Abstract
Purpose :
To estimate the velocity of the accommodation responses in a group of young subjects with a range of refractive errors, using an open-view real-time wavefront sensor. Our aim is to establish whether there is a difference in the accommodation dynamics between myopic and emmetropic subjects.
Methods :
Accommodation dynamics was measured in a group of 11 young normal subjects (age range: 21-34 y; mean: 27.8 y) with refractive errors ranging from 0 to -5.5 D spherical equivalent and less than -1 D of astigmatism. Accommodation dynamics was measured with an open-view binocular Hartmann-Shack sensor operating in real time (E. Chirre et al, Biomed. Opt. Express 6, 4200, 2015). The instrument provides the subject's relative defocus and aberrations for both eyes in real time (25 Hz). Each subject, underwent 3 runs of 3 cycles of accommodation and deaccommodation between a far target presented on a flat screen at 2.8 m and a near target at 0.35 m. For each accommodation instance, far and near steady states were determined and the mean velocity in the accommodation ramp was calculated.
Results :
The average speed of accommodation ranged among subjects from 2.1 to 5.5 D/sec (mean value: 3.6 D/ sec). For a 2.5 D demand, the average lag of accommodation was 0.50 D, with wide variability in individual values from 1.3 D to -0.5 D (only one case of lead). Correlation coefficients between velocity of accommodation and other variables were: R = 0.339 with refractive error; R = 0.323 with accommodation response; R = 0.568 with subject's age. Correlation coefficients of accommodation response with other variables were: R = 0.438 with refractive error; R = 0.281 with age. Refractive error and age were uncorrelated in our group (R=0.009).
Conclusions :
Although previous studies have found no clear relation between accommodation dynamics and myopia, our results suggest that there could be a mild dependence of the speed of accommodation with refractive error. However, this fact can be somehow masked by the stronger relationship between accommodation and age. To disentangle this two factors, a larger population should be studied.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.