He says in a classroom environment, while students may look at a screen for some of the time, they are generally looking up and around at things at different distances.
"If people had a prescription, a minor one that wasn't affecting them much day to day, suddenly chuck yourself on to a screen for a number of hours and that becomes more pronounced.
"Computers aren't responsible for creating a need for glasses ... but if you have a prescription it's going to become more noticeable."
Screen time is not damaging but it can exacerbate an existing condition. With people working from home and more online work for students, Ian says it's important that people are comfortable doing it.
"We're seeing reduced comfort from spending hours looking at a computer screen.
"There's the 20-20-20 rule: every 20 minutes, give your eyes a 20 second break looking at something 20 metres away. For young people it's important to get out to natural daylight. Spending all day inside looking at a device has strong implications for developing problems.
Eye strain can cause headaches, squinting, tiredness and eye dryness.
"People tend to blink less when they're staring at a screen."