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R Hamilton, H Mactier, C Malcolm, M Bradnam, J Dudgeon; Rod Electroretinograms (ERGs) in Infants With Treated Retinopathy of Prematurity (ROP) . Invest. Ophthalmol. Vis. Sci. 2002;43(13):4015.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To investigate the effect of laser photocoagulation of threshold ROP on the Naka-Rushton function derived from rod ERGs. Methods: ERGs were recorded from seven infants who developed ROP requiring treatment, six of whom had ERGs recorded prior to treatment. Six of these infants had further ERGs recorded up to six corrected months. One preterm infant who developed only mild (stage 1) ROP had six ERGs recorded between 30 and 50 corrected weeks. As part of a different study using a similar protocol, 25 full-term infants had ERGs recorded at birth. Rod responses to Ganzfeld blue flashes of varying intensities were recorded using a Burian-Allen electrode. Values of Vmax (saturated response amplitude), log σ (trolands evoking a half maximal response) and n (slope parameter) were calculated by curve fitting. Results:: (log σ)-1, a measure of retinal sensitivity, increased over time in five of the six treated infants who had more than one ERG study. The other treated infant's retinal sensitivity decreased initially, but recovered by six months' corrected age. Sensitivity of the mild ROP infant increased rapidly after birth, dropped slightly between 34 and 38 weeks after conception (coinciding with stage I changes) and by 50 weeks after conception was greater than that of the treated infants. All the preterm infants' (treated and mild ROP) retinal sensitivities were below the lower limit of normal for the full-term infants at comparable post-conceptional ages.Vmax increased over time in five of the six treated ROP infants; in a sixth, it decreased and had barely recovered by 64 weeks after conception. The mild ROP infant's Vmax was higher than those of the infants with treated ROP. Vmax values for all preterm infants (treated and mild ROP) were larger than those of the full-term group at comparable post-conceptional ages. Values of n showed no clear trend with time, and averaged 0.55 (sd 0.12) for the preterm infants, which is significantly less (P=0.001) than for the full-term group (1.16 (sd 0.79)). Conclusion: Infants treated with laser photocoagulation for threshold ROP tended to have lower saturated amplitudes and less sensitive retinae than a preterm infant of comparable maturity who developed only mild ROP. All the preterm infants in this study, whether or not they had ROP, showed reduced retinal sensitivity (log σ) but higher saturated amplitudes (Vmax), compared to term-born controls, suggesting that some aspects of retinal development may be promoted by early birth while others are reduced.
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