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At least 433 records · Page 24Linked to original sources
PubMed2006

Costs of refractive correction of distance vision impairment in the United States, 1999-2002.

OBJECTIVE: Correctable vision impairment caused by refractive error is common in the United States population. We estimated the direct costs of providing eyeglasses to all Americans (age> or =12) who need refractive correction to achieve good distance vision. DESIGN: Cross-sectional study of a nationally representative sample of United States citizens. PARTICIPANTS: Participants in the 1999-2002 National Health and Nutrition Examination Survey (NHANES), age > or = 12 years. The NHANES examines a nationally representative sample of the U.S. noninstitutionalized, civilian population. METHODS: Presenting and corrected visual acuity data were obtained using an autorefractor from 13,211 (93.0%) of the 14,203 participants who visited the NHANES Mobile Examination Center in 1999 through 2002. Need for refractive correction was defined by current use of corrective lenses for distance vision, improvement to good visual acuity following autorefractor correction (using several cutpoints to define good visual acuity), or both. MAIN OUTCOME MEASURES: Estimates of direct cost for refractive correction (1 pair of complete eyeglasses and a refraction examination) were computed based on Centers for Medicare & Medicaid Services fee schedules for 2000 and also based on expenditure data from the Medical Expenditure Panel Survey. RESULTS: The NHANES results indicate that >110 million Americans could or do achieve normal vision with refractive correction. The annual direct cost of correcting distance vision impairment is at least $3.8 billion. Of this amount, $780 million represents the annual cost of providing distance vision correction for persons > age 65. CONCLUSIONS: Correctable vision impairment due to refractive error is common in the United States population. These cost estimates provide useful information for public health endeavors aimed at provision of refractive correction to those who need it.

Adolescent↗
PubMed1996

Vision screening in junior schools.

A prospective study of routine school vision tests in 1809 children aged 8 and 10 y was undertaken in schools in the Cambridge Health District over two years (1988-1990) to establish whether a significant number of defects of vision were detected. Although the visual acuity of 31% of children who had an abnormal test was recorded as abnormal, most abnormalities were minimal. Only 15 (0.83%) had newly diagnosed problems requiring treatment. Almost all children with marked visual abnormalities had already been detected before school entry, at the 5 y school vision test or on another occasion. Near vision testing did not identify any previously undiagnosed child with significant defects who did not also have distant vision abnormalities. Satisfactory colour vision test results had been recorded for most children at the 5 y school entry vision test. These data do not justify the continued use of routine screening in junior schools.

Child↗
PubMed1999

Development of spatial and temporal vision during childhood.

Using the method of limits, we measured the development of spatial and temporal vision beginning at 4 years of age. Participants were adults, and children aged 4, 5, 6, and 7 years (n = 24 per age). Spatial vision was assessed with vertical sine-wave gratings, and temporal vision was assessed with an unpatterned luminance field sinusoidally modulated over time. Under these testing conditions, spatial contrast sensitivity at every frequency increased by at least 0.5 log units between 4 and 7 years of age, at which point it was adult-like. Grating acuity reached adult values at 6 years of age. Temporal vision was more mature: at 4 years of age temporal contrast sensitivity at higher temporal frequencies (20 and 30 Hz) and critical flicker fusion frequency were already adult-like. Sensitivity at lower temporal frequencies (5 and 10 Hz) increased by 0.25 log units after the age of 4 to reach adult levels at age 7. The results suggest that temporal vision matures more rapidly than spatial vision during childhood. Thus, spatial and temporal vision are likely mediated by different underlying neural mechanisms that mature at different rates.

Adolescent↗
PubMedDate not supplied

Color vision sensitivity in normally dichromatic species and humans.

Spectral-sensitivity functions for large, long-duration increments presented on a photopic white background indicate that wavelength-opponent mechanisms mediate detection in both normal and dichromatic humans. Normal humans exhibit high color-vision sensitivity as they discriminate the color of spectral flashes at detection-threshold intensities. However, dichromatic humans require stimuli up to about 0.4 log units above detection intensity to see certain colors. This low color-vision sensitivity in human dichromats may be an abnormal condition involving a defect in postreceptoral color processing. To test this hypothesis, we determined color-discrimination thresholds in normally dichromatic species: chipmunk, 13-lined ground squirrel, and tree shrew. For comparison, we also tested humans with normal and abnormal (deutan) color vision with the same apparatus and methods. Animals were trained to perform spatial two-choice discrimination tasks for food reward. Detection thresholds were determined for increments of white, 460 nm, 540 nm, 560 nm, 580 nm, 500 nm/long-pass, and 500 nm/short-pass on white backgrounds of 1.25 cd/m2, 46 cd/m2, and 130 cd/m2. Animals were also trained to respond to the colored increments when paired with the white increment when both were at equally detectable intensities. Color-discrimination thresholds were determined by dimming stimulus pairs (colored vs. white) until the subjects could no longer make the discriminations. Results indicated that the normally dichromatic species could discriminate colored stimuli from white at a mean intensity of 0.1 (+/-0.1) log units above detection threshold. The ability of normally dichromatic species to discriminate color near detection-threshold intensity is consistent with increment spectral-sensitivity functions that indicate detection by wavelength-opponent mechanisms. In keeping with previous studies, normal human trichromats discriminated color near detection-threshold intensities but humans with deutan color vision required suprathreshold intensities to discriminate the color of middle and long wavelengths. This high color-vision sensitivity of normally dichromatic species suggest that the low color-vision sensitivity in dichromatic humans is an abnormal condition and indicates a possible defect in their postreceptoral color-vision processing.

Animals↗
PubMed2001

Randomised controlled trial of an integrated versus an optometric low vision rehabilitation service for patients with age-related macular degeneration: study design and methodology.

A number of studies have measured the outcomes of low vision care but these have usually been longitudinal case series, thus constituting very low quality of evidence for effectiveness. To date, there have been no randomised controlled trials (RCTs) which have evaluated the effectiveness and cost effectiveness of different models of care in low vision. The size of the low vision population and the paucity of systematic evaluation have created a pressing need for evidence about cost-effectiveness in order to inform service developments for low vision rehabilitation. This paper describes the study design and methodology of a three-arm RCT currently under way in Manchester. The baseline population recruited is also described. A traditional hospital-based optometric service is being compared with an integrated service (comprising the addition of community-based rehabilitation officer input) and with more generic community input (which is non-integrated and is not vision specific). A wide range of outcome measures are being assessed at recruitment and 12 months post-intervention, including low vision specific and generic quality of life measures, patterns of low vision aid use, and task performance. The rationale for the trial is discussed and the main study outcomes are described.

Aged↗
PubMed1998

Sharp vision: a prerequisite for compensation to myopic defocus in the chick?

PURPOSE: Compensatory responses to focusing errors imposed by spectacle lenses in chicks, tree shrews and primates leave little doubt that active emmetropization can occur, and debate is now centered on whether this process is uni-directional or bi-directional in nature. To provide further insight into this emmetropization process, the studies reported in this paper addressed the question of whether access to sharp vision is necessary for compensation to myopic defocus in the chick. METHODS: Two different experimental paradigms were used to address the above question: (A) Myopic defocus was imposed, either with +15 or +40 d lenses alone or with +15 D lenses on eyes made myopic by 7 days of form deprivation; these treatments result in a shift in the plane of focus of the eye (far point) to 6.67, 2.5 cm and approximately 3.5 cm resp., with only objects at or closer than these planes being in focus. The addition to the lenses of stand-off cones, either 2.5 or 5 cm in length, further limited access to (or precluded) sharp vision by controlling how closely the chicks could approach objects. One group that had sharp vision precluded also underwent optic nerve section. (B) A range of positive lenses (+15 to +65 D) were used on their own to impose myopic defocus; for the high power lenses, access to sharp vision was very restricted because of the close proximity of the new far point (1.54 cm for +65 D lens). Refractive errors and axial ocular dimensions were measured in all experiments. RESULTS: In the first study (A), preclusion of sharp vision not only prevented compensation but resulted in increased eye growth and myopia. This myopia, like form-deprivation myopia, was unaltered by optic nerve section surgery. Limiting but not precluding sharp vision resulted in partial compensation. In the second study (B), good compensation was observed with the +15 D lens but compensation progressively declined for higher powers, with the +50 D lens having no apparent effect on eye growth and refraction and the +65 D lens inducing myopia instead of hyperopia. CONCLUSIONS: Together these results argue that some sharp vision is fundamental to compensation to impose myopia. The significance of this new finding in relation to the processes underlying active emmetropization is discussed.

Animals↗
PubMedDate not supplied

Two-year evolution of perchloroethylene-induced color-vision loss.

Progression of perchloroethylene-induced color-vision impairment was studied in 33 dry-cleaner workers at 12 establishments in Modena, Italy. In an initial survey, we evaluated exposure with personal passive samplers, and we assessed color vision with the Lanthony D-15 desaturated panel. Two years later, workers were reexamined. In 19 workers (subgroup A), exposure to perchloroethylene had increased (median of 1.7 ppm versus 4.3 ppm, respectively), whereas in the remaining 14 workers (subgroup B) exposure was reduced (2.9 ppm versus 0.7 ppm, respectively). Color vision worsened in subgroup A, but no vision changes were apparent in subgroup B. The results indicated that an increase in exposure during a 2-y period, even if slight, can cause color vision to deteriorate. A similar slight reduction in exposure did not lead to color-vision improvement; perhaps this lack of improvement resulted from (a) an insufficient reduction in exposure, (b) an insufficient reduction in duration of exposure, or (c) irreversible perchloroethylene-induced color-vision loss.

Adult↗
PubMed2001

Vision and hearing in old age.

The concomitant occurrence of hearing and visual impairment was investigated as part of an epidemiological longitudinal study of elderly people. An age cohort. originally consisting of 973 elderly people, was examined with visual and hearing tests three times at ages 70, 81-82 and 88. The best-corrected visual acuity was assessed. The hearing was measured by pure-tone audiometry and whispered and spoken voice (WSV). At age 70 there was no co-existence of visual and hearing impairments, and about 70% had normal vision and hearing. At 81-82 years 3-6% (WSV and audiometry. respectively) had low vision (VA < or = 0.3) and moderate to severe hearing loss, and more than one-tenth had normal vision and hearing. At 88 years 8-13% had low vision and moderate to severe hearing loss, and none of the men and less than one-tenth of the women had normal vision and hearing. At age 88 three times as many women as men had the combination of low vision and normal hearing. Normal vision with the combination of moderate to severe hearing loss was more often found in 88-year-old men. Mild impairments of the two senses were found in 0.5% at age 70 in 22%, 11% (WSV, audiometry) at age 81-82 and in 23%, 9% at age 88 years. At age 70 there was a statistical correlation between visual acuity and hearing measured with pure-tone audiometry in the male group. Those men with better hearing had slightly better visual capacity than those with hearing loss. No correlations were found for women at age 70 nor for women and men at ages 81-82 and 88. Ophthalmologists and audiology physicians should cooperate closely in the rehabilitation process to reduce disability and improve function and wellbeing among the oldest old.

Aged↗
PubMed2001

The Smith-Kettlewell Institute (SKI) longitudinal study of vision function and its impact among the elderly: an overview.

We present an overview of a multifaceted longitudinal study of vision function and its interaction with daily activities, health, and well-being among 900 persons aged 58 to 102 years at the first visit. Standard vision measures as well as nonconventional tests designed to assess visual performance under the nonideal conditions encountered in everyday life were used. Here we summarize a few of the findings to date, with an emphasis on a direct comparison of declines in different aspects of vision function with age. The rates of declines with advancing age vary widely for the different vision functions. Also described is the reading performance of the sample and its association with some of the vision measures. Furthermore, we describe some of the associations between vision test scores and extensive longitudinal health and functioning data collected by the Buck Center for Research in Aging. Findings show that many older people with good acuity are effectively visually impaired in performing everyday tasks involving low and changing light levels, stereopsis, glare, and low contrast. We also found that vision under nonideal conditions cannot be predicted from standard acuity on an individual basis.

Activities of Daily Living↗
PubMed2002

The proximity-fixation-disparity curve and the preferred viewing distance at a visual display as an indicator of near vision fatigue.

PURPOSE: This laboratory study investigates the relation between measures of fixation disparity (FD) (and other optometric measures) and near vision fatigue at a computer workstation. METHODS: Young adult subjects with normal binocular vision performed three blocks of a visual task of 30 min each. In Block A, the viewing distance was 100 cm, as a reference without near vision. In Block B, the viewing distance of 50 cm induced a defined near vision load. In Block C, subjects were free to choose a comfortable viewing distance. This preferred viewing distance was used as an indicator of near vision fatigue because subjects adopting longer viewing distances in Block C had more near vision fatigue at 50 cm in Block B. RESULTS: Subjects with preferred viewing distances longer than average (63 cm) had steeper slopes of FD as a function of viewing distance (100-30 cm), as shown by discriminant analyses. CONCLUSIONS: Thus, this steep proximity-FD curve indicates a weak disparity vergence system that may cause near vision fatigue. This may explain why some young adults prefer longer viewing distances at the computer workstation.

Computer Terminals↗
PubMed2006

Visual field defects and vision-specific health-related quality of life in African Americans and whites with glaucoma.

PURPOSE: To examine the relationship of visual field impairment to vision-specific health-related quality of life and symptoms in a large cohort (N=345) of African Americans and Whites of non-Hispanic origin diagnosed with glaucoma. MATERIALS AND METHODS: Participants consisted of persons > or =55 years of age recruited from university-affiliated ophthalmology and optometry practices in Birmingham, AL who had been diagnosed with glaucoma. Medical records were abstracted to collect information on demographics, visual acuity, and visual fields. A telephone survey was conducted to obtain information on vision-specific health-related quality of life [National Eye Institute Visual Function Questionnaire-25 (NEI VFQ-25)], glaucoma symptoms [Glaucoma Symptom Scale (GSS)], and cognitive status (Short Portable Mental Status Questionnaire). Visual fields were used to compute a visual field defect score for each eye based on the Advanced Glaucoma Intervention Study (AGIS) scoring system. RESULTS: Mean NEI VFQ-25 subscale scores ranged from the 50s to 80s. Scores for African Americans and Whites did not differ except for the general health and ocular pain subscales for which African Americans had slightly higher scores. For both African Americans and Whites, as the AGIS score became worse in the better and/or worse eye, there was a decrease in VFQ subscale score for most VFQ subscales including general vision, distance vision, near vision, social functioning, color vision, and peripheral vision (P<0.05). AGIS scores were unrelated to the GSS subscales in African Americans; for Whites, the visual but not the nonvisual subscale was related to AGIS score. CONCLUSIONS: Scores on most subscales of the NEI VFQ-25 and the 2 subscales of the GSS are highly similar in African Americans and Whites of non-Hispanic origin who have been diagnosed with glaucoma. In addition, for both African Americans and Whites, the VFQ subscales for the most part demonstrated good construct validity with respect to the extent of visual field impairment. Results imply that the NEI VFQ-25 and the GSS are appropriate instruments for studying the personal burden of glaucoma in studies whose samples involve both African American and White adults.

Black or African American↗
PubMed2005

The molecular basis of variation in human color vision.

Common variation in red-green color vision exists among both normal and color-deficient subjects. Differences at amino acids involved in tuning the spectra of the red and green cone pigments account for the majority of this variation. One source of variation is the very common Ser180Ala polymorphism that accounts for two spectrally different red pigments and that plays an important role in variation in normal color vision as well as in determining the severity of defective color vision. This polymorphism most likely resulted from gene conversion by the green-pigment gene. Another common source of variation is the existence of several types of red/green pigment chimeras with different spectral properties. The red and green-pigment genes are arranged in a head-to-tail tandem array on the X-chromosome with one red-pigment gene followed by one or more green-pigment genes. The high homology between these genes has predisposed the locus to relatively common unequal recombination events that give rise to red/green hybrid genes and to deletion of the green-pigment genes. Such events constitute the most common cause of red-green color vision defects. Only the first two pigment genes of the red/green array are expressed in the retina and therefore contribute to the color vision phenotype. The severity of red-green color vision defects is inversely proportional to the difference between the wavelengths of maximal absorption of the photopigments encoded by the first two genes of the array. Women who are heterozygous for red and green pigment genes that encode three spectrally distinct photopigments have the potential for enhanced color vision.

Color Perception↗
PubMed2004

Analysis of New Zealand's research productivity in ophthalmology and vision science: 1993-2002.

AIM: To assess New Zealand's research productivity in the area of ophthalmology and vision science over the decade 1993-2002. METHODS: New Zealand-based researchers involved in ophthalmology or vision science research, including ophthalmologists, optometrists and vision scientists were identified via professional colleges, universities and electronic databases. Peer-reviewed publications by these authors were identified by both searching electronic databases (MEDLINE/Pubmed) and personal communication with individual researchers. RESULTS: Eighty-five New Zealand-based researchers involved in ophthalmology or vision science research published 446 articles in 84 scientific journals during the 10-year period. The cohort consisted of 59 ophthalmologists and 26 other researchers based in a diverse range of ophthalmology, optometry and university departments. Significant collaboration was observed between groups within New Zealand and with international institutions. Comparing ophthalmologists and 'other' researchers, ophthalmologists produced 69% of all ophthalmology and vision science research publications and those classified as 'active ophthalmologist researchers' published an average of 11 (range 5-55) papers each during this decade, compared to eight (range 5-25) for the group 'other active researchers'. This was also reflected in the high productivity rate by ophthalmologists of 277 publications per 1000. Publications were identified in a wide range of journals with the majority in top 20-ranked ophthalmology journals. The trend over the decade highlighted an increase in number of scientific publications, from 43 per annum in 1993, to 68 per annum in 2002. CONCLUSIONS: Despite a relatively small and geographically isolated population, New Zealand ophthalmology and vision science research is highly active and collaborative, with significantly increased research productivity during the period 1993-2002. The present study is the first to document these trends and provides strong evidence to justify continued support for ophthalmology and vision science research in New Zealand.

Bibliometrics↗
PubMed2002

Determining magnification for reading with low vision.

BACKGROUND: In the past, practitioners have used distance and/or near visual acuity (VA) to calculate required magnification for low vision aids. Magnification was usually under-estimated when compared with the final magnification prescribed. Recent studies have emphasised the importance of acuity reserve in determining the required magnification for optimum reading rate. Two different approaches have been proposed for the appropriate acuity reserve to use in calculating magnification. These are a fixed acuity reserve of 0.3 log unit or an individual determination of optimum acuity reserve. The aim of this study was to investigate the magnification and reading rates with low vision aids selected by the two methods. METHODS: Nineteen low vision subjects with age-related macular degeneration (AMD) who were experienced magnifier-users were recruited. Reading rates and near VA with low vision aids determined by the fixed and individual acuity reserve methods were compared with the same measures made with the subjects' own magnifiers. RESULTS: There were no significant differences in reading rate and near VA measured with low vision aids selected by either the fixed or individual acuity reserve methods or the subjects' own magnifiers. Reading rate with low vision aids was not significantly different from reading rate for large print with conventional near additions. Thus, for experienced users, magnifiers do not cause reduced reading rate. CONCLUSIONS: The fixed acuity reserve method is simple to apply as only near VA and print size of the target reading task are required. For the individual acuity reserve method, reading rates at different print sizes need to be measured. We recommend the use of a fixed acuity reserve (0.3 log unit) for the calculation of required magnification for low vision patients. If near VA or reading rate are not satisfactory with the magnification calculated by this method, individual assessment of required acuity reserve is necessary.

Aged↗
PubMed2004

Molecular genetics of colour vision deficiencies.

Common variation in colour vision exists among both colour normal and colour deficient subjects. Differences at a few amino acid positions that influence the spectra of the L and M cone pigments account for most of this variation. The genes encoding the L and M photopigments are arranged in head-to-tail arrays on the X-chromosome, beginning with the L and followed by one or more M pigment genes. The L and M pigment genes are highly homologous, which predisposed them to unequal crossing over (recombination) resulting in gene deletions and in formation of L/M hybrid genes that encode a variety of pigments with either L-like or M-like spectra that account for the majority of colour vision defects. Only the first two pigment genes of the L/M array are expressed in the retina and, therefore, need to be considered in predicting colour vision. A common single amino acid polymorphism (serine or alanine) at position 180 of the L-pigment plays an important role both in variation in normal colour vision and in the severity of colour vision defects. Blue cone monochromacy is a rare form of colour vision deficiency that results from mutations that abolish function of both the L and M pigment genes. All the above defects are inherited as X-linked recessive traits. Tritanopia is also a rare autosomal dominant colour vision defect caused by mutations in the S pigment gene located on chromosome 7. Total colour blindness (achromatopsia or rod monochromacy) is a rare autosomal recessive trait caused by mutations in genes encoding the proteins of the photoreceptor cation channel or cone transducin that are essential for function of all classes of cone.

Color Vision Defects↗
PubMed2006

Improvement in colour vision parameters following successful trabeculectomy.

PURPOSE: To determine whether colour vision improves following reduction of intraocular pressure (IOP) in glaucoma patients. METHODS: The medical records of 29 glaucoma patients (41 eyes) were reviewed. Inclusion criteria required subjects to have made more than four visits to the Glaucoma Service Laboratory and to undergo a thorough eye examination including a Farnsworth-Munsell 100-hue colour vision test and Goldmann tonometry before and after pressure lowering. Colour vision parameters of total error score (TES), yellow-blue score (YBS) and red-green score (RGS) were measured. The study group consisted of 21 eyes of glaucoma patients who underwent uncomplicated trabeculectomy with an IOP reduction of >/= 20% from baseline. The control group consisted of 21 eyes of glaucoma patients matched for age and colour vision, who received medication and/or underwent surgery with a post-intervention IOP reduction of < 20% from baseline. The primary outcome was a comparison of pre- and post-intervention colour vision parameters between the two groups. RESULTS: There was a statistically significant improvement in TES (43 +/- 44, p < 0.001), RGS (19 +/- 27, p = 0.0077) and YBS (23 +/- 29, p = 0.0007) in the study group compared with the control group. The improvement in TES (r = 0.52, p < 0.001), RGS (r = 0.55, p < 0.001) and YBS (r = 0.40, p = 0.008) was correlated with the percentage of IOP reduction. There was no statistically significant difference between improvement in Y-B and R-G scores in the study group. CONCLUSION: Intraocular pressure reduction of >/= 20% post-trabeculectomy was associated with an improvement in colour vision. Colour vision tests may be useful as an adjunctive outcome measure for therapeutic interventions.

Case-Control Studies↗
PubMed1993

Suboptimal vision after vitreous surgery in diabetics.

Between 1979-1985, 105 diabetic patients underwent vitreous surgery for diabetic eye disease in one or both eyes. By spring 1991, 40 patients (38%) had died, and 36 (55%) of the living 65 patients had good or moderate vision (visual acuity, VA > or = 0.3 in the better eye), 13 (20%) had low vision (VA 0.05-0.25), and 16 (25%) were blind (VA < 0.05). For 19 of the 65 patients (29%) impaired vision was the main factor that limited independent activities. Of the 29 patients with suboptimal vision, 2 were employed, and none needed institutional care. Nine (31%) participated in all household activities, and 14 (48%) were able to read. Near vision aids were used by 14 of the 19 patients (74%) with ambulatory vision (VA > or = CF), but only 2 of them (11%) had accepted telescopic aids. Eight patients (28%) had a guide dog. In spite of vitreoretinal surgery, almost half of diabetic patients may end up with suboptimal vision, emphasizing the need for active visual rehabilitation.

Activities of Daily Living↗
PubMed1999

Preretinopic changes in the colour vision of juvenile diabetics.

AIMS: To examine the colour vision of juvenile patients suffering from diabetes mellitus without retinopathy in relation to metabolic and ophthalmic state. METHODS: Metameric matches, both Rayleigh (red/green) and Moreland (blue/green) were used to test the colour vision yearly of 10 juvenile patients. The patients were monitored over 4 years, and during the final year, their blood glucose level was determined directly after testing colour vision. An ophthalmic examination was performed on the day of colour vision testing and blood and urine were analysed regularly throughout the 4 years. Their results are compared with an aged matched control group of 20 subjects, seven of whom were retested after 9-16 months. RESULTS: After 4 years, the colour vision results show an enlarged matching range for the Moreland match, as well as a smaller increase in the matching range for the Rayleigh match. No significant correlation was found between blood glucose at the time of testing and any of the variables measured. CONCLUSION: The pattern of colour vision deficits in metameric matching shown by juvenile diabetics is consistent with postreceptoral alterations of the inner retina, at this preretinopic stage of disease. Duration of diabetes is correlated with both colour vision changes and morphological alteration of the retina.

Adolescent↗