Preparation of Deep Sclerectomy with Different Lasers - A Comparison

Klink T., Lieb W., Grehn F.,
Bayerische Julius-Maximilians-Universität Würzburg, Universitäts-Augenklinik (Würzburg)

Purpose: Deep sclerectomy is a non-penetrating filtering procedure. The purpose of using lasers is to simplify the procedure and reduce the rate of inadvertent perforations, which can occur during the preparation of the deep lamella. Different lasers were used in the study.
Method: Using enucleated pig eyes, we surgically prepared a superficial lamellar scleral flap like in a trabeculectomy procedure, followed by preparation of the deep lamella using a pulsed Erbium YAG-Laser, an ultrapulsed CO₂-laser (scanning mode) and an Excimer laser (scanning mode). Ablation was performed until aqueous percolated through the corneoscleral lamella. Finally the eyes were analysed histologically and with a scanning electron microscope (SEM).
Results: It was possible to ablate the remaining deep corneoscleral lamella and uncover Schlemm’s canal (in humans) with all types of used lasers without perforating into the anterior chamber. The CO₂- and Excimer laser can be used in the scanning mode, which results in a smoother surface as seen with the SEM. The histological work up showed that thermal tissue damage differs obviously between the various lasers.
Conclusions: Not only the Erbium YAG-Laser, but also the CO₂- and Excimer laser offer an alternative to microsurgical preparation of the deep scleral lamella. The selective and constant ablation of tissue decreases the number of inadvertent perforations. Clinical application of the Erbium and Excimer laser showed that using lasers considerably facilitates to find Schlemm’s canal as a guiding landmark in preparation of deep sclerectomy.

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