Age-related changes in geometry and transparency of human crystalline lens revealed by optical signal discontinuity zones in swept-source OCT images

Abstract

Background The shape and microstructure of the human crystalline lens alter with ageing, and this has an effect on the optical properties of the eye. The aim of this study was to characterise the age-related differences in the morphology and transparency of the eye lenses of healthy subjects through the optical signal discontinuity (OSD) zones in optical coherence tomography (OCT) images. We also investigated the association of those changes with the optical quality of the eye and visual function. Methods OCT images of the anterior segment of 49 eyes of subjects (9–78 years) were acquired, and the OSD zones (nucleus, C1–C4 cortical zones) were identified. Central thickness, curvature and optical density were measured. The eye’s optical quality was evaluated by the objective scatter index (OSI). Contrast sensitivity and visual acuity tests were performed. The correlation between extracted parameters and age was assessed. Results The increase in lens thickness with age was dominated by the thickening of the cortical zone C3 (0.0146 mm/year). The curvature radii of the anterior lens surface and both anterior and posterior nucleo-cortical interfaces decreased with age (− 0.053 mm/year, − 0.013 mm/year and − 0.006 mm/year, respectively), and no change was observed for the posterior lens radius. OCT-based densitometry revealed significant correlations with age for all zones except for C1β, and the highest increase in density was in the C2–C4 zones (R = 0.45, 0.74, 0.56, respectively, P < 0.001). Increase in OSI was associated with the degradation of visual function. Conclusions OCT enables the identification of OSD zones of the crystalline lens. The most significant age-related changes occur in the C3 zone as it thickens with age at a faster rate and becomes more opaque than other OSD zones. The changes are associated with optical quality deterioration and reduction of visual performance. These findings contribute to a better understanding of the structure–function relationship of the ageing lens and offer insights into both pathological and aging alterations.

Description of a new method to calculate the equator of the crystalline lens using AS‐OCT images: Accuracy in non‐dilated measurements

“…11 Subsequently, the segmented anterior and posterior lens borders were fitted to a second-degree polynomial function (Figure 1c), consistent with the literature. 12 Although the use of conic curves to model the corneal surface is widespread, 13 this model was chosen for its simplicity and good performance, providing small fitting errors. Furthermore, a second-degree polynomial is more reliable for extrapolation when compared with…”