# The correlation between myopia severity and stress–strain index (SSI) using the Corneal Visualization Scheimpflug Technology (Corvis ST)

## TL;DR

This study found that higher myopia severity is linked to lower corneal stiffness, as measured by a specialized eye imaging device.

## Contribution

The study reveals a novel correlation between myopia severity and corneal biomechanics using Corvis ST measurements.

## Key findings

- SSI values were significantly lower in individuals with more severe myopia (≥26.00 AL group).
- SSI correlated weakly with axial length and other eye parameters in the severe myopia group but not in the less severe group.
- The correlation between SSI and axial length was not influenced by corneal curvature or chamber depth.

## Abstract

This study aimed to investigate the correlation between myopia severity and the stress–strain index (SSI), measured with the Corneal Visualization Scheimpflug Technology (Corvis ST) device. The subjects were divided into two groups, based on both the axial length (AL) and spherical equivalent refraction (SER): 22–26.00 AL group (22 mm < AL < 26.00 mm) associated with SER of less than − 6.00D, and ≥ 26.00 AL group (AL ≥ 26.00 mm) associated with SER over − 6.00D. The differences in the Corvis ST-derived dynamic corneal response parameters and stiffness parameters between the two groups were investigated. The correlation between SSI and AL, SER, age, ratio of AL to radius of corneal curvature (CR) (AL/CR), and axial length minus anterior chamber depth (ACD) (AL-ACD) were analyzed. The SSI (0.95 ± 0.13 in the 22–26.00 AL group and 0.86 ± 0.15 in the ≥ 26.00 AL group) were significantly different between the two groups (P < 0.01). In the ≥ 26.00 AL group, there was evidence of a weak negative correlation between SSI and AL (r = − 0.265, P < 0.01), AL/CR (r = − 0.376, P < 0.01), and AL-ACD (r = − 0.224, P < 0.01); and a weak positive correlation between SSI and SER (r = 0.251, P < 0.01). However, in the 22–26.00 AL group, there was no correlation between SSI and AL, AL-ACD, AL/CR or SER (P > 0.05). SSI was significantly correlated with AL, which is the major determinant of SER, in the ≥ 26.00 AL group. This correlation was not affected with CR and ACD, as both AL/CR and AL-ACD also correlated with SSI at the same degree.

The online version contains supplementary material available at 10.1038/s41598-025-23834-x.