Ronald M Hansen1, Anne B Fulton. 1. Department of Ophthalmology, Children's Hospital and Harvard Medical School, Boston, Massachusetts 02115, USA. ronald.hansen@childrens.harvard.edu
Abstract
PURPOSE: To study deactivation of the rod photoresponse in infants using a paired-flash procedure. Rhodopsin content increases and scales the parameters of the activation of rod phototransduction as rods develop. However, little is known about the kinetics of deactivation in the rods of young infants. METHODS: ERG responses to pairs of flashes were used to study the recovery of the rod response in 4- and 10-week-old infants and mature control subjects. The amplitudes of rod isolated a-wave responses to a probe flash (+3.3 log scot td . s) presented 2 to 120 seconds after an equal-intensity test flash were measured. The interstimulus interval (ISI) at which the amplitude was half that of the response to the probe flash alone (t(50)) was determined by linear interpolation. RESULTS: Recovery time (t(50)) was significantly longer in infants than in adults (F = 18.9, df 2, 32; P < 0.01). The shape of the recovery function did not vary with age. The t(50) values were inversely proportional to the parameters of activation of rod phototransduction. CONCLUSIONS: These results are evidence that the kinetics of deactivation in infants are slower and may be set by the proportion of rhodopsin isomerized.
PURPOSE: To study deactivation of the rod photoresponse in infants using a paired-flash procedure. Rhodopsin content increases and scales the parameters of the activation of rod phototransduction as rods develop. However, little is known about the kinetics of deactivation in the rods of young infants. METHODS: ERG responses to pairs of flashes were used to study the recovery of the rod response in 4- and 10-week-old infants and mature control subjects. The amplitudes of rod isolated a-wave responses to a probe flash (+3.3 log scot td . s) presented 2 to 120 seconds after an equal-intensity test flash were measured. The interstimulus interval (ISI) at which the amplitude was half that of the response to the probe flash alone (t(50)) was determined by linear interpolation. RESULTS: Recovery time (t(50)) was significantly longer in infants than in adults (F = 18.9, df 2, 32; P < 0.01). The shape of the recovery function did not vary with age. The t(50) values were inversely proportional to the parameters of activation of rod phototransduction. CONCLUSIONS: These results are evidence that the kinetics of deactivation in infants are slower and may be set by the proportion of rhodopsin isomerized.
Authors: James D Akula; Julie A Mocko; Anne Moskowitz; Ronald M Hansen; Anne B Fulton Journal: Invest Ophthalmol Vis Sci Date: 2007-12 Impact factor: 4.799