[Trials in ab-interno sclerostomy with a pulsed dye laser using a scleral dye: reactive black 5]

Several reports have described the successful performance of ab interno sclerostomies using a pulsed dye laser (666 nm) a goniolens and methylene blue as a scleral dye. However, the laser energy was found to have a bleaching effect on the methylene blue; therefore, methylene blue was replaced by reactive black-5 (RB-5), which seemed to be a more stable dye. To assess laser parameters using RB-5 we compared the number of pulses needed to perforate excised human sclera at different pulse durations (4-8 microseconds), energy levels (50, 100, 130-150, 200, 300 mJ) and delivery angles (20 degrees, 30 degrees, 45 degrees, 90 degrees). Fewer pulses were needed at a shorter pulse duration and higher energy levels. Above 200 mJ, 8 pulses for perforation could not be reduced; however, the width of the fistula increased. With a decrease in the delivery angle, the number of pulses for perforation increased non-proportionally above the calculated increase of the length of the fistula. At an angle of 20 degrees no perforation could be achieved even if 200 pulses of the maximal energy of 200 mJ were applied. This indicates that eyes with flat anterior chambers cannot be successfully treated.