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D.R. Neal, J. Copland, R.R. Rammage; Objective measurement of accommodation using the COAS aberrometer . Invest. Ophthalmol. Vis. Sci. 2004;45(13):1735.
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Purpose: Recently a number of new technologies have been identified for correction of presbyopia. To develop these new treatment modalities, there is a need to objectively measure the range of accommodation, as well as how these different techniques introduce additional aberrations. This would allow a quantitative comparison of the efficacy of the different methods and provide feedback needed to improve the various processes. Methods: We have modified a COAS aberrometer to provide a measure of accommodation in two different ways. A variable visual stimulus was provided to the subject while simultaneously measuring the residual defocus and higher order aberrations. This method provides a measure of the static accommodation. However, it has been observed that accommodation has significant transient behavior. To measure dynamic accommodation an external target was aligned with the COAS internal target through a beam splitter placed in front of the measured eye. Either a near target or a far target was illuminated in succession. The near target was placed at a distance appropriate to the subject’s age or other condition. The COAS aberrometer was used to measure the full wavefront (including defocus, cylinder and high order terms) dynamically at 15 Hz while the stimulus was changed over a 6–8 diopter range. Results: The instrument was able to measure the accommodation range using either method. The static method provided a plot of defocus error as a function of visual stimulus. The point spread function could be presented at each stimulus to aid in identifying the accommodative mechanism. With the dynamic accommodation measure, we were able to observe changes in both the sphere and spherical aberration (see Figure). With some subjects, these terms had significant time–dependence, with an initial large response that quickly reduced in magnitude. Conclusions: We have developed a series of test methods that use the COAS aberrometer to make routine, quantitative measurements of accommodation. Both static and dynamic measurements were obtained that will be useful in developing new modalities for treatment of presbyopia. View OriginalDownload SlideView OriginalDownload Slide
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