Keratitis solaris and sunbeds.

Keratitis solaris is caused by ultraviolet radiation in the range 200-320 nm. The threshold dose for keratitis solaris is 40 J/m2 for short-term exposure. We measured the emission spectra of 22 sunbeds in the range 250-500 nm with a high-resolution double monochromator and calculated the exposure times for the threshold dose of keratitis solaris. Depending on the type of lamp used, the exposure times ranged from 90 s to 3.5 h. Lamps with short exposure times for keratitis solaris can induce keratitis solaris if protective goggles are not used (e.g., to achieve a uniform tan of the eye area) and if the eyes are opened briefly several times, perhaps, to look at a watch. Generally, sunbed users have no way of ascertaining the lamp type or its emission spectrum and of determining the exposure time for the threshold dose of keratitis solaris.