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Two studies presented at the American Academy of Ophthalmology meeting found associations between higher preoperative hemoglobin A1c and complications after cataract or glaucoma surgery. The findings do not show that lowering A1c before surgery prevents those outcomes, and researchers said prospective studies are needed.
Two studies presented at the American Academy of Ophthalmology (AAO) annual meeting linked higher preoperative hemoglobin A1c levels with increased risks of complications after cataract and glaucoma surgery. One analysis found a higher incidence of cystoid macular edema after cataract surgery among patients with higher A1c; a separate study associated A1c above 8.4% with a higher five-year risk of serious eye infection after glaucoma shunt surgery.
For the cataract analysis, Daniel Fraser, MD, of the University of Minnesota and colleagues reviewed VA Health System records from 2010 to 2022. They compared 6,808 patients who developed postoperative macular edema within six months of surgery with 121,164 who did not. Across the cataract surgeries analyzed, the reported incidence of pseudophakic cystoid macular edema was 5.3%.
The rate rose across A1c groups: it was 4.2% for patients with A1c below 6.3% and 6.9% for those at or above 8%. In the multivariable analysis, preoperative diabetic retinopathy was the strongest predictor: it was associated with 3.28 times the odds of postoperative edema, with risk increasing with retinopathy severity. Each one-percentage-point increase in A1c was associated with a 6% increase in the odds, after accounting for other variables in the model.
A separate glaucoma study, led by Mohsen Adelpour, MD, of the University of Arkansas for Medical Sciences, used TriNetX clinical research network data on adults with A1c records before tube shunt surgery. After propensity matching, the analysis included 4,182 people with A1c below 7.0%, 1,166 with levels of 7.0% to 8.4%, and 777 above 8.4%. The highest-A1c group had a five-year hazard ratio of 1.93 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.
A1c May Shape Preoperative Risk Talks
The results add evidence that blood sugar control may be relevant to eye-surgery risk discussions, not just a patient’s diabetes diagnosis. In the cataract study, A1c was associated with macular edema risk in addition to the stronger contribution from diabetic retinopathy. The glaucoma analysis points to a possible association between high A1c and later infection after shunt surgery.
For patients and clinicians, the findings may support discussing individual risk factors before an operation, including A1c, retinal disease, and other medical conditions. They do not establish a threshold at which surgery should be postponed or show that lowering A1c before surgery would prevent complications. Any decision about timing or diabetes management must account for the patient’s circumstances and be made with their treating clinicians.
Session moderator Jeff Pettey, MD, of the University of Utah Moran Eye Center said the cataract study’s A1c effect was statistically significant but modest: the odds rose 6% per one-percentage-point increase. That distinction matters when translating a population-level association into advice for an individual patient.
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Two Studies, Different Eye Operations
Cystoid macular edema is swelling in the retina’s central region after cataract surgery. Fraser told the meeting it is the most common vision-threatening complication of the procedure and can occur in up to 4% of treated eyes; the VA analysis reported a 5.3% incidence in its study population. Earlier small, single-center studies had suggested a relationship between preoperative A1c and postoperative edema, prompting the larger records-based review.
The glaucoma study examined a different outcome: blebitis or endophthalmitis, infections associated with glaucoma surgery. The researchers excluded people with prior endophthalmitis or active intraocular infection before surgery. The studies used separate databases and populations, so their risk estimates should not be combined or treated as directly comparable.
For the glaucoma analysis, pre-existing myopia was also associated with infection risk, with a reported hazard ratio of 3.58 (95% CI 1.57-8.15). The supplied meeting report also refers to a higher comorbidity burden, but does not provide a complete result for that factor.
“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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Association Does Not Prove Prevention
Both studies were retrospective analyses, which can identify associations but cannot establish that higher A1c caused the complications. The cataract study used VA data, which Fraser said was heavily weighted toward older white men; its findings may not apply equally to every patient population. The report also does not establish whether lowering A1c before surgery changes the risk.
In the glaucoma study, the confidence interval for the high-A1c group’s hazard ratio was broad, and the intermediate group did not show a statistically significant increase. The supplied report does not give further detail on the total number of infections or the complete findings for all other risk factors. It is also not clear from these analyses which A1c level, if any, should prompt a change in surgical timing or treatment.
Fraser cited the European PREMED trial, in which patients with diabetic retinopathy were assigned to additional treatments or no additional treatment around cataract surgery. The meeting report says no patients receiving subconjunctival triamcinolone developed edema and that adding bevacizumab did not provide an additional effect. Those results do not answer whether improving A1c itself prevents edema.
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Prospective Trials Could Guide Care
Fraser called for an interventional study to test whether patients with higher A1c benefit if their levels are brought down before cataract surgery, and whether that changes the rate of postoperative macular edema. The current findings can inform discussion of risk, but do not provide evidence for a specific A1c target or a recommendation to delay an operation.
Further research would also be needed to test whether the glaucoma infection association holds in other patient groups and settings, and whether changing preoperative A1c affects outcomes. Until such evidence is available, clinicians and patients will need to weigh the reported associations alongside retinopathy, myopia, other health conditions, and the reasons for surgery.
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Key Questions
What complication was linked to higher A1c after cataract surgery?
The study found an association with cystoid macular edema, swelling in the retina after surgery. Its reported incidence ranged from 4.2% among patients with A1c below 6.3% to 6.9% among those with A1c at or above 8%.
What did the glaucoma surgery study find?
Patients with preoperative A1c above 8.4% had a higher five-year hazard of blebitis or endophthalmitis than patients with A1c below 7.0%. The intermediate A1c group did not have a statistically significant increase.
Do the findings show that lowering A1c prevents complications?
No. These were retrospective studies that found associations. They did not test whether lowering A1c before surgery reduces the risk.
Does a high A1c mean cataract or glaucoma surgery should be delayed?
The studies do not set a threshold for delaying surgery. Decisions about surgical timing and diabetes management should be discussed with the treating eye-care and medical teams.
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