Large Spot Endolaser for Retinal Photocoagulation and Transvitreal Thermotherapy

Abstract

Diode laser transpupillary thermotherapy can be used for the treatment and choroidal tumors. A large spot endolaser probe was developed for endophotocoagulation and transvitreal thermotherapy. The aim of this study was to assess the probe's clinical performance for photocoagulation and transvitreal thermotherapy combined with macular elevation. Endolaser with a divergent beam giving a 3 mm spot size on the retina was developed. Vitrectomy was performed on ten eyes of five Dutch Belted rabbits. Threshold for photocoagulation was determined for the diode (810 nm) laser in four eyes. In another six eyes, the retina was detached with balanced salt solution prior to laser irradiation. The tissue effects were monitored clinically and with photography and microscopy. Threshold photocoagulation was induced with 150 mW power, for 1 minute, in attached retina. Following retinal detachment, no coagulation occurred at 200 mW (suprathreshold) power for 1 minute. A large spot endolaser probe may be useful for endophotocoagulation. It generates more gradual photocoagulation than standard endolaser probes, giving a more controllable reaction over a larger area. This may be useful for treatment of large areas of the retina when treating retinal detachments or ischemic retinopathies. When detached retina was irradiated, no retinal damage occurred at suprathreshold power. This development may allow for intraoperative transvitreal thermotherapy of choroidal neovascularization while protecting the retina with intentional intraoperative detachment of the retina.