Background To analyse the relationship of clinically significant cystoid macular oedema (CME after phacoemulsification to blood–aqueous barrier breakdown as determined by aqueous flare, visual acuity and retinal thickness in optical coherence tomography (OCT).

Materials and methods 30 eyes of 30 consecutive patients with clinically significant CME and vision loss were included. 46 pseudophakic and 45 phakic eyes without CME served as controls. Clinical data included age, gender, best-corrected visual acuity (BCVA) and spectral domain OCT volume scans. Retinal thickness measuring of the foveal central subfield was determined. Aqueous flare was measured quantitatively with the Kowa FM-500 Laser Flare-Cell Meter.

Results Patients with CME had significantly higher flare values compared with pseudophakic patients (p<0.0001). For patients with CME, aqueous flare values correlated significantly with BCVA (Spearman r_s=0.4, p=0.041), while there was no correlation with retinal thickness. Using flare values to predict CME, receiver operating characteristic analysis returned an area under the curve of 0.976.

Conclusions Aqueous flare as a marker for inflammation and breakdown of the blood–retinal barrier is increased in patients with CME after cataract surgery.