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Two studies presented at the American Academy of Ophthalmology meeting linked higher preoperative hemoglobin A1c with eye complications after cataract and glaucoma surgery. The cataract study found macular edema rates rose with A1c, while the glaucoma analysis found a higher five-year infection hazard in patients with A1c above 8.4%; neither study establishes that lowering A1c before surgery prevents these outcomes.
Two studies presented at the American Academy of Ophthalmology annual meeting linked higher preoperative hemoglobin A1c with complications after eye surgery: macular edema after cataract surgery and blebitis or endophthalmitis after glaucoma tube-shunt procedures. The findings, based on retrospective health-record analyses, point to A1c as a potential factor in preoperative risk discussions, but do not show that lowering it before surgery reduces complications.
For cataract surgery, researchers examined U.S. Veterans Health Administration records from 2010 to 2022. The analysis included 6,808 patients who developed postoperative macular edema within six months and 121,164 who did not. Across the cataract surgeries studied, pseudophakic cystoid macular edema (CME) occurred in 5.3%. Incidence rose from 4.2% among patients with preoperative A1c below 6.3% to 6.9% among those at or above 8%.
The multivariable analysis found that preoperative diabetic retinopathy was the strongest predictor: it was associated with 3.28 times the odds of CME, with odds increasing as retinopathy became more severe. A1c also remained a significant predictor after accounting for other factors. Each one-percentage-point increase in preoperative A1c was associated with a 6% increase in the odds of CME. That is an association from the analysis, not proof that A1c directly caused the complication.
A separate study used the TriNetX clinical research network to examine adults with recorded A1c before glaucoma tube-shunt surgery. After propensity matching, it compared 4,182 patients with A1c below 7.0%, 1,166 with levels from 7.0% to 8.4%, and 777 above 8.4%. The high-A1c group had a 1.93 five-year hazard for blebitis or endophthalmitis compared with the group below 7.0% (95% CI 1.04-3.58). The intermediate group did not have a statistically significant increase (HR 1.11, 95% CI 0.59-2.08). The supplied report does not include the full results of the glaucoma analysis.
A1c May Shape Preoperative Risk Talks
The findings may help eye-care teams identify patients who could benefit from more individualized counseling before surgery. For cataract patients, the reported pattern suggests that risk may rise across A1c levels rather than appearing only at a single threshold. Retinopathy remains a major part of that picture, and the cataract analysis found it to be a stronger predictor than A1c alone.
For patients considering glaucoma tube-shunt surgery, the infection association in the highest A1c group could be relevant to discussions about postoperative monitoring and individual risk. But the study does not establish that a particular A1c cutoff should trigger postponement or a change in treatment. The data also do not show that improving glucose control shortly before surgery would prevent CME or infection. Those decisions require evidence beyond an observed association.
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Two Procedures, Separate Complications
CME is swelling in the central retina after cataract surgery and can threaten vision. Daniel Fraser, MD, of the University of Minnesota, described it at the meeting as the most common vision-threatening complication of cataract surgery; the report said it can occur in up to 4% of surgically treated eyes in general estimates. In the VA analysis, the overall rate was higher, at 5.3%, among the studied cataract surgeries. Different study populations and methods mean those figures should not be treated as directly interchangeable.
Previous smaller, single-center studies had suggested a link between preoperative A1c and CME. Fraser’s group used a much larger VA dataset to examine the relationship. The authors acknowledged limits to the retrospective design and said the VA population was heavily weighted toward older white men, which may constrain how well the results apply to other groups.
The glaucoma study addressed a different outcome and operation: infection after tube-shunt surgery. Its investigators excluded patients with a history of endophthalmitis or active intraocular infection before surgery, then used propensity matching to compare A1c groups. Results from that analysis should not be conflated with the cataract findings, since the procedures, complications, data sources and A1c groupings differed.
“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 meeting
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Causation and Surgical Thresholds Remain Open
Both analyses were observational, so they show associations, not cause and effect. The cataract study did not test whether lowering A1c changes CME rates. Fraser called for an interventional study to compare outcomes when patients with higher A1c receive an effort to lower it before surgery. No established A1c level for delaying cataract surgery or changing its management was identified in the report.
The glaucoma estimate also carries uncertainty: its confidence interval was wide, and the report provides no absolute infection rates for the compared groups. It says the high-A1c group’s five-year hazard was 1.93 relative to the normal-A1c group, but does not establish how many patients experienced infection. Details of other findings from the glaucoma analysis, including the full multivariable results, are not available in the supplied report. The authors’ work was presented at a meeting; the material provided does not describe a peer-reviewed publication.
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Trials Could Test A1c-Lowering Strategies
The next evidence step identified by Fraser is an interventional study testing whether bringing A1c down before cataract surgery changes the chance of postoperative CME, particularly among patients in higher A1c ranges. Until such evidence is available, the study supports discussing a patient’s A1c and retinopathy as part of individualized counseling, not assuming that a preoperative target will prevent the complication.
For glaucoma tube-shunt surgery, further work would need to test whether the observed five-year infection association holds in other patient populations and clarify absolute risks and relevant clinical factors. The available report does not announce a trial, clinical guideline change or specific follow-up date. Patients should discuss their own surgical risks and diabetes management with their eye surgeon and usual medical team.
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Key Questions
What did the cataract surgery study find?
In the VA records analysis, CME incidence was 4.2% for patients with preoperative A1c below 6.3% and 6.9% for those at or above 8%. Each one-percentage-point A1c increase was associated with 6% higher odds of CME.
What was linked to infection after glaucoma surgery?
In the TriNetX analysis, patients with A1c above 8.4% had a 1.93 five-year hazard for blebitis or endophthalmitis compared with those below 7.0%. The report did not provide absolute infection rates, and the finding does not establish that A1c caused infection.
Do the studies show that lowering A1c prevents complications?
No. Both studies were retrospective analyses of health records. They did not test whether lowering A1c before surgery reduces the risk of macular edema or infection.
Should surgery be delayed because of a high A1c?
The report does not establish an A1c threshold for delaying either operation. Patients should discuss their individual risks, retinopathy status and diabetes care with their eye surgeon and medical team.
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