[5.9.13] A unit of retinal illuminance that is based on the fact that retinal illuminance is proportional to the product of the luminance of the distal stimulus and the area of the entrance pupil. It is defined as the product of object luminance (candelas per square meter) and pupillary aperture area (square millimeters); i.e., one troland is the retinal illuminance produced when the luminance of the distal stimulus is one candela per square meter and the area of the pupil is one square millimeter. The troland may be photopic or scotopic.
Note: The troland makes no allowance for interocular attenuation or for the Stiles-Crawford effect.
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