SLO radiant power and brightness

Available output in the Scanning Laser Ophthalmoscope (SLO) may be expresse d as radiant power at the beam pivot (SLO exit pupil), in units of microwat ts (muW). This power corresponds to dimensions of brightness (Like luminanc e and retinal illuminance) and to a range of related measures (like cd/m(2) , 1m/m(2), and the troland value) in both free and Maxwellian views. We dem onstrate that the conversion factor power/troland=1.26*10(-3) muW and 3.15* 10(-4) muW for SLO nominal visual angles 40 degrees and 20 degrees, respect ively, The factor permits measured SLO power to be expressed in units of br ightness and (inversely) brightnesses of everyday objects to be expressed i n units of SLO power. Examples of both conversions are given. Reference to the literature demonstrates the importance of expressing SLO power in brigh tness terms common to everyday activities and to visual function-testing in struments besides the SLO.