New Developments in the Lenticule Extraction Procedure

Abstract

31Over the last few years, surgical extraction of a refractive lenticule, or ReLEx ® , has evolved as a new treatment in the field of keratorefractive surgery. Currently, the VisuMax ® femtosecond (FS) laser (Carl Zeiss Meditec, Jena, Germany) is the only platform to offer this treatment.The 500 kHz VisuMax laser generates very fast pulses (10 -15 s range) in the near-infrared spectrum. Depending on the specific laser settings, each pulse conveys approximately 150 nJ, which causes localised photodisruption at the focal point. The generated plasma expands, creating a cavitation bubble, and, as individual cavitation bubbles fuse, the stroma is cut with a minimum of collateral damage. The VisuMax FS laser uses a high numerical aperture and a concave contact glass to focus the laser pulses with very high precision. Thus, laser spots of approximately 1 μm diameter are placed with a defined distance of 2-5 μm in a spiral pattern. To ensure centration on the visual axis, the patient fixates on a blinking light and suction is applied at the limbus to maintain stability of the eye. Initially, the posterior refractive surface of the lenticule is cut, followed by creation of the plano anterior surface, which is slightly enlarged in diameter to facilitate surgical manipulation.This review article reviews the current state of the technique, updated clinical results, 1 experimental studies and, finally, presents some of the challenges that need to be addressed by new technologies.Depending on the method used to access the lenticule, ReLEx can be split into FLEx, in which a laser-assisted in situ keratomileusis ( In contrast to LASIK, ReLEx is a one-laser approach, where the critical laser treatment is performed on the intact cornea rather than on exposed corneal stroma. Consequently, the potential variability associated with the excimer laser photoablation is avoided.In addition, the minimally invasive SMILE treatment has several theoretical advantages over flap-based treatments, including little trauma to the corneal surface, less corneal denervation and better biomechanical strength due to an almost intact anterior stroma. Since AbstractFor the last 20 years controlled excimer laser ablation of corneal tissue, either directly from the corneal stromal surface or from the corneal interior after creation of a superficial corneal flap, has become widely used to correct myopia, hyperopia and astigmatism.Recently, an intrastromal refractive procedure whereby a tissue lenticule is cut free in the corneal stroma by a femtosecond laser and removed through a small peripheral incision has been introduced. The procedure avoids creation of a corneal flap and the potential associated risks while avoiding the slow visual recovery of surface ablation procedures. The all-femtosecond-based flap-free intracorneal refractive procedure has been documented to be a predictable, efficient and safe procedure for correction of myopia and astigmatism. Technological developments related to further improved cutting quality, hyperopic and individualise...