Ultrastructural changes of human trabecular meshwork after photocoagulation with a diode laser.

A diode laser, which emitted infrared radiation at a wavelength of 810 nm, was used to perform trabecular photocoagulation in a human eye due for enucleation for malignant melanoma. For comparison, burns were applied with an argon blue-green laser (488-514.5 nm). With each laser, the treatment spot size was 100 microns and the pulse duration was 0.20 sec. Visible lesions were produced with a power of between 750 mW and 1.2 W with the diode laser, and 500-900 mW with the argon laser. The pattern of damage produced by both modalities was similar and essentially consisted of contraction or expansion of trabecular beams, with trabecular destruction occurring only in relation to high power exposures. These findings confirm that trabecular photocoagulation is not a process that depends upon the wavelength of the incident energy at the two spectral extremes of 488 nm and 810 nm.