A mate of mine in his late forties failed his HGV licence renewal medical at the eyesight check. Not at the serious stuff — cardiac, blood pressure, nothing like that. Just the eye chart. He'd been driving Class 1 for nineteen years. His optician had told him his vision was fine. The DVLA had different numbers in mind.
The eyesight standard for a Group 2 licence — that's HGV and LGV — is stricter than for a car licence. Most drivers don't look at it closely until they're sitting in front of a doctor with the D4 form on the desk. By then, if there's a problem, it's already a problem.
The Snellen scale — what 0.8 means
Eyesight for driving purposes gets measured on the Snellen scale. The classic letter chart on the wall. A score of 6/6 is "normal" — you can read at six metres what a person with standard vision reads at six metres. A score of 6/12 means you can read at six metres what a normal person reads at twelve. The lower the second number, the worse the vision.
For a standard Group 1 car licence, the threshold is 6/12 in the better eye — you need to read a number plate at 20 metres. Achievable with moderate correction.
For Group 2 — lorry and bus — the threshold is higher. You need a visual acuity of at least 0.8 (6/7.5) in your better eye. That's 6/7.5 Snellen: at six metres you need to read what a normal person reads at 7.5 metres. Better than what's needed for a car licence, and the measurement can be with glasses or contact lenses.
In your worse eye, the threshold is 0.1 (6/60). Six metres, what a normal person reads at sixty metres. That's a low bar — drivers with quite limited vision in one eye can still meet it. But the better-eye standard of 6/7.5 is what catches people. It's not as easy as it looks.
Field of vision — the test most drivers haven't heard of
Visual acuity is just part of it. Group 2 also requires a minimum horizontal field of vision of at least 160 degrees, with at least 70 degrees to the left and right and 30 degrees up and down. There must be no defects within a central 30-degree radius of your field of vision.
Field of vision problems don't show up on the Snellen chart. Someone can read the bottom line of the chart without difficulty and still have significant field of vision loss — from glaucoma, a previous stroke, a detached retina. The field of vision assessment is a separate test, usually done by an ophthalmologist or a specialist optometrist, and it's what the DVLA requires before they'll accept a medical in certain situations.
This catches drivers who've gradually lost peripheral vision and adapted without noticing. The eye fills in gaps. You might not be aware of what's missing until the field test maps it out.
Corrective lenses — and the limits on them
You can meet the Group 2 visual acuity standard with glasses or contact lenses. The constraint is on glasses: the maximum correction allowed is +8 dioptres. Anything beyond that and DVLA won't accept the corrected acuity as meeting the standard — the concern being that very strong positive lenses affect peripheral vision and distort distance perception significantly enough to create a risk.
If you wear glasses and your correction is higher than +8, you're looking at a specialist ophthalmology assessment before the DVLA will make a decision. Contact lenses don't have the same restriction — no specified power limit for contacts.
One thing worth knowing: if you need glasses to meet the standard, the condition goes on your licence. You must wear them whenever you drive. Driving without correction when the licence says "correction required" is a specific offence, separate from any question about whether you're above the threshold without them.
The D4 medical form and how it works
The D4 is the form a doctor completes to certify your medical fitness for a Group 2 licence. It covers eyesight, cardiovascular, neurological, diabetes, sleep apnoea, and other medical categories. For the eyesight section, the doctor does a basic acuity assessment — usually a Snellen chart in the surgery — and notes any abnormalities they spot.
If the doctor sees anything at the basic assessment that raises a question, or if there's a known condition in your history, the DVLA may ask for an ophthalmologist's report on top of the D4. That takes longer and costs more, but it's what the DVLA needs to make a licensing decision in complex cases.
Don't go to the D4 medical appointment having not had your eyes checked recently. If there's going to be a problem, it's far better to find out at an optician beforehand — when you have time to investigate it — than at the medical, when your renewal is ticking down and you can't drive until it's resolved.
When vision deteriorates during the licence
This is where drivers get caught. The Group 2 medical catches you at renewal. But if your eyesight deteriorates significantly between renewals, you have an obligation to notify the DVLA — you can't wait for the next D4.
Under the Road Traffic Act, licence holders have a duty to inform the DVLA if a medical condition or disability develops that may affect their fitness to drive. Eyesight that drops below the Group 2 standard qualifies. It doesn't matter that your renewal is two years away. If your vision has deteriorated to the point where you might not meet the 6/7.5 or 6/60 thresholds, or your field of vision has been compromised, that's a notifiable condition.
Notifying the DVLA doesn't automatically mean losing your licence. The DVLA assesses the specific situation — what the condition is, whether it's treatable, whether correction brings you back above the threshold. What it does do is put the responsibility where it belongs. Carrying on driving commercially when you know your vision has dropped below the Group 2 standard is a different and more serious problem.
Your optometrist is the right person to have this conversation with first. If there's any question about whether your acuity or field of vision meets Group 2 standards, get it assessed and get it in writing before the DVLA is involved. A clear optometrist's report that shows you above the threshold closes the question. Evidence of borderline or below-threshold vision that you drove on anyway does the opposite.
Common conditions that affect Group 2 eyesight
Glaucoma is the one that catches drivers most often — it damages peripheral vision progressively, and some people don't know they have it until the field test shows a problem. DVLA assesses glaucoma on a case-by-case basis. Controlled glaucoma, with field of vision above the minimum threshold, may still be compatible with a Group 2 licence. Uncontrolled or advanced glaucoma usually isn't.
Cataracts reduce acuity and — if severe enough — will push someone below the 6/7.5 threshold. Post-operative cataract correction, usually with an intraocular lens, can restore acuity above the threshold, and DVLA does grant Group 2 licences to drivers who've had cataract surgery. The detail is in the specific outcome of the operation and the post-operative assessment.
Macular degeneration, retinal detachments, diabetic retinopathy — each gets assessed individually. The DVLA has a medical advisory panel and uses specific criteria for each condition. A diagnosis isn't automatically disqualifying, but it does need to be disclosed and assessed.
After 45 and after 65
Group 2 licences have medical renewal requirements that don't apply to Group 1 car licences. From age 45, you need to submit a D4 medical certificate at each licence renewal — the renewal cycle is every five years up to age 65. After 65, the renewal cycle drops to every year, and the D4 goes in annually.
The renewal cycle isn't something that waits for you to feel like you need checking. It runs on a calendar, and if the licence expires because you missed the medical — for any reason — you can't drive until the renewal is sorted. Give yourself several weeks before the expiry date to book the appointment, complete the D4, and get it submitted to DVLA.
The practical upshot
Get your eyes checked by an optometrist who knows the Group 2 standard, before your D4 appointment, before you renew. If there's any question about your acuity or field of vision, better to know six months out than at the medical. And if your vision changes between renewals — cataract diagnosis, new glaucoma, anything that might affect your acuity or visual field — that's a DVLA notification, not something to hold until the next D4.
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