The role of peripheral ocular length and peripheral corneal radius of curvature in determining refractive error

The purpose of this study was to extend the knowledge of peripheral biometric component and its relationship to refractive status in healthy individuals by determining the correlation between peripheral ocular length to peripheral corneal radius ratio and the refractive error.

This prospective study was conducted on thirty-three healthy adult participants. Refractive error was assessed objectively and subjectively and recorded as the mean spherical equivalent. Central and peripheral ocular lengths at 30° were assessed using partial coherence interferometry under dilation with 1% tropicamide. Central and peripheral corneal radius of curvature was assessed using Scheimpflug topography. Peripheral ocular lengths at 30° were paired with peripheral corneal curvatures at the incident points of the IOLMaster beam (3.8mm away from corneal apex) superiorly, inferiorly, temporally and nasally to calculate the peripheral ocular length-peripheral corneal radius ratio. Descriptive statistics were used to describe the distribution and spread of the data. Pearson's correlation analysis was used to present the association between biometric and refractive variables.

Refractive error was negatively correlated with the axial length-central corneal radius ratio (r=-0.91; p<0.001) and with 30° peripheral ocular length-peripheral corneal radius ratio in all four meridians (r≤-0.76; p<0.001). The strength of the correlation was considerably lower when only axial length or peripheral ocular lengths were used.

Using the ratios of peripheral ocular length-peripheral corneal radius to predict refractive error is more effective than using peripheral corneal radius or peripheral ocular length alone.