VEP Responses to Superior and Inferior Half-Field Stimuli in Children with Periventricular Leukomalacia
Manca Tekavcic Pompe; Spela Markelj; Maja Sustar; Katja Groleger Srsen
University Eye Clinic and University Rehabilitation Institute
Ljubljana, Slovenia, Europe
Introduction: Periventricular leukomalacia (PVL) of prematurity may affect peripheral vision. A prior study found inferior visual field function to be affected to a greater extent than superior, probably due to the specific damage of the optic radiation (Jacobson et al, 2006). Reliable visual field testing is not always possible in preterm children with other visual, motor and cognitive problems. The aim of this study was to evaluate visual evoked potential (VEP) responses of the superior and inferior visual fields in prematurely born school-children with documented PVL and to compare them to healthy age-matched controls.
Methods: 15 prematurely born school-children (age 6-17 years) of mean gestational age 27+1/7 weeks (range: 23-35w) and birth weight 1340g (range: 780-1700g) with documented white matter brain damage were included in this study. Pattern reversal VEPs to standard full-field stimulus were recorded monocularly. In addition superior (SUP) and inferior (INF) pattern reversal visual field stimuli were also applied, the other half of the stimulus being an isoluminant homogenous background. P100 wave amplitude and latency were recorded. The amplitude coefficient was calculated as INF P100 amplitude/SUP P100 amplitude. Results were compared to an age-matched control group of 30 healthy term children.
Results: Eyes of prematurely born children show very similar P100 wave amplitude of the INF and SUP field stimulation (11.7±3.5 vs 11.6±7.1; p=0.35) and also very similar P100 wave latency of the INF and SUP stimulation (101.5±2.7 vs 100.2±6.1; p=0.43). The average amplitude coefficient in the pre-term group was 1.00±0.22. All eyes of healthy term children showed significantly larger P100 amplitude to INF compared to SUP field stimulation (21.2±12.5 vs 15.3±7.5; p<0.0001) The P100 latency was similar to INF and SUP field stimulation (99.4±2.7 vs 102.7±3.4; p=0.22). The amplitude coefficient for the group of healthy children was larger than 1 (average 1.40±0.35) in all eyes. The average amplitude coefficient in the preterm group was lower than the amplitude coefficient in the control group (1.00 vs 1.40; p<0.001).
Discussion: In preterm children, the inferior visual field amplitude is similar to that of the superior visual field amplitude. Preterm children do not show the normal larger inferior visual field amplitude found in healthy age-matched controls.
Conclusion: The use of superior and inferior visual field VEP stimuli can detect abnormalities in inferior visual field function in prematurely born children with PVL.
References: Jacobson L, Flodmark O, Martin L. Visual field defects in prematurely born patients with white matter damage of immaturity: a multiple-case study. Acta Ophthalmol Scand 2006; 84: 357-62