[Possible damage to the eye caused by light from ophthalmologic equipment]

Motivated by numerous findings of the damaging effect of intense light levels on the fundus we measured the spectral radiation of several ophthalmic illuminations and used it to calculate from it the spectral retinal irradiance. To evaluate the thermal hazard, we calculated the resulting temperature rise at the fundus. A measure for biological damage is the percentage of denaturated molecules, which is related to the temperature rise and its duration (essentially identical to the duration of illumination) by the so-called Arrhenius-integral. We used this measure to compare any illumination with experimentally evaluated threshold values for thermal damage. To evaluate the photochemical hazard we compared the spectral retinal irradiance with threshold values for photochemical induced lesions. Furthermore the illuminations were correlated with safety-guidelines likewise distinguishing between thermal and photochemical hazard. Under adverse conditions operation microscopes can present a thermal hazard to the patient's eye. Other ophthalmic illuminations are of less concern in this respect. A similar estimation applies to hazard from photochemical effects. The photochemical hazard can be diminished essentially by reducing the short-wavelength bluelight. Qualitatively, maximal permissible exposures according to safety guidelines are consistent with our thermal calculations as well as with photochemical hazard evaluation by comparing spectral retinal light levels with threshold irradiance for photochemical induced lesions. However, since quantitatively safety guidelines estimate the thermal hazard very conservatively, many common ophthalmic illuminations exceed the exposure limits, in some cases even drastically.