Using a computer program that compares bits of genetic material taken from tissue in the retinas of mice against records in a huge genetic data base from the mouse and human genome project, Harvard Medical School researchers identified approximately 300 photoreceptor genes. That is five times the number of retinal genes that were previously known. Two hundred sixty four of these were newly identified genes. Of these, 241 had homologs, or counterparts, in humans. The identification of the retinal genes means that researchers have discovered nearly all the genes responsible for vision, which could help in diagnosing and treating blinding diseases. The discovery could also lead to new methods for preserving and restoring the vision of those affected. “The more we know about how the genes work, the better we will be able to find ways to treat, and possibly, prevent disease,” said Connie Cepko, Harvard Medical School professor of genetics and senior author of the study. The research was reported in the November 30, 2001, Cell. The research was funded through the Foundation for Retinal Research and the National Institutes of Health.