Abstract
Purpose: :
Amblyopia is a form of cerebral visual impairment in the absence of an organic cause, with pattern reversal visual evoked potentials (PRVEP) demonstrating attenuated amplitudes and prolonged latencies. The aim of this study is to compare visual acuity impairment due to PRVEP abnormalities in strabismic and anisometropic amblyopic children.
Methods: :
This study was approved by the Ethics Committee of the Federal University of São Paulo (0503/08). The amblyopic group consists of 40 children (22 girls), aged 5-14 years (mean 8.7±2.2 years), 15 anisometropic, 21 strabismic and 4 with anisometropia and strabismus. A group of 19 healthy children (13 girls) aged 5-15 years (8.2±2.6 years) was used as control. PRVEP recording was obtained with checkerboard stimuli subtending 1°, 15' and 7.5' visual angles. P100 latency in milliseconds (ms), the amplitude between the peaks of N75 and P100 in microvolts (μV), as well as temporal dispersion calculated by the latency difference between components N135 and N75 were determined.
Results: :
Analyzing the ambliopic eyes, there were a statistically prolonged P100 latency for stilumus 15’ (p=0.002, 115.3±19.3) and 7.5’ (p=<0.001, 124.0±23.8) compared to controls (101.4±5.5, 103.2±6.8, respectively), with significantly lower amplitudes for stimulus 1° (p=0.004, 14.0±8.0), 15’ (p=<0.001, 11.6±7.6) and 7.5’ (p=<0.001, 9.5±6.3) as compared to controls (19.0±3.9, 17.8±5.9, 16.3±5.0). Positive Pearson correlation between visual acuity (logMAR) and P100 log latency for stimulus 1° (r=0.329, p=0.0382), 15’ (r=0.348, p=0.0278) and 7.5’ (r=0.317, p=0.0463). Negative Pearson correlation was found between log amplitude and visual acuity (logMAR) stimulus 1° (r=-0.658, p=<0.001), 15’ (r=-0.613, p=<0.001) and 7.5’ (r=-0.578, p=<0.001).
Conclusions: :
Maculo-occipital changes were found in amblyopic eyes assessed by PRVEP compared with controls. Delayed conduction and lower amplitudes for smaller stimuli (15’ and 7.5’) in amblyopic eye, suggest abnormality in the parvocellular pathway.
Keywords: electrophysiology: clinical • visual acuity • amblyopia