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Biomedical subjects

O Overbury

Publications and source records attributed to O Overbury.

9 recordsLinked to original sources
PubMed2000

Binocular vision in older people with adventitious visual impairment: sometimes one eye is better than two.

PURPOSE: To determine the effect of adventitious visual impairment (low vision) on monocular and binocular spatial contrast sensitivity of older people. DESIGN: A between-within repeated measures design. PARTICIPANTS: Fifty-nine older adults between the ages of 50 and 96; 49 of the observers had age-related macular degeneration (AMD). MEASURES: Visual acuity screening and spatial contrast sensitivity. RESULTS: In almost half of the population with AMD, the sensitivity to spatial information, as measured by spatial contrast sensitivity, is worse when both eyes are used than when the stimuli are viewed with only one eye. This "binocular inhibition" is not related to the contrast sensitivity of the better eye or to acuities. Furthermore, this inhibition process is reflected primarily in images with medium to low spatial frequency components (medium to large size bars). CONCLUSIONS: These results have important implications for understanding the functional impact of low vision in older people. They suggest that almost one-half of older people with AMD view the world best using only one of their eyes, whereas for the other half, there is an advantage to using binocular vision for certain visual tasks.

Aged↗
PubMed1999

Functional complaints, visual acuity, spatial contrast sensitivity, and glare disability in preoperative and postoperative cataract patients.

PURPOSE: To quantify cataract patients' functional visual complaints and correlate them with their objective glare disability and spatial contrast sensitivity (SCS) scores. SETTING: Sir Mortimer B. Davis Jewish General Hospital. Montreal, Quebec, Canada. METHODS: Thirty patients scheduled for cataract surgery with a visual acuity of 20/70 or better at the time of patient selection and no other ocular pathology were evaluated objectively and subjectively for visual function preoperatively and within 3 months postoperatively. Objective measures of SCS and visual acuity in the presence and absence of glare were obtained with the Optec 3000 vision tester. Subjective visual function was evaluated with the Activities of Daily Vision Scale (ADVS), a questionnaire that evaluates patients' visual function by assessing the degree of difficulty they experience in performing tasks involving distance vision, near vision, and glare conditions. RESULTS: Preoperatively, patients had decreased visual acuity and SCS in the presence of glare. The ADVS scores were correlated with visual performance. Postoperatively, there was a statistically significant improvement in all dependent measures (i.e., visual acuity and SCS in the presence of glare) as well as in the subjective report of visual performance assessed by the ADVS. CONCLUSION: Spatial contrast sensitivity, glare disability, and the ADVS questionnaire should be considered as adjuncts to visual acuity testing in evaluating certain cataract patients.

Adult↗
PubMed1997

Glare disability and contrast sensitivity before and after cataract surgery.

PURPOSE: To determine whether brightness-induced glare decreases spatial contrast sensitivity and visual acuity in preoperative cataract patients with functional visual complaints and to compare preoperative with postoperative results. SETTING: Sir Mortimer B. Davis Jewish General Hospital, Montreal, Quebec, Canada. METHODS: Twenty patients with a visual acuity of 20/70 or better at the time of chart selection and no other ocular pathology who were referred for cataract surgery were evaluated with the Optec 3000 vision tester to assess contrast sensitivity and visual acuity in the presence and absence of glare. Testing was done preoperatively and 1 and 3 months postoperatively. RESULTS: An analysis of variance indicated that there were statistically significant double interactions between the preoperative/postoperative and glare/no-glare variables and between the preoperative/postoperative and spatial frequency variables. Postoperatively, visual acuity and contrast sensitivity improved to within normal limits. There were no statistically significant differences in visual acuity and spatial contrast sensitivity between 1 and 3 months postoperatively. CONCLUSION: Spatial contrast sensitivity and glare testing provided objective assessment of patients who had good visual acuity yet also had functional complaints.

Adult↗
PubMed1987

Active-passive paradigm in assessing CCTV-aided reading.

Six male and seven female English-speaking university students, with corrected vision of 20/20 (6/6), were trained using the closed circuit television system (CCTV) as a reading aid. This was an attempt to identify the essential factors in CCTV-aided reading. Active and passive observers were trained in pairs, with the passive observer being the yoked control of the active observer. The control participants were trained alone using the same reading material without the use of a CCTV. All participants used material from the Thurstone Reading Kit throughout the five training sessions and were given a pre- and postreading test to assess the increase in reading speed measured in words per minute (WPM). The active observers increased their reading speed to a greater extent than the passive observers, and the passive observers to a greater extent than the control participants. Suggestions are made pertaining to future experimentation and use of the CCTV.

Analysis of Variance↗
PubMed1987

Canadian ophthalmologists and low vision: a national survey.

It is estimated that by the year 2000 there will be a 36% increase in the number of people over 65 years of age compared with the number in 1977. Since visual impairment in developed countries is largely age related, the number of people who require low-vision services is rapidly increasing. A questionnaire survey was carried out to assess the extent of provision of low-vision services by ophthalmologists in Canada; 119 physicians (13%) responded. The results show that few ophthalmologists provide low-vision care. This situation warrants immediate attention.

Age Factors↗
PubMed1987

Factors affecting the successful use of low-vision aids.

Telephone interviews were conducted with 100 partially sighted patients who had been using low-vision aids for at least 6 months. Only "near-vision" aids were examined. The patients were asked how often they used the aid(s), how satisfied they were with it and whether they had any specific complaints about it. There were no differences in the responses between head-borne and hand-held optical aids. The preferred range of dioptric power was 11 to 20 D.

Audiovisual Aids↗
PubMed1986

Multi-flash campimetry as an indicator of visual field loss in glaucoma.

Multi-flash campimetry is a computer-implemented technique used for the rapid assessment of temporal resolving power across the visual field. On the basis of previous reports that glaucoma patients exhibit impaired temporal sensitivity earlier than conventional perimetric field loss, the question of whether multi-flash campimetry might also be sensitive to the visual consequences of glaucoma was explored. Of the 27 patients that were tested, only one had normal temporal resolving power in both eyes, suggesting that multi-flash campimetry might be a useful aid in determining whether a patient should be diagnosed and treated as a glaucoma suspect or as a confirmed glaucoma patient.

Adult↗
PubMed1984

Evaluating visual loss with multi-flash campimetry.

Multi-flash campimetry is a computer-implemented psychophysical technique that allows temporal resolution to be assessed in 120 points per eye in a half hour. It has previously been reported that the results can serve to distinguish between multiple sclerosis patients and control subjects. We have now used this technique to measure temporal resolution in patients with amblyopia, cataracts, optic neuritis or macular degeneration. Our results indicate that multi-flash campimetry is at least as sensitive to visual loss in patients with amblyopia or cataracts as visual acuity testing with the Snellen chart and kinetic visual field testing with the Goldmann perimeter. Further, multi-flash campimetry may be more sensitive than the other two techniques to subtle residual loss in patients who have had optic neuritis and to early loss in patients with macular degeneration.

Adult↗