Posters

DSAEK donor stromal surface as a factor for postoperative visual quality: a scanning electronic microscopy study comparing manual vs automated microkeratome advance

Poster Details

First Author: A. Villarrubia SPAIN

Co Author(s):    A. Cano-Ortiz              

Abstract Details

Purpose:

The roughness that can be found in the stromal surface after the lamellar cut, has been one of the advocated reasons related to the unpredictability of the functional results despite a good anatomical appearance, mainly in DSAEK technique. With greater irregularity in the interface, we should find worse functional results. The goal of this study is try to show that the stromal surface is different if the cut of the tissue has been performed with a microkeratome cutting with a uniform speed versus a microkeratome which translational advance has to be made with the hand of the surgeon.

Setting:

Instituto de Oftalmología La Arruzafa. Córdoba. Spain.

Methods:

25 corneas for were dissected for endothelial transplantation: - Group A: (from 1 to 11) were cut with an automatic microkeratome with an uniform translation speed in a linear manner (Amadeus II; Ziemer Ophthalmic Systems AG, Port, Switzerland) - Group B: (from 13 to 17) wee dissected manually for DMEK surgery. - Group C: (from 18 to 25) were cut with a manual microkeratome with a no uniform translation speed in rotational manner (ALTK system; Moria, Antony, France). A small disc was obtained from the anterior cap with a 3 mm. punch and was fixed in 2% glutaraldehyde. The scanning electron microscopy was focused in the center of the stromal surface of this anterior cap and a snapshot of 1 squared mm. was analyzed. The Canny´s methods is a technique that can detect the edges of a surface. For optical purposes, a smooth surface should obviously be better than a rough one: and the Canny´s algorithm detects the irregularity index: this index is the ratio between the pixels that do not match with the background and the total amount of pixels in the snapshot. The limits of this index range between 0 and 1: 0 (0%) is an absolutely smooth picture (all pixels are black) and 1 (100%) is an absolutely rough picture (all pixels are white). The mean Irregularity Index was measured in 4 different thresholds and in all of them, the results were repeatable. In the threshold “20” the irregularity index was greater for the group C, followed by the group A; the group B shown a smooth surface of dissection (Irregularity Index: 17,118, 14,674 and 3,516 respectively).

Results:

Canny´s method is a useful option for a global detection of the edges after a scanning electron microscopy snapshot (from a stromal cornea surface) has been acquired. This method can be used to quantify the irregularities of the surface after a lamellar cut and to correlate the smoothness or the roughness of the cornea dissection with the functional results after lamellar surgery. Results show that the smoother surface is obtained with manual dissection for DMEK, followed by the tissue that has been cut with an automatic microkeratome; the worse quality of the interface is seen in the corneas that have been cut with the manual and rotational microkeratome.

Conclusions:

FINANCIAL DISCLOUSRE: NONE