opticians make telescopes. Optometrists write prescriptions for eyeglasses. Optometric opticians make eyeglass lenses.

Opthalmologists diagnose and treat disease of the eyes. An optometrist can perform an opthalmological exam but cannot prescribe medicine nor practice eyeball surgery.

Google Define:

optician ɒpˈtɪʃ(ə)n/Submit nounBRITISH a person qualified to prescribe and dispense glasses and contact lenses, and to detect eye diseases ( ophthalmic optician ) or to make and supply glasses and contact lenses ( dispensing optician ). US a dispensing optician.

In my understanding, a dispensing optician is a different thing than either an optometrist or an opthalmologist.

There are some good reasons one requires a professional prescription from eyeglasses; if you wear the wrong lenses for any length of time, it can screw up your eyesight. Although the effect is commonly temporary it _can_ be debilitating.

So a dispensing optician would be someone who sells eyeglasses, given a prescription from an optometrist or an opthalmologist.

It is quite definitely the case that opticians make telescopes. From time to time I call myself an astronomical optician. I don't grind glass much anymore but I am quite good at making astronomical telescope optics.

I'd better tell my optician to change the sign outside the shop then...

Pardon me while I drop by the chemist's shop to pick up some fuming nitric acid, sulfuric acid and glycerin.