Cetacean Lens Zones of Discontinuity—indices of Health and Development

Details of the lenses of eyes in two living Tursiops truncatus and one Grampus griseus were photographed. In the laboratory the lens cortex could be retro‐illuminated by a fundus camera and spatially periodic stria could be visualized, in large part because of the highly developed tapetum of the cetacean eye. Varying spaces were present between the stria. On a three‐dimensional basis, the best analogy is the layering of an onion. One photograph was digitized giving good quantification of the sizes of the layers and their number. Similar, but less easily resolved, lens cortex organization has been described frequently in humans as “zones of optical discontinuity.” These have been explained as a periodic temporal consequence of normal aging with layer thickness depending on general health. We found that young cetaceans have few “zones” and older cetaceans have many. Lens zones measurement may be developed to Provide objective data on history of cetacean health and age.