Endoscopic goniotomy with the free electron laser in congenital glaucoma rabbits

Purpose: Goniotomy is a surgical treatment of choice to treat primary infan tile glaucoma. Goniotomy has been studied in vitro in animal and human cada ver eyes with several lasers. The objective of this study was to investigat e the functional and morphologic effectiveness of goniotomy with the free e lectron laser in comparison with conventional needle goniotomy in early con genital glaucoma rabbits. Materials and Methods: Ten rabbits with early congenital glaucoma underwent goniotomy over 100 to 120 degrees with a needle or the free electron laser . The wavelength was 6.45 mu m, and the energy level ranged from 2.2 to 3.5 mJ at 30 Hz. Because most corneas were edematous in these rabbits, an Olym pus 0.8-mm diameter endoscope was coupled to the laser waveguide or the nee dle and inserted into the anterior chamber filled with a viscoelastic mater ial to perform the goniotomy. Intraocular pressures were followed up to 3 w eeks before an acute goniotomy was performed in the contralateral eye. All eye specimens were processed for light microscopic evaluation. Results: Incision of the pectinate ligaments and underlying trabecular mesh work was visualized through the endoscope on a video monitor during the sur geries. The mean intraocular pressure decreased after free electron laser g oniotomy and after needle goniotomy, and the edematous corneas became clear in some cases. Histologic study showed successful lysing of the pectinate ligaments by the free electron laser with no obvious collateral thermal dam age. However, some areas of peripheral anterior synechiae occurred. Similar results were observed in needle goniotomy cases. Conclusions: The free electron laser is capable of performing goniotomy in rabbit eyes with lower intraocular pressures in treated eyes 3 weeks after surgery. The histologic results of free electron laser goniotomy are compar able to those of conventional goniotomy. The endoscope provides beneficial visualization to perform the goniotomy in eyes with edematous corneas. The rabbit with early congenital glaucoma is also a useful infantile glaucoma s urgical model.