Next door to Al-Balal Halal Meat, which I so regularly walk straight past when I'm not looking, is an opticians at 114b High Street, which is only open on Thursdays, Fridays and Saturdays. The lucky proprietor is named J. McAndrew. You can phone on 0208 504 1935 if you want to make an appointment.
For those who can't wait, Amin Opticians further down the road have slightly more convenient opening hours, though don't plan to pop out for an eye test during your lunch hour. Maybe they play golf together on Wednesdays.