Optical low coherence reflectometry for noncontact measurements of flap thickness during laser in situ keratomileusis.

Objective: There is growing evidence that iatrogenic keratectasia after laser in situ keratomileusis (LASIK) for high corrections occurs more frequently than initially assumed, and that it may result from larger variation in flap thickness.

Design: Consecutive noncomparative case series

Participants: Thirty-four patients who underwent LASIK for myopia and astigmatism (first treatment group) and 10 patients who received re-LASIK (retreatment group).

Methods: Central corneal thickness and thickness of the lamella during LASIK were determined by optical low coherence reflectometry (OLCR) and contact ultrasound pachymetry.

Diametral ablation--a technique to manage decentered photorefractive keratectomy for myopia.

Purpose: Decentered ablation after photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK) is an intraoperative complication that may significantly influence the visual outcome. Currently, there is no accepted technique available to manage this problem.

Methods: A technique of reoperation for eccentric ablation after PRK called diametral ablation is presented that uses a transepithelial phototherapeutic keratectomy (PTK) that leaves epithelium over the area of primary PRK.

[A prospective clinical study of correction of myopic astigmatism by combined treatment with PRK and T-incision and photoastigmatic refractive keratectomy. The results after one year].

Background: In contrast to the correction of simple myopia there is no widely accepted technique for the correction of myopic astigmatism. Currently two techniques are available: the photoastigmatic refractive keratectomy (PARK) and the combination of arcuate keratotomies with standard PRK (PRK-T).

Methods: In two groups, 67 patients underwent a correction of myopic astigmatism in a total of 87 eyes (19 by PRK-T and 68 by PARK), and were followed for 1 year.

[Laser-induced pressure waves in the eye. Propagation characteristics].

Background: The characteristics of shock waves during photoablation were investigated for an IR and a UV laser. These stress waves may be harmful to ocular structures.

Material And Methods: The amplitude of shock waves was measured by a needle-shaped hydrophone in enucleated porcine eyes during excimer laser (193 nm, 23 ns, diameter of ablation 1.

Thermomechanical behavior of the cornea.

Shrinkage of corneal collagen is used during thermokeratoplasty, a method to remodel the corneal curvature. The goal of our investigations was to determine the optimal temperature range for maximal shrinkage of the collagen fibers with minimal damage. By means of a commercially available stress-strain-measuring device including a paraffin oil bath at temperatures varying from 35 degrees to 120 degrees C, strips of pig cornea measuring 5 mm in width and 9 mm in length were investigated in the stress range of sigma = (0.