Pattern Visual Evoked Potentials in Dyslexic Children.

PURPOSE: This study aimed to compare pattern visual evoked potential (PVEP) components in dyslexic and normal children. METHODS: This cross-sectional analytic study recruited 72 children, including 36 dyslexic and 36 normal participants aged 8-12 years. Visual examinations included measurement of distance visual acuity, refraction, and PVEP components of amplitudes and latencies with two different check sizes of 15 and 60 minutes (min) of arc at two contrast levels of 25% and 100%. RESULTS: Our results demonstrated significant differences between dyslexic and normal children in terms of P100 latency and amplitude of PVEP at 25% contrast, with check sizes of 15 and 60 min of arc. However, there were no significant differences between the two groups regarding P100 latency and amplitude at 100% contrast with check sizes of both 15 and 60 min of arc. CONCLUSION: Dyslexic participants showed reduced amplitude and prolonged latency in most PVEP components at low-contrast levels. These findings may support the magnocellular deficit hypothesis in dyslexic participants, even though the parvocellular pathway remains intact.

Effect of cataract type and severity on visual acuity and contrast sensitivity.

PURPOSE: To determine the effect of cataract type and severity in eyes with pure types of age-related lens opacities on visual acuity (VA) and contrast sensitivity in the presence and absence of glare conditions. METHODS: Sixty patients with senile cataracts aged 40 years or older with no other ocular pathologies were evaluated for VA and contrast sensitivity with and without glare. Lens opacities were classified according to the Lens Opacities Classification System (LOCS) III. VA was measured using the Snellen chart. Contrast sensitivity was measured with the Vector Vision CSV-1000E chart in the presence and absence of glare by calculating the area under log contrast sensitivity (log CS) function (AULCSF). RESULTS: Cataracts were posterior subcapsular in 26 eyes, cortical in 19 eyes and nuclear in 15 eyes. VA significantly decreased with increasing cataract severity and there was significant loss of contrast sensitivity at all spatial frequencies with increasing cataract severity. AULCSF significantly decreased with increasing cataract severity in the presence and absence of glare conditions. Contrast sensitivity was significantly reduced at high spatial frequency (18 cpd) in cortical cataracts in the presence of glare in day light and at low spatial frequency (3 cpd) in night light. CONCLUSION: Increased cataract severity is strongly associated with a decrease in both VA and AULCSF. Contrast sensitivity scores may offer additional information over standard VA tests in patients with early age-related cataracts.