Regional corneal biomechanics assessment as a function of age using Strain-Stress Index maps.

Purpose: To gain a better understanding of corneal Stress-Strain Index (SSI) maps in healthy eyes and to determine their changes with age.

Method: The eyes of 72 participants (age 43.1 ± 20.9 years, 69.5% female) were included in the analysis, considering the left and right eyes separately. Corneal biomechanics were assessed using a combination of the Pentacam and Corvis instruments, whose data enabled the production of the SSI maps. The corneas were divided into nine zones to facilitate zone-specific analysis of biomechanical behaviour. Regression analyses were conducted to evaluate the relationship between age and SSI values in each corneal zone.

Results: The mean overall SSI value of the cornea for all participants was 1.075. Considering different age groups, significant differences in SSI were seen between the young and older groups in the overall map from 0.938 ± 0.067 in 20-50-year-olds to 1.143 ± 0.064 in 50-80-year-olds (ANOVA, p < 0.001). The same effect was seen for each zone separately (ANOVA, p < 0.001). The corneal central apex and peripheral zones showed higher mean SSI values (1.153 ± 0.079) and hence, higher corneal stiffness compared with paracentral zones (0.890 ± 0.057).

Conclusion: This paper showcases a series of maps depicting corneal elasticity and explores the differences in corneal stiffening with age across various regions of healthy corneas. The results reveal that stiffening tends to accelerate in areas that are already stiffer and decelerate in weaker regions. This deeper insight into ocular physiology could enhance clinical care by enabling more personalised treatments based on the patient's age and the specific corneal regions being addressed.