Rod multifocal electroretinograms in mice

PURPOSE. To test the feasibility of recording rod multifocal electroretinog rams (ERGs) from the mouse eye. METHODS. Multifocal ERGs were recorded from normal mice (C57BL/6J) using an array of equal-sized hexagons. Local stimuli were blue (W47A), and the num ber of blank frames between successive flashes at the same location was fix ed at 14 (minimum 200 msec between flashes). Flash and surround intensity, and the number of hexagons, were varied to optimize the stimulus conditions for the mouse, and alterations in adaptation level were used to assess con e intrusion. Local response isolation was evaluated by comparing multifocal responses to full-field ERGs and by mapping local defects in laser-treated mice. RESULTS. Rod multifocal ERGs, although small, were clearly recordable and w ell formed under many conditions. Decreasing flash intensity or the size of stimulus elements, and/or increasing the surround intensity or adaptation level, decreased local response amplitudes. At the dimmest flash intensity (-0.70 log scotopic trolands [scot td]/s) and the smallest stimulus element (2.9 degrees x 3.5 degrees), local responses were nondetectable. Compariso ns with full-field ERGs supported the hypothesis that the local responses w ere not contaminated by contributions from dark-adapted retinal areas surro unding the multifocal display. With sufficiently bright (0.30 log scot td-s ) and relatively large (5.6 degrees x 6.9 degrees) stimulus elements, multi focal responses clearly revealed local retinal defects created with laser t reatment. CONCLUSIONS. Rod multifocal ERGs can be recorded from the mouse eye to prov ide topographical maps of retinal function that have sufficient spatial res olution to be of practical use. The technique will be useful in characteriz ing the natural history of regional loss in mouse models of human retinal d isease and in evaluating some forms of interventional therapy.