Corneal Power Profile Derived from Both Meridians is Better Correlated with the Peripheral Refractive Profile in Myopic Children 

Purpose : In children receiving corneal reshaping therapy, the myopia progression rate is associated with the change in corneal power, possibly due to its ability in reflecting refractive power changes towards peripheral fields, i.e., peripheral refractive profile – a hypothetical optical cue related to myopia development. As the peripheral refractive profile is typically acquired from refractive powers derived from two meridians (spherical-equivalent error, SE), it is unclear how well conventional topographic powers (axial, tangential, & refractive), which are derived from only a single meridional plane, can represent the peripheral refractive profile. This study compared the abilities of corneal power profile generated by the mean power (derived from the average of the steepest and flattest meridians) vs. conventional topographic powers in representing the peripheral refractive profile for myopic children.

Methods : A hundred fifty low-to-moderate myopic children (Age: 8 to 13 years, SE: –1.00DS to –5.75DS, Cylindrical error ≤1.50DC) with unremarkable ocular health were recruited. Peripheral refractive profile was determined using an open-field autorefractor along the horizontal field up to ±20° eccentricity in a 10° step. Corneal topography was measured by a Placido-disc based corneal topographer. Second-order polynomials (y=ax2+bx+c) were fitted to refractive and corneal power data (y) as a function of eccentricity (x) for each individual. The a-coefficients represent the refractive and corneal power shifts towards the periphery and were used for data analyses.

Results : Pearson’s correlations indicated that the peripheral refractive profile obtained from the open-field autorefractor were significantly correlated with the corneal power profiles derived from the mean (r=0.40), tangential (r=0.37), axial (r=0.20), and refractive power (r=0.17, all P
Conclusions : Corneal power profile derived from two meridians showed the highest correlation with the peripheral refractive profile, indicating the potential weakness of inferring peripheral refractive profile from the corneal powers derived from just one meridian.