnormal visual information leads to changes in visual perception, and brain-damage-related visual impairment may alter or prevent one or several cognitive visual functions. Abnormal visual perception opens a window into brain mechanisms that the psychophysicists otherwise do not have. Together with clinicians, psychophysicists can help visually impaired persons to understand the nature of their disability by thoroughly studying the nature of the altered image and the profile of cognitive visual functions.

Humans↗

Effectiveness of the Humphrey Vision Analyzer low vision slide on the partially sighted.

Subjective refractions were performed on a variety of low vision patients using the Humphrey Vision Analyzer (HVA) which incorporates a low vision slide. Twenty-one eyes were examined and results were compared with standardized trial frame refraction findings. The results indicate that the HVA is an effective alternative procedure for some low vision patients, although several factors, including design of the slide, patient alignment, and target illumination, need to be carefully considered if this technique is to replace the conventional low vision trial frame examination.

Adolescent↗

A comparison of low vision clinic data with low vision survey and blindness registration information.

PURPOSE: To determine whether low vision demographic data provided by low vision clinic data are comparable to that provided by blindness registration and disability questionnaire information. METHODS: Low vision demographic data for Canada and Ontario within the postcensus Health and Activity Limitation Survey (HALS 1991) were obtained from Statistics Canada. These data were compared with 4744 reports of low vision examinations obtained in a multi-center low vision clinic study in Ontario, Canada (1991-1994) and appropriate annual figures from the Canadian National Institute for the Blind (CNIB). RESULTS: Data from the low vision clinic study and the CNIB were similar. The low vision clinic study (and CNIB) reported far fewer adults (15 to 64 years) and far more seniors (65+ years) obtaining low vision examinations than suggested by HALS. CONCLUSIONS: HALS does not report on patients with low vision, as defined in low vision clinics. The differences between survey, low vision clinic, and blindness registration data are presented.

Adolescent↗

Preliminary investigation of the responsiveness of the Melbourne Low Vision ADL index to low-vision rehabilitation.

PURPOSE: To conduct a preliminary investigation on the ability of the Melbourne Low Vision ADL Index to detect changes in functional ability as a result of low-vision rehabilitation. METHODS: Twenty two subjects with age-related macular degeneration (ARMD) who were newly referred to the Kooyong Low Vision Clinic were recruited. The Melbourne Low Vision ADL Index was administered prerehabilitation and postrehabilitation. Changes in scores and effect size statistics were analyzed. RESULTS: The median total score for the subjects prerehabilitation was 67, and the median total score postrehabilitation was 76. The difference in prerehabilitation and postrehabilitation scores was statistically significant (Wilcoxon signed rank test = 248.5, p < 0.001). The mean change score for the total Melbourne Low Vision ADL Index was 9.3 (SD, 5.6). Thus the overall effect size statistic (mean change score divided by SD of prerehabilitation score) was 0.78. CONCLUSIONS: This preliminary investigation indicates that the Melbourne Low Vision ADL Index is responsive to a rehabilitation program for patients with ARMD. It has potential to be used as a measure of low-vision rehabilitation outcomes.

Activities of Daily Living↗

Quality of life of low-vision patients and outcomes of low-vision rehabilitation.

PURPOSE: The impact of low vision on self-reported quality of life and changes after low-vision intervention are investigated. METHODS: Literature reports from 1990 to 2000 are reviewed. RESULTS: Low vision is associated with increased risk for depression and decreased functional status and quality of life. Decreased visual acuity, visual field loss, and occasional blurred vision are also associated with decreased quality of life. Improvements in both functional status and quality of life occur after low-vision service delivery. CONCLUSIONS: Self-reported quality of life is a significant outcome measure for low-vision rehabilitation. Questionnaires that are more sensitive to rehabilitation services provided as well as patient needs and goals are required to facilitate development of rehabilitation plans and to compare techniques, devices, and programs. Attention should be given to measurement properties, validity, and reliability of instruments used currently and in development of new instruments.

Humans↗

Quality of life of low-vision patients and the impact of low-vision services.

PURPOSE: To investigate the functional status and quality of life of patients at a low-vision clinic and to evaluate the impact of low-vision services. METHODS: Interviews, including the Medical Outcomes Study 36-Item Short Form (SF-36), the Visual Function-14 (VF-14), and the 51-item Field Test Version of the National Eye Institute Visual Functioning Questionnaire (NEI-VFQ), were administered to 156 consecutive patients 1 week before and 3 months after their low-vision clinic visit. RESULTS: Low-vision patients scored lower (P < .001) in physical functioning and role limitations caused by physical and emotional health problems than published SF-36 scores of the age-appropriate United States normal population, patients with congestive heart failure, and clinically depressed patients. Low-vision services were associated with improvement in the subjective functional status of 150 patients (98.7%) and were rated "very useful" by 82 (53.9%) patients. The SF-36 scores did not change significantly after low-vision services. The VF-14 mean score improved from 35.8 to 41.2 (P < .001). Four NEI-VFQ subscale scores improved significantly (P < .001): general vision, near activities, distance activities, and peripheral vision. CONCLUSIONS: The SF-36, VF-14, and NEI-VFQ demonstrate that low-vision clinic patients perceive marked impairment of functional status and quality of life. Low-vision services are associated with high patient satisfaction. Vision-targeted questionnaires are more sensitive than general health-related quality of life questionnaires to changes in functional status and quality of life after low-vision services, and they may help elucidate the outcomes of low-vision services.

Adolescent↗

The UWCDot colour vision test and low vision.

PURPOSE: Previous studies have shown that colour vision defects are common in the low vision population even when properly designed tests are used. However, there are very few clinical tests available that are suitable for this group of patients. One of the more common is the Jumbo D-15 (JD15). Although this test uses caps more suitable for the reduced acuity, it requires the patient to have some knowledge of colour order and sufficient dexterity to manipulate the caps. We compared the JD15 with the University of Waterloo Colored Dot test (UWCDot), which has neither of these requirements, to determine whether the UWCDot test could be used as a substitute for the JD15. METHODS: The colour vision of 40 consecutive low vision patients was evaluated with both tests. Acuities ranged from 6/6 to 6/1600 with a median value of 6/30. RESULTS: All subjects could perform both tests. The kappa coefficient of agreement between tests was high at 0.85 when any major crossing was a failure on the JD15 and any mistake was a failure on the UWCDot. Classification of the type of defect was also reasonable when the defect was relatively severe. CONCLUSIONS: The UWCDot can be used as a substitute for the JD15 in the low vision clinic. Both tests identify individuals with moderate-to-severe deficiencies, but the UWCDot does not require any manual dexterity and it does not require knowledge of colour-order.

Adolescent↗

Principles of modern low vision rehabilitation.

Low vision rehabilitation is a new emerging subspecialty drawing from the traditional fields of ophthalmology, optometry, occupational therapy, and sociology, with an ever-increasing impact on our customary concepts of research, education, and services for the visually impaired patient. A multidisciplinary approach and coordinated effort are necessary to take advantage of new scientific advances and achieve optimal results for the patient. Accordingly, the intent of this paper is to outline the principles and details of a modern low vision rehabilitation service. All rehabilitation attempts must start with a first hand interview (the intake) for assessing functionality and priority tasks for rehabilitation, as well as assessing the patient's all-important cognitive skills. The assessment of residual visual functions follows the intake and offers a unique opportunity to measure, evaluate, and document accurately the extent of functional loss sustained by the patient from disease. An accurate assessment of residual visual functions includes assessment of visual acuity, contrast sensitivity, binocularity, refractive errors, perimetry, oculomotor functions, cortical visual integration, and light characteristics affecting visual functions. Functional vision assessment in low vision rehabilitation measures how well one uses residual visual functions to perform routine tasks, using different items under various conditions, throughout the day. Of the many functional vision skills known, reading skills is an obligatory item for all low vision rehabilitation assessments. Results of assessment guide rehabilitation professionals in developing rehabilitation plans for the individual and recommending appropriate low vision devices. The outcome from assessing residual visual functions is detection of visual functions that can be improved with the use of optical devices. Methods for prescribing devices such as image relocation with prisms to a preferred retinal locus, field displacement to primary gaze position, field expansion, and manipulation of light are practiced today in addition to, or instead of, magnification. Correction of refractive errors, occlusion therapy, enhancement of oculomotor skills, and field restitution are additional methods now available for prescribing devices leading to rehabilitation of visual functions. The outcome from assessing residual functional vision is detection of functional vision that can be improved with the use of vision therapy training. After restoration of optimal residual visual functions is achieved with optical devices, one can follow with training programs for restoration of lost vision-related skills. If an optical dispensary is available where prescribing of low vision devices routinely take place, this will help ensure familiarity and specialization of the dispensary and staff with low vision devices and their special dispensing requirements. The dispensing of low vision devices is an opportunity to introduce the device to the patient, train the patient in the correct use of the device for the task selected, and create a direct and continuous connection with the patient until the next encounter. Following assessment, prescribing, and dispensing of devices, a low vision practitioner, ophthalmologist or optometrist, is responsible for recommending and prescribing vision therapy training to improve residual functional vision. An attempt to present a template for a comprehensive modern low vision rehabilitation practice is made here by summarizing scientific developments in the field and stressing the multidisciplinary involvement required for this kind of practice. It is hoped that this paper and other initiatives from colleagues, the public, and government will promote and raise awareness of modern low vision rehabilitation for the benefit of all.

Humans↗

Is there a need for binocular vision evaluation in low vision?

The purpose of this study was to determine the need for a binocular vision evaluation in the management of low vision patients. Thirty subjects were selected with visual acuities of at least 6/60 in each eye. Twenty-three had age-related macular degeneration as the primary ocular pathology and seven had various other ocular conditions. The binocular vision evaluation comprised: detailed history and symptoms with an emphasis on the occurrence of near vision problems; modified binocular vision assessment which included cover test at near, ocular movements, convergence, Bagolini glasses, horizontal vergence reserves and prismatic measurement of any observed anomaly. History and symptoms revealed horizontal and vertical diplopia, jumbling of print, asthenopia, intermittent blurring and print being too small. Binocular vision assessment revealed exophoria at near, manifest horizontal deviations, convergence insufficiency, and vertical muscle imbalance. These anomalies occurred either singly or in combination. The results indicate that there is a need for binocular vision evaluation in low vision in order to reveal near vision disorders that may be partly attributable to binocular vision anomaly and not solely due to ocular pathology. This information should facilitate the implementation of the appropriate course of optometric management for these patients.

Aged↗

Thirty years in an urban low vision clinic: changes in prescribing habits of low vision practitioners.

PURPOSES: The purposes of this study were to determine the types of low vision devices (LVDs) prescribed by clinicians in a large optometrist led hospital low vision clinic and to investigate changes in these prescribing habits between 1973 and 2003. METHODS: Data were collected from departmental records for all patients attending the low vision clinic at Moorfields Eye Hospital in London, U.K., during the month of June in 1973, 1978, 1983, 1988, 1993, 1998, and 2003. The primary outcome measure was the type or types of LVDs prescribed to patients attending the clinic for the first time. Data were collected on the age, sex, and diagnosis of all patients attending the clinic. RESULTS: One thousand four hundred thirty-eight patient visits were identified, of which 563 (39%) were first attendances. The median age of the patients examined did not change significantly over this time. Eighty-four percent of the patients attending the clinic for the first time were prescribed at least one LVD. The devices most frequently prescribed to new patients were nonilluminated hand magnifiers, illuminated hand magnifiers, and illuminated stand magnifiers. There was a linear increase in the proportion of hand magnifiers prescribed between 1973 and 2003 (r = 0.62, p < 0.05) and a corresponding decrease in the number of near spectacle-mounted telescopes prescribed (r = 0.70, p < 0.05). CONCLUSIONS: Between 1973 and 2003, the low vision clinic at Moorfields Eye Hospital provided nearly 100,000 low vision consultations. The demographics of patients attending the clinic remained remarkably constant over this time. The number of spectacle-mounted devices prescribed to new patients fell between 1973 and 2003. It is thought this is in part the result of the increased availability of electronic magnification devices and the development of illuminated hand magnifiers. The development of the acrylic bright field magnifier and LED-illuminated LVDs have had particular clinical impact.

Eyeglasses↗

Low vision in east African blind school students: need for optical low vision services.

AIMS: There is increasing awareness of the needs of children with low vision, particularly in developing countries where programmes of integrated education are being developed. However, appropriate low vision services are usually not available or affordable. The aims of this study were, firstly, to assess the need for spectacles and optical low vision devices in students with low vision in schools for the blind in Kenya and Uganda; secondly, to evaluate inexpensive locally produced low vision devices; and, finally, to evaluate simple methods of identifying those low vision students who could read N5 to N8 print after low vision assessment. METHODS: A total of 230 students were examined (51 school and 16 university students in Uganda and 163 students in Kenya, aged 5-22 years), 147 of whom had a visual acuity of less than 6/18 to perception of light in the better eye at presentation. After refraction seven of the 147 achieved 6/18 or better. Eighty two (58.6%) of the 140 students with low vision (corrected visual acuity in the better eye of less than 6/18 to light perception) had refractive errors of more than 2 dioptres in the better eye, and 38 (27.1%) had more than 2 dioptres of astigmatism. RESULTS: Forty six per cent of students with low vision (n = 64) could read N5-N8 print unaided or with spectacles, as could a further 33% (n = 46) with low vision devices. Low vision devices were indicated in a total of 50 students (35.7%). The locally manufactured devices could meet two thirds of the need. CONCLUSION: A corrected distance acuity of 1/60 or better had a sensitivity of 99.1% and a specificity of 56.7% in predicting the ability to discern N8 print or better. The ability to perform at least two of the three simple tests of functional vision had a sensitivity of 95.5% and a specificity of 63.3% in identifying the students able to discern N8 or better.

Adolescent↗

Low vision rehabilitation: basic concepts and terms.

1. Ophthalmic professionals should avoid using the term "blindness' when referring to lesser levels of vision loss. Vision loss describes any type or degree of change in vision; blindness is total loss of sight. 2. Ophthalmologists deal with anatomy and organ function whereas rehabilitation counselors address the socioeconomic and skills aspects of vision loss. Successful visual rehabilitation must be a team effort with good communication between all professionals. 3. The replacement of the simple dichotomy between "legally sighted" and "legally blind" by normal vision, low vision, and blindness provides a more accurate and less stigmatizing classification.

Attitude of Health Personnel↗

Occupational therapy interventions in low vision rehabilitation.

Low vision can significantly decrease a person's functional ability and independence. With the continuing rise in age of our population, the number of people with low vision will increase substantially. Restoring and maintaining their ability to function independently through the use of specific interventions is an intricate process that calls for the collaboration of various health care professionals. Occupational therapists (OTs) and occupational therapy assistants are essential members of the multidisciplinary rehabilitation team providing such interventions. OTs in low vision rehabilitation enhance performance for specific activities of daily living by training skills that are dependent on residual vision, such as reading and writing. OTs also conduct environmental assessments in the home and in the workplace or school to improve and promote a safe environment for patients with low vision. OTs may also assist in developing rehabilitation programs for orientation and mobility, driving, and vision rehabilitation therapy. To prepare for the future needs of the ageing Canadian population, more low vision rehabilitation practitioners and more funding for multidisciplinary rehabilitation programs are required.

Humans↗

Outcome of low vision aid provision: the effectiveness of a low vision clinic.

PURPOSE: Although there is an increasing need for primary low vision (LV) care, few studies have considered the success rates of optometric LV rehabilitation. We considered the objective success and perceived benefit obtained by 57 elderly LV patients. METHOD: Tests of reading speed and questionnaires were administered in the patient's home after initial and follow-up visits to a LV clinic. Additional information was taken from the patient's clinic record. RESULTS: Benefits from attending the clinic were reported by 89.5% of patients and 81% of patients were regularly using low vision aids (LVA's). There was a discrepancy between ability to read 1M print in the clinic (75% of patients) and the reported ability to read regular-sized print at home (35%). Perceived benefit from visiting the clinic was strongly associated with the ability to perform daily living tasks and to read 2M print. There was some association between perceived benefit and frequency of using the LVA's, but not with duration of use. CONCLUSION: The results encourage a change in emphasis during LV assessments from sustained reading to the ability to perform daily living activities.

Activities of Daily Living↗

Impact of an interdisciplinary low vision service on the quality of life of low vision patients.

AIM: To investigate the impact of an interdisciplinary low vision service on the vision related quality of life of service users. METHODS: 71 patients were interviewed 2 weeks before their appointment with the service and again 6 months later to assess any changes in their vision related quality of life. The majority of these patients had age related macular degeneration. RESULTS: After contact with the service the majority of patients indicated a reduction in concern about most quality of life issues. They were significantly less anxious about deterioration of their vision, safety within the home, and coping with everyday life. CONCLUSION: Improvements in many areas of their vision related quality of life indicate that this interdisciplinary low vision service has a positive impact on the lives of service users. However many patients were still unable to carry out their preferred everyday activities, and feelings of loneliness and isolation were unchanged. The identification of issues unrelieved by input from the service will be important in planning future service delivery.

Activities of Daily Living↗

Design of the low vision quality-of-life questionnaire (LVQOL) and measuring the outcome of low-vision rehabilitation.

PURPOSE: To design and validate a vision-specific quality-of-life assessment tool to be used in a clinical setting to evaluate low-vision rehabilitation strategy and management. METHODS: Previous vision-related questionnaires were assessed by low-vision rehabilitation professionals and patients for relevance and coverage. The 74 items selected were pretested to ensure correct interpretation. One hundred and fifty patients with low vision completed the chosen questions on four occasions to allow the selection of the most appropriate items. The vision-specific quality of life of patients with low vision was compared with that of 70 age-matched and gender-matched patients with normal vision and before and after low-vision rehabilitation in 278 patients. RESULTS: Items that were unreliable, internally inconsistent, redundant, or not relevant were excluded, resulting in the 25-item Low Vision Quality-of-Life Questionnaire (LVQOL). Completion of the LVQOL results in a summed score between 0 (a low quality of life) and 125 (a high quality of life). The LVQOL has a high internal consistency (alpha = 0.88) and good reliability (0.72). The average LVQOL score for a population with low vision (60.9 +/- 25.1) was significantly lower than the average score of those with normal vision (100.3 +/- 20.8). Rehabilitation improved the LVQOL score of those with low vision by an average of 6.8 +/- 15.6 (17%). CONCLUSIONS: The LVQOL was shown to be an internally consistent, reliable, and fast method for measuring the vision-specific quality of life of the visually impaired in a clinical setting. It is able to quantify the quality of life of those with low vision and is useful in determining the effects of low-vision rehabilitation.

Activities of Daily Living↗

Acquisition and integration of low vision assistive devices: understanding the decision-making process of older adults with low vision.

The purpose of this study was to describe how older adults with low vision make decisions to use low vision assistive devices (LVADs). Analysis of participants' narratives, from both group and individual interviews, revealed three topic areas affecting device use. Two are discussed in this paper: Experiences and Characteristics Leading to Successful LVAD Use Decision Making and Challenges to Successful LVAD Use Decision Making. The third, Adjustment to Low Vision Disability, is briefly discussed. Of particular importance to occupational therapy practitioners in the growing field of low vision rehabilitation was the value placed on low vision rehabilitation services to assist with acquiring devices and integrating them into daily routines. Occupational therapy services were highly regarded. Participants demonstrated the importance of becoming a part of a supportive network of people with low vision to gain access to information about resources. They emphasized the need for systems and policy changes to reduce barriers to making informed decisions about LVAD use. Results indicate that occupational therapists working in low vision can support clients by facilitating development of a support network, acting as liaisons between clients and other health practitioners, especially ophthalmologists, and encouraging policy development that supports barrier-free LVAD acquisition and use. These topics should be incorporated into continuing and entry-level education to prepare practitioners for leadership in the field of low vision rehabilitation.

Aged↗