Your first stop is a darkened room with two machines. The first you rest your chin on, and put your head against a bar. You look into the machine and it gives a basic reading of whether you are short sighted or long sighted. Next the same machine tests the pressure in your eyeball. This is to check for any potential illness or disease related to sight, rather than dealing with eyesight strength.
This part is the only bit I'm not keen on. The machine puffs a tiny bit of air at your eye to record the pressure, and the 'pop' of the air coming toward me always makes me jump away from the machine! It's in no way painful, nor uncomfortable, but it's a natural reaction to move away from the air.
In the same room, the optician's assistant uses a different machine to take photos of the back of your eye. Again you just put your face against a machine, there's a bright light, and that's it done.
Next comes the official optician part of your eye test, in their room. That's where you read lines of letters through some funky looking robo-specs, like I'm doing in the photo above. Stuart will ask a series of questions and do visual tests to pin down what your prescription strength of lenses will need to be. All in all this takes around 10 - 15 minutes, and again there's no uncomfortable tests, or pain involved.