Purpose: To examine the relationship between visual acuity (VA) and radial deformation acuity (RDA) in children 6 to 12 years of age with amblyopia. Methods: RDA was measured in 35 participants with the Manchester RDA charts. VA was measured with the Early Treatment Diabetic Retinopathy Research Study (ETDRS) chart. Results: Median VA in non-amblyopic and amblyopic eyes was 0.04 logMAR (IQF -0.06 – 0.12) and 0.24 (IQF 0.12 – 0.04), respectively (Wilcoxon Signed Ranks test, z = -5.07, p < 0.001). Median RDA in non-amblyopic and amblyopic eyes was 2.73 log (IQF 2.53 – 2.87) and 2.63 log (IQF 2.53 – 2.77), respectively (Wilcoxon, z = -2.56, p < 0.05). Spearman correlation suggested that the amblyopic deficits in VA and RDA were related, r = -0.42, p < 0.05. Conclusion: A deficit in RDA was present in most children with amblyopia. A moderate relationship was noted between the amblyopic deficits found in VA and RDA.

Thesis (Ph.D.)--University of Western Australia, 2003.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1994. / Vita. Abstract. Includes bibliographical references (leaves 34-38). Also available via the Internet.

Issued also as author's dissertation. / Columbia contributions to philosophy and psychology, vol. XX, no. 2.

M. Phil. / Please refer to full text to view abstract / Prof. J.T. Ferreira

No description available.

Clinical relevance: Mobility and fall risk may be important considerations in choosing between intraocular lenses. Background: Fall risk in older adults increases when wearing multifocal spectacles, but little is known about mobility among individuals with different types of intraocular lenses. This study compared visual function, fall risk and balance control following bilateral implantation of monofocal or multifocal intraocular lenses. Methods: This was a non-randomised, cross-sectional study involving adults with bilateral intraocular lenses. Participants completed questionnaires concerning physical functioning, fall history and balance-related confidence. Binocular visual acuity, contrast sensitivity (Pelli-Robson chart and computerized testing), depth perception and glare sensitivity were assessed. Physical performance measures included the Sensory Organization Test, preferred gait speed, Dynamic Gait Index and wayfinding in a virtual environment. Results: Fifteen participants (mean ± standard deviation, 67.1 ± 6.8 years) had monofocal intraocular lenses and 14 participants (68.1 ± 6.1 years) had multifocal intraocular lenses. Contrast sensitivity in the monofocal group was significantly better than that in the multifocal group (p = 0.02) at intermediate and high spatial frequencies. Contrast sensitivity of the monofocal group also was less affected by glare than the contrast sensitivity of the multifocal group, at an intermediate spatial frequency (p = 0.02). However, the multifocal group had significantly better Dynamic Gait Index scores (p = 0.04), even after controlling for perceived physical function. Conclusions: The participants with monofocal intraocular lenses generally had better contrast sensitivity than did those with multifocal intraocular lenses. However, the scores on a mobility test that is associated with fall risk were worse for those with monofocal lenses.

Static Visual Acuity (SVA) has been called into question for some time as a measure of overall visual system function and as a predictor of performance on real-life tasks requiring vision (i.e., operating an automobile). Specifically, it has been pointed out that the targets employed in most SVA testing (high contrast, stationary letters) are an insufficient analog to actual targets encountered in everyday activities, which are often in motion and/or of less-than-perfect contrast. In addition, the size-threshold methodology typically used to measure SVA is incongruent with current theories of a multi-channel visual system. Dynamic Visual Acuity (DVA) and Contrast Sensitivity have been suggested as alternatives to SVA, but while each mitigates specific weaknesses of the SVA measure, neither addresses the shortcomings completely. Traditional DVA measures employ moving targets, but these targets are usually of perfect contrast and a size-threshold methodology is used to specify acuity levels. Contrast Sensitivity employs a contrast-threshold methodology and allows measurement of specific visual channels, but stationary targets are utilized. The present study combined the DVA and Contrast Sensitivity measures in an effort to retain the unique qualities of each while addressing their shortcomings, resulting in a more detailed picture of the human visual system and functioning than has yet been possible. By measuring contrast sensitivity to targets at a set of spatial frequencies spanning the human "window of visibility" and under conditions of motion representative of that encountered in everyday activities, it was hoped that a more powerful predictor of actual visual performance would be created. In addition, normative data was established for two separate age populations, in the hopes of learning more about specific changes that occur to the visual system during the aging process. Indeed, several effects and interactions among the three main variables (spatial frequency, velocity, age) were uncovered, which appears to indicate that the new test may provide more information about the visual system than DVA or contrast sensitivity by themselves. The ramifications of this effort to human factors and visual performance research are discussed along with recommendations for the continuation and application of this line of research.

Much research has been accomplished on the effects of target motion on visual acuity. Research has also been accomplished on the effects of target orientation on visual acuity. The contrast sensitivity function (CSF) also has been studied as a predictor of visual performance under dynamic conditions. However, no previous studies have combined these areas of research and examined the effect of target orientation on the Dynamic Contrast Sensitivity Function (DCSF). This study examined the effects of target orientation on the DCSF and found that diagonal lines (relative to vertical lines) decreased the DCSF, on average over 19%. Previous research indicated that target motion reduces contrast sensitivity, and at the same time shifts the peak of the CSF toward lower spatial frequencies. This study rotated the target in a circular path (velocities of 22°, 30°, and 39°/second) and found a similar decrement and shift in the CSF. The main effects for Target Orientation, Velocity, and Spatial Frequency and their two-way interactions were all statistically significant (p ≤ .05). Additionally, all velocity conditions were found to be statistically different from each other. These results advance the validity of our measurement device and procedures. The effect of target orientation presumably is a function of the magnocellular and parvocellular visual pathway systems and their roles in the detection of form and motion. While the magnocellular system is primarily responsible for detection of motion and large objects, the parvocellular system is responsible for the detection of color and fine detail. / Master of Science

A great deal of research has been conducted on the effects of vibration on visual acuity. The human contrast sensitivity function (CSF) has also been studied extensively as a predictor of visual performance under real-world conditions. However, no previous studies have combined the two lines of research and examined the effect of vibration on the CSF. Prior research indicates that increasing rates of vibration correspond to a decrease in traditional measures of visual acuity. However, other studies indicate that motion enhances target detection. The present study examined the effects of vibration upon the CSF and found that vibration lowers the threshold of detection for low spatial frequencies but raises the threshold for high spatial frequencies. A loss of contrast at high spatial frequencies due to retinal "smear" may be the cause of this increase in high spatial frequency thresholds under vibration. Physiological mechanisms of motion detection, direction selectivity, and visual pathways are also discussed. This study may have important implications for aerospace medicine and occupations which demand viewing a target or instrument panel under conditions of vibration. / Master of Science