May 27, 2026 · 4 min read
Why fit matters more than the frame
A frame that suits you and sits wrong is worse than a plain one that sits right. Where the lens sits changes what you see.
People choose a frame with a mirror and a shape in mind. Opticians choose one with four numbers in mind: how far the lens sits from your eye, how far apart your pupils are, how the frame tilts, and how it curves around your face.
The optical centre
Every lens has one point where the correction is exactly what was prescribed. Move that point a few millimetres off your pupil and the lens starts adding a prism you never asked for. Mild prescriptions forgive this. Strong ones do not — the symptom is a headache after an hour, and people usually blame the prescription rather than the fitting.
Progressives are unforgiving
A progressive lens is a corridor. Sit the frame two millimetres too low and the reading zone lands below where your eyes naturally drop, so you tilt your chin all day and decide progressives are not for you. They probably were.
This is the honest argument for measuring in person, and it is why I come to you rather than mailing a box. Ten minutes with a pupillometer and a mirror settles what an online size chart cannot.