Abstract
Purpose :
Variability across individuals is rarely explored in perceptual and physiological research. We tested the hypothesis that inter-subject differences in the biomechanics of the human lens could be measured in vivo.
Methods :
Inclusion criteria- age 44 through 55 years; best-corrected visual acuity (BCVA) of 20/20 or better in each eye; no abnormalities of the cornea, pupil or lens; no history of ocular trauma or surgery; and no sign of cataract in the undilated eye. Along with standard clinical exams, the test measures included distance-corrected near visual acuity (DCNVA), accommodative amplitude (AA) and the Near Acuity Visual Questionnaire (NAVQ, higher scores indicate greater difficulty with tasks such as reading small print). Longitudinal scans of the lens were performed with the Brillouin Optical Scanning System (BOSSTM, Intelon Optics), to measure the axial thickness and elasticity (“longitudinal elastic modulus”, LEM) of the lens.
Results :
Of 33 subjects, binocular LEM values were obtained from 28 subjects (9 males) and monocular values from a further 4 (2 males). Subject age (mean±SD of 49.8±3.3 years) was significantly correlated with vertical cup-to-disc ratio (CDR), AA and DCNVA (P≤0.001). DCNVA also correlated with CDR and AA (P<0.001). With eyes grouped by the degree of presbyopia (based on DCNVA, mild= 20/25 or 20/32; moderate= 20/40 or 20/50; severe= 20/63 or 20/80), analysis of variance tests showed the following significant differences in the clinical data: smaller CDR and greater AA for the mild group than the other two groups (P<0.001) and higher IOP in the severe group than the moderate (P=0.007). The NAVQ scores ranged from 0 to 100 (out of 100) and were significantly correlated only with DCNVA (P=0.006). Compared with the clinical measures, LEM was positively correlated with AA (P=0.005) and negatively correlated with DCNVA (P=0.02) and spherical equivalence (P=0.03). The BOSS data showed good repeatability within subjects (median variability within each eye of ≤6.1% for LEM and thicknesses) but varied considerably across subjects.
Conclusions :
Across this small range of participant ages and BCVAs (20/15 to 20/20), differences were found between individuals in terms of self-reported difficulty with near vision and in lens elasticity and size, even for those of the same age and/or DCNVA. Thus, BOSS scans provide a non-contacting measure of individual differences in lens biomechanics.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.