Experimental retinal and ciliary body photocoagulation using a new 670-nm diode laser

Evaluation of ocular tissue reactions to 670-nm diode laser.

Twelve eyes of 12 pigmented rabbits were used. Transscleral contact laser delivery of a new 670-nm diode laser was used to produce retinal laser lesions in four rabbits; endolaser application of this laser produced photocoagulation of the retina in another four rabbits; and ciliary body lesions were produced by transscleral application of this laser in a third group of four rabbits. The rabbits were killed either 2 days or 1, 3, or 6 weeks later; lesions were evaluated by gross examination and histology.

The mildest visible retinal lesions were produced by transscleral contact application at 0.2 J (2 seconds, 100 mW); explosive lesions began at 0.6 J. The mildest visible lesions were produced by endolaser application at 50 mW (spot size, 0.5 mm); intensive reactions started to occur at 300 mW, but no explosive lesions were produced below 600 mW. With contact transscleral application, substantial ciliary body reactions occurred at 0.5 and 1.0 J. Histologic examination disclosed destruction of the outer retina, pigment epithelium, and parts of the choroid in mild lesions, and of all retinal layers in the intense lesions.

In this experimental study, the 670-nm diode laser appears to be a promising modality for laser photocoagulation of the retina and ciliary body.