This might help, but seek advice from RAF Careers.
From the Association of Optometrists
website (but also repeated on RAF Website):
Royal Air Force
The minimum standards for both uncorrected and corrected vision vary for different roles and are determined by RAF medical staff.
Whatever role applicants are applying for, their spectacle or contact lens correction must not be greater than -6 dioptres or +6 dioptres in any meridian. If applicants have impaired colour perception (colour blindness) it wont prevent them from joining the RAF, but it may limit what roles you can choose.
Applicants need to take a copy with them of any acuity prescription from their optician when they go for the medical examination.
Medical conditions that preclude entry
If applicants have any of the conditions listed below, it means that they do not meet the current medical standard required to enter RAF service:
Eye disease, for example glaucoma, keratoconus, retinitis pigmentosa
Double vision (including ophthalmic migraine)
Visual field defects or blind spots
Corneal grafts or recurrent corneal ulcers
Cataract or cataract surgery
Detached retina
Vision only in one eye
Squint surgery in the previous six months
Laser eye surgery in the previous 12 months or below the minimum age of 22 at application
Any eye disorder which causes a disability (including eye injury which reduces function)
This list is provided for guidance only. If the applicant has a recurrent medical condition that is not listed, they are invited to contact theirr local Armed Forces Careers Office staff. Please note, AFCO staffs are not medically qualified, but the enquiry will be passed to an RAF medical specialist for guidance on their suitability for entry. Applicants should be aware that as part of the recruiting selection screening process, all applicants undergo a full medical by an RAF appointed Medical Examiner to confirm final suitability for service in their selected Branch/Trade.
In any case - Good Luck!