TL;DR
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Two retrospective studies presented at the American Academy of Ophthalmology meeting linked higher preoperative hemoglobin A1c with elevated eye-surgery risks. Cataract patients with A1c of 8% or higher had a 6.9% rate of cystoid macular edema; glaucoma shunt patients with A1c above 8.4% had a higher five-year hazard of blebitis or endophthalmitis than those with normal A1c. The findings show associations, not proof that lowering A1c before surgery prevents complications.
Two studies presented at the American Academy of Ophthalmology annual meeting linked higher preoperative hemoglobin A1c levels with increased risks of complications after cataract and glaucoma surgery. One large review found more cystoid macular edema after cataract surgery among patients with higher A1c; a separate analysis found a higher five-year hazard of serious eye infection after glaucoma shunt surgery for patients with A1c above 8.4%.
For the cataract analysis, Daniel Fraser, MD, of the University of Minnesota and colleagues reviewed Veterans Affairs Health System records from 2010 to 2022. The analysis included 6,808 patients who developed postoperative macular edema within six months of surgery and 121,164 who did not. Overall, cystoid macular edema, or CME, occurred after 5.3% of cataract surgeries in the study population.
The recorded CME rate rose across A1c groups, from 4.2% for A1c below 6.3% to 6.9% for A1c of 8% or higher. In multivariable analysis, diabetic retinopathy was the strongest predictor: it was associated with an odds ratio of 3.28, with risk increasing as retinopathy severity increased. Each 1 percentage-point increase in A1c was associated with a 6% increase in the odds of CME. The analysis found that A1c contributed risk in addition to retinopathy.
A separate study by Mohsen Adelpour, MD, of the University of Arkansas for Medical Sciences examined blebitis or endophthalmitis following glaucoma tube shunt surgery. 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%. Over five years, the high-A1c group had a hazard ratio of 1.93 for those infections compared with the normal-A1c group (95% CI 1.04-3.58). The intermediate group’s hazard ratio was 1.11 (95% CI 0.59-2.08), which was not statistically significant. The study also identified pre-existing myopia as an independent infection risk factor.
A1c May Inform Eye Surgery Counseling
The findings may help eye surgeons and patients discuss risk before surgery, particularly when diabetes or diabetic retinopathy is present. The cataract study suggests that A1c and retinopathy each add information about the likelihood of postoperative macular edema, while the glaucoma analysis flags a possible infection concern for patients with higher A1c.
They do not establish that postponing surgery or lowering A1c will prevent these outcomes. Fraser said the results could support more tailored preoperative counseling, but the size of the A1c association in the cataract analysis was modest: the odds rose by 6% per 1 percentage-point A1c increase. Any decision about timing or treatment needs to account for a patient’s full clinical situation, rather than relying on A1c alone.
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Two Studies, Different Eye Procedures
CME is swelling in the macula, the central part of the retina, after cataract surgery. Fraser described it as the most common vision-threatening complication of cataract surgery, occurring in up to 4% of surgically treated eyes in the general literature. In the VA analysis, the rate was 5.3% among the surgeries studied. Earlier small, single-center studies had suggested a link between preoperative A1c and CME; the VA review tested that association in a much larger dataset.
The glaucoma study addressed a different complication and procedure: blebitis or endophthalmitis after tube shunt surgery. The two analyses used different patient records, A1c thresholds and outcomes, so their figures should not be treated as directly comparable. At the meeting, Fraser also pointed to the European PREMED trial, in which patients with diabetic retinopathy undergoing cataract surgery were assigned to no added treatment, subconjunctival triamcinolone, or triamcinolone plus intravitreal bevacizumab. The report said no patients receiving the corticosteroid developed CME, while adding bevacizumab had no further effect.
“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
Whether Lowering A1c Changes Risk
Both analyses were observational, so they show associations rather than proving that elevated A1c caused the complications. The cataract review relied on VA records, a population Fraser said was heavily weighted toward older white men, which may limit how well the results apply to other patients. The source report also does not provide full details of the glaucoma study’s comorbidity findings.
It remains unknown whether actively lowering A1c before either operation reduces CME or post-shunt infection, and whether any particular threshold should prompt a change in surgical timing or care. Fraser called for an interventional study to test that question. The reported findings do not establish a universal A1c level at which surgery should be delayed.
Trials Could Test A1c Intervention
The clearest next research step identified by Fraser is an interventional study comparing outcomes when patients with higher A1c receive support to lower it before cataract surgery. Such research could clarify whether a change in A1c leads to fewer cases of CME and whether the benefit differs by retinopathy status. The source report gives no timeline for such a trial.
For now, the studies add evidence for discussing A1c, diabetic retinopathy and other patient-specific factors before surgery. Further research is needed to confirm the glaucoma infection association and to determine whether it should alter preoperative planning.
Key Questions
What did the cataract study find?
In a retrospective VA records analysis, CME occurred in 4.2% of patients with A1c below 6.3% and 6.9% of those with A1c of 8% or higher. The results show an association, not proof that A1c caused the complication.
What risk was reported after glaucoma shunt surgery?
Patients with preoperative A1c above 8.4% had a five-year hazard ratio of 1.93 for blebitis or endophthalmitis compared with patients whose A1c was below 7%. The intermediate A1c group did not have a statistically significant increase in the reported analysis.
Does the research show that lowering A1c prevents these complications?
No. Both reports describe observational analyses and cannot show that lowering A1c prevents CME or infection. Fraser said an interventional study is needed to test whether lowering A1c changes outcomes.
Does a high A1c mean cataract or glaucoma surgery should be delayed?
The studies did not establish a threshold that should lead to delaying surgery. The findings may inform preoperative counseling, but decisions require individual clinical assessment by the treating care team.
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