If you are a person who needs to wear glasses every time you drive, you must ensure you wear them each time to meet the “standards of vision for driving”. You should tell the DVLA if you have any issues with your eyesight which affects both your eyes, or the remaining eye if you have one eye.
This does not include being colour blind, or short/long sighted. You also do not need to inform DVLA if you have had corrective surgery and can meet the eyesight standards. There is a list of all the medical conditions which may affect your driving, and it is available through the DVLA website. It is important that you check your condition, as you could be prosecuted if you drive without meeting the standards for vision for driving.
The standards for driving are that you should be able to read a number plate from 20 metres away. You should have a visual acuity of at least 0.5 (6/12) measured on the Snellen scale, with glasses or contacts if required.