 To explore these alternative hypotheses, we will administer the Visual Discomfort Scale to a large sample of students and measure the prevalence, severity and symptom patterns of this problem in a college population. A stratified, random sample of 100 students will receive a vision and psycho-educational assessment to screen for concomitant conditions that might hamper reading performance or contribute symptoms of visual discomfort. Vision testing includes an optometric exam to assess accommodation and vergence, CSF to test for noisy SF channels, and electroretinograms ERG and visual evoked potentials VEP to measure LM cone sensitivity variation. 