A number of recent studies have demonstrated the success of Nd:YAG and diode laser transscleral cyclophotocoagulation in the treatment of advanced glaucoma. Wavelength selection, however, has seldom been based on a clear understanding of the optical properties of tissues involved. The optical properties of conjunctiva, sclera, and the ciliary body adjacent to the limbus were investigated to find an optimal wavelength range for transscleral cyclophotocoagulation. The absorption and scattering coefficients of these layers were determined in the 300-1200-nm wavelength range by the use of a one-dimensional inverse adding-doubling method. The measured optical properties of conjunctiva, sclera, and the ciliary body provide a basis for a comparative analysis of the laser wavelengths used clinically for transscleral cyclophotocoagulation.

The safety of irradiating human tonsils was shown. The diode laser is superior to the Nd:YAG laser because less heat affects collateral structures. The optical-thermal simulation detailed in this study can be used to predict the temperature rise in tissues undergoing irradiation.

Transscleral cyclophotocoagulation (TSCPC) is currently performed clinically as an effective treatment for end-stage glaucoma. We develop a theoretical model for the analysis of optical attenuation phenomena during TSCPC as a basis for selection of an optimal wavelength. A multilayered Monte Carlo model was developed to calculate the fluence and the rate of heat generation in each tissue layer for the wavelengths of Nd:YAG, diode, ruby, krypton yellow, and argon lasers. Of the five wavelengths under study, our theoretical results suggest that the diode laser wavelength offers the best penetration through the conjunctiva, sclera, and ciliary muscle and highest absorption within the ciliary pigment epithelium.

Corrections are given to the reported [Appl. Opt. 35, 3321 (1996)] units of the absorption and scattering coefficients mu (a) and mu (s), respectively. The corrections pertain to two figures, several tables, and the text describing results.

The optimal dosimetry parameters for irradiation of human tonsillar tissue at 805 nm with the MILTA technique is under 15 watts for approximately 1 minute.