Cataract surgery in diabetes: when to operate, and how to protect the retina before and after

"I have diabetes, and I was told I have a cataract and that surgery is now necessary. But I have heard that the operation can harm the retina in people with diabetes. Should I have it now, or wait?" This is one of the questions we hear most. The short answer: cataract surgery improves vision in most people with diabetes, but its success depends a great deal on the state of the retina before surgery and on follow-up afterwards. In this article we explain how we balance the two.

Why does surgery in a person with diabetes need special planning?

The cataract operation itself is not very different in someone with diabetes: we remove the natural lens that has become cloudy and put a clear artificial lens in its place. We explain the steps of the operation in detail in our article on cataract surgery.

The real difference is that the eye of a person with diabetes may have another disease behind the lens: diabetic retinopathy. The cloudy lens partly hides the retina from the doctor, and also hides the retina's effect on vision. So we need to know the state of the retina well before surgery, because a successful operation with an unstable retina may not give the expected vision.

The good news: surgery improves vision in most people with diabetes

In a multicenter study of tens of thousands of eyes, vision in people with diabetes improved after surgery by an average of about 5 lines on the eye chart. But final vision was slightly lower on average than in people without diabetes, and the more severe the retinopathy, the poorer the vision after surgery (Chancellor et al., 2021).

In other words, the operation helps, but the ceiling of improvement is set by the macula and the retina. That is why, before surgery, we explain honestly what can be expected, based on the state of each patient's retina.

What concerns us after surgery?

First: macular edema

After any cataract operation, temporary swelling of the macula can occur. It is uncommon in an ordinary eye: in a British study of more than 80,000 eyes, it happened in about 1 in 100 eyes without risk factors (Chu et al., 2016).

But the risk is higher in people with diabetes. In the same study, the risk was about twice as high in a person with diabetes even if the retina was healthy, and about six times higher when any degree of retinopathy was present, increasing with the severity of retinopathy (Chu et al., 2016).

In another British study of people with diabetes who had no previous edema, new edema needing treatment rose from about 3% in the year before surgery to about 5% in the year after it. The period of highest risk was between the third and sixth month after surgery, and the risk was clearly higher in those with moderate or severe retinopathy: about 10% and 13% respectively (Denniston et al., 2017).

Most importantly, an eye that had edema close to the center, or had been treated for edema before, is more likely to see it come back after surgery. In an American study, center-involving edema appeared in about 1 in 10 of these eyes within 4 months after surgery (Diabetic Retinopathy Clinical Research Network Authors/Writing Committee et al., 2013).

Second: progression of the retinopathy itself

Here the scientific picture is less clear. A recent review of 15 studies found that retinopathy progressed more after cataract surgery, including progression to sight-threatening stages, with evidence the researchers described as moderate (Lee et al., 2025). A large American study found that the risk of retinopathy turning proliferative, or of bleeding inside the eye, was higher in the first year after surgery (Loya et al., 2025).

On the other hand, a small but careful study found no difference in progression between the operated eye and the patient's other eye. Progression in both eyes was linked to higher long-term blood sugar (HbA1c) and insulin use, that is, more to the nature of the disease itself than to the operation (Squirrell et al., 2002).

The practical conclusion from these studies is the same: the first year after surgery needs close follow-up of the retina (Lee et al., 2025).

Before surgery: how do we prepare the eye?

The general rule is that identifying and treating retinopathy and macular edema before surgery affects the final visual result (Kelkar et al., 2018). Preparation therefore usually includes:

• An examination of the retina with the pupil dilated to grade the retinopathy, as far as the cloudy lens allows.
• Optical coherence tomography (OCT) of the retina, to see whether there is edema in the macula even if it is not visible on ordinary examination.
• Controlling any edema that is present. When edema is present at the time of surgery, injections into the eye, either anti-VEGF medicines or steroids, are the most appropriate way to control it and achieve a good visual result (Boscia et al., 2017). We explain the treatment options in our article on diabetic macular edema.
• Controlling blood sugar as far as possible, because higher long-term blood sugar has been linked to progression of retinopathy (Squirrell et al., 2002).

This does not mean that every person with diabetes must wait a long time. Sometimes the lens is so cloudy that it prevents examination of the retina or laser treatment, and then the operation itself becomes part of treating the retina. The decision is made for each eye, and no single approach suits every case.

During and just after surgery: how do we reduce the risk of edema?

The European Society of Cataract and Refractive Surgeons recommends non-steroidal anti-inflammatory drops, alone or together with steroid drops, after surgery to reduce inflammation and prevent swelling of the macula (European Society of Cataract and Refractive Surgeons, 2024).

In a European trial specifically in people with diabetes, some patients received, in addition to these drops, a steroid injection under the conjunctiva at the end of surgery. This group had a thinner macula at 6 and 12 weeks, and none of them developed cystoid swelling of the macula. An anti-VEGF injection into the eye during surgery, however, had no clear effect in these patients, who had no existing edema (Wielders et al., 2018b).

The surgeon chooses the right prevention according to the degree of retinopathy, any previous edema, and other factors in the eye.

Is the operation harder in someone with diabetes?

Slightly. In the large multicenter study mentioned above, a tear in the back of the lens capsule during surgery was a little more common in people with diabetes: about 2.3% compared with 1.6% (Chancellor et al., 2021). Diabetes and retinopathy also appeared among the risk factors for this complication in the British national database of more than 900,000 operations (Sim et al., 2024). This complication can usually be managed during the operation itself, but it can prolong recovery, so we take it into account when planning.

Is a multifocal lens right for me?

Choosing the type of implanted lens is a decision that needs discussion with each patient. In someone with diabetic retinopathy in particular, we take into account the state of the macula now and the chance that it will be affected in future. We explain the lens types, with the pros and cons of each, in our article on choosing an intraocular lens.

After surgery: follow-up is part of the treatment

Because the risk of edema peaks between the third and sixth month (Denniston et al., 2017), and because retinopathy may progress during the first year (Lee et al., 2025), follow-up of the retina after surgery is as important as the operation itself. Your doctor will set the follow-up visits according to the degree of retinopathy before surgery.

Questions patients often ask

Should I wait until my sugar is perfectly controlled?

Sugar control is important to protect the retina in the long term (Squirrell et al., 2002), but there is no single number that must be reached before every operation. What matters most is that the retina is stable and that any edema is under control (Boscia et al., 2017). The timing is decided in coordination between the eye doctor and the diabetes doctor.

Will the operation make my retina worse?

Most studies suggest that the risk of retinopathy progressing is slightly higher in the first year after surgery (Lee et al., 2025; Loya et al., 2025), while some researchers think part of this progression reflects the nature of the disease itself (Squirrell et al., 2002). So the answer is not to postpone surgery unnecessarily, but to prepare the retina beforehand and follow it afterwards.

Do I need an eye injection with the operation?

Not necessarily. If you have existing edema, an injection may be advised before or with the operation (Boscia et al., 2017). If there is no edema, prevention is usually with drops, and the surgeon may add other measures depending on your case (European Society of Cataract and Refractive Surgeons, 2024; Wielders et al., 2018b).

When will my vision improve?

Vision usually improves within weeks after surgery, but the final level depends on the state of the macula (Chancellor et al., 2021). If edema appears after surgery, treating it early helps vision recover.

Summary

Cataract surgery in a person with diabetes is beneficial and safe in most cases, but it is not "just a lens" operation. Its success starts before the day of surgery, with assessment of the retina and control of any edema, and continues afterwards with close follow-up during the first year. In this order, the patient benefits from the clarity of the new lens without being surprised by a retinal problem that could have been prevented or caught early. We make sure each patient understands this sequence before deciding.

This information is for health education and does not replace a medical examination.