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Content and legibility of outpatient appointment letters.

OBJECTIVES: To assess whether outpatient appointment letters can be read by visually impaired people and to examine the information they contain. DESIGN: Postal survey of hospital outpatient departments in England and Wales. MAIN OUTCOME MEASURES: Royal National Institute for the Blind (RNIB) guidelines for print size and weight, colour contrast between paper and print and use of capital letters; checklist of items of information contained. RESULTS: We asked 295 hospital trusts for copies of their outpatient appointment letters, and received 158 samples. In 87% the print size was too small to be read by visually impaired people. All used contrasting paper and print colour, but 13% used too light a print weight. Twelve percent used capital letters throughout which are harder to read than lower case lettering. Information content was variable. Twenty letters specifically designed for low vision clinics were assessed separately; all used adequate print size and weight, but 55% used capitals throughout. CONCLUSIONS: Most outpatient appointment letters are not easily read by visually impaired people. Important items of information are omitted from some letters.

Ambulatory Care↗

[A simplified screening test for the identification of individuals with diminished 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↗

Sociodemographic aspects and systemic diseases of cataract patients.

Sociodemographic analysis of 351 consecutive cataract patients operated on at the Oulu University Hospital in 1990 revealed that 30.0% of the patients lived alone at home, 62.0% lived with some other person and 7.9% were in institutions. The mean age was 70.6 +/- 12.4 years, the sex distribution (62.7% women, 37.3% men) corresponded with that in the general population of the same age. 78.8% of the patients had had surgery on the first eye, 29.0% of them had low vision or blindness (visual acuity less than 0.3 in the better eye). In the second eye surgery group (21.2% of the patients) low vision or blindness was found in 13.0%. Low vision was more common in institutionalized patients and in those with restricted mobility. In 80.9% of the operated eyes and in 41.5% of the fellow eyes the visual acuity was less than 0.3. 76.6% of the patients had medication for cardiovascular diseases, diabetes, asthma or mental disorders. Based on this survey the demand for cataract surgery is expected to increase in coming years. The majority would be suitable for day case surgery, but for patients living alone, having restricted mobility, poor general health, poor vision in the fellow eye or long distance to the hospital, hospitalization still seems to be a better alternative.

Adult↗

Prevalence of visual impairment among adults in China: the Beijing Eye Study.

PURPOSE: To estimate the prevalence and distribution of blindness and low vision in Northern China. DESIGN: Population-based cohort study. METHODS: The Beijing Eye Study included 4438 subjects with an age of 40+ years. Mean age was 56.2 +/- 10.6 years (range, 40 to 101 years). RESULTS: Forty-three (1.0%) individuals had low vision (<20/60 and >/=20/400 best-corrected vision), and 17 (0.4%) individuals were blind (best-corrected visual acuity in the better-seeing eye <20/400). Low vision/blindness were significantly associated with age (P < .001), myopic refractive error (P < .001), and level of educational background (P = .035). It was not associated with gender (P = .76) and rural vs urban area (P = .88). CONCLUSIONS: Blindness or low vision affects approximately one in 100 Chinese older than 40 years. An estimated 4.1 million Chinese older than 40 years have low vision, and an estimated 1.6 million Chinese older than 40 years are blind.

Adult↗

Application of stochastic measurement models to visual function rating scale questionnaires.

PURPOSE: To test hypotheses that low vision patient responses to visual function rating scale questionnaires conform to an additive conjoint structure and that the Likert score is a sufficient statistic for the latent patient trait; to compare results for two competing stochastic measurement models; and to determine if different questionnaires measure the same construct in low vision patients. METHODS: Visual function rating scale questionnaires were administered to 284 low vision subjects by telephone. Each subject was administered two of four questionnaires: ADVS, NEI VFQ-25 plus supplement, expanded VAQ, and VF-14. RESULTS: Data were analyzed with the Muraki item response model and the Andrich measurement model. The estimates of latent person, item, and response threshold measures from the two models are linearly related. The Muraki model produced a better overall fit to the item response data, the Andrich model produced a better fit to the average ratings for each person and item. Fit statistics for the Andrich model were proportional to the item-dependent discrimination parameter in the Muraki model. The ADVS was the most accurate measure and the NEI VFQ was the least. Reliability was similar for all four instruments. Person measures for each pair of instruments were linearly related indicating that all four instruments measured the same construct. The person measure estimate from the Andrich model is monotonic with the average rating. That relationship suggests a transformation of the Likert score that can correct the floor and ceiling effects in rating scale data. CONCLUSIONS: Patient responses to all four questionnaires conform to varying degrees to an additive conjoint structure. The Likert score is a sufficient statistic for the ADVS and the VAQ, but not for the NEI VFQ or VF-14. All four instruments measure the same construct in the low vision population, but they differ in measurement accuracy and precision.

Adult↗

The effect of laser in situ keratomileusis on low contrast vision.

PURPOSE: To determine the effects of laser in situ keratomileusis (LASIK) on low contrast visual acuity. METHODS: Thirty eyes of 15 LASIK patients with myopia and astigmatism were evaluated preoperatively, and 1 and 3 months postoperatively. High contrast visual acuity (HCVA), low contrast visual acuity (LCVA), and contrast threshold were determined. RESULTS: Mean spherical correction (SE) was -3.24 +/- 1.90 D; 16 eyes had a mean SE between -1.00 and -3.00 D, and 14 eyes were between -3.25 and -6.50 D. There was no significant change in HCVA observed at 1 and 3 months in any eye. There was a decrease in LCVA in eyes with a correction >3 D SE at 1 month (P=.04), which returned to normal at 3 months (P=.13). There was an increase in the contrast threshold at 1 month (P=.016). When eyes were divided into groups, those with >3D SE correction had an increase in contrast threshold at 1 month (P=.002); no change was seen in eyes with <3D SE correction (P=.15). At 3 months, contrast threshold was similar to baseline values in all eyes (P=.226). CONCLUSION: LASIK transiently decreased low contrast visual function in patients with greater than 3.00 D of myopic correction.

Adult↗

Visual disabilities among diabetics in Oman.

OBJECTIVE: The magnitude, determinants of visual impairment, bilateral blindness and low vision among diabetics in Oman were estimated as part of Oman Diabetic Eye Study 2002. This study presents the outcomes and additional risk of visual impairment in diabetics. METHODS: A cross-sectional study of 2,520 randomly selected diabetics was conducted in 2002 in 10 regions of Oman. The sample was represented by 5,564 diabetics referred for eye checks. Ophthalmologists noted the vision and ocular manifestations of diabetes. Physicians reported the systemic manifestations of diabetes. The magnitude of visual disabilities, bilateral blindness, legal blindness and low vision were estimated and compared to the rates in the population. RESULTS: The prevalence of visual impairment in diabetics was 28.4% (95% confidence interval [CI] 27.20-29.57). It was 34.6% (95% CI 32.93 to 36.32) in females and 21.2% (95% CI 19.59 to 36.32) in males. The prevalence increased in age. The prevalence of bilateral blindness (vision <0.05) was 0.7%, legal blindness 9.8% (vision <0.1) and low vision 27.7% (vision <0.5). CONCLUSION: The risk of visual impairment is 25 times more in diabetics than in the Omani population. Therefore, to prevent further increase of visual disabilities, the national health program should prioritize the eye care in diabetics and the predictors of visual disabilities should be further investigated.

Cross-Sectional Studies↗

Treating with spectacle lenses: a novel idea!?

A design approach to low-vision device development-vision multiplexing-was introduced recently. This approach has been applied successfully to the design of novel electronic and optical low-vision aids. This paper discusses the application of the vision-multiplexing concept to spectacle lens design to address issues of low vision and to resolve problems of color discrimination and glare in driving. Because spectacles are considered a fashion accessory as much as they are a vision aid, cosmetic considerations are critical to the design of such aids. Spectacle-borne devices that are not concealed or attractive are unlikely to be used widely. Efforts to combine the functionality of vision multiplexing with improved appearance are illustrated.

Biomedical Engineering↗

[Age-related macula degeneration and diabetic retinopathy -- differences in optic rehabilitation].

BACKGROUND: Age-related macular degeneration (AMD) and diabetes mellitus are the major contributing causes of visual impairment in the industrial nations. This study shows how far visual acuity (VA) and magnification demand (MD) influence the selection of suitable low vision aids. Based on this information, differences regarding the spectrum of prescribed magnifying devices between both patient groups will be presented. MATERIALS AND METHODS: Between January 2003 and October 2004, a total of 2500 patients was seen in our Low Vision Department. Among them were 1198 patients with AMD (48 %) and 296 visually impaired patients because of diabetic ocular involvement (12 %). In every patient, best corrected distance and near VA as well as the required MD were measured. Finally, matching of magnifying aids and discussing aspects of professional and social rehabilitation were the main parts of our interdisciplinary Low Vision Service. RESULTS: In AMD patients, the average of best corrected distance VA at the better eye was 0.24, the best corrected near VA was 0.19. In diabetes patients, the average of best corrected distance VA at the better eye was 0.28, the best corrected near VA was 0.22. The required mean MD was 4.0 x (related to the reading of newspaper text) compared to 7.6 x in patients with AMD. In 94 % of the visually impaired diabetes patients, optical magnifiers could be prescribed (e. g. magnifying eyeglasses, telescopes, monoculars, Galelean and Keplerian systems), whereas electronic devices were necessary in only 6 %. In comparison, 14.8 % of the patients with AMD had to be provided with electronic systems. CONCLUSIONS: In 94 % of the visually impaired patients caused by diabetes, reading ability could be restored using optical low vision aids. In AMD patients, this could be achieved in only 85.2 %. This fact can mainly be explained with the negative effect of absolute central scotomas on reading speed in AMD patients which leads, compared to diabetes patients, to elevated magnification factors. Therefore, the choice of certain magnifying devices depends not only on VA, but has mainly to be evaluated based on the individual MD.

Aged↗

The etiology of vision impairment in target population.

PURPOSE: research the etiology of vision impairment in target persons over 45 years old in Doumen county, Guangdong province. METHODS: Depending on the prevalences of the blindness among the person aged over 50 years, the theoretic sample rate is 1,000/4,8733 x 100% = 2.05%. The 8 districts were divided into 3 parts according to the local economic situation and the proportion of the population in the areas. In fact, the sampling rate is 932/10055 = 88.34%. RESULTS: We found that impairment < 0.3 accounted for 10.94%. The prevalence of bilateral blindness and low vision was 1.61% and 3.22%, respectively. Both prevalences of blindness and low vision were increased with age. The leading cuase of blindness was cataract (45.2%). The second was corneal opacity (16.7%). Prevalences of the low vision and the blindness were higher in females than in males (P < 0.005). CONCLUSIONS: Curable and preventable diseases were the leading cause for the blindness (70%). Prevalences of blindness and the low vision increase with age. We will continually follow up the population over 50 years of age in Doumen county.

Age Factors↗

Sensory supports for the visually impaired.

Because patients are spending less time in the hospital, nurses must use specific techniques to address visual loss and assist low-vision patients with discharge planning. A majority of low-vision patients can distinguish the color red; this can be used to code the tops of medication bottles. When speaking to a low-vision patient, talk softly and teach information in accordance with the patient's comprehensive ability. Attending to the tactile sense should be incorporated into daily care.

Humans↗

Evaluation of a national eye care programme: re-survey after 10 years.

AIM: To re-survey the Gambia after an interval of 10 years to assess the impact of a national eye care programme (NECP) on the prevalence of blindness and low vision. METHOD: Comparison of two multistage cluster random sample surveys taking into account the marked increase in population in the Gambia, west Africa. Samples of the whole population in 1986 and 1996 were taken. The definition of blindness is presenting vision less than 3/60 in the better eye, or visual fields constricted to less than 10 degrees from fixation. Low vision is less than 6/18 but 3/60 or better. Causes of blindness were determined clinically by three ophthalmologists. RESULTS: The crude prevalence of blindness fell from 0.70% to 0.42%, a relative reduction of 40%. During the same 10 year period, the population increased by 51% from 775 000 to 1 169 000. When the results were standardised for age, a west to east gradient was found for changes in risk of blindness over the 10 year period. This matched the phased west to east introduction of the NECP interventions. There was a modest but significant increase in the risk of low vision across the whole country. CONCLUSIONS: The overall reduction in risk of blindness, in those areas where the NECP has been active, appears to justify the programme and the support of donor organisations. The low vision cases due to cataract must now be addressed.

Blindness↗

[Utilization of optical devices and equipments by students with visual impairment].

PURPOSE: To verify perceptions and conduct of students with visual impairment regarding devices and equipment utilized in schooling process. METHODS: A transversal descriptive study on a population of 12-year-old or older students in schooling process, affected by congenital or acquired visual impairment, inserted in the government teaching system of Campinas during the year 2000. An interview quiz, created based on an exploratory study was applied. RESULTS: A group of 26 students, 46% of them with low vision and 53.8% affected by blindness was obtained. Most of the students were from fundamental teaching courses (65.4%), studying in schools with classrooms provided with devices (73.1%). Among the resources used in reading and writing activities, 94.1% of the students reported they used the Braille system and 81.8% reported that the reading subject was dictated by a colleague. Most of the students with low vision wore glasses (91.7%), and 33.3% utilized a magnifying glass as optical devices. Among the non-optical devices, the most common were the environmental ones, getting closer to the blackboard (75.0%) and to the window (66.7%) for better lighting. CONCLUSIONS: It became evident that students with low vision eye-sight made use of devices meant for bearers of blindness, such as applying the Braille system. A reduced number of low vision students making use of optical and non-optical devices applicable to their problems were observed, indicating a probable unawareness of their visual potential and the appropriate devices to improve efficiency.

Child↗

Visual impairment and the useful field of vision.

The aim of this study was to measure the useful field of vision (UFoV) in people with visual impairment and to compare results with clinical measures of vision. UFoV, visual acuity, contrast sensitivity and visual fields were measured in 36 participants with low vision and 22 age-matched controls in two age groups. For both the low vision and control groups the presence of distractors (cluttered field) increased the error rates on our UFoV measure but there was no significant effect of the presence of a central task (divided attention). Participants with low vision made more errors on UFoV than did controls, but this difference disappeared once their visual field defects were accounted for. By multiple regression analysis, age, visual fields and contrast sensitivity were shown to predict the different UFoV scores. As for observers with normal vision, standard clinical visual field tests may not fully describe the difficulties that may be encountered by people with visual impairment undertaking tasks in the cluttered environments and multiple demands of everyday life.

Adult↗

Lateral interactions between targets and flankers in low-level vision depend on attention to the flankers.

Detection of an oriented visual target can be facilitated by collinear visual flankers. Such lateral interactions are thought to reflect integrative processes in low-level vision. In past studies, the flankers were task-irrelevant, and were typically assumed to be unattended. Here we manipulated attention to the flankers directly, by requiring observers to judge the relative alignment of two flankers while ignoring a second flanker-pair. Under identical stimulus conditions, attended flankers produced typical lateral interactions, but ignored flankers did not. These data show that lateral interactions can depend on attention to the flanking context, revealing the functional consequences of attentional modulation in low-level vision.

Humans↗

Preferred retinal locus and reading rate with four dynamic text presentation formats.

BACKGROUND: Electronic display devices hold the potential to improve access to written material by people with low vision. For those with central field loss, the optimal form of electronic text presentation may vary according to the location of the preferred retinal locus, but this has never been investigated. In this study, we examined the relationship between preferred retinal locus location and reading rate for four electronic display formats (rapid serial visual presentation, horizontal scroll, vertical scroll, and page). METHODS: Short sentences were presented in each format to 35 low-vision (most with central field loss) and 14 age-matched control subjects. Subjects read aloud to determine maximum oral reading rate and read silently to determine preferred silent reading rate. RESULTS: With the exception of page format, maximum oral reading rates were faster than silent preferred reading rates for both groups of subjects. For the low-vision group, there was no significant difference in maximum oral reading rates between the four display formats; and when reading at a preferred silent rate, page format was faster than the other three formats. Though page format was read more quickly, half of the low-vision subjects preferred the horizontal-scroll format. Contrary to our predictions, there was no significant effect of preferred retinal locus location (vertical vs. lateral) on reading rate and no significant interaction between preferred retinal locus location and display format. CONCLUSIONS: The differences between maximum oral and preferred silent reading rates and the lack of a relationship between reading rates and preferred display format reinforce the importance of patient preference in the evaluation and selection of a device or display format during rehabilitation.

Adult↗

Pediatric and adolescent population with visual impairment: study of 385 cases.

OBJECTIVE: To analyze data on the pediatric population attending the Ophthalmologic Clinic's Low Vision Service at the São Paulo University Medical School. METHODS: Low vision ophthalmologic assessment, from April 1998 to December 2003, of 385 children and adolescents with mean age of 7 years; 51.7% males and 48.3% females. The main data analyzed were age, diagnosis, anatomic site of the ocular injury, visual acuity, and prescription of optical aids. RESULTS: 45.4% were below 6 years, and 54.6% were between 6 and 16 years. 35.5% experienced moderate visual impairment, 26% had severe visual impairment, 8.6% had profound visual impairment, 10.6% were near blind, and 1.6% were blind. The main causes of visual impairment included congenital glaucoma (30.6%), macular retinochoroiditis due to congenital toxoplasmosis (16.7%), congenital cataract (12.8%), retinal and macular inherited disorders (11.7%), and optic atrophy (9.8%). Among school-age children, 52.9% received a prescription of optical aids. The most widely used optical aids for distance were 2.8 X 26 (34.4%); 4.2 X 12 (30.3%); and 6 X 17 (26.8%) telescopic systems. The most frequently prescribed optical aid for near vision was the 2x magnifying bar (33.3%). CONCLUSIONS: There is a need for prevention of primary (congenital infections), secondary (congenital glaucoma and retinopathy of prematurity), and tertiary (congenital cataract) visual impairment. The prescription of optical aids for school-age children will help them perform better at school and contribute to their social inclusion.

Adolescent↗

Causes of blindness and visual impairment in urban and rural areas in Beijing: the Beijing Eye Study.

OBJECTIVE: To evaluate the causes of visual impairment and blindness in adult Chinese in an urban and rural region of Beijing, China. DESIGN: Population-based prevalence survey. PARTICIPANTS: From a rural region and an urban region of Greater Beijing, 4439 of 5324 > or=40-year-old invited subjects participated in the study (response rate, 83.4%). Using the World Health Organization (WHO) standard and the United States standard, blindness was defined as best-corrected visual acuity (BCVA) in the better-seeing eye of <20/400 and of <2/20, respectively, and visual impairment was defined as best-corrected vision of <20/60 and > or =20/400, and of <20/40 and > or =2/20, respectively. METHODS: Determination of BCVA, pneumotonometry, frequency doubling perimetry, evaluation of photographs of the fundus and lens, and clinical examination. MAIN OUTCOME MEASURE: Causes of visual impairment and blindness. RESULTS: Visual acuity measurements were available for 8816 eyes of 4409 subjects (99.3%). Using the WHO standard and the U.S. standard, 49 (1.1%) subjects and 95 (2.2%) subjects, respectively, had low vision, and 13 (0.3%) subjects and 15 (0.3%) subjects, respectively, were blind by definition. Taking the whole study population, the most frequent cause of low vision/blindness was cataract (36.7%/38.5%), followed by degenerative myopia (32.7%/7.7%), glaucoma (14.3%/7.7%), corneal opacity (6.1%/15.4%), and other optic nerve damage (2.0%/7.7%). Age-related macular degeneration (AMD) (2.0%/7.7%) and diabetic retinopathy (0%/7.7%) were responsible for a minority of cases. In subjects 40 to 49 years old, the most frequent cause of low vision and blindness was degenerative myopia. In the 50- to 59-year age group, the most frequent cause was cataract, followed by degenerative myopia. In the 60- to 69-year-old subjects and the > or =70-year group, the most frequent cause of low vision and blindness was cataract, followed by degenerative myopia and glaucoma. CONCLUSIONS: The most frequent cause of low vision and blindness in adult Chinese is cataract, followed by degenerative myopia and glaucomatous optic neuropathy, with degenerative myopia dominating in younger groups and cataract dominating in elder groups. In contrast to studies in Western countries, AMD and diabetic retinopathy appear to play a minor role as a cause of visual impairment in elderly Chinese.

Adult↗