Choosing an optimum wavelength for diode laser photocoagulation

Based upon threshold laser retinal injury studies in rhesus monkeys, there are indications that narrow, retinal absorption bands exist within the 700- 900 nm, near-infrared spectral region. Since these studies were conducted in rhesus monkeys with short-pulse laser exposures, the data may only apply to single-pulse conditions and not be directly related to repetitively pulsed laser photocoagulation. However, these interesting animal data show a range of thresholds of a factor of ten over a spectral range of only 150 nm. It is speculated that, by shifting from one diode wavelength by only 40 nm, the required power may be only 20% of that required at a slightly shorter wavelength. Since this animal data may apply to the human retina, it deserves experimental verification with repetitively pulsed exposures and histological studies.