Tirzepatide Retinopathy Risk Not Increased in Type 2 Diabetes Study vs dulaglutide
A SURPASS-CVOT retina substudy found no increased diabetic retinopathy progression with tirzepatide compared with dulaglutide over 36 months.
Tirzepatide produced larger blood sugar reductions than dulaglutide in high-risk adults with type 2 diabetes, but it did not increase diabetic retinopathy development or progression in a 36-month retinal substudy. The findings offer reassurance for patients and clinicians using tirzepatide, while reinforcing the need for routine diabetic eye screening.
Study Details
Tirzepatide, sold as Mounjaro for type 2 diabetes, is a once-weekly medication that activates both GIP and GLP-1 pathways. It can lower A1c substantially and often quickly. That strength has raised an important clinical question: could rapid glucose improvement worsen diabetic retinopathy in some patients?
This concern is not theoretical. Diabetic retinopathy is caused by long-term damage to small blood vessels in the retina, usually from chronic high blood sugar. Better glucose control reduces long-term eye risk, but rapid correction of high blood sugar has been linked in prior diabetes trials to temporary early worsening of retinopathy, especially in people with more advanced baseline eye disease.
The SURPASS-CVOT retina substudy was designed to look directly at this issue. It included adults with type 2 diabetes and cardiovascular disease who either already had diabetic retinopathy or macular edema, or were considered at higher retinal risk because they had lived with type 2 diabetes for at least 15 years and had an A1c of 8.0% or higher.
Methodology
The substudy included 920 participants from the larger SURPASS-CVOT trial. Of these, 449 received tirzepatide up to 15 mg once weekly, while 471 received dulaglutide 1.5 mg once weekly. Dulaglutide was used as the active comparator because these were high-risk patients, making placebo less appropriate.
Participants had standardized retinal photographs at baseline and again at 12, 18, 24, and 36 months. Researchers assessed retinal changes using the Early Treatment Diabetic Retinopathy Study severity scale, a standard grading system used to track diabetic retinopathy. They also looked at clinically important eye outcomes, including retinal laser treatment, vitreous hemorrhage, anti-VEGF eye injections, vitrectomy, and sustained vision loss.
Key Findings
Tirzepatide lowered A1c more than dulaglutide at 6 months, with a 2.18 percentage-point reduction compared with 1.28 percentage points for dulaglutide.
At 36 months, worsening by 2 or more steps on the ETDRS diabetic retinopathy severity scale occurred in 21.3% of the tirzepatide group and 23.3% of the dulaglutide group.
The difference in retinopathy progression between groups was not statistically significant.
Time to first 2-step or greater retinopathy progression did not differ significantly between tirzepatide and dulaglutide.
Secondary eye outcomes, including retinal procedures, vitreous hemorrhage, anti-VEGF injections, vitrectomy, and significant visual loss, also did not show meaningful between-group differences.
Implications for Practice
For patients, the main message is reassuring but not casual. Tirzepatide was associated with stronger glucose lowering without a detectable increase in diabetic retinopathy progression compared with dulaglutide over 36 months. That matters because many people starting GLP-1 or dual incretin therapy may worry that faster A1c improvement could harm their eyes.
For clinicians, the study supports the idea that tirzepatide can be used in high-risk type 2 diabetes patients without an obvious excess retinal safety signal compared with an established GLP-1 receptor agonist. The retina substudy is especially relevant because it included patients with existing retinopathy or higher baseline risk, not just low-risk patients.
The practical approach should remain the same: improve glucose control, but do not separate metabolic treatment from eye care. Patients with type 2 diabetes should have appropriate retinal screening, and those with existing diabetic retinopathy should be followed by eye care professionals at intervals based on severity. If a patient has advanced retinopathy, macular edema, visual symptoms, or a very high baseline A1c, clinicians may want to coordinate more closely with ophthalmology when intensifying glucose-lowering therapy.
This study does not mean retinopathy risk no longer matters. It means that, in this substudy, tirzepatide did not appear to add retinopathy risk beyond dulaglutide despite greater A1c reduction. That is a meaningful safety signal for diabetes practice, but it does not replace routine eye exams.