Risks After Cataract, Glaucoma Surgery Tied To Higher Hemoglobin A1c Levels

TL;DR

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Two retrospective analyses presented at the American Academy of Ophthalmology meeting found higher preoperative hemoglobin A1c was associated with increased risks of complications after cataract and glaucoma surgery. The findings do not show that lowering A1c before surgery prevents those outcomes, and researchers called for further study.

Two retrospective studies reported at the American Academy of Ophthalmology annual meeting linked higher hemoglobin A1c before eye surgery with greater risks of complications: cystoid macular edema after cataract surgery and blebitis or endophthalmitis after glaucoma tube-shunt surgery. The findings point to A1c as a possible factor for preoperative risk discussions, but do not establish that lowering it before surgery reduces complications.

For the cataract analysis, Daniel Fraser, MD, of the University of Minnesota and colleagues reviewed VA Health System records from 2010 through 2022. The analysis included 6,808 patients with postoperative macular edema within six months of surgery and 121,164 patients who did not develop the condition. Overall, pseudophakic cystoid macular edema occurred in 5.3% of cataract surgeries in the study population.

Incidence rose across A1c groups, from 4.2% below 6.3% to 6.9% among patients whose preoperative A1c was at least 8%. In adjusted analysis, diabetic retinopathy was the strongest predictor: it was associated with 3.28 times the odds of macular edema, with risk increasing as retinopathy severity rose. Each 1 percentage-point increase in A1c was associated with a 6% increase in odds. The study reported an odds ratio of 1.06 per percentage-point increase.

A separate analysis by Mohsen Adelpour, MD, of the University of Arkansas for Medical Sciences examined glaucoma shunt surgery records in the TriNetX research network. After propensity matching, researchers compared 4,182 patients with A1c below 7%, 1,166 with A1c from 7% to 8.4%, and 777 with A1c above 8.4%. The high-A1c group had a 5-year hazard ratio of 1.93 for blebitis or endophthalmitis compared with the below-7% group. The intermediate-A1c group did not have a statistically significant increase. The report also identified pre-existing myopia as an independent infection risk factor.

A1c May Inform Eye-Surgery Counseling

The findings could help clinicians and patients discuss risk before surgery, particularly for people with diabetes or diabetic retinopathy. In the cataract study, A1c added information beyond the presence of retinopathy, while retinopathy itself had a stronger association with macular edema. The glaucoma analysis suggests that very high A1c may also be relevant to infection risk after shunt surgery.

But these are associations from observational analyses, not evidence that a particular A1c threshold should determine whether surgery proceeds. Fraser said the results could prompt more tailored counseling as measured A1c rises. He also called for an interventional study to test whether lowering A1c before cataract surgery changes the rate of macular edema. The studies do not establish a treatment plan or show that postponing surgery improves outcomes.

Two Procedures, Different Complications

Pseudophakic cystoid macular edema 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, with prior estimates indicating it occurs in up to 4% of surgically treated eyes. The 5.3% figure in the VA analysis comes from its particular study population and should not be treated as a universal rate.

Blebitis and endophthalmitis are infections involving eye tissues; the glaucoma analysis focused on these outcomes after tube-shunt surgery. Adelpour said few studies had examined the relationship between preoperative A1c and these infections. The two presentations therefore address separate procedures and outcomes, and their risk estimates should not be directly compared.

Researchers also discussed prior work on preventing macular edema. An audience member pointed 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. According to the meeting report, no patients receiving triamcinolone developed edema, while adding bevacizumab provided no further benefit. That trial concerned treatment approaches in patients with retinopathy; it did not test whether lowering A1c before surgery prevents edema.

“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

Causation and Surgical Cutoffs Remain Open

Neither analysis can show that high A1c caused the complications or that bringing A1c down would prevent them. The cataract study was retrospective, and Fraser acknowledged limitations in the VA data, which are heavily weighted toward older white men. Its results may not apply equally to other patient populations. The glaucoma findings also come from clinical records rather than a trial assigning patients to different A1c levels.

The meeting report does not establish an A1c level at which clinicians should delay either operation, change treatment, or use an additional preventive measure. In the cataract analysis, the reported effect was a 6% increase in odds per 1 percentage-point rise, while retinopathy was a stronger predictor. For glaucoma surgery, the elevated hazard was reported for the group above 8.4%; the 7.0%-8.4% group did not show a significant increase compared with the below-7% group. How these results should guide individual decisions remains unsettled.

Trials Could Test A1c-Lowering Strategies

Fraser called for an interventional study to test whether patients with higher A1c who lower it before cataract surgery experience fewer cases of cystoid macular edema. The report did not announce a trial or provide a timeline. Until such evidence is available, clinicians will need to interpret the observational findings alongside other risk factors, including diabetic retinopathy and its severity.

Further research is also needed to assess the glaucoma infection association and determine how it should affect preoperative counseling or care. No new clinical guideline or surgical threshold was announced at the meeting. For now, the next step is additional evidence testing whether the associations translate into a practical change in outcomes.

Key Questions

What complications were linked to higher preoperative A1c?

The studies linked higher A1c with cystoid macular edema after cataract surgery and with blebitis or endophthalmitis after glaucoma tube-shunt surgery. They did not prove that A1c caused either complication.

How much did macular edema risk change in the cataract study?

Observed incidence rose from 4.2% for A1c below 6.3% to 6.9% for A1c of at least 8%. In adjusted analysis, each 1 percentage-point increase in A1c was associated with 6% higher odds of edema.

Does the research show that lowering A1c prevents complications?

No. Both findings came from retrospective analyses. Fraser called for an interventional study to test whether lowering A1c before cataract surgery reduces macular edema.

Did the researchers recommend delaying surgery above a particular A1c?

No surgical cutoff or recommendation to delay surgery was announced. The studies do not establish what A1c level should change an individual patient’s treatment or timing.

Source: rss