Measurements of preferred walking speed in subjects with central and peripheral vision loss.

BACKGROUND: Previous mobility studies have used Preferred Walking Speed (PWS) in order to determine the walking efficiency in terms of the Percent Preferred Walking Speed (PPWS) of visually impaired adults. PWS has been measured in previous studies using the sighted guide (SG) and non-sighted guide (NSG) techniques. This study compared the NSG, SG and string (ST) (subjects walked by holding on lightly to a cardboard tube attached to a piece of string) techniques of measuring PWS in visually impaired subjects. METHODS: Forty visually impaired subjects with central and peripheral vision loss were recruited. PWS was measured using the NSG, SG and ST techniques. For each technique, PWS was determined by recording the time taken for a subject to walk an unobstructed, straight 20-m corridor. RESULTS: There were no significant differences in PWS using the SG, NSG and ST techniques. CONCLUSION: For assessing walking efficiency, either the SG, NSG or ST technique could be employed when measuring PWS in visually impaired subjects.

Does mobility performance of visually impaired adults improve immediately after orientation and mobility training?

BACKGROUND: Previous studies that have attempted to determine the effect of orientation and mobility training on mobility performance of visually impaired adults have had a number of limitations. With the inclusion of a control group of subjects, this study investigated the effect of orientation and mobility training on mobility performance of a group of visually impaired adults. METHODS: Vision was measured binocularly as high- and low-contrast visual acuity, letter and edge contrast sensitivity, and Humphrey kinetic visual fields. The subjects' mobility performance was assessed as percentage preferred walking speed (PPWS) and error score before and after mobility training. RESULTS: Orientation and mobility training did not enhance mobility performance compared with the control group, who did not receive training, when performance was measured immediately after training. PPWS improved for both groups with short-term practice only, but there was no improvement in error score due to either practice or training. CONCLUSIONS: There was no immediate improvement in mobility performance of visually impaired adults after orientation and mobility training. Familiarity with the route may play an important role in measured improvement of mobility performance after orientation and mobility training.

Eye movements and reading with large print and optical magnifiers in macular disease.

PURPOSE: Reading rate has been the main performance measure in studies that have compared reading with large print and optical magnifiers; eye movement characteristics have not been considered. We compared both eye movement characteristics and reading rates for subjects with macular disease reading without and with a range of low-vision devices. METHODS: Silent reading rate and eye movement characteristics for text passages at critical print size of 21 subjects aged 14 to 88 years with macular disease were measured with and without their preferred low-vision device. Saccadic frequency was determined from a sequencing task comprising five letters each separated by 5 degrees. Eye movements were recorded using an infrared limbal reflection system. RESULTS: There were no significant differences in reading rate, fixation durations, saccade numbers per word, or percent retrace time when using a low-vision device compared with reading without a low-vision device. The percentage of regressions was, however, lower with the low-vision device. Saccadic frequency in the sequencing task was predictive of reading performance with and without a low-vision device. CONCLUSIONS: When reading at critical print size, in terms of reading rate or saccades per word, there was no advantage to using large print over an optical low-vision device.

Oral and silent reading performance with macular degeneration.

Previous studies have shown that reading rate for very large print (6 degrees, 1.86 logMAR character size) is a strong predictor of oral reading rate with low vision devices (LVDs). We investigated whether this would apply using large print sizes more readily available in clinical situations (e.g. 2 degrees, 1.4 logMAR), for subjects with macular degeneration. We assessed rauding rates--reading for understanding. A combination of near word visual acuity and large print reading rate (without LVDs) provided the best prediction of oral rauding rates (with LVDs). However, near word visual acuity alone was almost as good. Similarly, silent rauding rate was predicted best by near word visual acuity alone. We give near visual acuity limits as a clinical guide to expected oral and silent reading performance with LVDs for patients with macular degeneration.

Repeatability and intercorrelations of standard vision tests as a function of age.

PURPOSE: We assessed repeatability and intercorrelations of five standard vision tests in subjects with normal vision. METHODS: Seventy-eight subjects (aged 21 to 68 years) completed five measurements each of high- and low-contrast visual acuity, near visual acuity and contrast sensitivity (Pelli-Robson chart). RESULTS: Except for correlations between high- and low-contrast visual acuity (r = 0.78), intercorrelations between tests were low to moderate (r < 0.5). For each measure, variability for the group was about one line on the chart (one triplet for the Pelli-Robson chart) and the minimum variability for an individual subject was about one third of this. On average, 1 to 2 lines can be expected to be lost over the normal lifespan on each test. Variability in responses did not increase significantly with age for any test. CONCLUSIONS: The criterion for judging change on commonly used clinical vision tests is about one line for subjects over a wide age range.

[A simplified screening test for the identification of individuals with diminished vision in developing countries]. / Prueba de tamizaje simplificada para identificar a personas con visión disminuida en países en desarrollo.

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.

Prueba de tamizaje simplificada para identificar a personas con visión disminuida en países en desarrollo / A simplified screening test for identifying people with low vision in developing countries

Se han creado pruebas sencillas pero útiles para el tamizaje de personas con visión disminuida en países en desarrollo. Estas pruebas, que miden la visión de lejos y de cerca y que se basan en el uso de una figura en E, fueron evaluadas y respaldadas mediante ensayos en que participaron personas de 4 a 90 años de edad, y se han puesto a prueba en los servicios de salud, educación y rehabilitación de 32 países en desarrollo. Se han calculado su sensibilidad y especificidad como instrumentos para la detección de la visión disminuída: en la prueba de visión a distancia, la sensibilidad es de 85 por ciento y la especificidad, de 96 por ciento; en la prueba de visión cercana, la sensibilidad es de 100 por ciento y la especificidad, de 84 por ciento. Se ha demostrado que el contenido y el formato de las pruebas son adecuados para países en desarrollo y se ha comprobado la utilidad de las mismas para el tamizaje de la visión disminuida

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 4­90 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.

Prueba de tamizaje simplificada para identificar a personas con visión disminuida en países en desarrollo / A simplified screening test for identifying people with low vision in developing countries

Se han creado pruebas sencillas pero útiles para el tamizaje de personas con visión disminuida en países en desarrollo. Estas pruebas, que miden la visión de lejos y de cerca y que se basan en el uso de una figura en E, fueron evaluadas y respaldadas mediante ensayos en que participaron personas de 4 a 90 años de edad, y se han puesto a prueba en los servicios de salud, educación y rehabilitación de 32 países en desarrollo. Se han calculado su sensibilidad y especificidad como instrumentos para la detección de la visión disminuída: en la prueba de visión a distancia, la sensibilidad es de 85 por ciento y la especificidad, de 96 por ciento; en la prueba de visión cercana, la sensibilidad es de 100 por ciento y la especificidad, de 84 por ciento. Se ha demostrado que el contenido y el formato de las pruebas son adecuados para países en desarrollo y se ha comprobado la utilidad de las mismas para el tamizaje de la visión disminuida

Rediscovering mycophenolic acid: a review of its mechanism, side effects, and potential uses.

Oral mycophenolic acid (MPA) therapy has been investigated in the treatment of moderate to severe psoriasis since the early 1970s and has been found to be both safe and effective. By inhibiting de novo purine biosynthesis, it functions as an antifungal, antibacterial, antiviral, and immunosuppressive agent. The recent availability of mycophenolate mofetil (MMF), a morpholinoester of MPA, has created renewed interest in the antipsoriatic properties of MPA. MMF is currently indicated for the prevention of organ rejection in transplant recipients and is used concomitantly with cyclosporine and corticosteroids. This review focuses on the pharmacology of MPA and MMF, studies of MPA in the treatment of psoriasis, and therapy with MMF. There is a potential application of MMF in the treatment of severe psoriasis and other inflammatory dermatoses, as well as topical MPA for the treatment of psoriasis.

Referral to low vision services by ophthalmologists.

PURPOSE: People in need of low vision rehabilitation services often experience delays in referral to services. This study investigates referral criteria of Australian ophthalmologists, the frequency of referral of their patients with low vision and their perceptions of low vision services. METHODS: A survey was sent to a representative, random sample of 200 ophthalmologists. They were asked about criteria used for the referral of their patients with low vision. The survey included questions on the frequency with which they prescribed low vision devices (LVD) and referral of their patients to low vision and rehabilitation services and peer support groups. Perceptions of the quality and availability of low vision services were also investigated. RESULTS: The response rate was 82%. Approximately 11% of ophthalmologists' patients have low vision. It is uncommon for ophthalmologists to prescribe LVD but 67% refer most of their patients with low vision. It is less common for them to refer to rehabilitation services (29%) or peer support services (18%). The perceived local availability of services influences the rate of referral. Ophthalmologists who used the criteria of moderate low vision (< 6/21 to < 6/60) are more likely to refer more of their patients than those who use the criteria of severe low vision. CONCLUSIONS: Australian ophthalmologists refer most of their visually impaired patients to low vision services, but infrequently to rehabilitation services or peer support groups. Differences in perceived need for low vision services indicated by the criteria used for referral, and the perceived availability, influence the rate at which ophthalmologists refer their patients for services. Ophthalmologists are encouraged to refer patients with permanent visual loss to low vision services earlier.

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.

Evaluation of the efficacy of contrast sensitivity measures for the detection of early primary open-angle glaucoma.

We investigated the relative efficacy of contrast sensitivity (CS) measures for the identification of early primary open-angle glaucoma (POAG) patients. The contrast sensitivity function (CSF) was sampled at five spatial frequencies using a standard oscilloscope technique and measures of CS were also obtained using the Cambridge Gratings, Pelli-Robson CS Charts, Melbourne Edge Test (MET), and the High and Low Contrast Bailey-Lovie Letter Charts. Of the techniques evaluated, the High and Low Contrast Bailey-Lovie Letter Charts and the oscilloscope technique at the peak of the CSF exhibited the highest levels of sensitivity and specificity for differentiating between the POAG patients and normals. However, the relatively low levels of sensitivity and specificity obtained for the oscilloscope and chart tests overall indicate that, regardless of the pass/fail criterion selected, CS is unsuitable for screening for early POAG.

Age-related maculopathy. II: The nature of the central visual field loss.

This is the second of three papers dealing with age-related maculopathy (ARM) and its effects on visual function (Swann, P.G. and Lovie-Kitchin, J.E. Age-related maculopathy. I: A review of its morphology and effects on visual function. Ophthal. Physiol. Opt. 10, 149-158 (1990)). We investigated the nature or character of the central visual field loss in ARM and pre-age related maculopathy (PARM) and compared them with age-matched normal subjects. Central visual fields were examined using the Friedmann Visual Field Analyser, Mark II, the Bausch and Lomb Autoplot Tangent Screen and Amsler charts. The central visual field defects in ARM were predominantly paracentral with a relative sparing of foveal sensitivity. PARM subjects did not show significant visual field defects. However, three PARM subjects did show slight distortions with the Amsler charts. The third paper in this series will compare the efficacy of the three methods of visual field investigation in the detection of these defects.

Age-related maculopathy. I: A review of its morphology and effects on visual function.

Age-related maculopathy (ARM) is a leading cause of permanent vision loss in elderly people. ARM therefore constitutes an important public health problem which will increase in magnitude as the number of aged people in the general population becomes greater. The consequences of this condition are exacerbated by the fact that treatment, especially of the atrophic form of the disease, is ineffective. While laser photocoagulation may be helpful in the exudative form of ARM, there is often an inexorable progression towards severe vision loss in these patients. Therefore considerable attention needs to be paid to the aetiology of ARM, the potential for its prevention or delayed onset and its recognition through functional disturbances. This is the first of three papers dealing with ARM and its effects on visual function. We review its morphology and the visual disturbances that may ensue. The second and third papers will discuss the nature and detection of the central visual field loss due to ARM.

Investigation of central visual fields in patients with age-related macular changes.

The effect of early macular pigmentary and drusen changes on the central visual field was investigated in elderly patients with normal visual acuities. Visual field measurements were taken with the Humphrey Field Analyser using its 24-2 and 10-2 full threshold programs. No significant differences were found between two patients groups, one with and one without the macular changes. We conclude that fine pigmentary changes and hard drusen do not cause changes in visual functioning and can be accepted as normal age-related changes.

Temporal summation in age-related maculopathy.

We measured temporal summation in subjects with atrophic age-related maculopathy (ARM) and age-matched control subjects at photopic and scotopic luminance levels. Although the ARM subjects did show longer critical durations in each case these differences were not statistically significant. This result, in conjunction with our earlier work on temporal discrimination, indicates that the processes which are responsible for temporal summation of the eye (presumably located at the receptors) are more resistant to the degenerative processes of ARM than are those responsible for temporal discrimination. This may be because the simple threshold procedure used here does not sufficiently stress the temporal response system to show a deficit.

High and low contrast acuity and clinical contrast sensitivity tested in a normal population.

Visual acuities obtained with a high contrast Bailey-Lovie chart (HCBL) and a low contrast Bailey-Lovie chart (LCBL) were compared with clinical contrast sensitivity function (CSF) measurements in a group of normal subjects with a wide range of refractive errors. We found high and significant correlations for the measurements obtained with the visual acuity tests, and between measurements obtained with the acuity tests and the CSF chart. These results indicate that the CSF test provides little additional information as a screening test in routine practice, and could probably be restricted in its use to patients in whom ocular disease is suspected.