Abstract
Purpose:
To describe the magnitude and variability of transverse chromatic aberration (TCA) in the human eye, and to identify the ocular parameters that might determine its magnitude.
Methods:
Two different psychophysical procedures were used to quantify TCA. First, a red and a blue square, presented on a black screen, had to be matched in size by the subjects with their right eyes, using the arrow keys on keyboard. Second, two filled red or blue squares, flickering on top of each other at 2 Hz, had to be adjusted in brightness and in size to minimize the perceived flicker by subjects. Biometric ocular parameters in the right eyes were measured with a commercially available low coherence interferometer, the Lenstar LS 900 (Haag Streit, Switzerland). Corneal power, thickness, anterior chamber depth, lens thickness, vitreous chamber depth and axial length were correlated to psychophysical date. Sixteen subjects with no ocular pathologies other than refractive errors, with ages ranging from 22 to 58 years, participated in the study.
Results:
TCA varied widely among subjects, as was evident from the perceived differences between the red and the blue square which ranged from 0 to 3.2%. The two different psychophysical procedures to measure TCA provided highly correlated results, suggesting that no major confounders existed. The measurements of TCA were affected neither by changes in brightness of the blue or red nor by individual refractive errors. Comparing to optical parameters in the subjects’ eyes, only lens thickness was significantly correlated to TCA (p<0.01). However, since lens thickness and the gradient index structure in the lens both change with age, inter-individual differences in TCA could just be due to differences in age.
Conclusions:
The high inter-individual variability in TCA is largely determined by lens thickness. Since age is the major factor determining lens thickness, TCA increases inevitably with age.
Keywords: 630 optical properties •
414 aging: visual performance •
626 aberrations