Whitepapers and Tech Notes:
Wavelength Selection in Retinal Photocoagulation
The most effective wavelengths for retinal photocoagulation are those that are poorly absorbed by macular xanthophyll, and maximally absorbed by melanin in the RPE and choroids, and by hemoglobin. The green wavelength, with its minimal absorption by xanthophyll and strong absorption in melanin and hemoglobin, has long been considered the “standard of care” for treatment of the retina. There are some limitations when using the green wavelength to treat in the retina, however. Read this whitepaper to learn about the role of the yellow wavelength (561 – 577 nm) and the red wavelength (659-670 nm) to perform retinal photocoagulation.
The Yellow Wavelength – High-Power Minus Collateral Damage
Retinal specialist David Dyer, MD, Retina Associates, Missouri, USA, explains that when treating inside the macular pigment area, 561nm yellow creates a more predictable, controlled burn than traditional 514/532nm green wavelengths, resulting in low scotoma formation. This, in turn, enables more precise control over the interaction between the laser beam and tissue.
Care must be taken to ensure appropriate pattern selection, based on the curvature of the eye i.e. small pattern for periphery, macula, etc. It is also important to consider pigmentation and media opacity. Threshold power is also an important consideration. The level of power used should be a function of the location of treatment and the tissue environment. Focusing the slit lamp is essential for titration; the focus of the slit lamp and the laser should be as similar as possible in order to precisely administer the laser. The power is then titrated until the desired effect is achieved.