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LS Gray, D Seidel, G Heron; Reduced Blur Accommodation Responses in Late-onset Myopia are Improved by the Addition of Free-space Stimulation . Invest. Ophthalmol. Vis. Sci. 2002;43(13):1490.
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Purpose:Inaccurate accommodation responses to blur-only stimuli have been shown in late-onset myopia (LOM). The aim of this experiment was to determine whether free-space and binocular stimulation would improve the quality of accommodation responses in LOM subjects. Methods:10 emmetropic subjects (mean age 22.32.3 years) and 10 LOM subjects (mean age 21.81.5 years) participated with informed consent in the study. A specially modified Canon R-1 infrared optometer was used to measure accommodation stimulus-response (SR) curves, accommodation microfluctuations while viewing a 3D target, and step accommodation responses to 1D and 2D step changes in stimulus vergence. Measurements were made in a random order. Three conditions were presented: 1. Monocular blur-only stimulus, 2. Monocular free-space stimulus, 3. Binocular free-space stimulus. Each condition was presented on a separate day to avoid fatigue effects. Results:Accommodation SR curves in the LOM group showed improved accuracy with the free-space stimulus. Microfluctuations were significantly (p<0.01) smaller in magnitude in the LOM group with the free-space stimulus, due to reductions in the low frequency components of the fluctuations. A significant (p<0.01) increase in the percentage of correct step accommodation responses to the free-space stimulus was found in the LOM group. However, step response times in the LOM group with the free-space stimulus were not significantly different than those found with the blur-only stimulus, and were significantly (p<0.01) longer than those found in the emmetropic group. Binocular stimulation produced no significant improvements in accommodation response in the LOM group. Non-significant improvements in accommodation responses were found in the emmetropic group with both free-space and binocular stimulation. Conclusion:1. Free-space stimulation produces significant improvements in static accommodative accuracy in LOM subjects compared with blur-only stimulation. 2. The quality of dynamic accommodation responses in LOM subjects was found to improve significantly with free-space stimulation. 3. LOM subjects appear to rely upon proximity driven stimuli to improve accommodative response accuracy.
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