The No-Glasses Rule
Canada is one of the few countries with a total ban on glasses.
Unlike the US, UK, or EU, Immigration, Refugees and Citizenship Canada (IRCC) does not allow glasses in passport or PR card photos under any circumstances — even with a medical certificate. If you normally wear glasses, you'll need to remove them for this photo specifically.
This is one of the most common mistakes for applicants used to other countries' rules, so it's worth double-checking before you submit.