Color Vision Deficits During Laser Lithotripsy using Safety Goggles for Coumarin Green or Alexandrite but not with Holmium:YAG Laser Safety Goggles
Teichman J, Johnson A, Yates J, Angle B, Dirks M, Muirhead J, Thompson I, Pearle M

PURPOSE: Laser lithotripsy requires urologists to wear laser eye protection. Laser eye protection devices screen out specific light wavelengths and may distort color perception. This study tests whether urologists risk color con-fusion 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 Farnsworth-Munsell 100-Hue Test (FM-100) without (control) and with lager eye pro-tection devices for cournarin green, alexandrite and holmium:YAG lasers. Error scores were tabulated. The pattern of color deficits was characterized with confusion angles, confusion index (C-index), scatter index (S-index) and color axes. Laser eye protection devices were tested with spectrophotometry for spectral transmittance and optical density.

RESULTS: The D-15 transposition errors (mean plus or minus standard deviation) for control, holmium:YAG, alexandrite and cournarin 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 plus 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 alexan-drite and pronounced color confusion for the cournarin green laser eye protection. The confusion angles and scatter indexes mimicked a congenital blue-yellow deficit for cournarin green laser eye protection. Color axes showed no significant deficits for control or holmium:YAG laser eye protection in any subject, red-green axis deficits in 3 of 6 tested with alexandrite and blueyellow axis deficits in 12 of 12 tested with cournarin green (p 0.001). Spectrophotometry showed that laser eye protection for coumarin green blocks less than 550 nm., alexandrite blocks light greater than 650 nm. and holmium:YAG blocks light greater than 825 nm.

CONCLUSIONS: Laser eye protection for coumarin green causes pronounced blue-yellow color confusion, whereas alexandrite causes mild red-green color confusion among urologists, holmium:YAG causes no significant color confusion compared to controls. The differences are explained by laser eye protection spectrophotometry characteristics and visual physiology.

Journal of Urology, Vol. 159, Number 3, 683-689, Mar 1998

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