Optimization of dye-enhanced ab interno laser sclerostomy

Purpose. Dye-enhanced ab interno laser sclerostomy is a procedure recently described by Latina et al (1992) in which an electric current is used to drive ionic dye into corneal-scleral tissue. Subsequently a focused laser beam is aimed at the dye-labeled region, and a filter is created in ab interno fashion. Saraff and Lee (1994) have previously reported optimization of laser sclerostomy by optimization of probe construction and application time. However, as we shall demonstrate, the procedure could be further improved by selection of different electrical power sources and ionic dyes. Methods. By careful consideration of these two additional parameters, one can optimize the localization of the dye target, and thus increase the efficiency of the procedure. As described by Chuck et al (1995), use of a constant voltage power source, as opposed to one of constant current, results in greater local dye concentration. This theoretical model is discussed. Additionally, if one chooses dyes with low diffusion properties in the cornea-sclera, one can also improve localization. The relative rates of corneal diffusion of the common, clinically approved ionic dyes sodium fluorescein, its derivative Rose Bengal, methylene blue and indocyanine green were investigated. All four of these dyes conveniently have absorption peaks at readily available laser wavelengths. That is, they maximally absorb argon blue-green, dye yellow, dye red and 810 nm diode laser radiation, respectively. Results and Conclusions. The dye most often used for dye-enhanced laser sclerostomy, methylene blue, is the second most diffusible dye of the four, second only to fluorescein. Thus increased dye localization and procedure efficiency could be acheived by either application with constant voltage, and/or utilization of either Rose Bengal or indocyanine green and the appropriate laser source.