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PubMed2006

Low vision service models in Alberta: innovation, collaboration, and future opportunities.

As Alberta's population ages over the next 20 years, the number of older adults experiencing age-related blindness or vision loss is likely to at least double. To prevent a crisis in low vision service provision, we need to build upon, and extend, existing partnerships between the CNIB and ophthalmologists, optometrists, government policy makers, and other service providers. Future service models for low vision rehabilitation should also emphasize interventions such as counselling and peer support that enhance quality of life. With thoughtful planning, adequate funding, and involvement of all stakeholders, Alberta has the potential to become a world leader in the field of low vision treatment and rehabilitation.

Alberta↗
PubMed1991

Low vision aids and the presbyope.

When light rays emerge divergent from a low vision device, a presbyopic patient requires a near addition to focus the image. The magnitude of the divergence and the near addition power used by a presbyope can substantially alter the magnification effects of a device. This study examines the effects of different emerging divergences and near addition powers on the magnification of low vision devices. The emerging divergence of 54 fixed focus stand magnifiers was measured using trial lenses and a telescope. The magnifiers represented a range of powers and manufacturers. The emerging divergence was not predictable. It could not be correlated to magnifier power. Although mathematical formulas exist to calculate the effect of the divergence and near addition on magnification, tables were developed to simplify this determination.

Humans↗
PubMed2006

Orientation and mobility training for adults with low vision.

BACKGROUND: Orientation and mobility (O&M) training is provided to people who are visually impaired to help them maintain travel independence. It teaches them new orientation and mobility skills to compensate for reduced visual information. OBJECTIVES: The objective of this review was to assess the effects of (O&M) training, with or without associated devices, for adults with low vision. SEARCH STRATEGY: We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (which contains the Cochrane Eyes and Vision Group Trials Register) in The Cochrane Library, MEDLINE, SIGLE, EMBASE, National Research Register, Zetoc, LILACS, and the reference lists of articles. Updated searches were in 2006. SELECTION CRITERIA: We planned to include randomised or quasi-randomised trials comparing (O&M) training with no training in adults with low vision. DATA COLLECTION AND ANALYSIS: Two authors independently assessed the search results for eligibility, evaluated study quality and extracted the data. MAIN RESULTS: Two small studies satisfied the inclusion criteria. They were consecutive phases of development of the same training curriculum and assessment tool. The intervention was administered by a volunteer on the basis of written and oral instruction. In both studies the randomisation technique was inadequate, being based on alternation, and masking was not achieved. Training had no effect in the first study while it was found to be beneficial in the second. Reasons for this may have been: the high scores obtained in the first study, suggestive of little need for training and small room for further improvement (a ceiling effect), and the refinement of the curriculum allowing better tailoring to patients' specific needs and characteristics, in the second study. AUTHORS' CONCLUSIONS: The review found two small trials with similar methods, comparing (O&M) training to physical exercise, which were unable to demonstrate a difference. Therefore, there is little evidence on which type of orientation and mobility training is better for people with low vision who have specific characteristics and needs. Orientation and mobility instructors and scientists should plan randomised controlled studies to compare the effectiveness of different types of (O&M) training. A consensus is needed on the adoption of standard measurement instruments of mobility performance which are proved to be reliable and sensitive to the diverse mobility needs of people with low vision. For this purpose, questionnaires and performance-based tests may represent different tools that explore people with low vision's subjective experience or their objective functioning, respectively.

Adult↗
PubMed2005

Prevalence and burden of self-reported blindness, low vision, and visual impairment in the French community: a nationwide survey.

OBJECTIVE: To estimate the prevalence of self-reported visual impairment and its association with disabilities, handicaps, and socioeconomic consequences. METHODS: A national survey was conducted on a random stratified sample of 359 010 French citizens living in the community; 21 760 subjects were selected at random and 16 945 persons (78%) agreed to further questioning. Four thousand ninety-one randomly selected caregivers were interviewed. Four subgroups of subjects were defined (blind or light perception only, low vision or still have form perception, other visual problems, and no visual problems). These were compared after adjustment for age, comorbidity, and household size differences. RESULTS: The prevalence of blindness was 0.10% and of low vision, 1.94%. Subjects with blindness needed assistance with daily activities more often than subjects with no visual problems; they also needed more house modifications. Many subjects with blindness (46.8%) and subjects with low vision (29.0%) were registered for social allowances. Subjects with blindness had fewer paid activities (4.5%) than subjects with no visual problems (20.7%). Social allowances increased considerably (by 277) between those with low vision and those with blindness. Monthly household incomes were lower (P<.001) for subjects with low vision (1255) and blindness (1587) than for subjects with no visual problems (1851). MAIN OUTCOME MEASURES: Collected data included social demography, home description, household income, handicaps, disabilities, social allowances, and daily activities. CONCLUSION: The results demonstrate associations between self-reported visual impairment and daily living.

Activities of Daily Living↗
PubMed2004

Psychometric properties of the Veterans Affairs Low-Vision Visual Functioning Questionnaire.

PURPOSE: To describe psychometric properties of a self-report questionnaire, the Veterans Affairs (VA) Low-Vision Visual Functioning Questionnaire (LV VFQ-48), which was designed to measure the difficulty visually impaired persons have performing daily activities and to evaluate low-vision outcomes. METHODS: The VA LV VFQ-48 was administered by telephone interview to subjects with visual acuity ranging from near normal to total blindness at five sites in the VA and private sector. Rasch analysis with the Andrich rating scale model was applied to difficulty ratings from 367 subjects, to evaluate measurement properties of the instrument. RESULTS: High intercenter correlations for item measure estimates (intraclass correlation coefficient [ICC]=0.97) justified pooling the data from these sites. The person measure fit statistics (mean square residuals) confirm that the data fit the assumptions of the model. The item measure fit statistics indicate that responses to 19% of the items were confounded by factors other than visual ability. The separation reliabilities for pooled data (0.94 for persons and 0.98 for items) demonstrate that the estimated measures discriminate persons and items well along the visual ability dimension. ICCs for test-retest data (0.98 for items and 0.84 for persons) confirm temporal stability. Subjects used the rating categories in the same way at all five centers. Ratings of slight and moderate difficulty were used interchangeably, suggesting that the instrument could be modified to a 4-point scale including not difficult, slightly/moderately difficult, extremely difficult, and impossible. Fifty additional subjects were administered the questionnaire with a 4-point scale to confirm that the scale was used in the same way when there were four rather than five difficulty ratings. CONCLUSIONS: The VA LV VFQ-48 is valid and reliable and has the range and precision necessary to measure visual ability of low-vision patients with moderate to severe vision loss across diverse clinical settings.

Activities of Daily Living↗
PubMed1992

Obstacles encountered in the development of the low vision enhancement system.

The Johns Hopkins Wilmer Eye Institute and the NASA Stennis Space Center are collaborating on the development of a new high technology low vision aid called the Low Vision Enhancement System (LVES). The LVES consists of a binocular head-mounted video display system, video cameras mounted on the head-mounted display, and real-time video image processing in a system package that is battery powered and portable. Through a phased development approach, several generations of the LVES can be made available to the patient in a timely fashion. This paper describes the LVES project with major emphasis on technical problems encountered or anticipated during the development process.

Audiovisual Aids↗
PubMed1990

[A survey of blindness and low vision in Shanxi Province].

In accordance with the unified criteria and methods over the country, a sampling survey of blindness and low vision was carried out in Shanxi province in April, 1987. The sample population was 53,656 persons and the actual number examined was 51,664 (96.3%). The provincial prevalence of blindness was 0.46%, i.e. 0.18% in cities and 0.50% in rural areas, with senile cataract as the leading cause for blindness (29.7%). The prevalence of monocular blindness was 0.85% and that of low vision 1.23%. The authors also proposed key points for the prevention and treatment of blindness and low vision.

Adolescent↗
PubMedDate not supplied

Assessment of educational services available to blind and low vision school children in Lagos, Nigeria.

A descriptive study to assess the educational services available to children attending the Pacelli School for the Blind in Lagos, Nigeria. A standardised methodology was used with structured and semi-structured questionnaires. Observations were also made in some areas. Of the 26 children aged 10-15 years who were identified as having low vision, 15 (57.7%) of them had significant improvement in distance and near vision after refraction while one third (31%) had improvement in their reading with low power magnifying lenses. All except 4 (25%) teachers were well educated but none seemed to have appreciable knowledge about the teaching of low vision children as all these children were taught Braille like their blind peers. While educational facilities available were reasonably adequate for blind children, no visual aids were available for low vision children. It is recommended that appropriate educational facilities, optical and non-optical devices should also be provided particularly for low vision children to enable them achieve their optimal potential in life.

Adolescent↗
PubMed1989

Psychophysics of reading. VIII. The Minnesota Low-Vision Reading Test.

This is the eighth in a series of papers dealing with the role of vision in reading. In previous papers, we have evaluated the effects of stimulus and subject variables on reading rate using a drifting-text procedure. In this paper, we describe a new test of reading rate that uses static text, called the Minnesota Low-Vision Reading Test (MNread). It is microcomputer-based, and more easily set up and administered than the drifting-text procedure. It is of potential value as a standardized psychophysical test of reading and should be useful in research, clinical, and educational applications. Some types of low-vision aids rely on drifting text and others on static text. Is reading performance different for these two modes of text presentation? We measured reading rate as a function of angular character size for normal and low-vision subjects with drifting and static text. Although reading rates were highly correlated for the two modes of text presentation, normal subjects usually read static text more rapidly. The reverse was true for low-vision subjects; their reading rates for drifting text were slightly higher (average 15%) than for static text.

Adult↗
PubMed1996

A simplified screening test for identifying people with low vision in developing countries.

Simple but effective tests have been produced for screening subjects with low vision in developing countries. These tests of distance and near vision, based on the E test, were evaluated and validated in trials with people aged 4-90 years, and have been field tested in the health, education and rehabilitation services in 32 developing countries. Their sensitivity and specificity as screening tools for low vision have been calculated; sensitivity of 85% and specificity of 96% for the distance vision test, and sensitivity of 100% and specificity of 84% for the near vision test. The content and format of the tests have been demonstrated to be appropriate for developing countries, and their effectiveness for screening for low vision has been confirmed.

Adolescent↗
PubMed1991

Primary success with low vision aids in age-related macular degeneration.

The benefit obtained from various low vision aids (LVAs) was studied in 65 consecutive patients with atrophic (70.3%) or disciform (29.7%) age-related macular degeneration (ARMD). 13.8% were able to read newsprint with age-related reading correction under proper lighting conditions. The primary success achieved with LVAs was good, 91.4% of patients being able to read newsprint. In most cases a simple magnifier (52.3%), high-powered reading glasses (10.8%) or Fonda's glasses (12.8%) were sufficient. The magnification preferred was 5x or less in 25.6% and greater than 5x to 9x in 48.8%. Patients with disciform degeneration required higher magnification than those with atrophic degeneration. It is concluded that most patients with ARMD found low vision aids useful for reading purposes and that a simple optical device was sufficient to achieve reading vision.

Age Factors↗
PubMed2001

Charles Bonnet syndrome in glaucoma patients with low vision.

PURPOSE: To characterize the nature and frequency of Charles Bonnet syndrome in glaucoma patients with low vision. PATIENTS AND METHODS: All patients attending the glaucoma clinic during a period of 10 months who had visual acuity of 20/80 or less in both eyes were included in this study. Each patient was questioned about the occurrence of visual hallucinations. Those who responded positively had a thorough interview relating to the characteristics of the hallucinations. Medical history and social history were taken, followed by a complete ocular examination. RESULTS: Eighty-nine patients met the inclusion criteria. Eleven patients (12.3%), eight men and three women, admitted to having experienced visual hallucinations. Except for one case, the patients did not disclose this experience previously. Eight patients had one repeatable hallucination, and three patients experienced more than one sight. The visions were usually sharp, and the figures were occasionally incomplete. Most hallucinations were chromatic. Frequency of hallucinations varied between daily and weekly, and duration was mostly a few minutes. In addition to glaucoma, nine of the eleven patients had other ocular findings that could have contributed to the reduction of vision. CONCLUSION: Visual hallucinations are not rare in glaucoma patients with low vision. Patients tend to conceal their experience of visual hallucinations, but a discussion of these phenomena with the patient and assurance of their harmless nature will reduce his or her anxiety and concerns.

Aged↗
PubMedDate not supplied

Checklist for the evaluation of low vision in uncooperative patients.

PURPOSE: To present a checklist for the evaluation of low vision in uncooperative patients; in this specific case, children with neurological deficits. METHOD: The checklist includes several behavioral indicators obtainable with a standard clinical examination. Each test is assigned a score (0=failure, 1=success). The final visual quotient score is obtained by dividing the partial score by the total number of tests performed. Eleven children with cerebral visual impairment were studied using behavioral and preferential looking techniques. RESULTS: Visual quotient was >0 in all patients, indicating that residual visual function was always detectable. Average visual quotient was 0.74. CONCLUSION: Visual quotient can be useful both for follow-up examinations and comparison and integration with other evaluation methods (behavioral and instrumental) of residual visual capacity. In particular, if combined with preferential looking techniques, visual quotient testing permits characterization of the entire spectrum of low vision.

Child↗
PubMed2006

Surgical treatment of low vision.

Recent advances in technology are driving a renewed search to find surgical solutions for low vision rehabilitation. The scope of surgery is now being pushed beyond the initial goal of repairing existing anatomical structures. Today, the goal for vision rehabilitation is no less than replacing damaged ocular tissues with artificial ones. Surgical management of low vision may be subdivided into two categories, those procedures aimed at restoring ultrastructural visual function and those aimed at enhancing visual acuity of the residual retina with various levels of magnification. This paper briefly reviews advances in ultrastructural restoration by repair and considers in more detail enhanced acuity through magnification or replacement.

Humans↗
PubMed1997

The validity of current clinical tests of contrast sensitivity and their ability to predict reading speed in low vision.

PURPOSE: Contrast sensitivity (CS) testing using chart tests of CS is becoming increasingly common in low vision assessment. Yet we know little about the validity of these charts, i.e. which region of the spatial frequency spectrum is being measured. In this study we aimed to determine the validity of currently available CS charts by comparison against oscilloscope-based CS. We also determined their relative ability to predict reading speed. METHODS: CS was measured with five commercially available charts and the contrast sensitivity function was determined with sinusoidal gratings presented on a Joyce screen using a two-alternative forced choice staircase technique in 36 observers with low vision and 3 with normal vision. Reading rate was also measured with the subject reading with his or her own optical low vision aid. RESULTS: The results show that the Pelli-Robson chart and the Cambridge gratings are good measures of medium to low spatial frequencies, as would be predicted from their design, while the Regan and UW charts correlated with medium to high frequencies. The Vistech chart was a good predictor of CS at each spatial frequency. CONCLUSIONS: The best chart test of CS depends on which region of the CS curve is of interest. All the charts were good predictors of reading rate.

Adult↗
PubMed2005

Registered blindness and low vision in Kuwait.

AIM: To estimate the incidence rates and major causes of registered blindness and low vision in Kuwait. METHODS: Data on age, gender and cause of blindness and low vision were collected from the Visual Disability Committee while evaluating Kuwaiti citizens applying for a blindness allowance from January 2000 to December 2004. Criteria for legal blindness in Kuwait are visual acuity 6/60 or less in the better eye with best possible correction or a visual field less than 20 degrees around the central fixation point. Incidence rates per 100,000 person years of observation were calculated for both genders in four age subgroups and four severity categories. The causes of registered blindness were classified according to the International Classification of Diseases, 10th edition. RESULTS: 412 persons were registered as blind, 272 males (66.01%) and 140 females (33.98%), mean age 28.7 +/-25.2 years, 39.32% below 20 years of age, 31.79% 21-40 years, 18.68% 41-60 years, and 9.95% 61 years and over . Male gender was prevalent for all age subgroups. The overall incidence rate was 9.97 per 100,000 person years of observation, 13.33 for the male and 6.69 for the female patients. The incidence rates rose from 7.35 for those 20 years and younger to 14.80 for the age subgroup 41-60 and 23.16 for those 61 years and above. The rates of severe visual impairment classified in categories 4 and 5 were higher than the rates for categories 2 and 3. Retinitis pigmentosa was the leading cause of blindness, followed by congenital anomalies and optic atrophy. In the subgroup below 20 the rate of optic atrophy was highest, followed by congenital malformations, retinitis pigmentosa and retinopathy of prematurity. In the next age subgroup (21-40 years), the rate of retinitis pigmentosa was three times as high as in the younger subgroup, followed by optic atrophy, congenital malformations and albinism. In the subgroup 41-60 the incidence rate for phthisis bulbi was twice as high as the rates for retinitis pigmentosa and optic atrophy. For those 61 years and older, the incidence rate of phthisis bulbi was almost five times as high as that for optic atrophy. The incidence rates for the male patients were higher for the major causes of disability in all age subgroups. CONCLUSIONS: The overall incidence rate of registered blindness for Kuwait is less than in many other national registries. The marked prevalence of the male gender in all age subgroups is specific for Kuwait. The rates of the leading causes of registered blindness reflect the prevalence of the younger subgroups in our registry. Additional data on co-morbidity and dedicated efforts to reveal unrecognized and unregistered blindness, particularly among females, will overcome the limitations of the registry, and will serve to outline the tendencies in avoidable vision loss and monitor the efficacy of the prevention programs in the future.

Adolescent↗