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Two studies presented at the American Academy of Ophthalmology meeting found associations between higher preoperative hemoglobin A1c and complications after eye surgery. One linked A1c levels to cystoid macular edema after cataract surgery; another found a higher five-year infection hazard among glaucoma shunt patients with A1c above 8.4%. The retrospective findings do not establish that lowering A1c before surgery would prevent these outcomes.
Two retrospective studies presented at the American Academy of Ophthalmology (AAO) annual meeting linked higher preoperative hemoglobin A1c levels with increased risks of complications after cataract surgery and glaucoma shunt surgery. The findings may help inform discussions with patients who have diabetes, but they do not show that lowering A1c before an operation reduces those risks.
In the cataract study, University of Minnesota researcher Daniel Fraser, MD, and colleagues analyzed Veterans Affairs health system records from 2010 through 2022. They identified 6,808 patients with postoperative macular edema within six months of surgery and compared them with 121,164 patients who did not develop it. Overall, pseudophakic cystoid macular edema (CME) occurred after 5.3% of the cataract surgeries in the analysis.
CME incidence rose across A1c groups, from 4.2% for patients with A1c below 6.3% to 6.9% for those at or above 8%. In the multivariable analysis, diabetic retinopathy was the strongest predictor: it was associated with 3.28 times the odds of CME, with risk rising by retinopathy severity. Each 1 percentage-point increase in A1c was associated with a 6% increase in the odds of CME (odds ratio 1.06; 95% CI 1.05-1.08). The researchers reported that A1c added predictive information beyond retinopathy.
A separate analysis by Mohsen Adelpour, MD, of the University of Arkansas for Medical Sciences examined blebitis or endophthalmitis after glaucoma tube shunt surgery. In the propensity-matched analysis, 777 patients with A1c above 8.4% had a five-year hazard ratio of 1.93 compared with patients below 7% (95% CI 1.04-3.58). The intermediate A1c group, from 7.0% to 8.4%, did not have a statistically significant increase compared with the below-7% group.
A1c May Inform Eye Surgery Counseling
The results point to preoperative A1c as a possible risk marker for two different postoperative problems: retinal swelling after cataract surgery and serious eye infection after glaucoma shunt surgery. For clinicians and patients, the findings may support more individualized discussions about risk, particularly when A1c is high or diabetic retinopathy is present.
They do not establish a new A1c threshold for delaying surgery or changing treatment. Fraser said the cataract findings could help prompt more specific preoperative counseling, while calling for an interventional study to test whether reducing A1c changes CME rates. The reported association per 1% A1c increase was statistically significant but modest, and individual risk depends on more than this measure alone.
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Two Operations, Different Complications
Pseudophakic CME is swelling in the central retina after cataract surgery. Fraser described it at the meeting as the most common vision-threatening complication of the procedure, occurring in up to 4% of surgically treated eyes in general estimates. Earlier, smaller single-center studies had suggested a connection with preoperative A1c; the VA analysis examined the question in a much larger patient population.
The glaucoma analysis focused on blebitis or endophthalmitis after tube shunt surgery. Adelpour said few studies have examined the relationship between A1c and these infections. His team used the TriNetX clinical research network and excluded people with a prior endophthalmitis diagnosis or active intraocular infection before surgery. The two studies are separate analyses and their risk estimates should not be treated as directly comparable.
At the meeting, Fraser also referred to the European PREMED trial, in which patients with diabetic retinopathy undergoing cataract surgery were assigned to no additional treatment, subconjunctival triamcinolone, or triamcinolone plus intravitreal bevacizumab. As summarized in the report, no patients who received the corticosteroid developed CME, and bevacizumab did not add an observed benefit. That trial addressed treatment around surgery, not whether lowering A1c beforehand prevents CME.
“The incidence of cystoid macular edema in patients with diabetes was 5.3%, higher than the general population, but it grew to 6.9% in patients with a hemoglobin A1c above 8.”
— Daniel Fraser, MD, University of Minnesota, speaking at the AAO annual meeting
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Whether Lowering A1c Changes Risk
Both reports are based on retrospective data, which can show associations but cannot establish that higher A1c caused the complications. The cataract study used VA records, a population Fraser said was heavily skewed toward older white men, which may limit how well its results apply to other groups. The source report does not provide the full details of the glaucoma analysis beyond its matched patient groups and reported outcomes.
It remains unknown whether actively lowering A1c before either operation would reduce complication rates, what A1c level—if any—should prompt a change in surgical timing, and how clinicians should balance these risks against the reasons for proceeding with surgery. The glaucoma study also identified pre-existing myopia as an independent risk factor for infection (hazard ratio 3.58; 95% CI 1.57-8.15), underscoring that A1c is not the only factor involved.
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Trials Needed Before Changing Practice
Fraser called for an interventional study comparing outcomes among patients whose A1c is actively lowered before cataract surgery with outcomes among patients receiving usual care. Such research could test whether reducing A1c changes CME risk and clarify whether any threshold is useful for counseling or planning.
Until that evidence is available, the meeting findings support discussion of individualized risks rather than a proven instruction to postpone surgery or alter diabetes treatment. Further research would also be needed to test whether the glaucoma shunt infection association holds in other patient populations and whether preoperative interventions affect those outcomes.
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Key Questions
What eye complication was linked to higher A1c after cataract surgery?
The cataract analysis linked higher preoperative hemoglobin A1c with a greater incidence of pseudophakic cystoid macular edema, or CME, within six months of surgery. The study was retrospective, so it found an association rather than proof of cause.
How did CME rates vary by A1c group?
In the reported analysis, CME incidence was 4.2% among patients with A1c below 6.3% and 6.9% among those with A1c of 8% or higher. Overall, CME occurred after 5.3% of the cataract surgeries studied.
What did the glaucoma shunt study find?
Patients with preoperative A1c above 8.4% had a 1.93 five-year hazard ratio for blebitis or endophthalmitis compared with patients whose A1c was below 7%. The intermediate group did not show a statistically significant increase against the below-7% group.
Should patients delay eye surgery to lower A1c?
The studies do not establish that delaying surgery or lowering A1c prevents these complications. They also do not set a threshold for changing surgical plans. Patients should discuss their individual circumstances with their ophthalmologist and diabetes-care clinician.
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