Comparative Evaluation of Corneal Residual Beds Created by Two Generation Femtosecond Laser Using Scanning Electron Microscopy

Abstract

Purpose: : To evaluate the smoothness of the corneal residual bed after flap creation by a 5^th generation femtosecond laser (iFS Advanced Femtosecond Laser) and a previous generation (IntraLase®) using scanning electron microscopy (SEM).

Methods: : A corneal flap was created in 8 fresh cadaver eyes using a 5^th generation femtosecond laser and a previous version. Round and elliptical shape flaps were created with 100 &110 µm depth. Residual beds were fixed using 2% cacodylate glutaraldehyde and processed for SEM evaluation. The residual bed surfaces as well as the edges were examined. Standardized photographs were taken and compared.

Results: : Mean donor age was 78.0 ±9.0 years. Mean time from dead to preservation was 9:15 ±5:17 hours. Stromal beds in the 5^th generation group were smoother, edges were more oblique and fewer irregularities were seen at the interface compared to the previous model.

Conclusions: : The higher repetition rate (150 KHz) used in the 5th generation femtosecond laser allows for tighter spot separation. This leads to the use of less energy and lowers tissue response. Thus helps creating smoother stromal bed that may lead to better surgical outcome.

Keywords: microscopy: electron microscopy • refractive surgery: comparative studies