Abstract
Purpose :
Ex vivo studies have often reported increases in lens size and stiffness with increasing age. In this study, we used Brillouin spectroscopy to compare age-related changes in the elastic modulus (“stiffness”) and thickness of human lenses in vivo with those of ex vivo porcine lens.
Methods :
Lens scans were performed on Brillouin Optical Scanning System (BOSSTM) devices. At Site 1, 3 scans were performed on 1 eye of each subject, on each of 3 BOSS devices. At Site 2, both eyes were scanned once per subject, with the data for OD and OS analyzed separately. Intact porcine eyes were placed on a 3D-printed mount on the chinrest of the BOSS for scanning; each eye was scanned 3 times.
Results :
Thirty-one subjects (24 – 63 years old) were tested at Site 1. Lens thickness (Y), measured through the center of the lens, increased linearly with increasing subject age (X), (Y = 4.058 + 0.019*X). The data from approximately 60 subjects (19 – 70) at Site 2 showed similar increases (Y = 3.864 + 0.022*X for OD and Y = 3.545 + 0.027*X for OS). Thickness also increased between the lenses from young (n= 12; about 8 weeks old) and old (n= 8; about 8 months old) porcine eyes, with values of 8.4±0.40 and 9.8±0.64 mm, respectively (P< 0.001). The stiffness also increased significantly from the young (3.741±0.050 GPa) to old (3.916±0.242 GPa) porcine eyes (P= 0.038). However, there was a slight downward trend in the stiffness for the Site-1 subjects, and a significant difference between the stiffness values for subjects younger than 45 years of age (n= 15, 3.35±0.033 GPa) and the older subjects (n= 16, 3.30±0.044 GPa, P< 0.001). The results were confirmed at Site 2 for subjects younger than 45 years old (n= 42 OD, 3.33±0.057 GPa) versus those older than that (n= 16 OD, 3.27±0.050 GPa, P< 0.001), with similar results for OS.
Conclusions :
Consistent with the literature, the thickness of both the human and porcine lenses increased with age, as did the stiffness of the porcine lenses measured with Brillouin scattering. However, counter to Helmholtz’s model, but consistent with at least one earlier study, the in vivo stiffness values were stable, or showed a slight linear decrease, with increasing subject age. This may, in part, reflect the substantial inter-subject variability. Thus, scanning with the BOSS device provides information about the crystalline lens that is not accessible by other non-contacting techniques.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.