COLOR-VISION DEFICITS DURING LASER LITHOTRIPSY USING SAFETY GOGGLES FOR COUMARIN GREEN OR ALEXANDRITE BUT NOT WITH HOLIMIUM-YAG LASER SAFETY GOGGLES

Purpose: Laser lithotripsy requires urologists to wear laser eye prote ction. Laser eye protection devices screen out specific light waveleng ths and may distort color perception. This study tests whether urologi sts risk color confusion when wearing laser eye protection devices for laser lithotripsy. Materials and Methods: Urologists were tested with the Farnsworth Dichotomous Test for Color Blindness (D-15) and the Fa rnsworth-Munsell 100-Hue Test (FM-100) without (control) and with lase r eye protection devices for coumarin green, alexandrite and holmium:Y AG lasers. Error scores were tabulated. The pattern of color deficits was characterized with confusion angles, confusion index (C-index), sc atter index (S-index) and color axes. Laser eye protection devices wer e tested with spectrophotometry for spectral transmittance and optical density. Results: The D-15 transposition errors (mean plus or minus s tandard deviation) for control, holmium:YAG, alexandrite and coumarin green laser eye protection were 0 +/- 0, 0 +/- 0, 0.3 +/- 0.5 and 6.4 +/- 1.6, respectively (p = 0.0000001). The FM-100 error scores (mean p lus or minus standard deviation) were 20 +/- 15, 20 +/- 14, 91 +/- 32 and 319 +/- 69, respectively (p = 0.0001). The confusion index scores indicated a mild color confusion for the alexandrite and pronounced co lor confusion for the coumarin green laser eye protection. The confusi on angles and scatter indexes mimicked a congenital blue-yellow defici t for coumarin green laser eye protection. Color axes showed no signif icant deficits for control or holmium:YAG laser eye protection in any subject, red-green axis deficits in 3 of 6 tested with alexandrite and blue-yellow axis deficits in 12 of 12 tested with coumarin green (p < 0.001). Spectrophotometry showed that laser eye protection for coumar in green blocks light less than 550 nm., alexandrite blocks light grea ter than 650 nm. and holmium:YAG blocks light greater than 825 nm. Con clusions: Laser eye protection for coumarin green causes pronounced bl ue-yellow color confusion, whereas alexandrite causes mild red-green c olor confusion among urologists, holmium:YAG causes no significant col or confusion compared to controls. The differences are explained by la ser eye protection spectrophotometry characteristics and visual physio logy.