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Mikel Aldaba, Meritxel Vilaseca, Montserrat Arjona, Jaume Pujol; Accommodative Response Measurements Based On Double Pass Images. Invest. Ophthalmol. Vis. Sci. 2011;52(14):836.
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© ARVO (1962-2015); The Authors (2016-present)
To measure accommodative response (AR) by means of a double-pass (DP) system looking for the best retinal image for different accommodative stimulations. Results from the DP system were compared to those obtained with a Hartmann Shack (HS) sensor, and the AR in the first steps of stimulation was also analyzed.
AR was measured with an open field DP system developed in our laboratory. DP images contain complete information on the aberrations and scattering of the eye (Díaz-Doutón et al, IOVS 2006). For each object position an axial scanning was performed in order to find the best retinal image; from the vergence of this image we calculated the AR of the patient. Simultaneously, HS images were recorded, and AR was calculated based on the retinal image quality and the defocus from the Zernike terms. AR was calculated in order to have no accommodative error at 1D stimulation.Ten young healthy adults were enrolled in the study with a mean ± SD in age of 28.75 ± 2.12 years (range: 25 to 31 years), subjective spherical refraction of +0.15 ± 0.56 D (+0.75 to -0.25 D), subjective astigmatic refraction of +0.15 ± 0.56 D (0 to -0.5 D), best corrected visual acuity of 1.17 ± 0.07 (1.0 to 1.25). Patients were corrected according to their subjective refraction, had monocular vision and were instructed to focus on a fixation test during measurements. Accommodation was stimulated from 0 to 5 D using a push-up method, in steps of 0.5 D from 0 to 2 D, and steps of 1D from 2 to 5 D.
When measuring with the DP system, accurate AR were generally obtained: 0.39 ± 0.29 D for 0 D stimulation, 1 ± 0 D for 1 D, 1.87 ± 0.37 D for 2 D, 2.85 ± 0.51 D for 3 D, 3.79 ± 0.45 D for 4 D, and 4.68 ± 0.53 D for 5 D. AR measurements assessed using HS data and based on the best retinal image were in good agreement with the former DP ones, with a mean difference of 0.11 D. On the other hand, defocus based measurements highlighted a higher mean difference: 0.28 D.In the first steps of stimulation (specifically from 0 to 2 D) an accurate AR was measured, although a slightly reduced accommodative range of 1.48 D was found. This could probably be attributed to the lead of accommodation in far vision.
We measured AR from the best retinal image obtained with a DP system. When comparing the results with HS measurements, we found higher differences when this last was based on defocus, and not on the retinal image quality. The method developed is simple and robust and therefore it could be implemented in medical instruments for clinically assessing accommodation.
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