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At least 1,225 records · Page 68Linked to original sources
PubMed1995

'When is VISION asked too much'?

The last two decades a shift took place from substitutional/compensatory training to utilisation of residual vision regarding rehabilitation of the visually impaired. Some of the visually impaired are able to use their visual perception nearly as complete as normal seeing people in spite of a severe visual disability. On the other hand, people with nearly normal functions can be severely visually handicapped. To illustrate this, two cases are presented. The first case is a man, aged 47 years, with a juvenile macular degeneration on both eyes. In spite of a very low visual acuity of less then 0.05, he finished an university education and he is able to maintain himself very well in a leading position in a scientific environment, by using adequate low vision devices. Also for his leisure activities, as photography and speed skating, he relies upon visual perception. The second case is a woman, aged 30 years, with nearly normal visual functions, who is not able to read for longer periods caused by conflicting information from the body- and eye movements, and the visual input. This causes sickness during reading. She is unable to use books for her study and is working with recordings on tape. The results of a comprehensive visual assessment will be related to the specific low vision devices and its use.

Adult↗
PubMed2000

Dynamic vision based on motion-contrast: changes with age in adults.

Data are presented for a computerized test of dynamic vision in a sample of 1006 healthy subjects aged between 20 and 85 years. The test employed a form-from-motion stimulus: i.e., within a random-dot display, Landolt rings of the same average luminance as their surroundings become visible only when the dots within the ring are moved briefly, while those of the surround remain stationary. Thus, detection of gap location is based upon motion contrast (form-from-motion) rather than luminance contrast. With the size and exposure duration of the centrally presented ring held constant, motion contrast was manipulated by varying the percentage (between 20 and 100%) of moving dots within the ring. Subjects reported gap location (left, right, top, bottom). A gradual decline of dynamic vision with age was found for all motion-contrast levels. Beyond 70 years of age, chance-level performance occurred in almost half of the subjects. The data provide the basis for applications including diagnostic screening for glaucoma, visual disturbances in brain-damaged patients, as well as assessment of the dynamic vision of drivers of motor vehicles and athletes.

Adult↗
PubMed2003

Behavioral evidence of color vision deficiency in a protanomalia chimpanzee (Pan troglodytes).

Although color vision deficiency is very rare among Old World monkeys and apes, one male chimpanzee (Lucky) was identified as protanomalous by genetic and physiological analyses. This study assessed behavioral phenotypes of Lucky and four chimpanzees with normal color vision by discrimination task using the modified Ishihara pseudo-isochromatic plates. Lucky could not discriminate the stimuli that the other chimpanzees could. This is the first behavioral evidence of color vision deficiency in chimpanzees.

Animals↗
PubMed1992

The role of binocular vision in prehension: a kinematic analysis.

This study examined the contribution of binocular vision to the control of human prehension. Subjects reached out and grasped oblong blocks under conditions of either monocular or binocular vision. Kinematic analyses revealed that prehensile movements made under monocular viewing differed substantially from those performed under binocular conditions. In particular, grasping movements made under monocular viewing conditions showed longer movement times, lower peak velocities, proportionately longer deceleration phases, and smaller grip apertures than movements made under binocular viewing. In short, subjects appeared to be underestimating the distance of objects (and as a consequence, their size) under monocular viewing. It is argued that the differences in performance between the two viewing conditions were largely a reflection of differences in estimates of the target's size and distance obtained prior to movement onset. This study provides the first clear kinematic evidence that binocular vision (stereopsis and possibly vergence) makes a significant contribution to the accurate programming of prehensile movements in humans.

Adult↗
PubMed2005

Explantation of an AcrySof Natural intraocular lens because of a color vision disturbance.

PURPOSE: To describe a patient who complained of color vision disturbance after implantation of a clear intraocular lens (IOL) in one eye and a yellow IOL in the other. DESIGN: Interventional case report. METHODS: A 50-year-old woman complained of binocular imbalance and "yellow vision" in her left eye after implantation of a visible blue light-filtering yellow IOL. A clear IOL had been implanted in her right eye 1 month before. She requested explantation of the yellow IOL. RESULTS: The yellow IOL was exchanged for a clear one, which resolved the unbalanced color vision. CONCLUSIONS: Patients may be intolerant of the color disturbance that results when dissimilarly colored IOLs are implanted. It is advisable to avoid this practice.

Acrylic Resins↗
PubMed2006

Capabilities of potential vision test measurements: clinical evaluation in the presence of cataract or macular disease.

PURPOSE: To determine the usefulness of a battery of potential vision tests (PVTs) including potential acuity meter (PAM), laser interferometer (LI), critical flicker/fusion frequency (CFF), superilluminated pinhole at distance (SPH(d)) and near (SPH(n)), and optimal reading speed (ORS) by their independence of the effects of cataracts and sensitivity to macular disease (MD). SETTING: Department of Optometry, University of Bradford, Bradford and Leeds General Infirmary, Leeds, United Kingdom. METHODS: Potential vision test measurements were determined in 76 patients with age-related cataract and no other eye disease, 52 patients with MD and clear ocular media, and 28 patients with normal, healthy eyes. RESULTS: Potential vision tests were independent of the degrading effects of cataract up to a visual acuity (VA) level of 20/200 or worse (CFF), 20/125 (ORS and SPH), and 20/40 (PAM and LI). A high degree of association was found between PVT scores and distance VA in the MD group for SPH(d) (r2 = 0.93), SPH(n) (r2 = 0.89), and PAM (r2 = 0.71). A moderate correlation was found for LI (r2 = 0.55), CFF (r2 = 0.50), and ORS (r2 = 0.45). CONCLUSIONS: Potential acuity meter and LI showed very limited independence to moderate/dense cataracts and inaccurate predictions in patients with MD. Superilluminated pinhole was relatively unaffected by moderate/dense cataract and yet provided accurate predictions in the presence of MD and clear ocular media. Critical flicker/fusion frequency showed the greatest ability to bypass cataracts, although its ability to predict VA in patients with early MD was limited. The ORS was relatively unaffected by moderate/dense cataract, but its poor ability to predict VA in MD may limit its clinical suitability as a PVT.

Aged↗
PubMed2006

Cost utility for penetrating keratoplasty in patients with poor binocular vision.

PURPOSE: Cost-utility and cost-effectiveness analyses are of increasing importance to clinicians and health policy experts. This study determines the costs in Germany and other countries in relation to gain of utility for patients with bilateral poor vision owing to corneal disease undergoing penetrating keratoplasty (PK) in 1 eye. DESIGN: A cost-utility analysis was performed using retrospective clinical data and high-level evidence-based data. PARTICIPANTS: Sixty patients (mean age, 46.3 years) with bilateral poor vision who underwent PK for corneal disease. METHODS: Visual acuity and utility values were obtained before and 1 year after PK and after suture removal. A 10-year graft survival rate of 80% was assumed. Expenses included costs for the corneal transplant and surgery, medication, and optical rehabilitation. A discount rate of 5% was applied for costs and quality-adjusted life years (QALYs). Cost-utility analysis encompassed a 10-year period after surgery. MAIN OUTCOME MEASURES: The number of QALYs was calculated for the study group undergoing PK. This was divided into the cost of the procedure to get the number of euros spent per QALY gained. RESULTS: Median binocular preoperative visual acuity was -log mean angle of resolution (-logMAR) 0.91+/-0.53 (Snellen equivalent 20/160) yielding a utility value of 0.67. After suture removal and optical rehabilitation, binocular visual acuity increased to median -logMAR 0.36+/-0.36 (20/46) with a utility value of 0.79. Over the 10 years after surgery and considering graft survival and discounting, a cost utility of 9551 euros per QALY was gained (equivalent to US11,557 dollars). One-way sensitivity analysis yielded a range from 7706 euros to 12874 euros per QALY, highlighting the robustness of the model. CONCLUSIONS: Although an expensive procedure, PK is cost effective in patients with bilateral poor vision.

Adolescent↗
PubMed1997

Taxi drivers' accidents: how binocular vision problems are related to their rate and severity in terms of the number of victims.

Recent studies do not agree on the possible relationship between medical conditions and traffic safety; most of them do not control for exposure factors. In this study, we estimate the effect of binocular vision problems on taxi drivers' distributions of crashes (frequency). Moreover, given a crash, we estimate the effect of binocular vision problems on the distributions of the number of victims per crash (dead or injured). Our data and models permit the simultaneous consideration of many variables: age, medical condition, exposure factors measured by distance driven and time behind the wheel, qualitative risk factors, other characteristics of the driver, and crash circumstances in the models for the number of victims. Results show that taxi drivers have a large average number of crashes per year, larger for those with binocular vision problems compared with healthy ones, but not more severe in terms of the number of victims. The driver's past record (number of crashes and demerit points in the previous year) is a significant predictor of the number of crashes. Age is associated significantly with the number and the severity of crashes with older drivers having a better record than the youngest group (30 years old or less).

Accidents, Traffic↗
PubMed2000

Vision and cognition in Alzheimer's disease.

Alzheimer's disease (AD) is known to affect visual pathways, but potential concomitant effects on vision and cognitive performance are not well understood. We studied 43 individuals with AD of mild severity and 22 individuals without dementia on a battery of tests designed to measure multiple aspects of basic and higher-order visual perception and cognition. All subjects performed on the same visual and cognitive test batteries. The results showed no differences between groups on tests of static visual acuity, stereoacuity, dynamic visual acuity or motion direction discrimination. However, individuals with AD performed significantly worse on tests of static spatial contrast sensitivity, visual attention, shape-from-motion, color, visuospatial construction and visual memory. Correlation analyses showed strong relationships between visual and cognitive scores. The findings show that AD affects several aspects of vision and are compatible with the hypothesis that visual dysfunction in AD may contribute to performance decrements in other cognitive domains. The pattern of involvement indicates that AD affects multiple visual neural pathways and regions. It is possible that better understanding of vision-related dysfunction could aid diagnosis and interventions to improve functional capacity in patients with dementia.

Aged↗
PubMed2001

Binocular summation for grating detection and resolution in foveal and peripheral vision.

Peripheral monocular grating resolution has been shown to be limited by the sampling density of the underlying retinal ganglion cells. We wanted to determine if peripheral resolution is also sampling limited binocularly; and, if so, how great is any improvement in either detection or resolution when viewing binocularly? We measured detection and resolution acuity for sinusoidal gratings in foveal and peripheral vision both monocularly and binocularly. Detection and resolution acuity were very similar in foveal vision and displayed a binocular improvement of 5% over best monocular acuity. However, in peripheral vision, while detection acuity improved by 6% binocularly, resolution acuity improved by 16%, with a subsequently smaller aliasing zone. This improvement was greater than predicted by probability summation and implies that the two monocular ganglion cell sampling arrays combine at a higher level resulting in a higher binocular sampling density.

Female↗
PubMed2006

Fixational eye movements in normal and pathological vision.

Most of our visual experience is driven by the eye movements we produce while we fixate our gaze. In a sense, our visual system thus has a built-in contradiction: when we direct our gaze at an object of interest, our eyes are never still. Therefore the perception, physiology, and computational modeling of fixational eye movements is critical to our understanding of vision in general, and also to the understanding of the neural computations that work to overcome neural adaptation in normal subjects as well as in clinical patients. Moreover, because we are not aware of our fixational eye movements, they can also help us understand the underpinnings of visual awareness. Research in the field of fixational eye movements faded in importance for several decades during the late 20th century. However, new electrophysiological and psychophysical data have now rejuvenated the field. The last decade has brought significant advances to our understanding of the neuronal and perceptual effects of fixational eye movements, with crucial implications for neural coding, visual awareness, and perception in normal and pathological vision. This chapter will review the type of neural activity generated by fixational eye movements at different levels in the visual system, as well as the importance of fixational eye movements for visual perception in normal vision and in visual disease. Special attention will be given to microsaccades, the fastest and largest type of fixational eye movement.

Fixation, Ocular↗
PubMed1994

Visual morbidity in giant cell arteritis. Clinical characteristics and prognosis for vision.

PURPOSE: To characterize visual morbidity in giant cell arteritis and to assess prognosis with respect to treatment. METHODS: Record review of 185 patients with coded diagnosis of giant cell (cranial) arteritis examined at the Bascom Palmer Eye Institute from January 1, 1980, to January 31, 1993. RESULTS: Forty-five patients with biopsy-proven giant cell arteritis had visual symptoms, and 41 individuals (63 eyes) lost vision. The visual loss was unilateral in 19 patients (46%), sequential in 15 (37%), and simultaneous in 7 (17%). Anterior ischemic optic neuropathy developed in 88% of eyes, visual acuity was 20/200 or worse in 70%, 21% had no light perception, and the majority of field defects in testable eyes, aside from central scotomas associated with loss, showed altitudinal or arcuate patterns. Six patients lost vision during corticosteroid therapy for systemic symptoms of giant cell arteritis, whereas in 39 patients visual symptoms prompted steroid treatment. For visual symptoms, 25 patients received intravenous methylprednisolone, whereas 20 received oral prednisone alone. In the 41 patients with visual loss, vision was unchanged in 20 (49%), it worsened in 7 (17%), and it improved in 14 (34%). Subsequent fellow eye involvement was observed only with oral therapy, and a greater percentage of patients (9/23 [39%] versus 5/18 [28%]) improved after intravenous treatment. CONCLUSIONS: In the authors' series, patients with visual loss due to giant cell arteritis had a 34% chance for some improvement in visual function after corticosteroid treatment. Intravenous therapy may diminish the likelihood of fellow eye involvement and was associated with a slightly better prognosis for visual improvement.

Administration, Oral↗
PubMed2002

Paediatric community vision screening with combined optometric and orthoptic care: a 64-month review.

We report a new model of community-based secondary vision screening and demonstrate that a high proportion of children can be effectively managed in such a clinic without referral to the hospital eye service (HES). We performed a 64-month retrospective study of a secondary vision screening clinic providing the combined skills of an optometrist and orthoptist in a community setting. Particular attention was given to the diagnosis and management of children not referred to the HES. During this period, 1755 children were sent appointments and 74% (1300) attended the clinic. The community orthoptist and school nurses referred 53% of the patients and health visitors, general practitioners and community medical officers made 32% of the clinic referrals. Spectacles were prescribed for 41% of the children and 8% were prescribed patching. Sixteen per cent of the children were referred on to the HES. This model of care using the combined expertise of the orthoptist and optometrist is able to diagnose and manage the majority of children who have failed primary vision screening and avoids unnecessary referrals to the HES.

Ambulatory Care↗
PubMed2002

Temporal detection in human vision: dependence on eccentricity.

Studies of human perception of time-varying luminance often aim to estimate either temporal impulse response shapes or temporal modulation transfer functions (MTFs) of putative temporal processing mechanisms. Previously, temporal masking data have been used to estimate the properties and numbers of these temporal mechanisms in central vision for 1 cycle per degree (cpd) targets [Fredericksen and Hess (1998)]. The same methods have been used to explore how these properties change with stimulus energy [Fredericksen and Hess (1997)] and spatial frequency [Fredericksen and Hess (1999)]. We present here analyses of the properties of temporal mechanisms that detect temporal variations of luminance in peripheral vision. The results indicate that a two-filter model provides the best model for our masking data, but that no multiple filter model provides an acceptable fit across the range of parameters varied in this study. Single-filter modelling shows differences between processing mechanisms at 1 cpd in central vision and those that operate eccentrically. We find evidence that this change is because of differences in relative sensitivities of the mechanisms, and to differences in fundamental mechanism impulse responses.

Electronics↗
PubMed2006

[Influence of body position on ocular cycloposition in patients without binocular vision].

PURPOSE: Positionally induced cyclotorsion could be an important factor concerning correction of astigmatism in refractive surgery. Previous studies have shown no influence of body position on cycloposition in healthy subjects with normal binocular vision. METHODS: 10 subjects (median value of age 44.2 years) without binocular vision due to an organic eye disease or to strabismus were examined using three-dimensional video-oculography (3D-VOG). This non-invasive method can record changes in the position of both eyes simultaneously in the x-, y- and z-axes. The cycloposition of the eyes was recorded first in a seated position with both eyes open (test 1), then in a supine position with the right eye closed (test 2), then in a supine position with occlusion of both eyes (test 3), and then in a supine position with both eyes open (test 4). In each of these 4 situations, the eyes were recorded for 1 minute. Cyclovergence was calculated as the difference between the right and the left eye positions. RESULTS: The range of cycloposition of the right and left eye in all 4 tests was very small. 95 % confidence intervals for cycloposition of the right and left eyes and for cyclovergence: cycloposition right eye/cycloposition left eye/cyclovergence: 0.72;0.76/- 0.07;0.01/0.71;0.79 (test 1), 0.23;0.29/0.19;0.33/- 0.81;- 0.63 (test 2), - 0.92;0.7/- 0.51;- 0.37/- 0.79;- 0.45 (test 3), 0.14;0.52/- 0.07;0.31/0.59;0.21 (test 4). There was no statistically significant difference of the cycloposition between the 4 test situations. CONCLUSIONS: The cycloposition of the eyes does not significantly change between seated and supine positions of the body, either in subjects with, or without binocular vision. This means for refractive surgery that a correction of astigmatism, to be performed in the supine position of the patient, can be based on a measurement of the axis of astigmatism obtained in the seated position.

Adult↗
PubMed2000

Monocular and binocular vision in the control of goal-directed movement.

In the present research the authors examined the time course of binocular integration in goal-directed aiming and grasping. With liquid-crystal goggles, the authors manipulated vision independently to the right and left eyes of 10 students during movement preparation and movement execution. Contrary to earlier findings reported in catching experiments (I. Olivier, D. J. Weeks, K. L. Ricker, J. Lyons, & D. Elliott, 1998), neither a temporal nor a spatial binocular advantage was obtained in 1 grasping and 2 aiming studies. That result suggests that, at least in some circumstances, monocular vision is sufficient for the precise control of limb movements. In a final aiming experiment involving 3-dimensional spatial variability and no trial-to-trial visual feedback about performance, binocular vision was associated with greater spatial accuracy. Binocular superiority appeared to be most pronounced when participants were unable to adjust their limb control strategy or procedure on the basis of terminal feedback about performance.

Adult↗
PubMed2004

Prevalence of non-vision-impairing conditions in a village in Chakwal district, Punjab, Pakistan.

PURPOSE: To determine the prevalence of non-vision-impairing ocular conditions (NVIC) and estimate the number of primary eye care treatments per 1000 population per month. METHODS: A cross-sectional study in a random sample of 1670 people was done to determine the load of NVIC in a village in Chakwal district. RESULTS: The prevalence of NVIC was 30.6% (306 per 1000 population). NVIC with the exclusion of presbyopia accounted for 14.6%. The main NVIC were allergic conjunctivitis (3.7%), bacterial conjunctivitis (3.5%), pterygium/pinguicula (2.6%) and acute/chronic dacryocystitis (1%). The average Complaint Frequency (CF) per month/1000 population was 55, excluding complaints of near vision and watery eyes. CONCLUSIONS: The foundation of a comprehensive district eye care strategy in the light of VISION 2020 - the Right to Sight - remains an effective primary eye care service whose elements are treatment of NVIC, detection and referral of cataracts and refractive errors, and promotion of eye health.

Adolescent↗
PubMed2005

Vision and self-rated health: longitudinal findings from an older Australian population.

PURPOSE: To assess temporal associations between vision and self-rated health. METHODS: We examined 3654 Australian residents (82.4% response) aged 49+ years in the Blue Mountains Eye Study, during 1992 to 1994, and re-examined 2334 in 1997 to 1999. Change in vision was defined if baseline and 5-year visual acuity (VA) changed by > or =10 letters (2 lines). Change in self-rated health was defined if overall health ranking (excellent, good, fair, poor) changed by > or =1 step. RESULTS: Of 2285 participants with data from both examinations, 59.8%, 23.9%, and 16.3% reported unchanged, declined, and improved self-rated health, respectively. Among persons whose self-rated health declined, the proportions with a decline in presenting VA, no change, or improvement were similar (25.2%, 23.8% and 22.5%, respectively, p for trend = 0.5). Among participants with decline, no change, or improvement in self-rated health, a similar magnitude in the age-sex adjusted mean VA decline (-1.0 to -2.7 letters) was observed. After adjusting for age, sex, hospitalizations, and incident chronic conditions, declining VA was not associated with increased decline in 5-year self-rated health (multivariate-adjusted odds ratio 0.99, 95% CI 0.75-1.30). CONCLUSION: There were no parallel 5-year changes in self-rated health and vision in this population.

Aged↗