Experimental microendoscopic photoablative laser goniotomy as a surgical model for the treatment of dysgenetic glaucoma

Purpose: The aim of this study was to investigate the feasibility of photoablative Er:YAG laser goniotomy under microendoscopic control in a surgical cloudy corneal model of primary infantile glaucoma. Methods: Pectinate ligaments of 12 freshly enucleated cadaver porcine eyes were treated by ab interno single-pulse (5 mJ, 200 s) Er:YAG laser (2.94 m) photoablation. Through a clear corneal incision near the limbus an ophthalmic microendoscope (18 and 20 gauge) was inserted into the anterior chamber. Internal structures were observed and photoablative laser goniotomy was conducted under video guidance. Following treatment all eyes were prepared for light and scanning electron microscopy. Results: Anterior chamber angle structures and tissue photoablation were clearly visualized on the videoscreen using ophthalmic microendoscopy. Energy settings of 5 mJ per pulse proved to be sufficient for reproducible photoablation of pectinate ligaments, accompanied by the root of the iris falling back and exposing trabecular meshwork. This was confirmed histopathologically. Scatter thermal damage was less than 30 m. Conclusion: This new therapeutic modality, which combines endoscopic visualization of the internal structures with photoablative laser goniotomy, can be effective in the management of dysgenetic glaucoma in the presence of a cloudy cornea. High reproducibility of contact laser photoablation enabled sufficient control of incision depth and was not accompanied by inadvertent tissue damage to adjacent intraocular structures.