The porcine lens demonstrates subtle changes in the variability of the focal length, and the variability increases as the incubation temperature rises. In contrast, lens clarity is relatively stable at temperatures up to 47.5 °C, above which dramatic changes, indicative of the formation of cataracts, occur. The lens content of Hsp70 was elevated in lenses exposed to heat shock only up to 50 °C. These data suggest that in a stressful environment, Hsp70 may be associated with protection against loss of clarity. In addition, the functional measures BVD SEM and clarity assess different qualities of the lens, with the former likely more sensitive to subtle changes in the protein structure.