Early tissue response to transscleral neodymium: YAG cyclophotocoagulation

Transscleral cyclophotocoagulation was performed with a neodymium: YAG laser on five patients 24-72 hr before enucleation for a blind, painful eye. The thermal mode at 20 ms and a maximum offset between aiming and therapeutic beams were kept constant. Variable parameters evaluated were energy levels between 2 and 8 J and distance from the limbus of 0.5-3.0 mm. Because of the underlying distortion in three of the eyes, meaningful interpretation by light microscopic evaluation was possible only in the other two. This suggested that the early histologic hallmark of the procedure is similar to that previously observed in human autopsy eyes with ciliary epithelial damage and elevation from underlying tissue. In addition, fibrin and scant inflammatory cells were seen in the space between ciliary epithelium and stroma. Minimal damage was observed in the ciliary muscle. These findings suggest that direct damage to the ciliary epithelium is the most likely mechanism of reduced aqueous production by this cyclodestructive procedure. The findings also support the concept that an anterior placement of approximately 1.0-1.5 mm posterior to the limbus is most likely to damage the ciliary epithelium of the pars plicata.