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R. D. Hamer, V. D. R. M. Franca, M. F. Costa, D. F. Ventura; Evaluation of Effect of Fetal Growth Restriction (FGR) on Visual Acuity Development in Fullterm Brazilian Newborns: Preliminary Results Using Preferential-looking (PL) and Sweep Vep (sVEP). Invest. Ophthalmol. Vis. Sci. 2009;50(13):3816.
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© ARVO (1962-2015); The Authors (2016-present)
To evaluate potential effects of FGR on grating acuity (VA) development in a group of fullterm Brazilian infants using behavioral (Teller Acuity Cards, TAC) and visual evoked potential (sVEP) methods.
Forty-one infants between 6 and 24 weeks postnatal age were tested. 18 were FGR: birthweights were all at or below the 10th percentile. 23 control (CNTL) infants were tested, with all indices within the normal range. Infants had no genetic abnormalities, and all were born at ≥ 37 weeks gestational age. Mothers did not smoke, drink alcohol or use drugs. Behavioral: TAC (abbreviated staircase, 4 reversals). sVEP: Sinusoidal luminance gratings (161 cd/m2 mean luminance) phase-reversing at 3, 6, or 10 Hz were swept linearly from low to high SF. VA was estimated by extrapolating the 2nd harmonic amplitude to zero µV. Peak amplitude (Apk), peak signal-to-noise ratio (SNRpk), and phase at the peak (PHpk) were recorded.
VAs for both groups were close to the norms [TAC: Salomao & Ventura, IOVS 36:657, 1995; sVEP: Norcia & Tyler (6-Hz), VR 25: 1399, 1985]. FGR and CNTL VAs did not differ statistically for either TAC or sVEP at any TF. But TF had an effect within groups; for young FGR infants (<10 wks) tested at both 3 and 6 Hz, their sVEP VAs at 3 Hz were lower than at 6 Hz. In addition, young FGR infants’ peak amplitudes were higher than CNTLs’ at the low TF. Moreover, the young FGR infants tended to have larger phase lags (at all TFs) than CNTLs.
The results suggest: (1) FGR does not appear to reduce TAC or 6- & 10-Hz sVEP grating acuity up to 24 wks postnatal. (2) sVEP measures of amplitude (SNR) and phase can reveal effects on suprathreshold mechanisms in addition to any changes in extrapolated acuity (Mirabella et al., Pediatr Res 60: 435, 2006). (3) Relatively larger phase lags in young FGR infants, and larger Apk at 3 Hz, are both consistent with slower initial visual processing in FGR infants that "catches up" with age. (4) This trend suggests plasticity and action of compensatory mechanisms in FGR infants once postnatal visual experience begins. (5) Many factors underly FGR. However, one meriting further investigation is intrauterine malnutrition, since our FGRs were not premature and other risk factors were excluded. More research must be done, over a larger age range, to confirm these preliminary results and to evaluate whether FGR affects asymptotic visual performance at older ages.
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