Abstract
Abstract: :
Purpose: Preterm children (< 32 weeks) are at increased risk from a variety of cerebral lesions, resulting in an increased incidence of visual, binocular and oculomotor deficits. A proportion of preterm children (28%) exhibit reading difficulties in the presence of a normal IQ. We wished to determine if there was any association between reading ability in preterm children and their oculomotor control or visual performance. Methods: We recruited 24 preterm children (PT) with normal IQ (≥85) who were free from major neurological deficits and attending mainstream school, and 19 full term (FT) age matched controls. Both groups were tested on a number of standard saccade, antisaccade and pursuit paradigms, using infrared oculography. Visual and binocular performance were assessed by means of near/distance LogMAR acuity, cover test, TNO, prism fusion range (blur and break point), accommodative facility, amplitude and near point, and convergence (RAF rule). Overall reading ability was assessed using the Graded Word Reading Test and reading accuracy, comprehension and rate were assessed using the Neale Analysis of Reading Ability II. Results: Mean values of LogMAR (near), stereopsis, fusion range, accommodation and convergence, were not significantly different between the two groups. Mean LogMar (dist) was reduced for the PT group (0.04) compared to FT (-0.01) (p=0.02). In terms of oculomotor control PT made far more antisaccade errors than FT (p=0.02). Pooled standardised reading scores for the PT group were normal (Graded Word 104, Accuracy 101, Comprehension 100 and Rate 107). However 21% of PT had demonstrable reading difficulties (> 1 SD below the standardised mean) in one or more areas. Saccade accuracy was reduced for the PT sub-group with reading difficulties (mean saccade gain left -1.23, SD 0.28; right 1.34, SD 0.23) compared to PT with normal reading ability (mean saccade gain left -1.00, SD 0.10; right 0.99, SD 0.15) (p=0.086 left, p=0.024 right), whilst performance in other areas did not show any significant differences. Conclusions: The PT group had some specific deficits of oculomotor control and visual function compared to FT. In line with previous literature a proportion of the PT group had reading difficulties in terms of accuracy, comprehension and rate, despite a normal IQ. The reading difficulties experienced by some PT children were associated with a reduction in saccade accuracy, though it is probable that the reasons for the reading difficulties are multi-factorial and may include other non-ocular causes.
Keywords: ocular motor control • binocular vision/stereopsis • reading