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Direct spectral transmittance data over the wave band 200–2500 nm were obtained for the ocular media of the thirteen-lined ground squirrel (Spermophilus tridecemlineatus) using a Zeiss (Oberkochen) DMR-21 dual-beam recording spectrophotometer. These data were used to calculate cumulative transmittance curves for each of the interfaces between optical media in the ground squirrel eye. Although radiation in the wave band 300–2500 nm can penetrate the cornea, our data show that the yellow pigment of the crystalline lens absorbs all wavelengths below 410 nm, while the vitreous humour absorbs most radiation longer than 1400 nm. The ground squirrel retina is, therefore, effectively protected from both near ultraviolet and infrared radiation, both of which are known to have deleterious effects on retinal photoreceptors.

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We have confirmed previous observations that polycarbonate lenses are more susceptible to penetration by sharp, high-speed missiles than blunt missiles. We have also found that reducing lens center thickness and applying a MAR coating further reduces the penetration resistance. Therefore, the use of 2-mm center thickness and MAR-coated polycarbonate lenses should be discouraged for industrial eye protectors where sharp missile hazards are possible.

Background: Scratches and other surface abrasions on protective eyewear can shorten their life cycle by scattering light from the image, which will compromise visual performance. Although scratch and abrasion resistance testing is well developed, there is little information available regarding visual acuity through lenses scratched in an actual work environment. Methods: We collected protective eyewear from mine and smelting operations that had been returned because vision through the lenses was unacceptable due to scratches and abrasions. Forward scattered light was measured on both cleaned and partially cleaned lenses using both haze and light diffusion measurements. Visual acuity through a selection of lenses was determined for both high and low contrast letters under photopic light levels. Results: Lenses with scratches in the central region had haze values ranging from one to 30 per cent. The highest haze values were measured on lenses that were both scratched and covered with dirt, whereas haze values less than 10 per cent were measured on lenses that had the dirt removed and just had scratches in the central region. Light diffusion values were highly correlated with haze. Visual acuity for high and low contrast letters became worse as the percentage haze increased but the linear correlation was only moderate. Conclusion:The appearance of the scratches on the lens surfaces strongly suggests that they were a result of improper lens cleaning. The findings also suggest that haze values less than two per cent or a luminance reduction factor less than 3.0 cd/(m 2 lx) are unlikely to affect high and low contrast acuity.