If you always wear specs then you can take the photograph with your specs but you need to ensure that the lens/glass does not obscure your eyes. Tell the photographer that there should not be any glare on the glass from flash/lights. The same applies for for your face, your cheeks or forehead should not have any glare as well.
If you need more details please search for CIC Photograph requirements, a PDF file with all the details is available. If you don't find that please let me know I will upload here.
I am in Bangalore and went to GK Vale for these photographs. The pictures came back horrible, almost like mug shots but as per specifications
Its always good to carry the specifications along when you go as I found that the studio was not aware of Canada requirements in particular. The studios are more aware of US/Singapore/Australia specifications