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Daphne McCulloch, Helen Mactier, Lesley Farrell, Gen Hanazono, Ruth Hamilton; Luminance-response functions for light-adapted electroretinograms (ERGs) in preterm infants at risk of retinopathy of prematurity (ROP). Invest. Ophthalmol. Vis. Sci. 2013;54(15):602. doi: https://doi.org/.
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Scotopic retinal sensitivity in infants at risk of ROP is improved by early supplementation with high-dose vitamin A(1). Here we report the sensitivity and amplitude of light-adapted ERGs in this population.
In a double-blind, controlled trial, eligible infants born before 32 weeks’ gestation and/or <1501 g birth-weight were randomised to receive additional intramuscular vitamin A 10,000IU three times weekly from birth for two weeks or until oral feeding was established. ERGs were measured at 36 weeks postmenstrual age (PMA) before any ROP treatment. Following dark-adapted ERGs(1), 46 infants were light-adapted (30 cd/m^2) for 10 minutes for a luminance-response (LR) series to white flashes from 0.01 to 500 cd.s/m^2. Parameters calculated using non-linear regression were saturated amplitude (sAMP) for a- and b-waves, and b-wave sensitivity (luminance at semi-saturation).
All parameters for light-adapted LR series were immature (>1.5 log units below adult values). The 90% CI were 5.0 to 19µV for a-wave sAMP, 19 to 73 µV for b-wave sAMP and 1.1 to 8.5 cd.s/m^2 for b-wave sensitivity. B-wave amplitudes were typically fit with simple logistic growth functions; only 4 cases showed reduced b-waves for strong stimuli (photopic hills). Plasma retinol was higher in supplemented infants at 7 and 28 days after birth (p<0.03) but did not differ between groups at 36 weeks’ PMA. Supplementation did not affect any of the light-adapted LR parameters. Low birth weight and short gestation were strong risk factors for ROP as was postnatal illness based on duration of oxygen requirement and length of hospital stay (p<0.01). LR functions from the 36 infants without ROP did not differ from those of the 8 who developed stage 1 or 2 disease. In two infants who developed stage 3+ ROP requiring treatment, b-wave LR functions were markedly reduced (ANOVA p<0.01). Five of seven infants who developed severe ROP could not undergo ERG testing because of ongoing respiratory support.
We present normative ranges for light-adapted ERGs at 36 weeks’ PMA for infants without ROP. Parameters for infants who developed mild disease did not differ from normals. Two infants who developed severe ROP showed reduction in light-adapted b-wave sensitivity and sAMP in advance of treatment. 1. Mactier et al. 2012 J Paediatrics, 160, 954-959
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