Algorithm for Correcting the Keratometric Error in the Estimation of the Corneal Power in Keratoconus Eyes after Accelerated Corneal Collagen Crosslinking.

PURPOSE

To analyze the errors associated to corneal power calculation using the keratometric approach in keratoconus eyes after accelerated corneal collagen crosslinking (CXL) surgery and to obtain a model for the estimation of an adjusted corneal refractive index ( ) minimizing such errors.

METHODS

Potential differences (Δ) among keratometric ( ) and Gaussian corneal power () were simulated. Three algorithms based on the use of for the estimation of an adjusted keratometric corneal power ( ) were developed. The agreement between (keratometric power using the keratometric index of 1.3375), , and was evaluated. The validity of the algorithm developed was investigated in 21 keratoconus eyes undergoing accelerated CXL.

RESULTS

overestimated corneal power between 0.3 and 3.2 D in theoretical simulations and between 0.8 and 2.9 D in the clinical study (Δ). Three linear equations were defined for to be used for different ranges of . In the clinical study, differences between and did not exceed ±0.8 D = 1.3375. No statistically significant differences were found between and ( > 0.05) and and ( < 0.001).

CONCLUSIONS

The use of the keratometric approach in keratoconus eyes after accelerated CXL can lead to significant clinical errors. These errors can be minimized with an adjusted keratometric approach.