By Joanne Bachman, OD   |  PCLI—Tacoma, WA

Ami Halvorson, OD

PCLI—Portland, OR

From the EDITOR   Cystoid macular edema is an often underestimated complication of cataract surgery. With its potential to cause significant visual impairment and increased healthcare costs, early detection and management are essential. In this article, my colleague Joanne Bachman explores CME’s risk factors and treatment strategies that can optimize post-surgical outcomes and preserve patients’ vision.

Cystoid macular edema (CME) is a common complication after cataract surgery that can lead to visual impairment and increased patient distress. It can also raise perioperative costs by up to 47%. Given that cataract surgery is the most performed procedure in the U.S., CME contributes significantly to both visual morbidity and healthcare expenses. If untreated or poorly managed, CME can cause permanent macular damage and vision loss. However, when detected early, it is typically treatable with favorable outcomes.

What is CME?

CME is an inflammatory condition that causes retinal swelling and cystic changes. The breakdown of perifoveal capillaries leads to fluid accumulation in the macula. A key diagnostic sign is when a patient with good vision after cataract surgery experiences a sudden decline in acuity to 20/40 or worse around a month later.

CME typically develops 4 to 6 weeks after cataract surgery, though it can appear anywhere from weeks to months post-surgery. The incidence of CME is estimated at 1 to 2%, while up to 40% of patients undergoing phacoemulsification may show subclinical CME on same-day OCT. Fortunately, most cases are asymptomatic and self-resolving, requiring no treatment.

Causes and Risk Factors

CME is believed to result from a combination of surgical trauma, inflammation, and abnormal vascular permeability. Several risk factors can increase the likelihood of developing CME following cataract surgery:

1.  Inflammation — A prolonged inflammatory response post-surgery is a key trigger for CME. If uveitis is present, it’s important to check for vitreous prolapse or retained lens material, both of which require follow-up with the surgeon.
2. Pre-existing Retinal Disease — Conditions like diabetic retinopathy, retinal vein occlusion, epiretinal membrane (ERM), and macular degeneration can predispose patients to CME due to existing retinal vascular changes. For instance, a pre-existing ERM increases the risk of CME by 5.6%, central retinal vein occlusion (CRVO) by 4.4%, and a history of retinal detachment repair by 3.9%.
3. Eye Surgery — Intraoperative complications can elevate CME risk. For example, posterior capsule rupture increases the likelihood by 2.6%, while using a pupillary expansion device during surgery raises the risk by 5.4%.
4. Medications — Certain medications like prostaglandin analogs can increase CME risk. Additionally, patients on immunosuppressive drugs for chronic inflammatory conditions may also have a heightened risk.
5. Diabetes — Diabetes is a significant risk factor for post-surgical CME. Diabetic patients typically experience more inflammation after surgery, which increases the risk of CME. For those with diabetic retinopathy, the risk increases by 6.2%. Even diabetics without retinopathy face a 1.8% higher risk due to leakier blood vessels.

Symptoms

The most common symptom of CME is blurred or distorted central vision. Other symptoms include:

• Reduced contrast sensitivity
• Difficulty reading or seeing fine details
• Altered color perception

Diagnosis

1. Optical Coherence Tomography (OCT) — Detects macular thickening and cystic spaces in the outer plexiform layer.
2. Fluorescein Angiography — Reveals perifoveal petaloid staining, with or without leakage from the optic disc.
3. Clinical Diagnosis — With mild CME, distinguishing between normal and abnormal findings during a fundus examination of the macula can be challenging. As the condition progresses, a CME blister typically appears as a diffuse, red, and swollen area around the macula, often with a honeycomb-like thickening and yellowing that decreases in size as it moves away from the macula.

Management

The management of CME typically involves a combination of anti-inflammatory treatments and close monitoring:

1. Nonsteroidal Anti-inflammatory Drugs (NSAIDs) — These help reduce inflammation by inhibiting the COX enzyme, which prevents prostaglandin synthesis.
2. Corticosteroids — Topical corticosteroids are potent anti-inflammatory agents that effectively reduce macular swelling. The most common approach is to combine a topical steroid with an NSAID, as this combination provides the most significant benefit.
3. Intravitreal Injections — For persistent or severe cases of CME, corticosteroids or anti-vascular endothelial growth factor (VEGF) injections may be used to manage macular edema, particularly if topical treatments fail.

Prevention

To prevent CME, the primary focus is on managing underlying conditions like diabetes and high blood pressure and taking preventative measures after cataract surgery, which often include:

1. Prophylactic NSAIDs and Steroids — The most common preventative approach is to prescribe a combination of NSAIDs and steroids post-operatively to reduce inflammation and the risk of CME developing.
2. Patient Education — For patients with pre-existing conditions that increase the risk of post-op CME, educating them about their higher risk is essential. Inform them of potential symptoms and encourage prompt reporting of any vision changes. Emphasize the importance of following post-op care instructions to minimize risks.
3. Monitoring and Follow-Up — Regular post-operative visits are crucial to detect early signs of CME and intervene before significant vision loss occurs. Follow-up should occur every 1 to 3 weeks until CME resolves. If CME persists or worsens after 2 months, refer the patient promptly to a retinal specialist for further evaluation and treatment.

Conclusion

Cystoid macular edema is a significant concern following cataract surgery, but it is generally manageable with early diagnosis and appropriate treatment. If the edema becomes chronic (lasting more than 6-9 months), it can permanently damage the photoreceptors and lead to irreversible vision loss. Early detection using OCT imaging, coupled with anti-inflammatory therapies, is crucial in preventing long-term visual impairment.

Clinical Tip

If VA is lower than expected 2-8 weeks post-op, uncorrectable with refraction or pinhole, and no other ocular pathology is evident, consider CME and obtain a macula OCT scan.