REVIEW Development of Rod Function in Term Born and Former Preterm Subjects

Purpose. To provide an overview of some of our electroretinographic (ERG) and psychophysical studies of normal development of rod function and their application to retinopathy of prematurity (ROP). Methods. ERG responses to full-field stimuli were recorded from dark adapted subjects. Rod photoreceptor sensitivity (SROD) was calculated by fit of a biochemical model of the activation of phototransduction to the ERG a-wave. Dark adapted psychophysical thresholds for detecting 2 ° spots in parafoveal (10 ° eccentric) and peripheral (30 ° eccentric) retina were measured and the difference between the thresholds, 10-30, was examined as a function of age. SROD and 10-30 in term born and former preterm subjects were compared. Results. In term born infants, (1) the normal developmental increase in SROD changes proportionately with the amount of rod visual pigment, rhodopsin, and (2) rod-mediated function in central retina is immature compared with that in peripheral retina. In subjects born prematurely, deficits in SROD persist long after active ROP has resolved. Maturation of rod-mediated thresholds in the central retina is prolonged by mild ROP. Conclusions. Characterization of the development of normal rod and rod-mediated function provides a foundation for understanding ROP. (Optom Vis Sci 2009;86:E653–E658