Macular Oedema After Cataract Surgery: Causes, Risk Factors, Treatment and Outcomes

Cystoid macular oedema is the most common cause of unexplained visual loss after an otherwise technically successful cataract surgery. Most patients recover a good visual outcome with prompt recognition and appropriate treatment, but a minority develop chronic or recurrent oedema that limits final vision. This post is written for both patients and referring optometrists and GPs, and covers the complete evidence base for macular oedema after cataract surgery, from mechanism and risk factors through to diagnosis, stepwise treatment, and prevention.

What is macular oedema after cataract surgery?

Macular oedema after cataract surgery, also known as pseudophakic cystoid macular oedema (PCMO) or Irvine-Gass syndrome, is an accumulation of fluid within the layers of the macula, the central retina responsible for detailed vision, occurring in the weeks after otherwise successful cataract surgery. It is the most common cause of suboptimal vision following uncomplicated phacoemulsification.

The macula is the region of the retina responsible for central, detailed vision, including reading and facial recognition. When fluid accumulates in the outer plexiform and inner nuclear layers of the macula, it collects in cystic spaces arranged in a characteristic petaloid, or spoke-wheel, pattern visible on fluorescein angiography and optical coherence tomography (OCT). The term cystoid refers to these cyst-like fluid pockets, though true epithelium-lined cysts do not form.

The condition was first described by Irvine in 1953 following intracapsular cataract extraction, and further characterised by Gass and Norton in 1966 using fluorescein angiography, which is the origin of the name Irvine-Gass syndrome.

How common is macular oedema after cataract surgery?

The incidence depends on how it is measured and which patient population is examined. Clinically significant PCMO, causing noticeable vision loss requiring treatment, occurs in approximately 1 to 5 percent of routine cataract surgery patients.

Smarlamaki et al. (Cureus, 2025), a systematic review and meta-analysis of 143 studies, found a pooled cumulative PCMO incidence of 5 percent after uncomplicated cataract surgery. Iftikhar et al. (Ophthalmology, 2023), an IRIS Registry analysis of 3.7 million cataract surgeries, found CME rates of 3 to 41 percent using OCT detection, but clinical CME causing measurable vision loss at only 0.1 to 2.4 percent. Ferro Desideri et al. (Diagnostics, 2025), a systematic review, confirmed that subclinical OCT-detected macular thickening is substantially more common than clinically significant oedema, with most subclinical cases resolving spontaneously. Persistent chronic PCMO, not resolving within three months, occurs in approximately 0.02 to 1 percent of cases.

The wide range in reported incidence across these studies reflects differences in detection method (clinical examination versus OCT versus fluorescein angiography), the timing of assessment after surgery, and the risk profile of the patient population studied.

What causes macular oedema after cataract surgery?

The primary mechanism is surgical trauma triggering an inflammatory cascade that increases the permeability of the retinal blood vessels, allowing fluid to leak into the macular tissue.

Surgical trauma releases arachidonic acid from cell membranes at the site of the surgical wound and lens capsule. This triggers the prostaglandin and leukotriene synthesis pathway via the cyclooxygenase (COX) and lipoxygenase enzymes. Prostaglandins, particularly PGE2 and PGF2α, are potent mediators of vascular permeability and cause breakdown of the blood-retinal barrier. Fluid then leaks from the perifoveal capillaries into the outer plexiform and inner nuclear layers of the macula, accumulating in the cystic spaces characteristic of the condition.

Vitreomacular traction may also contribute to the mechanism. Residual vitreous connections to the macula can transmit traction following surgery, independently promoting oedema in addition to the inflammatory pathway. In diabetic patients, pre-existing endothelial dysfunction and blood-retinal barrier compromise significantly amplify the inflammatory response, which is one reason diabetic patients are at higher risk, discussed further below and in our companion guide to cataract surgery with diabetes.

Uveal pigment disturbance and iris manipulation during surgery releases additional prostaglandins. This is particularly relevant for patients using prostaglandin analogue glaucoma eye drops, whose eyes already carry a higher baseline prostaglandin exposure, a topic covered in more detail in our guide to cataract surgery with glaucoma.

Early theories attributed CMO primarily to vitreous incarceration in the surgical wound, which was relevant in the intracapsular extraction era in which Irvine first described the syndrome. Modern phacoemulsification with posterior capsule preservation has substantially reduced this mechanism, but prostaglandin-mediated inflammation remains the primary driver of PCMO today.

Who is at higher risk of macular oedema after cataract surgery?

Several patient and surgical factors significantly increase the risk of developing PCMO. Pre-operative identification of high-risk patients allows appropriate counselling and, in some cases, prophylactic measures, discussed further below.

Ocular risk factors (Smarlamaki et al., 2025; Ferro Desideri et al., 2025): diabetic retinopathy carries a relative risk of approximately three to four times baseline, with pre-existing blood-retinal barrier compromise the primary driver and risk further elevated in patients with pre-operative diabetic macular oedema. Uveitis dramatically increases risk through chronic intraocular inflammation, and patients with a history of uveitis require aggressive perioperative anti-inflammatory prophylaxis. Retinal vein occlusion, whether branch or central, is a significant independent risk factor. Epiretinal membrane, through vitreomacular interface abnormalities, predisposes to post-operative oedema. Age-related macular degeneration carries weaker but still relevant evidence for increased risk. A previous episode of PCMO in the fellow eye is one of the strongest predictors of recurrence in the second eye.

Systemic risk factors: diabetes mellitus increases risk even in the absence of diabetic retinopathy. Use of prostaglandin analogue eye drops for glaucoma is particularly associated with PCMO, with the mechanism involving additional prostaglandin-mediated blood-retinal barrier disruption on top of the surgical inflammatory response.

Surgical factors: posterior capsule rupture with vitreous loss substantially increases risk, as vitreous in the anterior segment promotes sustained inflammation. Iris trauma or prolonged iris manipulation, intraocular lens dislocation, and longer surgical time with greater phacoemulsification energy delivery are all associated with higher risk.

For patients with a strong pre-existing risk of macular compromise, such as significant diabetic retinopathy, uveitis, or established epiretinal membrane, lens selection also warrants specific consideration: diffractive premium lenses such as multifocal or trifocal designs are generally best avoided in favour of a standard monofocal lens, since any degree of macular oedema will compound the contrast sensitivity loss inherent to diffractive optics. This mirrors the lens selection principles discussed in our guides to multifocal IOLs and EDOF lenses.

For referring optometrists and GPs: patients with any of the risk factors above should be informed pre-operatively that they have a higher likelihood of requiring additional post-operative monitoring, and potentially treatment, for PCMO. This is worth flagging explicitly in the referral letter.

What are the symptoms of macular oedema after cataract surgery?

The hallmark symptom is unexplained blurry or reduced central vision in an eye that appeared to have recovered well from cataract surgery.

Onset is typically two to twelve weeks post-operatively, with a peak incidence at four to six weeks. Patients describe central blur that is disproportionate to any refractive error or posterior capsule opacification present, reduced contrast sensitivity and colour saturation, and sometimes metamorphopsia, in which straight lines appear wavy or bent. The characteristic clinical pattern that patients describe is that their vision was not as good as it was a few weeks ago, that is, a progressive decline after an initial period of good recovery, rather than vision that never improved in the first place. Vision may be relatively well preserved in mild cases despite significant macular thickening evident on OCT, which is why symptoms alone cannot be relied upon to exclude the diagnosis.

For referring optometrists and GPs: any patient presenting with reduced vision or central blur at the four to six week post-operative appointment should be assessed for PCMO. OCT is the investigation of choice and should be arranged promptly rather than attributing the change to residual refractive error.

How is macular oedema diagnosed after cataract surgery?

Optical coherence tomography (OCT) is the gold standard investigation. It demonstrates cystic fluid spaces in the outer plexiform and inner nuclear layers, disruption of the normal foveal contour, and increased central macular thickness. Quantitative central subfield thickness measured on OCT provides a baseline against which treatment response can be objectively monitored over subsequent visits.

Fluorescein angiography (FFA) classically demonstrates the petaloid leakage pattern in the late phase of the angiogram. It remains useful in equivocal cases or to assess the integrity of the blood-retinal barrier directly, but is less commonly used as a first-line investigation than OCT given the convenience and non-invasive nature of OCT imaging.

Clinical examination with slit lamp funduscopy may appear entirely normal in early or mild cases, which is why OCT and FFA are considerably more sensitive than clinical examination alone for detecting PCMO. The differential diagnosis for reduced vision after cataract surgery is broad and includes posterior capsule opacification, uncorrected refractive error, corneal oedema, intraocular lens dislocation, endophthalmitis, and retinal detachment, all of which should be considered and excluded as part of a thorough assessment.

How is macular oedema after cataract surgery treated?

Treatment follows a stepwise escalation from topical therapy to more invasive interventions depending on the severity, duration, and response to treatment.

Step 1, topical anti-inflammatory therapy (first-line): topical NSAIDs, such as ketorolac, bromfenac, or nepafenac, inhibit COX-mediated prostaglandin synthesis and are a well-established first-line treatment. Ferro Desideri et al. (Diagnostics, 2025) confirm that topical NSAIDs reduce macular thickness and improve visual acuity in most early cases, typically used for three to six months. Topical corticosteroids, such as prednisolone acetate or dexamethasone, are added to or used alongside NSAIDs to reduce the broader inflammatory cascade, and this combination is standard first-line practice. Most mild to moderate cases resolve within three months of intensive topical therapy.

Step 2, periocular corticosteroid injection (if topical therapy is inadequate after six to eight weeks): sub-Tenon triamcinolone acetonide injection delivers sustained corticosteroid to the posterior segment, avoids systemic side effects, and is effective in cases resistant to topical therapy. A 2025 real-world case series showed a median resolution time of 29 days after periocular triamcinolone in escalated cases, but also noted a median delay of 108 days before escalation was actually undertaken in routine practice, suggesting that earlier escalation may meaningfully improve outcomes (Ahmadyar et al., BMC Ophthalmol, 2023; real-world management series, PubMed, August 2025).

Step 3, intravitreal injection (for persistent or severe cases): the intravitreal dexamethasone implant (Ozurdex) is a sustained-release biodegradable implant delivering dexamethasone over approximately three months, with robust evidence for macular thickness reduction and visual acuity improvement in refractory PCMO. It carries a risk of intraocular pressure elevation in approximately 25 to 30 percent of patients and accelerated lens opacification, the latter being less relevant in eyes that are already pseudophakic. Intravitreal triamcinolone acetonide has a shorter duration of action than Ozurdex but is also effective, with real-world data showing a median resolution time of 73 days. Intravitreal anti-VEGF agents, including bevacizumab and ranibizumab, are used in refractory cases or where vascular endothelial growth factor is thought to contribute, particularly in diabetic or vascular PCMO; the evidence base for anti-VEGF is smaller than for corticosteroids in non-diabetic PCMO, but anti-VEGF may be preferred when a steroid response with IOP elevation is a specific concern. Oral acetazolamide reduces macular fluid through carbonic anhydrase inhibition, a different mechanism to the anti-inflammatory approaches above, and is used in selected refractory cases, limited in practice by its systemic side effects.

Step 4, surgical intervention (rare): pars plana vitrectomy is reserved for cases where vitreomacular traction is a specific contributing factor, or where medical therapy has comprehensively failed after an extended treatment period. This is rarely required.

For referring optometrists and GPs: if PCMO does not respond to intensive topical therapy after six to eight weeks, prompt referral back to the operating ophthalmologist or a retinal specialist is recommended. The real-world outcome data above suggests earlier escalation improves outcomes, and the College of Optometrists UK guideline (August 2025) recommends urgent referral if there is no improvement after six weeks of topical therapy.

What are the outcomes and prognosis for macular oedema after cataract surgery?

The majority of patients with PCMO recover good vision with appropriate treatment. However, outcomes depend significantly on the duration of oedema before treatment is started and the presence of underlying risk factors.

Most acute PCMO, with onset within the first three months after surgery, resolves completely with topical therapy, and visual recovery to the pre-oedema level of vision is typical. Chronic PCMO, persisting beyond three to six months, carries a more guarded prognosis, as prolonged fluid accumulation can cause photoreceptor damage and a permanent reduction in visual acuity. Visual acuity recovery correlates closely with the duration and severity of the oedema, which is the principal reason prompt diagnosis and treatment escalation matter clinically rather than simply being a theoretical concern.

Recurrence after initial resolution occurs in a minority of cases, particularly in high-risk groups such as those with uveitis or diabetes. In diabetic patients specifically, post-operative PCMO may be more persistent and may ultimately require intravitreal anti-VEGF therapy consistent with standard diabetic macular oedema treatment protocols. The Smarlamaki et al. (2025) meta-analysis confirms that clinically significant PCMO resolves in the majority of patients overall, but that high-risk subgroups have substantially worse outcomes than the general cataract surgery population.

How can macular oedema after cataract surgery be prevented?

Prophylactic topical NSAIDs have strong supporting evidence: pre-operative and peri-operative NSAID drops reduce PCMO incidence in high-risk patients. The PREMED study (Netherlands, 2017) established that combined NSAID plus steroid prophylaxis reduces PCMO rates compared with steroid prophylaxis alone.

Intraoperative subconjunctival steroid injection has also been shown to be effective. Teo et al. (Eye, 2023) demonstrated that a single intraoperative subconjunctival steroid injection significantly reduced the incidence of pseudophakic macular oedema across a cohort of 20,066 consecutive phacoemulsification surgeries.

Minimising surgical trauma through smaller incisions, reduced phacoemulsification energy, and careful iris handling reduces the inflammatory stimulus that drives PCMO. Where significant diabetic macular oedema is present before surgery, treating it with anti-VEGF therapy before proceeding with cataract surgery is recommended, as discussed in our guide to cataract surgery with diabetes. For glaucoma patients on prostaglandin analogue drops, withholding the prostaglandin analogue and switching to an alternative IOP-lowering medication in the perioperative period is considered in high-risk cases, a decision that should be made jointly with the patient's treating ophthalmologist.

Arranging an assessment

If you have noticed reduced or blurry central vision in the weeks after cataract surgery, or if you have been identified as having risk factors for PCMO before surgery, a prompt assessment including macular OCT is the appropriate next step. Dr Ross MacIntyre brings subspecialty fellowship training in complex cataract surgery from the Wilmer Eye Institute, Johns Hopkins University, to the assessment and management of pseudophakic macular oedema, and further detail on his surgical practice is available at drmacintyre.com/cataract-surgery-melbourne, including a published five-year surgical outcomes audit.

I consult at Northern Eye Consultants, Northpark Private Hospital, Bundoora, and at Bass Coast Eye Centre, Wonthaggi. A referral from your GP or optometrist is required. Referrals can be addressed to Dr Ross MacIntyre at either location.

Contact Northern Eye Consultants to arrange an appointment. For referral information for GPs and optometrists, visit the Northern Eye Consultants for-referrers page. For information on the underlying condition being treated, see our guide to cataract surgery, and for patients with coexisting risk factors, our companion guides to cataract surgery with diabetes and cataract surgery with glaucoma.

References

1. Smarlamaki R, et al. Risk Factors and Cumulative Incidence of Cystoid Macular Edema After Simple Cataract Surgery: A Systematic Review and Meta-Analysis. Cureus. 2025;17(5):e84212.
2. Ferro Desideri L, et al. Incidence, Pathogenesis, Risk Factors, and Treatment of Cystoid Macula Oedema Following Cataract Surgery: A Systematic Review. Diagnostics. 2025;15(6):667.
3. Iftikhar M, et al. Cystoid Macular Edema after Cataract Surgery in the United States: IRIS Registry Analysis. Ophthalmology. 2023;130(9):1005-1014.
4. Teo MAL, et al. Intraoperative subconjunctival steroid reduces the incidence of pseudophakic macular oedema: a cohort study of 20,066 consecutive phacoemulsification surgeries. Eye (Lond). 2023;37(10):2077-2081.
5. College of Optometrists UK. Pseudophakic Cystoid Macular Oedema Clinical Management Guideline. August 2025.
6. Irvine SR. A newly defined vitreous syndrome following cataract surgery. Am J Ophthalmol. 1953;36(5):599-619.
7. Gass JDM, Norton EWD. Cystoid macular edema and papilledema following cataract extraction. Arch Ophthalmol. 1966;76(5):646-661.