Pupillometric measures of retinal sensitivity in infants and adults with retinitis pigmentosa.

Steady-state pupil diameter was measured in darkness and over a 9 log unit range of Ganzfeld illumination in 20 normal adults, 28 normal infants, 59 adults with retinitis pigmentosa, and 30 children at risk for retinitis pigmentosa. Pupil threshold was defined as the retinal illuminance necessary to decrease pupil diameter by 1.0 mm relative to the diameter in darkness. Spectral measurements in normal adults confirmed that pupil threshold was determined primarily by rods with this procedure. Pupil thresholds of newborns and infants did not differ significantly from those of normal adults. In patients with retinitis pigmentosa, elevations in pupil threshold were related to rod loss as indexed by reductions in rod ERG amplitude. Electroretinographic follow-up of 13 of the children at risk for retinitis pigmentosa showed normal rod ERG function in 5 children who had pupil thresholds within the normal range and significant rod ERG loss in 8 children who had elevated pupil thresholds.