Ozempic and Eye Problems: Diabetic Retinopathy, Vision Changes, and Screening Guidance

The SUSTAIN 6 trial looked at heart outcomes with semaglutide. It found a clear rise in diabetic retinopathy problems compared with placebo (a dummy treatment).

Key data from SUSTAIN 6:

• Retinopathy complications happened in 3.0% of the semaglutide group, against 1.8% in the placebo group. These complications were vitreous haemorrhage (bleeding inside the eye), blindness, or the need for an injection into the eye or laser treatment (photocoagulation)
• Hazard ratio: 1.76 (95% CI 1.11 to 2.78)
• Most of the extra cases were in people who already had retinopathy at the start. They were also in those whose HbA1c (average blood sugar) fell the fastest

Interpretation:

This fits a well-known pattern called "early worsening". It can happen whenever blood sugar improves quickly. The same effect is seen when insulin treatment is stepped up. Here is why.

Long-term high blood sugar changes how the retina controls its blood flow. When sugar drops fast, those changes are disrupted. This briefly makes the lack of blood supply (ischaemia) worse.

Important context:

• People with no retinopathy at the start showed no extra risk
• The SUSTAIN 6 group was high-risk. They had long-standing diabetes and known heart disease. They do not reflect every Ozempic user
• Data beyond 2 years suggest the early worsening settles down. Overall, semaglutide does not speed up retinopathy in the long run

The SmPC (the official product information) lists diabetic retinopathy complications as a known side effect of semaglutide.

Diabetic retinopathy is the top cause of preventable blindness in working-age adults in the UK. About 30% of people with type 2 diabetes already have some retinopathy when they are diagnosed.

Stages of diabetic retinopathy:

• Background retinopathy (R1): tiny bulges (microaneurysms) and small dot-shaped bleeds. Vision is not affected. This is the most common stage at diagnosis
• Pre-proliferative retinopathy (R2): cotton wool spots, beaded veins, and abnormal tiny vessels (IRMA). It points to a real lack of blood supply in the retina
• Proliferative retinopathy (R3): new blood vessels grow (neovascularisation) on the optic disc or elsewhere. This carries a high risk of vitreous haemorrhage (bleeding in the eye) and the retina being pulled away (tractional retinal detachment)
• Diabetic maculopathy (M1): swelling (oedema) or deposits within one disc diameter of the fovea, the centre of vision. This can cause central vision loss at any stage of retinopathy

Why a fast HbA1c drop makes retinopathy worse:

• Long-term high blood sugar damages the tiny support cells and thickens the walls in retinal vessels
• To cope with high glucose, the retina raises its blood flow as a back-up
• When glucose falls fast, this back-up is switched off, and the lack of blood supply shows through
• The starved retina releases VEGF (vascular endothelial growth factor, a signal that grows blood vessels). This drives new vessel growth and swelling at the macula
• The risk tracks with how big and how fast the HbA1c drop is, not with which drug is used

People whose HbA1c falls by more than 22 mmol/mol (2.0%) within 3 months face the highest risk of early worsening.

Not everyone starting Ozempic is at risk of retinopathy. Spotting those who are lets you target screening and monitoring.

Higher risk patients:

• Already have pre-proliferative or proliferative retinopathy (R2 or R3)
• Long history of diabetes (more than 10 years)
• HbA1c above 75 mmol/mol (9.0%) when Ozempic starts, where a large drop is expected
• Past laser treatment (photocoagulation) or injections into the eye (intravitreal anti-VEGF)
• High blood pressure at the same time (systolic above 140 mmHg), which worsens retinopathy on its own
• Pregnancy (this does not apply to Ozempic, which must not be used in pregnancy, but it matters if someone switches from Ozempic to insulin)

Pre-treatment assessment:

• Check that retinal screening is up to date. The NHS Diabetic Eye Screening Programme (DESP) invites patients once a year
• If the last screen was more than 12 months ago, arrange a new retinal photograph before starting Ozempic
• Look at the most recent screening grade. Anyone with R2 or worse should be discussed with the eye team (ophthalmology) before treatment begins
• Record baseline vision. A quick Snellen chart check at the GP surgery gives a useful reference

Lower risk patients:

• No retinopathy at the start (R0), or background retinopathy only (R1)
• HbA1c below 64 mmol/mol (8.0%), where the HbA1c drop will be small
• Diabetes for under 5 years
• Blood pressure well controlled

These patients can start Ozempic with standard yearly screening and no extra eye review.

NICE NG 28 and the Royal College of Ophthalmologists advise closer retinal checks when you step up blood sugar treatment in people who already have retinopathy.

Recommended screening schedule while on Ozempic:

• No baseline retinopathy (R0): carry on with standard yearly DESP screening. No extra monitoring is needed
• Background retinopathy (R1): yearly screening is still fine. Think about a 6-month interim screen if HbA1c falls by more than 15 mmol/mol (1.5%) in the first 3 months
• Pre-proliferative retinopathy (R2): arrange an ophthalmology review before starting Ozempic. Screen every 3 to 4 months during the first year of treatment
• Proliferative retinopathy (R3) or maculopathy (M1): active eye care should already be in place. Discuss with the retinal specialist before starting semaglutide. Check more often, every 2 to 3 months

Practical considerations:

• The NHS DESP uses digital retinal photography, which is good enough for screening
• People with R2 or higher may need an OCT scan (optical coherence tomography) to check for swelling at the macula
• If new visual symptoms appear during treatment, such as blurred vision, floaters, or loss of part of the visual field, refer urgently to ophthalmology. Do this whatever the last screen showed
• Note retinal screening dates in the diabetes care plan so follow-up is not missed

Slowing the dose increase may help. Stretching each step to 8 weeks instead of 4 slows the HbA1c improvement and may lower the risk of retinopathy worsening.

Trials have not formally tested this approach, though.

Apart from the retinopathy concern, some people report visual symptoms while taking Ozempic. Most are harmless and come from changing blood sugar rather than direct harm to the eye.

Blurred vision during dose changes:

• The eye's focus shifts when blood glucose changes a lot. The lens takes in glucose, then swells or shrinks as plasma glucose goes up or down
• People starting Ozempic may get short-term blurred vision during the first 2 to 4 weeks as blood glucose improves
• This settles on its own once glucose levels are steady. Advise patients not to change their glasses or contact lens prescription during this time

Dry eyes:

• Some patients report this, but the SmPC does not list it as a common side effect
• It may come from being dehydrated through drinking less (linked to nausea), or from the medication itself
• Lubricating eye drops (artificial tears) ease the symptoms

Floaters:

• New floaters need urgent checking, especially with flashing lights or loss of part of the visual field. This rules out vitreous haemorrhage (bleeding in the eye) or a detached retina
• In people with known proliferative retinopathy, new floaters are a warning sign. They should prompt a same-day ophthalmology review

Visual disturbance from hypoglycaemia (low blood sugar):

• Blurred or double vision can happen during a low blood sugar episode. This is more likely in people also taking sulfonylureas or insulin
• It clears once blood glucose is brought back above 4.0 mmol/L

The SmPC does not list semaglutide as directly harming the optic nerve or retina, apart from the effect of fast blood sugar change.

You must weigh the retinopathy signal from SUSTAIN 6 against the real blood sugar and heart benefits of semaglutide. For most people, the balance clearly favours treatment.

Arguments for starting Ozempic despite retinopathy concerns:

• SUSTAIN 6 showed a 26% drop in major heart events. This was driven by a 39% drop in non-fatal stroke
• Good blood sugar control over the long term lowers lifetime retinopathy risk. The UKPDS showed that every 11 mmol/mol (1%) fall in HbA1c cuts small-vessel complications by 37%
• The early worsening is usually short-lived (3 to 6 months) and can be managed with eye monitoring
• People who develop macular swelling during fast blood sugar improvement respond well to anti-VEGF injections (ranibizumab, aflibercept)

Risk mitigation strategies:

• Start at 0.25 mg. In high-risk patients, think about stretching each dose step to 8 weeks to slow the HbA1c fall
• Get blood pressure well controlled. Aim below 140/80 mmHg, or below 130/80 mmHg if retinopathy is present, per NICE NG 136
• Make sure retinal screening is current before starting
• Consider an HbA1c target that allows a gradual, not sudden, improvement

When to avoid Ozempic:

• Active proliferative retinopathy waiting for laser or anti-VEGF injections. Settle the retinopathy first, then think again
• People who decline retinal screening or cannot get it

For most people with type 2 diabetes, and especially those with no retinopathy at the start, the eye risk from Ozempic is small. It should not put you off prescribing.