What is the prevalence of clinically significant macular edema in eyes with posterior sub‑capsular cataract before cataract surgery, and how does it increase in patients with diabetes, diabetic retinopathy, uveitis, or other inflammatory ocular conditions?

Prevalence of Macular Edema in PSC Cataract Before Surgery

The prevalence of clinically significant macular edema in eyes with posterior subcapsular cataract before cataract surgery is extremely low in uncomplicated cases (0.1-2.35%), but this baseline risk increases substantially in patients with diabetes, diabetic retinopathy, and uveitis. 1

Baseline Prevalence in Uncomplicated Cases

The incidence of clinical cystoid macular edema (CME) following modern cataract surgery ranges from 0.1% to 2.35% in the general population without significant risk factors. 1 This represents the postoperative rate, suggesting that preoperative macular edema in uncomplicated PSC cataracts is rare, as most CME develops as a consequence of surgical trauma and inflammation rather than preexisting pathology.

Risk Stratification by Comorbid Conditions

Diabetes and Diabetic Retinopathy

Patients with diabetes demonstrate dramatically elevated risk that correlates directly with retinopathy severity:

• No diabetic retinopathy: Central retinal thickness increases by 9.7 μm postoperatively 2
• Nonproliferative diabetic retinopathy: Central retinal thickness increases by 22.7 μm postoperatively 2
• Proliferative diabetic retinopathy: Central retinal thickness increases by 73.8 μm postoperatively, representing nearly an 8-fold increase compared to diabetics without retinopathy 2

Poor glycemic control (elevated HbA1c) and insulin dependence are independent risk factors for developing postoperative macular edema, with HbA1c showing strong correlation (r = 0.607, P < .001) with central retinal thickness increase. 2 Younger diabetic patients paradoxically face higher risk than older patients. 2

Uveitis and Inflammatory Conditions

Uveitis represents one of the most well-established preoperative risk factors for developing pseudophakic CME. 3, 1 Eyes with preexisting inflammatory ocular conditions have substantially elevated baseline risk compared to the general population, though specific prevalence data for preoperative macular edema in PSC cataracts with uveitis is not quantified in the available evidence.

Other High-Risk Conditions

Additional preoperative factors that increase CME risk include:

• Retinal vein occlusion 3
• Epiretinal membrane 3
• History of posterior segment inflammatory disease 4

Clinical Implications

The key distinction is that most macular edema associated with PSC cataracts develops postoperatively rather than preoperatively. 1 The surgical trauma and inflammatory cascade triggered by cataract extraction are the primary drivers of CME development, not the cataract itself.

Common Pitfalls

• Do not assume that PSC cataracts inherently cause preoperative macular edema; the cataract type itself is not listed as a risk factor 3, 1
• The presence of diabetes alone (without retinopathy) confers minimal additional risk compared to non-diabetic patients (5.14% vs 5.79% postoperative CME prevalence) 5
• Intraoperative complications, particularly posterior capsule rupture and vitreous loss, are more significant risk factors (odds ratio = 3.35) than most preoperative conditions 5