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PubMed1985

Differentiation of asymptomatic patients from symptomatic patients by the slope of the forced vergence fixation disparity curve.

Eighty-nine optometry students were divided into an asymptomatic group and a symptomatic group on the basis of a case history. A forced vergence fixation disparity (FD) curve was generated for each subject using a Disparometer (Vision Analysis, Columbus, Ohio). Slopes were calculated for each curve. In addition, each curve was labeled steep or flat based on a previously determined cutoff point of -0.96 min/delta (Sheedy, 1980). Steep curves did not correlate well with symptomatic patients, whereas flat curves did not correlate well with asymptomatic patients. An independent t-test found no significant difference between the two groups.

Fixation, Ocular↗
PubMed2006

Perspectives on low vision service in Canada: a pilot study.

BACKGROUND: A review of the literature and current practice patterns for vision rehabilitation care in Canada provide a basis for this pilot study, which was undertaken to explore related issues from the perspectives of older adults and low vision service providers. The pilot study was overseen by a number of collaborators whose names are listed at the end of this paper. METHODS: Thirty people aged 60 years or older who had vision impairments and were clients of the Canadian National Institute for the Blind were surveyed by telephone. Ophthalmologists, optometrists, and opticians completed a mail questionnaire. Vision rehabilitation practitioners and nurses, ophthalmic technicians, and service providers for low vision technical aids were surveyed by e-mail. RESULTS: Ophthalmologists are a primary source of referrals to low vision services, but low functional vision does not always trigger such referrals, nor are referrals always timely. Optometrists are primary providers of low vision services, including dispensing of low vision aids, but such aids are expensive, and inadequate training in their use may contribute to noncompliance. Costs associated with providing low vision assessments and services are higher than compensation to vision service providers, whose capacity to meet increasing demand is limited. In addition, there are disparities between rural and urban areas and among provinces in the availability of, and funding for, services and aids. INTERPRETATION: On the basis of the findings, an emergent theory is proposed on the consequences resulting from lack of planning and standards for vision rehabilitation care. The implications of this study form the basis for further research.

Aged↗
PubMed2002

Intravitreal triamcinolone in subfoveal recurrence of choroidal neovascularisation after laser treatment in macular degeneration.

BACKGROUND: Laser treatment of extrafoveal well delineated choroidal neovascularisation in exudative age related macular degeneration has a high rate of failure with subsequent severe vision loss from subfoveal involvement. Laser treatment may limit scotoma size, but is unpalatable because of early persistent vision loss. Intravitreal triamacinolone injection may be an acceptable alternative therapy in such disparate cases. METHODS: 14 consecutive patients with recurrent neovascularisation were treated with a single 4.0 mg injection of triamacinolone and followed for up to 1 year. Visual results were compared with published data from the Macular Photocoagulation Study of recurrent neovascularisation. RESULTS: Mean visual acuity remained stable at about 20/200 throughout the study period in the treated patients. This is comparable to the outcomes in the Macular Photocoagulation Study for laser retreated patients, and better than the observation group. CONCLUSIONS: Intravitreal triamcinolone may be an acceptable treatment of subfoveal recurrent neovascularisation while avoiding early persistent vision loss from laser retreatment.

Anti-Inflammatory Agents↗
PubMedDate not supplied

Addressing health disparities through promoting equity for individuals with intellectual disability.

Intellectual disabilities (ID) are conditions originating before the age of 18 that result in significant limitations in intellectual functioning and conceptual, social and practical adaptive skills. IDs affect 1 to 3% of the population. Persons with ID are more likely to have physical disabilities, mental health problems, hearing impairments, vision impairments and communication disorders. These co-existing disabilities, combined with the limitations in intellectual functioning and in adaptive behaviours, make this group of Canadians particularly vulnerable to health disparities. The purpose of this synthesis article is to explore potential contributory factors to health vulnerabilities faced by persons with ID, reveal the extent and nature of health disparities in this population, and examine initiatives to address such differences. The review indicates that persons with ID fare worse than the general population on a number of key health indicators. The factors leading to vulnerability are numerous and complex. They include the way society has viewed ID, the etiology of ID, health damaging behaviours, exposure to unhealthy environments, health-related mobility and inadequate access to essential health and other basic services. For persons with ID there are important disparities in access to care that are difficult to disentangle from discriminatory values and practice. Policy-makers in the United States, England and Scotland have recently begun to address these issues. It is recommended that a clear vision for health policy and strategies be created to address health disparities faced by persons with ID in Canada.

Adult↗
PubMed2006

Subtle binocular vision anomalies in migraine.

A literature review reveals old references to an association between migraine headache and binocular vision anomalies, but a lack of scientific evidence evaluating these claims. In a masked case control study, we investigated binocular vision using standard clinical tests in people with migraine and in controls. Some test results suggest that heterophoria and fixation disparity are more common in the migraine group. The migraine group also had slightly reduced stereopsis. We found significant correlations between some migraine variables and some binocular vision variables (e.g., duration of worst headache and impaired stereopsis) but our analyses do not suggest that a causal relationship is likely. In conclusion, people with migraine have on average a slightly higher prevalence of heterophoria and aligning prism, and reduced stereopsis compared with controls. However, the differences are subtle and our data do not support the use of binocular vision interventions prescribed solely on the basis of the presence of migraine.

Adult↗
PubMed1980

Stereopsis and fixation disparity following prolonged monocular occlusion.

The effects of 12 days of continuous monocular occlusion on the stereoscopic acuity and the magnitude of the fixation disparity associated with a given amount of prism-forced vergence were investigated in six adult subjects with normal binocular vision. After the period of occlusion, all six subjects were able to perceive stereopsis, although four of the six subjects demonstrated a slight but reversible elevation in stereothresholds. The general shape of the fixation disparity curve for a given individual was not altered by occlusion, but changes in the magnitude of the fixation disparity were observed for some subjects.

Adult↗
PubMed2004

Reasons patients recommend laser in situ keratomileusis.

PURPOSE: To evaluate the reasons patients who have had laser in situ keratomileusis (LASIK) recommend it to others and examine the disparity between high levels of satisfaction and patient reports of night-vision symptoms and/or dry eye after LASIK. SETTING: Northeastern Eye Institute, Scranton, and the University of Pittsburgh, Pittsburgh, Pennsylvania, and the University of California at Los Angeles, Los Angeles, California, USA. METHODS: Questionnaires assessing symptoms and satisfaction after LASIK were mailed to 2,100 patients. The questionnaires included items about night-vision symptoms and satisfaction and an open-ended question for patients to give their reasons for recommending LASIK to others. The open-ended responses were categorized and tabulated. RESULTS: Four hundred thirty-four patients provided reasons for recommending LASIK to others. Sixteen categories of reasons were identified. "No more spectacles/contact lenses" was listed by 180 patients (42%), followed by "better vision" (21%) and "convenience" (15%). Women were significantly more likely to cite "better comfort" (27 women versus 3 men; chi square = 8.99, P =.003) and "better quality of life" (41 women versus 9 men; chi square = 7.36, P =.007) as a reason for recommending LASIK. Of the 35 patients who reported dissatisfaction with post-LASIK vision, 20 (57%) would recommend LASIK to a friend because "LASIK helps others." CONCLUSIONS: Categories of reasons for recommending LASIK to others were similar to reasons given by patients for seeking LASIK. Some patients who reported dissatisfaction with their vision said they would recommend LASIK, suggesting that recommendation of LASIK to others is not necessarily a measurement of the quality of a patient's vision after LASIK.

Adult↗
PubMed2001

Progressive outer retinal necrosis and acute retinal necrosis in fellow eyes of a patient with acquired immunodeficiency syndrome.

PURPOSE: To describe an unusual concurrence of acute retinal necrosis and progressive outer retinal necrosis in fellow eyes of a patient with acquired immunodeficiency syndrome (AIDS). METHODS: Interventional case report. In a 37-year-old man with AIDS and herpes zoster keratitis in the right eye, progressive outer retinal necrosis developed in the right eye and acute retinal necrosis developed in the left eye. RESULTS: Disparate presentations of retinitis persisted in each eye, and retinal detachment and vision loss ensued in both eyes despite antiviral therapy. CONCLUSION: Distinct features of acute retinal necrosis and progressive outer retinal necrosis do not necessarily reflect systemic factors, and they may be variant manifestations of the same underlying infection.

Acquired Immunodeficiency Syndrome↗
PubMed1978

Merging of modalities in the optic tectum: infrared and visual integration in rattlesnakes.

The optic tectum of pit vipers (Crotalinae) contains a layer of infrared-sensitive neurons subjacent to the visual layer; these indirectly receive input from the facial pit organs. They respond transiently to the appearance or motion of warm objects within their 25 degrees to 70 degrees excitatory receptive fields (some have inhibitory regions) and presumably allow the snake to orient or strike toward prey. The infrared and visual spatiotopic tectal maps have similar but not identical axes; the infrared magnification is greater than that for vision. Bimodal neurons have receptive fields for each modality that reflect the disparity of the two maps. This finding suggests that (i) during development the infrared and visual fibers spread out independently to fill available tectal sites and (ii) bimodal neurons form local connections without regard to establishing spatial correspondence between the two modalities.

Animals↗
PubMed2000

Community care partnership: planning with the community.

We are at the threshold of transitioning from an illness delivery system to a health delivery system. "Partnerships for Health in the New Millennium," kicked off in January 2000 by Donna E. Shalala, Secretary of Health and Human Services, and Surgeon General David Satcher, launching "Healthy People 2010," have provided us with the prevention agenda for our nation. The leadership challenge ahead for us in the communities where we live and work is to develop a shared vision of health with our community partners which is committed to eliminating disparities in health for all our populations.

Community Networks↗
PubMed1995

Influence of the luminance signal and red-green and yellow-blue opponent chromatic signals in figural-stimuli stereograms.

The influence of color signals on stereopsis has been studied using figural-stimuli stereograms with variations introduced according to the opponent chromatic channels (red-green and yellow-blue), derived from Boynton's color-vision model. We used wallpaper stereograms, which enable the rank-order disparity ranges of the chromatic and luminance signals to be compared with the rank-order disparity range of proximity, a particular spatial configuration of the stereogram in which there are no variations in chromaticity and/or luminance. The results indicate that both chromatic signals contribute to stereopsis as does the luminance signal, contradicting the model of Hubel and Livingstone. The results also show there are no clear dependencies upon the kind of signal processed, as luminance and chromatic variations are processed with the same efficiency.

Color Perception↗
PubMed2005

Functional outcomes and patient satisfaction after laser in situ keratomileusis for correction of myopia.

PURPOSE: To determine subjective patient satisfaction and self-perceived quality of vision after laser in situ keratomileusis (LASIK) to correct myopia and myopic astigmatism. SETTING: Department of Ophthalmology, Academic Hospital Maastricht, Maastricht, The Netherlands. METHODS: A validated questionnaire consisting of 66 items was self-administered by 142 consecutive patients. Seven scales covering a specific aspect of quality of vision were formulated. Aspects included global satisfaction, quality of uncorrected and corrected vision, quality of night vision, glare, daytime driving, and night driving. Main outcome measures were responses to individual questions and scale scores, and correlations with clinical parameters including refractive outcome, uncorrected visual acuity, best corrected visual acuity, ablation depth, and scotopic pupil-optical zone disparity were obtained. RESULTS: The mean score for the overall satisfaction was 4.1 +/- 0.71 (SD) (scale 0 to 5.0). A total of 92.2% of patients were satisfied or very satisfied with their surgery, 93.6% considered their main goal of surgery achieved, and 92.3% would choose to have LASIK surgery again. Satisfaction with uncorrected vision was 3.03 +/- 0.71. The mean score for glare was 3.0 +/- 0.9. At night, glare from lights was believed to be more important than before surgery by 47.2%. Glare from oncoming car headlights after surgery was reported by 58.4% and was believed to be more bothersome for night driving than before surgery by 52.8%. Night driving was rated more difficult than before surgery by 39.4%, whereas 59.3% had less difficulty driving at night. There was a significant correlation between the uncorrected vision score and the postoperative spherical equivalent (r = 0.245) and postoperative astigmatism (r = 0.265). There was no correlation between the glare or night vision scores and the degree of correction, the amount of ablation depth, or the disparity between the scotopic pupil and the optical zone. CONCLUSIONS: Self-perceived uncorrected vision after LASIK surgery for the correction of myopia and myopic astigmatism appears to be very good and is related to the postoperative residual error. Although the majority of patients postoperatively experienced glare, particularly with driving at night, this was not related to the pupil-optical zone disparity or degree of correction.

Adult↗
PubMed2001

Motion direction, speed and orientation in binocular matching.

The spatial differences between the images seen by the two eyes, called binocular disparities, can be used to recover the volumetric (three-dimensional) aspects of a scene. The computation of disparity depends upon the correct identification of corresponding features in the two images. Understanding what image features are used by the brain to solve this matching problem is one of the main issues in stereoscopic vision. Many cortical neurons in visual areas V1 (ref. 2), MT (refs 3, 4) and MST (refs 5, 6) that are tuned to binocular disparity are also tuned to orientation, motion direction and speed. Although psychophysical work has shown that motion direction can facilitate binocular matching, the psychophysical literature on the role of orientation is mixed, and it has been argued that speed differences are ineffective in aiding correspondence. Here we use a different psychophysical paradigm to show that the visual system uses similarities in orientation, motion direction and speed to achieve binocular correspondence. These results indicate that cells that multiplex orientation, motion direction, speed and binocular disparity may help to solve the binocular matching problem.

Depth Perception↗