Corrected entry: We are shown a flashback to Kevin and Paul as toddlers. Paul is shown wearing glasses, but at that age, there is no possible way to tell if a toddler has eye problems, since eyes are still developing at that age. The only definitive eye problem that could be diagnosed is complete blindness, which Paul obviously is not. It could be argued that they only did that to differentiate Paul from Kevin, but that could easily have been accomplished in other ways, like simply having Kevin in his parent's lap and Paul in his parent's lap. Putting glasses on a baby relies on way too much suspension of belief.
Corrected entry: (Unsure of the exact episode): Kevin comes home from school to watch the liftoff of Apollo 13. Apollo 13 lifted off on a Saturday, April 11, 1970.
Correction: School is not mentioned at all during the episode. He is not shown to watch the liftoff, he only sees on the news that there is some sort of trouble with the shuttle.
Correction: This just isn't true - children even as young as under a year old wear glasses. Doctors dilate the pupils and analyze the light reflection to figure the prescription.