Photographic documentation of the retina has been used in practices for more than a century, and today standard seven-field (7F) and four-wide (4W) imaging remains the gold standard for assessing diabetic retinopathy (DR) using the Early Treatment Diabetic Retinopathy Study (ETDRS) severity scale. With new imaging technology entering the market, a recent study published in Ophthalmology Science found ultra-widefield (UWF) imaging of the 7F area had the same reproducibility as standard 7F imaging when evaluating ETDRS DR severity.
Still, the investigation found variability between the two imaging modalities, particularly in eyes with early DR and moderate nonproliferative DR. Specifically, UWF imaging appeared to better identify early DR changes, but this technique wasn’t as sensitive in detecting intraretinal microvascular abnormalities, which can be a hallmark of moderate nonproliferative DR.
The research team compared ETDRS severity between the two imaging modalities and incorporated peripheral DR lesions into the grading system. Mask graders determined the ETDRS levels through three methods: standard 7F imaging, UWF within the 7F region (7F UWF) and the entire UWF image (global ETDRS).
Of the 166 paired images that were evaluated, the study found an exact agreement in about 49% of eyes between the standard 7F and 7F UWF ETDRS levels. Agreement rates varied depending on DR severity and were less frequent in early DR (31%) and moderate nonproliferative DR (27%). In 156 eyes with 7F UWF and global UWF ETDRS levels, the researchers observed exact agreement in 143 eyes (92%).
Also of note: peripheral lesions contributed to a higher DR severity 8% of the time and changed the status to proliferative DR in 2% of cases. Reproducibility of the three ETDRS evaluations was comparable.
Since the study found a moderate agreement in the ETDRS DR severity scale between standard 7F and UWF imaging, clinicians should use caution in interchanging data between the two modalities, the researchers suggested.
The global ETDRS scale is a reproducible grading method and extends the advantage of a comprehensive scoring system outside the 7F region, yet its value on progressions rates has yet to be determined, they suggested.
Domalpally A, Barrett N, Reimers J, et al. Comparison of ultrawide field imaging and standard imaging in assessment of early treatment diabetic retinopathy severity scale. Ophthalmology Science. May 25, 2021. [Epub ahead of print].