Abstract
Purpose :
Studies spanning over five decades has shown consistently that the longitudinal chromatic aberrations (LCA) of the human eye has been about 2 D. The span of two-diopter between the shorter and longer wavelength of light clearly suggests that there is potential for any of the wavelengths within that range to be in focus at the retinal plane. In this study, we tried to identify the wavelength in focus or wavelength that optimizes the retinal image quality in the human eye.
Methods :
Objective wavefront refraction measured using a Shack Hartmann based aberrometer (COAS) G-200 model at 840 nm wavelength were performed in 46 young subjects, and the COAS software predicted refractions for the wavelengths of 450 nm, 555nm, and 670 nm at 3mm pupil size. The gold standard subjective refraction using a clinical phoropter performed in all the subjects in polychromatic light. Subjective refraction plotted on the objective longitudinal chromatic aberration data plot might potentially identify the wavelength that probably focuses image on the retina.
Results :
The longitudinal chromatic aberration for 3 mm pupil for subject population were determined to be 1.86 D as expected. About 52% of the subject population’s subjective refraction matched objective refraction at the wavelength of around 555 nm (green), and about 22% subjective data matched close to 650 nm wavelength objective refraction. Both shorter and longer wavelengths had about 13% each.
Conclusions :
The wavelength that optimizes the retinal image focus found to be different for different subject and is found that nearly half of the subject population still used mid wavelength region of the visible spectrum to optimize their vision. We suggest applying objective metric like visual strehl ratio (VSX) will substantially improve the effectiveness of predicting the optimal wavelength in focus on the retinal plane.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.