Optometry and Vision Sciences - Research Publications

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Subject: Vision × Author: Anderson, Andrew ×

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    Oscillopsia and the Influence of Stress and Motivation in Fusion Maldevelopment Nystagmus Syndrome
    Cham, KM ; Anderson, AJ ; Abel, LA (ASSOC RESEARCH VISION OPHTHALMOLOGY INC, 2013-03)
    PURPOSE: We examined factors influencing perceptual stability in observers with fusion maldevelopment nystagmus syndrome (FMNS). In addition, we also investigated the effect of visual demand, task-related physiologic stress, and motivation on the nystagmus waveform. METHODS: Perception of oscillopsia during daily activities was assessed via a questionnaire. Perception of oscillopsia in the laboratory was assessed using central and peripheral (10°) light emitting diodes (LEDs) in front of a background display of random, fixed-contrast shapes. Task-induced stress was achieved via a time restricted acuity task with or without concurrent mental arithmetic challenge, and motivation varied using a reward-penalty paradigm. The experiments have been previously described elsewhere. RESULTS: Six out of nine subjects reported experiencing oscillopsia in certain daily activities. in the laboratory, the percentages of trials with perceptions of motion of the led and background were as follows: neither, 60% to 70%; background only, 20% to 30%; both, 5% to 15%, and LED only, 5% to 15%. Over all trials, six of nine experienced oscillopsia for both the low- and high-contrast image respectively (i.e., three subjects never experienced oscillopsia). The background was frequently seen moving for both images regardless of contrast and/or condition. Trials with and without oscillopsia did not differ when comparing foveation. In the second experiment, task-related physiologic stress and motivation were reflected in an increase in heart rate; nystagmus waveform intensity increased and foveation decreased. The magnitude of changes in heart rate was uncorrelated with changes in waveform parameters for all experiments, however. CONCLUSIONS: Preliminary results suggest that the FMNS group does perceive spatially inhomogeneous oscillopsia, similar to infantile nystagmus syndrome (INS), in certain visual environments. In investigating the effect of stress and motivation on FMNS, a new, if tentative, finding suggests that task-induced stress and/or motivation may have a negative impact on the nystagmus. Taken together, our findings provide an insight into the particular environments and tasks that are likely to present particular challenges to persons with FMNS.
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    How Useful Is Population Data for Informing Visual Field Progression Rate Estimation?
    Anderson, AJ ; Johnson, CA (ASSOC RESEARCH VISION OPHTHALMOLOGY INC, 2013-03)
    PURPOSE: Bayesian estimators allow the frequency of visual field progression rates in the population (the prior distribution) to constrain rate estimates for individuals. We examined the benefits of a prior distribution accounting for one of progression's major risk factors--whether intraocular pressure is treated--to gauge the maximum benefit expected from developing priors for other glaucoma risk factors. METHODS: Our prior distribution was derived from published data from either treated (matched-prior condition) or untreated (unmatched-prior condition) glaucoma patients. We simulated MD values (6-monthly) with true underlying progression rates drawn from the same distribution as the prior for the matched-prior condition. We estimated rates through linear regression, and determined the likelihood of obtaining this estimate as a function of a range of true underlying progression rates (the likelihood function). The maximum likelihood estimate of rate was the most likely value of the posterior distribution (the product of the prior distribution and likelihood function). RESULTS: For short (4) visual field series, the matched-prior condition, unmatched-prior condition, and linear regression gave median errors (estimated minus true rate) of 0.02, 0.20, and 0.00 dB/y, respectively. Positive predictive values for determining rapidly progressing (<-1 dB/y) rates were 0.46, 0.42, and 0.38, with negative predictive values of 0.93, 0.94, and 0.95. For more extended series the magnitude of the differences between techniques decreased, although the order was unchanged. CONCLUSIONS: Performance shifts in bayesian estimators of visual field progression are modest even when prior distributions do not reflect large risk factors, such as IOP treatment.