• Among people with diabetes overall: pooled estimates put diabetic macular edema (DME) prevalence at about 5.5%. Depending on diabetes type, duration, retinopathy severity, and whether the measure is any edema versus vision-threatening edema, estimates vary. A clinical textbook reports visual loss from macular edema in 5% to 20% of people with diabetes.
• After cataract surgery: there is not one universal percentage, because postoperative macular edema may be new DME, worsening of pre-existing DME, or postoperative cystoid macular edema. In one OCT-based study of diabetic patients undergoing cataract surgery, 18% developed postoperative macular edema, peaking about one month after surgery. In practical terms, that is about 18 of every 100 diabetic surgical patients. The study is available here.
• Risk is strongly dependent on diabetic retinopathy before surgery. Even patients with diabetes but no retinopathy have an elevated relative risk of new DME after surgery, while those with established retinopathy have substantially higher risk. A review reports relative risks of approximately 1.8-fold without retinopathy and 6.2-fold with pre-existing retinopathy, versus non-diabetic controls, in a large database analysis summarized here.

• Normal young adult ECD: about 3,000 cells/mm². - Kanski's Clinical Ophthalmology, 10th ed., p. 210
• Typical example in type 2 diabetes: mean ECD 2,511 ± 252 cells/mm², compared with 2,713 ± 132 cells/mm² in age-matched non-diabetic controls, a difference of about 200 cells/mm² in one prospective study. Patients with diabetes for over 10 years had a mean ECD of 2,429 cells/mm², versus 2,609 cells/mm² for diabetes duration 10 years or less. See the study report.
• A meta-analysis of 18 observational studies found significantly lower ECD in diabetes: standardized mean difference -0.352 (95% CI -0.538 to -0.166), with considerable variation between studies. The meta-analysis is here.

Relevance before cataract surgery

• 28 of every 100 diabetic patients with NPDR
• 7 of every 100 diabetic patients with PDR

Best available figures

Important clarification

Practical conclusion

• Treat active PDR with PRP before cataract surgery whenever the fundus view allows.
• Consider anti-VEGF and individualized retinal-surgeon planning.
• If cataract prevents PRP, early postoperative PRP or combined cataract-vitrectomy-endolaser may be appropriate in selected eyes.

“In active pre-existing PDR, historical data found postoperative vitreous hemorrhage in 20% of eyes versus 6.5% in non-PDR/background DR, corresponding to an approximate relative risk of 3.1. This estimate predates modern phacoemulsification and current retinal treatment, and should not be generalized to adequately treated, quiescent PDR.”

“In patients with pre-existing NPDR, cataract surgery was associated with approximately a 1.5-fold higher 1-year risk of progression to PDR and about a 2-fold higher risk of vitreous hemorrhage, compared with matched NPDR patients who did not undergo surgery. In the subgroup with diabetes duration of at least 5 years, vitreous hemorrhage risk was 2.5-fold higher.”

Statistics that support the claim

1. Meta-analysis
   • A 2025 systematic review and meta-analysis found that diabetes was associated with a higher odds of posterior capsular opacity after cataract surgery: OR 2.92 (95% CI 1.80-4.72).
   • This means diabetic patients had approximately three times the odds of PCO compared with non-diabetic patients in the pooled evidence. See the 2025 meta-analysis.
2. Prospective study, 42 diabetic vs 42 non-diabetic eyes
   • PCO severity was significantly greater in diabetic eyes at:
     • 6 months: p = 0.002
     • 12 months: p = 0.03
   • There was no significant difference at 3 months.
   • Source: Ebihara et al., 2006.
3. Case-control study, 100 diabetic vs 100 matched non-diabetic patients
   • PCO severity became significantly greater in the diabetic group from 18 months onward.
   • Diabetic patients were significantly more likely to require Nd:YAG posterior capsulotomy for visually significant PCO: log-rank p = 0.0139.
   • Source: Hayashi et al., 2002.
4. Prospective study, 75 diabetic vs 75 non-diabetic eyes, hydrophobic acrylic IOL
   • At 1 year, median objective PCO score was:
     • 2.95% in diabetic eyes
     • 1.30% in non-diabetic eyes
     • Difference: p < 0.001
   • This study did not find a statistically significant difference at 4 years, and Nd:YAG capsulotomy occurred in 2.66% in each group. It illustrates that the association is not uniform across all studies and time points.
   • Source: Praveen et al., 2014.

Recommended wording for the slide

Diabetes is associated with greater posterior capsular opacification after cataract surgery.
Studies show higher objective PCO severity from 6-18 months postoperatively, and a meta-analysis reports approximately 3-fold higher odds of PCO in diabetic versus non-diabetic patients.
The magnitude of risk varies with IOL type, diabetes duration, surgical factors, and follow-up period.

Avoid saying

“Diabetic patients always develop more severe PCO.”

Best statistics for the slide

Important high-risk subgroups

• Male patients with diabetes: odds were 1.63-fold higher than the reference group (p = 0.048).
• Diabetes plus hypertension: odds were 3.96-fold higher (p < 0.001).
• Posterior capsular rupture, which was more common in diabetes in the meta-analysis, was associated with an OR 3.43 (95% CI 1.79-6.59) for postoperative endophthalmitis.

Recommended slide wording

Diabetes is associated with a modestly increased risk of postoperative endophthalmitis after cataract surgery.
Meta-analysis: 0.261% vs 0.242% in non-diabetic patients, corresponding to OR 1.17 (95% CI 1.11-1.24). Risk is higher with comorbid hypertension and intraoperative posterior capsular rupture.