What did the SUSTAIN 6 trial show about retinopathy?

SUSTAIN 6, the cardiovascular outcomes trial of semaglutide, reported an imbalance in diabetic retinopathy complications between the semaglutide and placebo arms. This raised a signal that has prompted further trials and observational follow-up rather than a settled conclusion. The finding has not been consistently replicated in the same magnitude across all subsequent semaglutide studies.

Is retinopathy worsening caused by the drug or by the rapid HbA1c improvement?

Rapid HbA1c reduction is itself a recognised risk factor for transient retinopathy worsening, regardless of which agent achieves it — this is well described with insulin intensification, for example. What remains uncertain is the relative contribution of this general phenomenon versus any agent-specific effect for semaglutide and related molecules.

Do people with existing diabetic retinopathy need extra monitoring before starting treatment?

UK product information addresses retinopathy considerations for the relevant agents, and specialist diabetic eye-screening pathways already exist within NHS diabetes care. The intensity of pre-treatment retinal screening in someone with pre-existing retinopathy is a matter for the prescriber and eye-screening service, not a self-directed decision.

What visual symptoms should prompt urgent review?

Any sudden visual change — new floaters, blurring, visual field loss or vision loss — during incretin therapy requires urgent qualified clinical assessment. This applies whether or not there is a known history of diabetic retinopathy.

Diabetic retinopathy and rapid HbA1c reduction

Rapid HbA1c reduction in adults with pre-existing diabetic retinopathy has been associated with transient worsening of retinopathy in some trials. The SUSTAIN 6 cardiovascular outcomes trial of semaglutide reported an imbalance in retinopathy complications and prompted ongoing investigation.

What is known

Rapid HbA1c reduction is a known risk factor for transient diabetic retinopathy worsening, independent of agent class.
Specific to semaglutide, SUSTAIN 6 raised a signal that has been the subject of further trials and observational studies.

What remains uncertain

The relative contribution of agent-specific effects versus the general rapid-HbA1c phenomenon.
Optimal pre-treatment retinal screening intensity.

Trial limitations

Retinopathy ascertainment varies between trials.

FAQs

What did the SUSTAIN 6 trial show about retinopathy?: SUSTAIN 6, the cardiovascular outcomes trial of semaglutide, reported an imbalance in diabetic retinopathy complications between the semaglutide and placebo arms. This raised a signal that has prompted further trials and observational follow-up rather than a settled conclusion. The finding has not been consistently replicated in the same magnitude across all subsequent semaglutide studies.
Is retinopathy worsening caused by the drug or by the rapid HbA1c improvement?: Rapid HbA1c reduction is itself a recognised risk factor for transient retinopathy worsening, regardless of which agent achieves it — this is well described with insulin intensification, for example. What remains uncertain is the relative contribution of this general phenomenon versus any agent-specific effect for semaglutide and related molecules.
Do people with existing diabetic retinopathy need extra monitoring before starting treatment?: UK product information addresses retinopathy considerations for the relevant agents, and specialist diabetic eye-screening pathways already exist within NHS diabetes care. The intensity of pre-treatment retinal screening in someone with pre-existing retinopathy is a matter for the prescriber and eye-screening service, not a self-directed decision.
What visual symptoms should prompt urgent review?: Any sudden visual change — new floaters, blurring, visual field loss or vision loss — during incretin therapy requires urgent qualified clinical assessment. This applies whether or not there is a known history of diabetic retinopathy.