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Benefits of electronic vision enhancement systems (EVES) for the visually impaired.

PURPOSE: To examine whether objective performance of near tasks is improved with various electronic vision enhancement systems (EVES) compared with the subject's own optical magnifier. DESIGN: Experimental study, randomized, within-patient design. METHODS: This was a prospective study, conducted in a hospital ophthalmology low-vision clinic. The patient population comprised 70 sequential visually impaired subjects. The magnifying devices examined were: patient's optimum optical magnifier; magnification and field-of-view matched mouse EVES with monitor or head-mounted display (HMD) viewing; and stand EVES with monitor viewing. The tasks performed were: reading speed and acuity; time taken to track from one column of print to the next; follow a route map, and locate a specific feature; and identification of specific information from a medicine label. RESULTS: Mouse EVES with HMD viewing caused lower reading speeds than stand EVES with monitor viewing (F = 38.7, P <.001). Reading with the optical magnifier was slower than with the mouse or stand EVES with monitor viewing at smaller print sizes (P <.05). The column location task was faster with the optical magnifier than with any of the EVES (F = 10.3, P <.001). The map tracking and medicine label identification task was slower with the mouse EVES with HMD viewing than with the other magnifiers (P <.01). Previous EVES experience had no effect on task performance (P >.05), but subjects with previous optical magnifier experience were significantly slower at performing the medicine label identification task with all of the EVES (P <.05). CONCLUSIONS: Although EVES provide objective benefits to the visually impaired in reading speed and acuity, together with some specific near tasks, some can be performed just as fast using optical magnification.

Aged↗

Visual impairment and unintentional injury mortality: the National Health Interview Survey 1986-1994.

PURPOSE: To examine the relationship between reported visual impairment and unintentional injury mortality. DESIGN: Mortality linkage study of a population-based survey. METHODS: Mortality linkage through 1997 of 116,796 adult participants, aged 18 years and older, from the 1986 to 1994 National Health Interview Survey was analyzed with respect to reported visual impairment using Cox regression models. The average follow-up was 7.0 years, and 295 unintentional injury deaths were identified. After controlling for survey design, age, sex, and the presence and number of eye diseases, participants with severe, bilateral visual impairment were at increased risk of death relative to participants without visual impairment (hazard ratio: 7.4; 95% confidence interval: 3.0-17.8). CONCLUSIONS: Our data provide evidence that severe, bilateral visual impairment is associated with an increased risk of unintentional mortality among adults in the United States.

Adolescent↗

Complex visual hallucinations in the visually impaired: the Charles Bonnet Syndrome.

Visually impaired patients may experience complex visual hallucinations, a condition known as the Charles Bonnet Syndrome. Patients usually possess insight into the unreality of their visual experiences, which are commonly pleasant but may sometimes cause distress. The hallucinations consist of well-defined, organized, and clear images over which the subject has little control. It is believed that they represent release phenomena due to de-afferentation of the visual association areas of the cerebral cortex, leading to a form of phantom vision. Cognitive defects, social isolation, and sensory deprivation have also been implicated in the etiology of this condition. This condition, which is most common in the elderly, frequently goes unrecognized in clinical practice, due to both lack of awareness among doctors and patients' reluctance to admit to hallucinatory experiences, for fear of being labeled mentally unstable. Furthermore, patients who comprehend the unreality of their hallucinations may be distressed by the real fear of imminent insanity. Sensitive and sympathetic history taking is essential to ascertain the existence of hallucinations. Reassurance and explanation that the visions are benign and do not signify mental illness have a powerful therapeutic effect. Hallucinatory activity may terminate spontaneously, on improving visual function or on addressing social isolation. There is no universally effective drug treatment but anticonvulsants may play a limited role in aborting the hallucinations. Physician awareness and empathy are the cornerstones of management.

Anticonvulsants↗

Vision impairment and driving.

Driving is the primary mode of travel in many countries. It facilitates the performance of routine daily activities and is thus integral with the concept of quality of life. Vision is inarguably a fundamental component of safe driving. Drivers with certain eye conditions reduce their driving exposure and restrict their driving to the safest times, yet there is preliminary evidence that some eye conditions increase the risk of crashes. Visual acuity is only weakly related to crash involvement, whereas peripheral vision appears to play a more critical role. Color vision deficiency by itself is not a threat to safe driving. Based on the current literature, it is unclear whether other types of visual sensory impairment have a significant impact on driving safety and performance. Tests of visual attention and processing speed show great promise as methods of identifying high-risk drivers. There is a serious need for well-designed studies in key practical areas, such as the safety of low-vision drivers who use bioptic telescopes, the impact of monocular vision impairment on safety, and the effectiveness of vision rescreening policies after initial licensure. For ophthalmologists to guide patients about driving fitness, valid and reliable assessment tools must be developed and made widely available.

Accidents, Traffic↗

Cause-specific prevalence of bilateral visual impairment in Victoria, Australia: the Visual Impairment Project.

PURPOSE: To study the cause-specific prevalence of eye diseases causing bilateral visual impairment in Australian adults. DESIGN: Two-site, population-based cross-sectional study. PARTICIPANTS: Participants were aged 40 years and older and resident in their homes at the time of recruitment for the study. The study was conducted during 1992 through 1996. METHODS: The study uses a cluster stratified random sample of 4744 participants from two cohorts, urban, and rural Victoria. Participants completed a standardized interview and eye examination, including presenting and best-corrected visual acuity, visual fields, and dilated ocular examination. The major cause of vision loss was identified for all participants found to be visually impaired. Population-based prevalence estimates are weighted to reflect the age and gender distribution of the two cohorts in Victoria. MAIN OUTCOME MEASURES: Visual impairment was defined by four levels of severity on the basis of best-corrected visual acuity or visual field: <6/18 > or =6/60 and/or <20 degrees > or =10 degrees radius field, moderate vision impairment; severe vision impairment, <6/60 > or =3/60 and/or <10 degrees > or =5 degrees radius field; and profound vision impairment <3/60 and/or <5 degrees radius field. In addition, less-than-legal driving vision, <6/12 > or =6/18, and/or homonymous hemianopia were defined as mild vision impairment. In Australia, legal blindness includes severe and profound vision impairment. RESULTS: The population-weighted prevalence of diseases causing less-than-legal driving or worse impairment in the better eye was 42.48/1000 (95% confidence interval [CI], 30.11, 54.86). Uncorrected refractive error was the most frequent cause of bilateral vision impairment, 24.68/1000 (95% CI, 16.12, 33.25), followed by age-related macular degeneration (AMD), 3.86/1000 (95% CI, 2.17, 5.55); other retinal diseases, 2.91/1000 (95% CI, 0.74, 5.08); other disorders, 2.80/1000 (95% CI, 1.17, 4.43); cataract, 2.57/1000 (95% CI, 1.38, 3.76); glaucoma, 2.32/1000 (95% CI, 0.72, 3.92); neuro-ophthalmic disorders, 1.80/1000 (95% CI, 0, 4.11); and diabetic retinopathy, 1.53/1000 (95% CI, 0.71, 2.36). The prevalence of legal blindness was 5.30/1000 (95% CI, 3.24, 7.36). Although not significantly different, the causes of legal blindness were uncorrected refractive errors, AMD, glaucoma, other retinal conditions, and other diseases. CONCLUSIONS: Significant reduction of visual impairment may be attained with the application of current knowledge in refractive errors, diabetes mellitus, cataract, and glaucoma. Although easily preventable, uncorrected refractive error remains a major cause of vision impairment.

Adult↗

Five-year incidence of open-angle glaucoma: the visual impairment project.

PURPOSE: To determine the incidence of open-angle glaucoma (OAG) in Melbourne, Victoria, Australia. DESIGN: Population-based cohort study. PARTICIPANTS: Total of 3271 participants aged 40 years and older from Melbourne, Victoria, Australia. MAIN OUTCOME MEASURES: Five-year incidence of OAG. METHODS: Participants were recruited through a cluster random sampling from nine urban clusters. Baseline examination was conducted from 1992 through 1994, and the follow-up data were collected from 1997 through 1999. Each participant both at baseline and follow-up underwent a standardized ophthalmic examination including intraocular pressure measurement, visual field assessment, cup-to-disc ratio measurement, and paired stereo photographs of the optic disc. Glaucoma was assessed by a consensus group of six ophthalmologists that included two glaucoma specialists. Glaucoma was diagnosed as possible, probable, or definite. RESULTS: The overall incidence of definite OAG was 0.5% (95% confidence limits [CL], 0.3, 0.7); probable and definite incidence of OAG was 1.1% (95% CL, 0.8,1.4); and possible, probable, and definite OAG incidence was 2.7% (95% CL, 1.8, 3.7). The incidence of possible, probable, and definite OAG increases significantly as age increases (P < 0.001). The incidence of definite OAG increases from 0% of participants aged 40 to 49 years to 4.1% of participants aged 80 years and older. The incidence of probable and definite OAG increases from 0.2% of participants aged 40 to 49 years to 5.4% of participants aged 80 years and older. The incidence of possible, probable, and definite OAG increases from 0.5% of participants aged 40 to 49 years to 11% of participants aged 80 years and older. A nonsignificant but higher incidence of definite OAG among men was observed in this study when compared with women (odds ratio, 2.2; 95% CL, 0.9, 5.9). Fifty percent of the definite OAG participants were undiagnosed. CONCLUSIONS: The incidence of OAG increases significantly with age. The undiagnosed cases suggest the need to develop novel community screening strategies for glaucoma.

Adult↗

Five-year change in visual acuity and incidence of visual impairment: the Blue Mountains Eye Study.

PURPOSE: To describe the 5-year change in visual acuity and the incidence of visual impairment in a population-based cohort. DESIGN: Population-based epidemiologic study. PARTICIPANTS: Of the 3654 participants of the Blue Mountains Eye Study (BMES I) baseline examination (aged 49 years+ during 1992-1994), 2335 were reexamined during the 5-year follow-up examinations from 1997 to 1999 (BMES II), and 543 persons had died since BMES I. METHODS: Visual acuity was measured using a logarithm of the minimum angle of resolution chart in both eyes separately before and after standardized refraction. Pupils were dilated and a detailed examination was performed. MAIN OUTCOME MEASURES: Visual impairment, after best refractive correction, was defined as any (visual acuity </=20/40; </=41 letters) and severe (visual acuity </=20/200; 0-5 letters) in keeping with the Beaver Dam Eye Study. Incident binocular visual impairment was defined as visual acuity </=20/40 in both eyes at follow-up, where visual acuity was >20/40 in both eyes at baseline. Incident binocular severe visual impairment was defined as visual acuity </=20/200 in both eyes at follow-up, where visual acuity was >20/200 in both eyes at baseline. The incidence for three other levels of visual impairment is also given: <20/40, <20/70, and <20/200. Monocular visual impairment was defined as impairment in one eye only at follow-up, where both eyes were unimpaired at baseline. Incident doubling and halving of the visual angle were calculated. RESULTS: Incidence rates for visual impairment increased significantly with age. Any incident impairment </=20/40 occurred binocularly in 41 persons (1.9%) and monocularly in 150 persons (7.1%). Severe incident impairment </=20/200 occurred binocularly in 3 persons (0.1%) and monocularly in 44 persons (2.1%). Incident impairment <20/40 occurred binocularly in 37 persons (1.7%) and monocularly in 134 persons (6.3%). Impairment <20/70 occurred binocularly in 15 persons (0.7%) and monocularly in 84 persons (3.8%). Impairment <20/200 occurred binocularly in 3 persons (0.1%) and monocularly in 44 persons (1.9%). Women consistently had a higher incidence of visual impairment than men, although this was often not statistically significant after adjusting for age. Increasing age was a strong predictor of visual impairment. CONCLUSIONS: This study has documented the 5-year incidence and causes of visual impairment in an older Australian population.

Age Distribution↗

Incidence of blindness and low vision in a sample population: the Priverno Eye Study, Italy.

PURPOSE: To study the incidence of blindness and low vision over a 7-year period. DESIGN: Population-based cohort study. PARTICIPANTS: The survivors of the original cohort of 860 persons from Priverno, Italy, aged 45 to 69 years, were reexamined. Of the 760 eligible survivors, 619 (81.4%) had a 7-year follow-up visit. METHODS: Baseline and follow-up examinations included the collection of anamnestic and ophthalmologic data by the same observers using the same methods and classification criteria to minimize sources of variability. MAIN OUTCOME MEASURES: Best-corrected visual acuity (VA) measured at 4 m by standardized logarithmic chart was expressed as the logarithm of the minimum angle of resolution (logMAR). World Health Organization definitions of blindness and low vision were adopted (respectively, VA > 1.3 logMar and VA > 0.6 to 1.3 logMar in the better eye or in either eye). Participants at risk for visual impairment were those without blindness or low vision in one or both eyes at baseline; participants at risk for one-eye visual impairment were those without blindness or low vision in both eyes at baseline. RESULTS: A total of 33 participants were defined as incident cases of visual impairment. The overall incidence figures for blindness, low vision, one-eye blindness, and one-eye low vision were respectively 0.2% (95% confidence interval [CI], 0.0-0.9), 1.3% (95% CI, 0.7-2.6), 1.2% (95% CI, 0.6-2.4), and 2.9% (95% CI, 1.8-4.6). CONCLUSIONS: This study provides population-based estimates of the incidence of visual impairment in an adult, free-living European population. With respect to the younger participants, older subjects at baseline were at higher risk for incident visual impairment, the main causes of which were cataract, myopia, and diabetic retinopathy. The incidence of visual impairment in the subgroup aged 55 to 64 years at baseline was significantly higher than that found in Beaver Dam 5-year study and similar to that found in Beaver Dam 10-year Study, when the same definitions were adopted. This difference may be partially explained by social and cultural habits of the female samples, but many other factors may play a role.

Aged↗

Visual impairment in children born prematurely from 1972 through 1989.

PURPOSE: To investigate the incidence and causes of visual impairment in children born prematurely in Finland from 1972 through 1989, and to determine what conditions and factors were associated with its occurrence. DESIGN: Retrospective, cross-sectional study. SUBJECTS: All visually impaired individuals from 0 to 17 years of age who had been born at fewer than 37 gestational weeks in Finland from 1972 through 1989 for whom records were available in the Finnish Register of Visual Impairment were eligible for this study. METHODS: Data in the Finnish Register of Visual Impairment relating to 556 children were supplemented with data from hospital records, and from the Register of Births, the Register of Congenital Malformations, the Finnish Care Register, and the Finnish Cancer Register. Data relating to causes associated with visual impairment in particular were collected. Data relating to the children born prematurely were compared with data relating to children born at full term. The chi-square test (Mantel-Haenszel), the Mann-Whitney U test, Fisher exact test, and stepwise logistic regression analysis were used in statistical analysis of the data. MAIN OUTCOME MEASURES: Visual acuity, ophthalmologic diagnoses, associated systemic disease, multiple handicap, gestational age, birth weight, 5-minute Apgar scores, and prenatal, perinatal, and infantile or juvenile disorders or disease and treatment. RESULTS: One hundred twenty-five of the 556 visually impaired children (23%; 11/100000 children less than 18 years of age) had been born preterm. Retinopathy of prematurity, optic atrophy, and cerebral amblyopia were the main diagnoses associated with visual impairment (in 46%, 28%, and 12% of cases, respectively). Sixty-six percent of those born prematurely with visual impairment were also affected by other handicaps (mental, motor, auditory), 54% by cerebral palsy and 36% by epilepsy. Eighty-eight of the 125 children (70%) born preterm with visual impairment were blind. Very low birth weight (<1500 g), young gestational age (fewer than 30 weeks), prenatal infection, hyperbilirubinemia, respiratory disorders, asphyxia, and lengthy mechanical ventilation were associated with an increased risk of visual impairment. CONCLUSIONS: Premature birth was a major risk factor of severe visual impairment and blindness in childhood. The visual impairment often was accompanied by cerebral palsy, epilepsy, and other motor and mental handicaps. Retinopathy of prematurity, optic atrophy, and cerebral amblyopia were the main diagnoses associated with visual impairment. During the 18 years covered by the study, the increasing incidence of survival of infants born weighing fewer than 1500 g was associated with increasing incidence of blindness.

Adolescent↗

Blindness and vision impairment in a rural south Indian population: the Aravind Comprehensive Eye Survey.

OBJECTIVE: To determine the prevalence of blindness and vision impairment in a rural population of southern India. DESIGN: A population-based cross-sectional study. PARTICIPANTS: A total of 17200 subjects aged 6 years or older, including 5150 subjects aged 40 years or older from 50 clusters representative of three southern districts of Tamil Nadu in southern India. METHODS: All participants had preliminary screenings consisting of vision using a LogMAR illiterate E chart and anterior segment hand light examinations at the village level. Subjects aged 40 years or older were offered comprehensive eye examinations at the base hospital, including visual acuity using LogMAR illiterate E charts and refraction, slit-lamp biomicroscopy, gonioscopy, applanation tonometry, dilated fundus examinations, and automated Humphrey central 24-2 full threshold perimetry; subjects younger than 40 years of age who had any signs or symptoms of ocular disease were also offered comparable examinations at the base hospital. MAIN OUTCOME MEASURES: Visual impairment was defined as best-corrected visual acuity <6/18, and blindness was defined using both Indian (<6/60) and World Health Organization (<3/60) definitions. RESULTS: Comprehensive examinations at the base hospital were performed on 5150 (96.5%) of 5337 persons 40 years of age or older. Among those 40 years of age and older, presenting visual acuity at the <3/60 level was present in 4.3% (95% confidence interval [CI]: 3.8, 4.9) and 11.4% (95% CI: 10.6, 12.3) at the <6/60 level. After best correction, the corresponding figures were 1.0% (95% CI: 0.79, 1.2) and 2.1% (95% CI: 1.7, 2.5). Over 70% of subjects improved their vision by at least one line, and nearly a third by three lines after refraction. Age-related cataract was the most common potentially reversible blinding disorder (72.0%) among eyes presenting with blindness. CONCLUSIONS: Blindness and vision impairment remain major public health problems in India that need to be addressed. Cataracts and refractive errors remain the major reversible causes for the burden of vision impairment in this rural population.

Adolescent↗

Prevalence of uncorrected binocular distance visual acuity in Hispanic and non-Hispanic adults. Results from the HHANES and the NHANES I.

OBJECTIVE: This study aimed to provide a comparative analysis of American population-based prevalence of uncorrected binocular distance visual acuity in Hispanics and non-Hispanics. DESIGN: The study design was a population-based survey. PARTICIPANTS: Data from the Hispanic Health and Nutrition Examination Survey between 1982 and 1984 and the National Health and Nutrition Examination Survey I from 1974 through 1975 were analyzed to investigate the epidemiology of uncorrected binocular distance visual acuity in adults 25 to 74 years of age in Cuban Americans (N = 391), Mexican Americans (N = 1350), Puerto Ricans (N = 504), African Americans (N = 245), and non-Hispanic white Americans (N = 2571). MAIN OUTCOME MEASURE: Uncorrected binocular distance visual acuity in both eyes was assessed using Sloan letters or Landolt rings. RESULTS: Prevalence rates of 20/50 or worse uncorrected binocular distance visual acuity were 22%, 24%, 19%, 18%, and 32% for African Americans, Cuban Americans, Mexican Americans, Puerto Ricans, and non-Hispanic whites, respectively. After adjustment for gender and age, the rates were significantly higher (P < 0.05) for non-Hispanic whites compared to each of the other ethnic groups. Significant increases in the prevalence of 20/50 or worse distance visual acuity were observed for increasing age groups (25-39, 40-59, and 60-74 years) within each gender-ethnic subgroup. Analysis of differences in prevalence by gender (controlling for age) indicated a slightly higher prevalence of 20/50 or worse distance visual acuity in women than in men (range of odds ratios, 1.1-2.1). Based on 1993 census population estimates in the United States, more than 42 million adults 25 to 74 years of age have an uncorrected binocular distance visual acuity of 20/50 or worse. Approximately 1.7 million of these adults are of Hispanic origin. CONCLUSION: The prevalence of impaired uncorrected binocular distance visual acuity generally is lower in Hispanics than in non-Hispanic whites.

Adult↗

Burden of moderate visual impairment in an urban population in southern India.

OBJECTIVE: To assess the prevalence and causes of moderate visual impairment in an urban population in southern India. DESIGN: Population-based, cross-sectional study. PARTICIPANTS: A total of 2522 (85.4% of the eligible) persons of all ages, including 1399 persons 30 years of age or older, from 24 clusters representative of the population of Hyderabad city. TESTING: The eligible subjects underwent a detailed ocular evaluation, including logarithm of the minimum angle of resolution (logMAR) visual acuity, refraction, slit-lamp biomicroscopy, applanation tonometry, gonioscopy, cataract grading, and stereoscopic dilated fundus evaluation. Automated threshold visual fields and slit-lamp and fundus photography were done when indicated by standardized criteria. MAIN OUTCOME MEASURE: Moderate visual impairment was defined as presenting distance visual acuity less than 20/40 to 20/200 or visual field loss by predefined standardized conservative criteria in the better eye. RESULTS: In addition to the 1% prevalence of blindness in this sample reported earlier, moderate visual impairment was present in 303 subjects, an age-gender-adjusted prevalence of 7.2% (95% confidence interval [CI], 4.5%-9.9%; design effect, 2.7). The major cause of moderate visual impairment was refractive error (59.4%, 95% CI, 52.3%-66.5%) followed by cataract (25.3%, 95% CI, 19%-31.6%). Multivariate analysis showed that the prevalence of moderate visual impairment was significantly higher in those 40 years of age or older (odds ratio, 10.9; 95% CI, 8-15) and females (odds ratio, 1.89; 95% CI, 1.41-2.53) and lower in those belonging to the highest socioeconomic status (odds ratio, 0.27; 95% CI, 0.14-0.51). However, because of the pyramidal age distribution of the population, 38.1% of the total moderate visual impairment was present in those younger than 40 years of age. The proportion of moderate visual impairment caused by refractive error was higher in the younger than in the older age groups (P < 0.0001). CONCLUSIONS: Projecting the results to the 26.5% urban population of India, there would be 18.4 million (95% CI, 11.5-25.2 million) persons with moderate visual impairment in urban India alone. Refractive error was the major cause of moderate visual impairment in the population studied. The absolute proportion of moderate visual impairment in those younger than 40 years of age was considerable. The eyecare policy of India, apart from dealing with blindness, should address the issue of the relatively easily treatable uncorrected refractive error as the cause of moderate visual impairment in an estimated 10.9 million persons in urban India.

Adolescent↗

Familial left ventricular hypertrabeculation in two blind brothers.

So far, left ventricular hypertrabeculation (LVHT) has been described to occur only sporadically. In a 49-year-old man with Leber's hereditary optic neuropathy (LHON) due to the primary LHON mutation G3460A, arterial hypertension was reported since 2000 and palpitations since 1995. ECG revealed Wolff-Parkinson-White syndrome. Transthoracic echocardiography and cardiac MRI showed myocardial thickening and LVHT. Pindolol markedly improved the cardiac abnormalities. Surprisingly, LVHT was also found in the 50-year-old brother of the index patient who also had LHON and also carried the G3460A mtDNA mutation. This brother also had Wolff-Parkinson-White syndrome and myocardial thickening, but without hypertension. It is concluded that LVHT, previously described to occur only sporadically, may be hereditary in single cases.

Family Health↗