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D Newsham, PC Knox; Oculomotor Control - A Problem for Lightweights? . Invest. Ophthalmol. Vis. Sci. 2002;43(13):958.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: The survival rate for very low birth weight (VLBW) infants (<1500g) has dramatically increased, although survivors are at increased risk of a variety of lesions including intraventricular haemorrhage (affecting tissues predominantly around the head of the caudate nucleus and cerebellum) and periventricular leucomalacia. For those with normal IQ there are continuing concerns over their levels of academic achievement and the increased incidence of reading and learning difficulties. Given a higher incidence in this group of motor and eye motility problems (Powls et al, 1997, Arch Dis Child Fetal Neonatal Ed. 76:82), that could contribute to the reading difficulties, we are investigating oculomotor control in a cohort of children born in 1991. Methods: A group of 14 VLBW children with normal IQ (≷85) and no gross ocular motility or neurological deficits and 15 full term age matched controls were tested on a number of standard saccade, anti-saccade and pursuit paradigms. Subjects sat with their head stabilised and monocularly viewed a display. For all tasks the fixation, saccade and pursuit targets were small dark squares (0.3°x 0.3°) presented on a light background (contrast 90%). In all saccade tasks, targets appeared randomly 5° to the left or right of fixation; in pursuit tasks, targets stepped 5° to the left or right, then moved at 14°/s back through the centre of the display. Movement of the left eye was recorded using infrared oculography. Results: Pooled values of saccade amplitude, peak velocity and duration were not significantly different between the two groups, though saccade gain was more variable within the VLBW group. Saccade latency was significantly longer for the VLBW group (mean 204ms, SD 54ms) compared to the controls (mean 181ms, SD 44ms) (p<0.001). Analysis of the anti-saccades revealed a significantly higher error rate for the VLBW group (78%, SD 15%) compared to the full terms (62%, SD 18%) (p=0.02). Smooth pursuit latency, and eye velocity at the end of the open loop period, were similar for both groups. Peak slow eye velocity was significantly reduced for the VLBW group, but for rightward pursuit only. Conclusion: The VLBW group shows subtle deficits of oculomotor control when compared to full term controls. There is also an increased anti-saccade error rate in the VLBW group, which may be indicative of a lesion affecting the frontal cortex or due to developmental delay. An increased anti-saccade error rate has been shown to be associated with dyslexia (Biscaldi et al, 2000, Perception 29:509). The oculomotor deficits in VLBW children may be associated with the higher incidence of reading difficulties that have been reported.
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