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PubMed1995

The illuminated high contrast macular grid: a pilot study.

BACKGROUND: Analysis of visual disturbances in the central 10 degrees provides valuable data for the low vision clinician. Amsler grid testing in the visually impaired can be poorly visible and it can be difficult to transcribe results. Automated perimeters will accurately map retinal defects, but the equipment is expensive and this technique is time consuming. An Amsler grid was modified using principles of luminance and contrast to improve its accuracy, and its efficacy was compared to an automated perimeter. METHODS: Eighteen visually impaired patients (28 eyes) were prospectively evaluated at the Emory Low Vision Laboratory. Each patient had three central threshold visual field tests: automated perimetry (Humphrey model 690), conventional Amsler Grid, and Illuminated High Contrast Macular Grid (IHCMG). The Humphrey central 10-2 threshold automated visual field examination was performed to map the patient's retinal function. RESULTS: The Humphrey analysis identified (mean +/- one standard deviation) 2.4 +/- 1.4 defects per patient with an average percent defect area of 33.4 +/- 14.8 degrees. The IHCMG technique was not significantly different from the Humphrey technique for identifying the number of defects (2.25 +/- 1.5) (p > 0.05) or the percent defect area (26 degrees +/- 20 degrees) (p > 0.05). The conventional Amsler grid technique significantly under-evaluated the retinal defects compared to the Humphrey analysis of the number of defects (p < 0.01) and percent area of defects (p > 0.001). CONCLUSIONS: The IHCMG technique can be used as a simple, rapid and accurate analysis of the central 10 degrees visual field in the low vision patient.

Aged↗
PubMed1985

Disease-associated visual image degradation and spherical refractive errors in children.

Retrospective clinical data from 496 eyes of 256 children attending a low vision clinic were analyzed to determine the relation between disease states which involve visual image degradation and refractive error. Refractive data from 1023 normal vision children were used as a control. The low vision children were grouped according to their disease classification and the acknowledged age-of-onset of their visual disability. It was found that there was an overall inability to emmetropize and a trend towards myopia. It was also observed that the diseases which led to myopia were associated with a peripheral or peripheral plus central impairment of vision and that those conditions in which foveal vision was primarily impaired showed a mild hypermetropic trend. Eyes in which the visual impairment was not congenital but occurred before the age of 3 years tended to develop hypermetropia. The deviation from emmetropia decreased with increasing age-of-onset of the visual impairment, as did the variation about the mean refraction. The plastic period for emmetropization is estimated to end at 8 to 9 years of age.

Adolescent↗
PubMed1991

Long-term prognosis of pigmentary glaucoma.

Outcome, prognosis and course of pigmentary glaucoma were studied in 38 patients (75 eyes). The mean age of the subjects at the time of diagnosis was 34.0 years and at the time of the study 44.1 years. The follow-up time ranged from 2 to 30 years with a mean follow-up time of 10.1 years. At the time of the study eighty-nine percent of the eyes had normal vision (0.7 or better), 3% slight impairment of vision (0.6-0.3), 5% low vision (0.2-0.05) and 3% were blind. Visual field defects were mild in 78%, moderate in 13% and severe in 8% of the eyes. One eye (1%) had normal fields. In 8 patients the stage of the field defects was asymmetrical between the two eyes. All were able to read at least monocularly with glasses. No one was blind, retired early or professionally limited because of pigmentary glaucoma. Thirty-nine eyes were on topical treatment. Fifteen eyes had additionally been treated with laser trabeculoplasty when the glaucoma could not be stabilized with topical treatment combined with systemic acetazolamide. Further twenty eyes had undergone trabeculectomy, 18 of them when medical treatment had failed and 2 following LTP. The non-involved eye of a patient suffering from a monocular disease was without treatment. The mean intraocular pressure at the time of the diagnosis was 33.5 mmHg (SD 10.4 mmHg) and at the final visit 17.5 mmHg (SD 3.4 mmHg). Four eyes were operated for cataracts and one for retinal detachment.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed2006

The Impact of Vision Impairment Questionnaire: an evaluation of its measurement properties using Rasch analysis.

PURPOSE: To explore the psychometric properties of the Impact of Vision Impairment scale (IVI) by using Rasch analysis. METHODS: Three hundred fourteen first-time referrals to low-vision clinics completed the 32-item IVI. The data were Rasch-analyzed with a partial credit model using RUMM2020 software (RUMM Laboratory, Perth, WA, Australia). The overall fit of the model, response scale, individual item fit, differential item functioning, unidimensionality, and person-separation reliability were assessed. RESULTS: Initially, 26 items displayed disordered thresholds. However, collapsing the response scale to three categories (4 items) and four categories (28 items) produced ordered response thresholds for all items. Four items with high proportions of missing responses, poor spread, high skewness, and deviation between observed and expected model curves were then removed. This adjustment produced overall fit to the Rasch model (item-trait interaction chi(2) = 118.3; P = 0.32). The final mean (SD) person and item fit residuals ere 0.06 (0.85) and -0.20 (1.45), respectively. The person-separation reliability was 0.9, indicating that the scale was able to discriminate between several different groups of participants. The revised scale was well targeted to the participants, with similar mean locations for items (0.00) and persons (0.16). A significant difference between participants of mild, moderate, and severe visual impairment (ANOVA; P 0.001) supported the criterion validity of the Rasch-scaled IVI. CONCLUSIONS: The results provide support for the measurement properties of the Rasch-scaled 28-item version of the IVI and of its potential for assessing outcomes of low-vision rehabilitation. A raw score-to-Rasch person measure conversion is supplied.

Adult↗
PubMed2006

Costs and utilization of end-stage glaucoma patients receiving visual rehabilitation care: a US multisite retrospective study.

PURPOSE: Glaucoma is a prevalent ophthalmologic disease and leading cause of blindness. A retrospective analysis was conducted to evaluate resources and costs for end-stage glaucoma patients receiving visual rehabilitation care (VRC). MATERIALS AND METHODS: A chart review was conducted in 3 United States VRC centers. Charts of patients with primary open-angle glaucoma as the primary cause of vision loss (1998 to 2003) were selected, yielding 81 records. Data were collected from patient-level billing and reimbursement records (ophthalmologist/optometrist visits, glaucoma medications, procedures, and specialized low-vision and glaucoma-related services). Visual rehabilitation services included utilization of low-vision devices, assessment of daily functioning, orientation and mobility training, and patient counseling. RESULTS: Mean age at baseline was 72.7 years [standard deviation (SD)=17.2, range: 29 to 95]. Of those with known sex (n=77), 55.8% were women. Medicare was the payer type for most patients (59.3%), whereas 20% had Medicaid. Mean number of visits was 7.1 (SD=6.1) in year 1 and 3.7 (SD=4.2) in year 2, for an annual mean of 5.4 (SD=5.0) visits overall. Total mean cost per patient in year 1 was greater than year 2 [$2170 (SD=$2252) vs. $1202 (SD=$1080), respectively]; of the total 2-year costs, 15% were VRC, 37% ophthalmology care, and 48% pharmacy. Analysis of nonpharmacy costs revealed that VRC accounted for 28% and ophthalmology for 72%. CONCLUSIONS: End-stage glaucoma is associated with appreciable resource utilization and costs, because of both vision rehabilitation and ophthalmology care. Advanced primary open-angle glaucoma has a substantial cost-of-illness, warranting improved management in early stages of disease.

Adult↗
PubMed2003

A survey of blindness and poor vision in leprosy patients.

OBJECTIVE: To determine the prevalence, cause and distributions of blindness and poor vision in patients with leprosy. METHODS: An epidemiological survey of blindness and poor vision among 1045 cases of leprosy was carried out in Taixing City of Jiangsu Province, China. RESULTS: The prevalence of bilateral blindness was 7.67%, unilateral blindness 4.4%, bilateral poor vision of various degrees 9.28% and unilateral poor vision 5.84%. The prevalence of eye complications varied significantly among different groups of patients; females had a higher prevalence than males, multibacillary patients higher than paucibacillary patients, and in-patients higher than out-patients. Corneal disease was the most common cause of blindness in study groups, followed by iritic disease and cataract; while the main cause of poor vision was cataract, then corneal and iritic diseases. Treatable blindness accounted for 62.7% of the cases and treatable poor vision for 88.6% of the patients studied. 56.62% of cases with eye complications expressed their willingness to be treated. CONCLUSIONS: Although prevention and treatment of low vision and blindness in leprosy patients is very hard, it is necessary for doctors and medical workers to make clear of the factors to cause low vision and blindness, especially those in leprosy patients so that some measures for prevention and treatment of the disease could be taken accordingly.

Adult↗
PubMed1984

Contrast sensitivity. The visual rehabilitation of the patient with macular degeneration.

Contrast sensitivity functions (CSFs) were determined on a large group of patients with macular degeneration to better assess qualitative aspects of their residual vision. Contrast sensitivity was also determined through the telescopic low-vision aids of selected patients. In general, the patients have a substantial loss of contrast sensitivity for all spatial frequencies. The preferred eye of these patients appeared to be related to the peak of the CSF more so than to the Snellen visual or resolution acuity. Through the low-vision aid, not only was there the predictable increase in resolution acuity but also a notable increase in peak contrast sensitivity. These findings indicate that contrast sensitivity testing provides useful information that should be considered in the visual rehabilitation of the patient with macular degeneration.

Aged↗
PubMed1997

Top-down learning of low-level vision tasks.

Perceptual tasks such as edge detection, image segmentation, lightness computation and estimation of three-dimensional structure are considered to be low-level or mid-level vision problems and are traditionally approached in a bottom-up, generic and hard-wired way. An alternative to this would be to take a top-down, object-class-specific and example-based approach. In this paper, we present a simple computational model implementing the latter approach. The results generated by our model when tested on edge-detection and view-prediction tasks for three-dimensional objects are consistent with human perceptual expectations. The model's performance is highly tolerant to the problems of sensor noise and incomplete input image information. Results obtained with conventional bottom-up strategies show much less immunity to these problems. We interpret the encouraging performance of our computational model as evidence in support of the hypothesis that the human visual system may learn to perform supposedly low-level perceptual tasks in a top-down fashion.

Algorithms↗
PubMed1997

Visual-field measurements and driving eligibility.

BACKGROUND: A 50-year-old black man with an ocular history of open-angle glaucoma was seen for a vision rehabilitation examination, with goals of improving his vision for work and determining his eligibility for driving. He was referred to the clinic through state services for the visually impaired. METHODS: A low-vision evaluation was performed and baseline information was obtained, including distance- and near-visual acuities, visual fields, and subjective refraction. This information was used to determine if he was eligible for services and if any low-vision devices would benefit him. RESULTS: The patient demonstrated moderately decreased visual acuity in the right eye (6/15) and very reduced visual acuity in the left eye (6/120). His visual fields varied depending on the test performed, ranging from 85 degrees to 140 degrees horizontal diameter. He was able to remove his spectacles and perform near tasks quite well. CONCLUSIONS: The patient was counseled that if he used one of the field tests he could qualify for services, but if he chose the other test he would qualify for driving and not qualify for services. The ramifications of using different field tests and understanding their parameters when assessing eligibility for services and benefits can be significant.

Automobile Driving↗
PubMedDate not supplied

[Transcutaneous electrostimulation of the primary elements of the visual system in children after the extraction of a congenital cataract].

Courses of transcutaneous electrostimulation of the visual analyzer periphery according to E. B. Kompaneets were administered to 31 children (56 eyes) aged 4 to 12 because of low vision acuity after congenital cataract extraction. The amplitude of stimulating pulses was from 150 to 400 microA. The first course consisted of 5-8 sessions, repeated courses of 4 sessions. The results were assessed by vision acuity check-ups and recordings of visual [correction of auditory] evoked potentials (AEP). Vision acuity improved from 0.1 to 0.9 after a course of treatment. AEP amplitude was reduced in all the patients to 15.4 microV on an average, the time of the pulse conduction in the auditory system was normal (113.2 ms). Electrostimulation effects on the AEP were negligible. Electrostimulation may be recommended to children with low vision acuity and low values of the AEP amplitude after congenital cataract extraction.

Cataract↗
PubMedDate not supplied

The global burden of trachomatous visual impairment: II. Assessing burden.

This paper builds on results of a previous paper on the prevalence of trachomatous visual impairment as the foundation for assessing the global burden of trachomatous blindness and low vision: approximately 2.9 million cases of trachomatous blindness and 3.8 million low visioned corresponding to a global prevalence of trachomatous visual impairment equal to 1.3/1,000 in 1990 was estimated. For each visually impaired person, the years of life lost due to premature mortality and the years lived in a handicapped state are added to yield a single measure of disease burden called handicap adjusted life years (HALYs). Age, gender and visual acuity group specific HALYs are multiplied by the prevalence of trachomatous visual impairment to yield an estimate of the global burden of trachoma visual impairment equal to 80 million HALYs. Analysis of the distribution of the global burden by age, gender, visual acuity and region provide direction for trachoma research and programme priorities. Sensitivity analysis reveals that the burden estimates of trachomatous visual impairment may vary from as low as 15 million to as high as 500 million HALYs. Given this degree of variability, burden comparisons with other blinding and non-blinding conditions for the purposes of identifying health sector priorities may be misleading.

Adolescent↗
PubMed1993

The epidemiology of blindness and visual loss in Hamar tribesmen of Ethiopia. The role of gender.

We conducted a population-based survey in the Hamar tribe of Ethiopia to assess the problem of blindness and ocular morbidity. Blindness was detected in 1.9% of the Hamar. Among the age group 40 and over < 1.0% of men and 13% of women were blind. Women with low vision or blindness comprised 30% of all women while men with low vision or blindness only comprised 8% of men in the age stratum. Cataract is responsible for the excess blindness in women. Even mild visual disability is less common in men. In Hamar society men have two roles: as herders and as warriors. Warriors with visual loss will be less successful in defending themselves. We suggest that Hamar men who develop visual loss have increased mortality compared to women with visual loss. Vision loss in women does not appear to have life-threatening consequences. Cessation of hostilities between the Hamar and their neighbours could, conceivably, lead to an 'increase' in the incidence of vision loss among men.

Adolescent↗
PubMed2002

[Prevalence of glaucoma and normal intraocular pressure among adults aged 50 years or above in Shunyi county of Beijing].

OBJECTIVE: To estimate the prevalence of glaucoma and normal intraocular pressure among older adults aged 50 years or above in Shunyi county of Beijing. METHODS: Cluster sampling was used in randomly selecting 5 555 individuals aged 50 years or above in Shunyi county in fall, 1996. The examines received the visual acuity and general eye examination, and in the mean time attention was paid to rule out glaucoma, including inquiry of family and personal history of glaucoma, measurement of anterior chamber depth and intraocular pressure, examination of the optic disc. RESULTS: The examinations about glaucoma were finished in 4 880 individuals. The response rate was 87.85%. In this population, the prevalence of glaucoma was 2.07%. The prevalence of the primary angle closure glaucoma, primary open angle glaucoma and secondary glaucoma was 1.66%, 0.29% and 0.12% respectively. The prevalence of the variety of glaucoma was increasing by aging. The visual function in 64.00% of glaucoma patients was damaged in certain degree. The rate of the bilateral blindness among glaucoma patients was 16.00%. These patients were all 60 years old or above. The rates of unilateral blindness, bilateral allow vision and unilateral low vision were 17.00%, 23.00% and 8.00%, respectively. The mean and standard deviation of the intraocular pressure among the normal eyes were (13.53 +/- 2.20)mm Hg(1 mm Hg = 0.133 kPa). The tendency of the mean normal intraocular pressure is decreasing by aging. CONCLUSIONS: Glaucoma is a serious eye disease leading to blindness according to the prevalence and the visual function of the glaucoma patients. The mean intraocular pressure among the normal eyes is lower than the expected value. The lower value (18 mm Hg) of the upper limited normal intraocular pressure should be used in screening glaucoma patients among the older adults.

Age Factors↗
PubMed1987

An evaluation of visual acuity with the Corning CPF 527 lens.

The effect of visual acuity on the Corning 527 photochromatic lens was studied for a group of 50 normal patients and 53 low vision patients. Visual acuity was measured at 10 feet using three Lighthouse Low Vision Distance Acuity Charts, whose letters were randomly arranged. Acuity measurements were performed under three conditions: through a plano lens, a Corning 527 lens and an equivalent neutral density filter, each placed over the best corrective lenses. No statistically significant difference in acuity measurements were found between these three conditions.

Absorption↗
PubMed2005

Causes of severe visual impairment and blindness in schools for visually handicapped children in Iran.

AIMS: This survey was conducted on children in schools for the blind in Tehran (from 2002 to 2003) to determine the causes of severe visual impairment and blindness and to identify preventable and treatable conditions. METHODS: The study was performed on 362 students at different grades in three schools for the blind. Patient sex, age, family history of blindness or low vision, visual acuity, causes of blindness, and treatable and preventable conditions were studied. RESULTS: Of the 362 cases, 210 (58%) were boys and 152 (42%) were girls. Mean age was 13.5 (SD 4) years. Severe visual loss was seen in 80.9%. Retinal diseases were the most common cause for low vision (51%); cataract, optic nerve atrophy, corneal and anterior segment diseases, glaucoma, anophthalmia, and globe malformations were other major causes of blindness. Treatable aetiologies and positive family history of blindness were seen in 25.7% and 36% of the patients, respectively. The incidence of preventable diseases, excluding familial disorders, was low. CONCLUSION: In addition to the prevention and treatment of some conditions, premarital genetic counselling and family planning control in families with inherited diseases could decrease the number of blind children in the future in Iran.

Adolescent↗
PubMed1997

[Contrast sensitivity of several blindness-inducing eye diseases and the influence of tinted filter lens].

OBJECTIVES: To evaluate the effects of tinted filter lens on the visual rehabilitation of blind and low vision patients induced by optic nerve atrophy, glaucoma and retinitis pigmentosa. METHODS: The contrast sensitivity of 22 cases with optic nerve atrophy (34 eyes), 17 glaucoma (30 eyes), 18 retinitis pigmentosa (30 eyes) and 30 normal people (60 eyes) with and without yellow and red filter lens was tested. RESULTS: The results demonstrated that a yellow filter lens could improve the optic nerve atrophy patient's contrast sensitivity at 1.5, 3, 6 and 12 c/deg, while a red filter lens could increase the contrast sensitivity at limited spatial frequencies, but it could also decrease the contrast sensitivity at some other spatial frequencies. CONCLUSION: Yellow filter lens could be applied as a non-optical visual aid in the visual rehabilitation of the blind and low vision patients induced by these three diseases, as the above results show contrast sensitivity improvement in the low spatial frequency and the peak of the contrast sensitivity curves.

Adolescent↗
PubMed1990

The Edridge-Green lecture vision at low light levels: role of spatial, temporal and contrast filters.

One of the most impressive features of our vision is the fact that we see with good sensitivity over such a large range of light levels. This process is usually termed light adaptation by which it is meant that the sensitivity of individual neurones within the retina automatically adapts to suit the prevailing lighting conditions. Although this is usually thought about in terms of single neurones, its effectiveness is greatly enhanced by the fact that individual neurones have distinctive properties. The fact that individual neurones can be considered as acting as neural filters along the dimensions of size, time, orientation and contrast means that visual information is distributed across the whole neuronal population which in turn plays an important role in extending our dynamic range. In this paper the distributed nature of visual processing is emphasized and its role in extending the range of light levels over which we can see is highlighted.

Adaptation, Ocular↗
PubMed2007

Public health impact of neovascular age-related macular degeneration treatments extrapolated from visual acuity.

PURPOSE: To estimate the potential public health impact of treatment with new medications intended to preserve vision in patients with neovascular age-related macular degeneration (AMD). METHODS: A Markov model was used to simulate the natural history of AMD over the lifetime of patients with diagnosed neovascular AMD from clinical trials and epidemiologic surveys. It applied to a cohort of patients aged 75 years, with newly diagnosed neovascular AMD in one eye, whose visual acuity was 0.7 logMAR. Probabilities were calculated for the risk of AMD in the remaining eye and for premature mortality. Results of the model were expressed as the duration of low vision (worse eye VA>1.0 and better eye VA>0.7 logMAR) and blindness (bilateral VA >1.0 logMAR). Health consequences of blindness and low vision were estimated for depression, hip fractures, institutionalization, and life expectancy. RESULTS: For AMD patients with a 50% probability of VA >1.0 logMAR at 1 year, in one eye, the probability of lifetime bilateral blindness was >47%. The patients would live approximately 7 years with monocular vision >1.0 logMAR and an additional 4 years with bilateral blindness and a >15% probability of depression due to AMD. Life expectancy was decreased by approximately 2 years, >90/1000 patients would sustain a new hip fracture, and 1.5% of the patients would require institutional care for visual impairment due to AMD. To achieve a defined public health outcome (visual impairment and consequent comorbidity), it was necessary for the VA effectiveness of new treatments to increase in parallel with disease severity. CONCLUSIONS: Comorbidity related to visual impairment contributes significantly to the public health impact of AMD. Aggressive lesions need highly effective treatments. Models may be used to compare the public health impact of placebo-controlled clinical trial results.

Aged↗