Senescent eharjges to human visionhave beenwell documented, butthe factorsresponsible for these changesareonly partially understood, Theproposed research is intended to provide fundamental data on aging of the human visual systehl usfrig pftychophystaalmethods that separatethe relative contributions of optical and neural mechanisms. Because imicholthe sensitivity loss of cone pathwaysoccursat early stages of processing, wewillexamine age-related kissesin cone photoplgmenlopticaldensity in thecentral 10[unreadable]of retina for normal andsex-linked dichromats whosegenes havebeen sequanced to look for genetic correlates of photopfgment optical density andreceptor longevity," It is hypothesized that senescent changes in conephotopigment density will notbeuniform with retinal eccentricity, and the outcome of triteexperiment witt be important for theoretical and practical reasons.A secondaimof the proposed researchteto quantify senescent changes in the temporal properties of isolated color mechanisms through measurements of the temporal contrast sensitivity function and the impulse responsefunction. Thethird aimis to determine senescent changes Inspatial properties of isolated color mechanisms through measurementsof thearea of complete spatial summation (Rteoo'aarea). Age-relatedchanges in spatial summation are predicted basedonour previous work,and documented tossesof retinal ganglioncells with age, but wedo not knowwhetherthis will befound in all color pathways,the fourthaimis atsoconcernedwith spatial properties erfrodandcone pathways,butwill measure spatiallcontrast sensitivity functions for isolated mechanisms. Thefinal aim is basedon our previouswork showing thai, at[unreadable] perceptual level, the visual systememploys mechanisms that compensate, in part, for lossesin sensitivity attowierlevels. Color appearance mechanisms will beprobed by measurementsof age-relatedchanges in chromatic perceptive fieldsoverareas of retina associated wit) different relative tosses of cones andganglion cells. Sensitivity of isojateo* cone mechanisms and color appearance wffl be measuredfor individuals beforeand aftercataract extraction andimplantation of intnvocular lenses.Theseexperiments will provide newinformation on mechanisms that promote color constancy deapttesubstantialvariations inthe retinalimage dueto lenticular senescence. Each ofthese aims willincWdeidetailed tests of individualyounger andolder observers, and measurements on selected conditions with a large groupof individuate rangingin agefromapproximately 12to 85years. In addition to providing basic dataon the aging visualsystem, the experiments will provide probesfor models of howthe visual system adaptsand compensates fof degradations in the optical and neural images that occurwith senescence anddisease. PERFORMANCE Slti(8) forpanfeatfoa <%, fluff) University of California, Davis Medical Center Department of Qphthaimotoov 4860 YStreet. Suite 2400 Sacramento, CA 95817 Name :':;;''[unreadable]'.]'.'.' Werner, John Sfeon Knau,HolgerK, SchefrJn, BrooJceiE. Handel, James Ti Morse, Uwrence Neitz, Maureen Shinomori, Keizo onPage11. Vmcontinuation pagesu itMdMtoprovidetherequiredinformation intheformat shownbelow. Organization Role on Project UC-Davis Medical Center Principal Investigator DC-Davis Medical Center Research Associate UC-Davis Medical Center Research Associate UC-Davis Medical Center Collaborator/Consultant UC-Davis MedicalCenter Collaborator/Consultant Medical College of Wisconsin Collaborator Medical College ofWisconsin Collaborator Kochi University of Technology, Japan Collaborator PHS338 (Rev. 4/98) Pag* 2 BB Number fMJQSstameua^itf atMebottom ttwougroiftth[unreadable]Bppllo[unreadable]9on.DonauMsuHl)MS[unreadable]uchM3[unreadable],3b. cc Prindpal InvBsttQfttof/Prooram Director (Last, tint. mticHo):. Wemer, John Simon iframeof th* principal investigator/programdirector at the top of each printed pageandeachcontinuation page. (Fortype specifications, see [unreadable]on page6.) RESEARCH GRANT TABLE OF CONTENTS [unreadable] . i PageNumbers Face Page .,4 1 Description,