Abstract
Purpose:
Most epidemiologic studies, such as the National Health and Nutrition Examination Survey (NHANES), identify diabetic macular edema (DME) as the presence of hard exudates or photocoagulation scars within one disc diameter from the foveal center on monocular fundus photographs (MFP). The prevalence of DME in populations based on this assessment may not reflect the true number of people who have foveal DME, as would be reflected by increased central subfield thickness (CST) on optical coherence tomography (OCT). This study was designed to compare the prevalence of DME based on MFP with DME based on CST on OCT.
Methods:
We retrospectively reviewed the clinical data and ocular images of all patients with a diagnosis of diabetic retinopathy from July 2011 to June 2014 at a university-based practice of two retina specialists. The two best quality color 30 or 60 degree MFP centered on the fovea and the optic nerve and spectral-domain OCT CST map from a single visit for each available eye of each patient were graded independently by a retina specialist to determine the presence of DME. DME on MFP was defined as described in NHANES. DME on OCT was defined by CST values used as eligibility criteria by the Diabetic Retinopathy Clinical Research Network in trials evaluating treatments for foveal-involving DME.
Results:
Among 306 eyes of 183 patients, DME was diagnosed by MFP in 53.6% and by OCT in 27.1%, for a difference of 26.5% (95% confidence interval [CI], 19.0-34.0%). Of the 164 eyes diagnosed with DME on MFP, only 32.3% (95% CI, 25.2-40.1%) had DME as defined on OCT, including 23.2% (95% CI, 16.9-30.4%) with both DME on OCT and visual acuity of 20/32 or worse. Of the 142 eyes not diagnosed with DME on MFP, 21.1% (95% CI, 14.7-28.8%) demonstrated DME on OCT, and 14.8% (95% CI, 9.4-21.7%) had both DME on OCT and a visual acuity of 20/32 or worse.
Conclusions:
These data suggest that the majority of eyes diagnosed with DME on MFP do not have increased CST on OCT, while many eyes without DME on MFP have increased CST on OCT, including many with visual impairment that potentially would benefit from anti-vascular endothelial growth factor (VEGF) therapy. These findings highlight caution regarding extrapolation of prevalence of eyes that may benefit from anti-VEGF therapy for DME from previously reported data using MFP to define DME.