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Two studies presented at the American Academy of Ophthalmology meeting linked higher preoperative hemoglobin A1c with increased risks after eye surgery. A large VA review found more cystoid macular edema after cataract surgery at higher A1c levels, while a separate analysis found a higher five-year risk of blebitis or endophthalmitis after glaucoma shunt surgery among patients with A1c above 8.4%. The retrospective findings do not establish that lowering A1c before surgery reduces either risk.
Two studies presented at the American Academy of Ophthalmology annual meeting found that higher preoperative hemoglobin A1c was associated with increased risks of complications after cataract and glaucoma shunt surgery. A large review linked higher A1c with more cystoid macular edema after cataract operations, while a separate analysis found a greater five-year risk of serious eye infection among glaucoma shunt patients whose A1c exceeded 8.4%.
In the cataract study, researchers reviewed Veterans Affairs health system records from 2010 through 2022. They compared 6,808 patients who developed postoperative macular edema within six months of surgery with 121,164 who did not. Across the reviewed surgeries, cystoid macular edema (CME) occurred in 5.3%. The rate rose across A1c groups, from 4.2% among patients whose preoperative A1c was below 6.3% to 6.9% among those with A1c of 8% or higher.
Patients who developed CME had a mean preoperative A1c of 7.6%, compared with 7.3% among those who did not. In the adjusted analysis, pre-existing diabetic retinopathy was the strongest predictor: it was associated with 3.28 times the odds of CME, with greater risk as retinopathy severity increased. Each one-percentage-point increase in A1c was associated with a 6% increase in the odds of CME, and the researchers said A1c added predictive information beyond retinopathy.
Daniel Fraser, MD, of the University of Minnesota, presented the cataract findings. The separate glaucoma analysis, presented by Mohsen Adelpour, MD, of the University of Arkansas for Medical Sciences, used the TriNetX clinical research network. After propensity matching, it included 4,182 patients with A1c below 7.0%, 1,166 with A1c from 7.0% to 8.4%, and 777 with A1c above 8.4%. The high-A1c group had a 1.93 hazard ratio for blebitis or endophthalmitis over five years compared with the group below 7.0%. The intermediate-A1c group did not have a statistically significant increase.
A1c May Help Shape Surgical Risk Discussions
The findings may help eye-care teams identify patients who could benefit from more detailed preoperative risk counseling. In the cataract analysis, the observed CME rate was higher at A1c levels of 8% or above, while the glaucoma analysis found a higher long-term infection hazard in its highest-A1c group. These outcomes can affect vision and follow-up care, making risk information relevant to patients and clinicians planning surgery.
But the results do not establish a blood-sugar threshold at which surgery should be delayed, or show that lowering A1c before an operation prevents complications. Fraser said the study supports a closer discussion of risk as A1c rises, while moderator Jeff Pettey, MD, questioned how much clinical action should follow from the relatively modest association measured for each one-point A1c increase. Treatment and timing decisions require individual clinical judgment, not these observational results alone.
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Two Studies, Different Eye Operations
CME is swelling in the central retina after cataract surgery and is a known vision-threatening complication. Fraser said it occurs in up to 4% of surgically treated eyes in the general context cited in his presentation. Earlier, smaller single-center studies had suggested a connection between preoperative A1c and CME; the VA review examined that association in a much larger dataset. Its overall CME rate of 5.3% refers to the reviewed patient group, which included people with diabetes, and should not be treated as a general-population estimate.
The glaucoma study addressed a different complication and operation: blebitis or endophthalmitis after tube shunt surgery. Researchers excluded patients with a prior history of endophthalmitis or an active intraocular infection before surgery. The two studies used different populations, data sources and outcome measures, so their findings describe separate associations rather than a single combined estimate of risk across eye surgery.
At the meeting, Fraser also referred to the European PREMED trial. In patients with diabetic retinopathy undergoing cataract surgery, that trial compared no additional treatment with subconjunctival triamcinolone, alone or alongside intravitreal bevacizumab. The presentation reported that no patients given the corticosteroid developed CME, and that adding the anti-VEGF drug showed no further effect. This trial offers related treatment evidence, but does not answer whether reducing A1c before surgery changes CME risk.
“I would like to see an interventional study.”
— Daniel Fraser, MD, University of Minnesota
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Whether Lowering A1c Changes Outcomes
Both analyses were retrospective and observational, so they show associations rather than proving that elevated A1c caused the complications. The cataract study relied on VA records, a population Fraser said was heavily skewed toward older white men. The glaucoma results also come from recorded clinical data and do not show that lowering A1c would reduce infection risk.
The source report did not provide the total number of glaucoma infections or absolute infection rates for each A1c group. The high-A1c hazard ratio had a 95% confidence interval of 1.04 to 3.58, while the intermediate group’s interval included no clear increase. The supplied account also notes that pre-existing myopia raised infection risk independently of A1c, with a hazard ratio of 3.58; it begins to mention higher comorbidity burden but provides no further result. The independent effects of other patient or surgical factors are not fully detailed in the report.
It remains unclear whether a particular A1c level should prompt a change in surgical timing, additional preventive treatment or a different follow-up plan. The cataract findings do not identify a proven target A1c, and the glaucoma analysis does not establish that preoperative glucose management changes the five-year outcome.
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Trials Needed to Test Prevention
Fraser called for an interventional study to test whether bringing patients with higher A1c into a lower range before cataract surgery lowers their CME rate. Such a trial could help distinguish a modifiable risk from a marker associated with other health factors. No such study or treatment recommendation was announced in the supplied report.
For now, the findings may inform conversations between patients and their eye-care teams about individual risk factors, including A1c, diabetic retinopathy and, for glaucoma shunt surgery, myopia. The meeting report does not specify a new clinical guideline or a threshold for delaying either operation. Further research would be needed before the associations can support a preventive protocol.
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Key Questions
What complication was linked to higher A1c after cataract surgery?
The study linked higher preoperative hemoglobin A1c with a greater incidence of cystoid macular edema, or swelling in the central retina, within six months after cataract surgery.
How did CME rates differ across A1c groups?
In the VA review, CME occurred in 4.2% of patients with preoperative A1c below 6.3% and 6.9% of those with A1c of 8% or higher. These are results from the reviewed study population, not a guarantee of an individual patient’s risk.
What was found after glaucoma shunt surgery?
In a separate analysis, 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 7.0%. The intermediate group did not show a statistically significant increase.
Do the studies show that lowering A1c prevents these complications?
No. The studies were observational and did not test whether lowering A1c before surgery changes outcomes. Fraser said an interventional study would be needed to assess that question.
Do the findings recommend delaying surgery at a particular A1c?
No surgery-delay threshold was established in the report. The findings may support individualized risk discussions, but decisions about timing and care should be made with a qualified eye-care professional.
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