Photoreceptor Function in Retinopathy of Prematurity
There is new evidence for photoreceptor involvement before and after resolution of the active, vascular phase of retinopathy of prematurity (ROP). Based on these findings we hypothesize that the greater the deficit in photoreceptor function the more severe the acute phase ROP. Infants (enrolled at age 10 wks) and children (enrolled at age 8 - 12 yrs) will be categorized by severity of ROP (None, Mild, Moderate, Severe) and will be given electroretinographic (ERG) and psychophysical tests of photoreceptor function. In all subjects the activation of rod phototransduction, and of dark-adapted, rod visual thresholds will be measured in parafoveal and peripheral retina. Rod responses will be measured to determine if there is significant variation between ROP categories. High refractive errors in ROP frequently develop during the years when photoreceptors mature. In this project about retinal mechanisms, the secondary hypothesis is: the greater the photoreceptor dysfunction within ROP category, the greater the refractive error. All subjects will have cycloplegic refractions, as well as acuities, measured. To evaluate the developing retinal processes and spherical equivalent for causative relations, a longitudinal study of rod thresholds, acuity and refractive error between ages 10 weeks and three years will be conducted. The parameters of these courses, as well as the retinal response parameters obtained in the other studies of retinal function, will be used to test the secondary hypothesis. In the children, other photoreceptor functions including deactivation of rod phototransduction, activation of cone phototransduction, and rod increment threshold functions will be investigated. The parameters obtained will be used in further tests of the main and secondary hypotheses, and for within subject evaluation of relative involvement of rods vs. cones, activation vs. deactivation, and receptoral vs. postreceptoral mechanisms. This project, based on an entirely new perspective of ROP, will lead not only to much more information about retinal and visual function in ROP, but also to new knowledge about fundamental ROP disease processes.