Contribution Of Corneal Epithelial Refractive Power Mapping For Understanding Unexpected Postoperative Refractive Surprise

To develop a corneal epithelial refractive power map and evaluate its contribution in understanding unexpected post laser vision correction refractive surprise.

Refractive Surgery Unit, Ophthalmology Department, Hadassah Medical Center, Jerusalem, Israel

A proprietary optical formula was developed by using the corneal epithelial index of refraction and a simplified approximation of the Munnerlyn equation to convert the epithelial thickness map into a vergence map. The formula was applied to the postoperative epithelial thickness maps (AS-OCT Optovue RTVue-100) of 13 patients that were diagnosed with an unexpected refractive surprise after laser vision correction. The generated refractive power of the postoperative corneal epithelial pattern was then compared to the vertex adjusted postoperative refractive surprise of the patients. Mean absolute differences and correlations with the postoperative refractive errors were tested.

The overall mean absolute difference in spherical and cylindrical components between the generated refractive power map and the postoperative vertex adjusted spherical and cylindrical refractive powers were respectively 0.3 +/- 0.58D (p=0,25) and 0.2 +/- 0.42 (p=0.4). No statistically significant correlation was found between the mean absolute difference and the type and magnitude of postoperative refractive errors.

The conversion of the corneal epithelial thickness distribution into an epithelial refractive power mapping was found to be a useful tool for understanding the source of unexpected postoperative refractive errors after laser vision procedures.