Integration of spectral domain optical coherence tomography with ultra-wide field imaging can increase accurate detection of diabetic macular oedema and epiretinal membrane.
Reviewed by Dr Lloyd P. Aiello.
Findings of a retrospective, comparative cohort study demonstrate the benefits of integrating spectral-domain optical coherence tomography (SD-OCT) with ultra-widefield (UWF) imaging in a diabetic retinopathy (DR) telemedicine screening programme.
Dr Aiello, a professor of ophthalmology at Harvard Medical School and director of the Beetham Eye Institute of Joslin Diabetes Center, Massachusetts, United States, presented study data from 422 eyes of 211 patients with diabetes who were consecutively imaged between 8 January and 16 March 2020, using the commercially available platform Monaco (Optos), which allows SD-OCT and UWF imaging in a single sitting. Participants were seen in a UWF image-based DR teleophthalmology programme at the Joslin Diabetes Center.
The results showed that the dual imaging substantially increased detection and reduced false positive assessments of diabetic macular oedema (DMO) and epiretinal membrane (ERM). “Given the reduced effort, compact footprint and reduced overall cost of integrated SD-OCT/UWF devices, their use in large DR screening programmes could substantially improve disease identification and reduce unnecessary referrals,” said Dr Aiello.
“However, it should be noted that this study only evaluated 422 eyes and all images were evaluated in a centralised reading centre using standardised protocols,” he said. “Thus, the applicability of the findings in other settings is unknown.”
Because US Food and Drug Administration (FDA) approval of normative OCT measurements for the Monaco instrument is pending, the OCT images were evaluated qualitatively using a standardised template. Each scan was evaluated for macular pathology, including looking at the foveal contour and looking for macular oedema, ERM, signs of macular degeneration and other macular diseases. The UWF graders were masked to the OCT images and OCT findings, and graders evaluating the SD-OCT images were masked to the UWF images.
The 211 patients included in the study had a mean age of 53.5 years. Based on UWF grading, DR was absent in 58% of eyes and 93% of eyes had no DMO. Eyes with DR spanned the spectrum of severity, but the distribution was weighted towards less severe disease, with most eyes having mild non-proliferative DR. Sixty eyes (14.2%) were graded as having referrable DR, which was defined as moderate non-proliferative DR or worse or any level of macular oedema.
With UWF imaging, less than 1% of eyes were ungradable for determining DR severity and less than 1% were ungradable for determining DMO presence. For both modalities, less than 1% were ungradable for overall macular pathology.
Macular pathology was identified by UWF in 8.1% of eyes and by OCT imaging in 13% of eyes. DMO was the most commonly identified pathology on UWF imaging (75%) but accounted for only 36% of macular disease identified by OCT. ERM accounted for 29% of macular pathology on UWF imaging but 52.7% of macular disease by OCT.
Comparisons between the UWF and SD-OCT gradings showed good agreement when the determination was that DMO was not present; when UWF imaging alone found that DMO was not present, SD-OCT found DMO in only 1.5% of those eyes. When the UWF image grading identified DMO present, however, the determination was not confirmed by SD-OCT in 75% of those cases.
“Overall, UWF image grading suggested that DMO was present in 4.7% of eyes, [whereas] grading by SD-OCT determined DMO was present in only 2.1% of the cohort,” Dr Aiello explained. “Thus, UWF alone had low sensitivity and low positive predictive value for DMO detection, but high specificity and high negative predictive value compared [with] SD-OCT.”
The results were similar in considering detection of clinically significant macular oedema (CSMO), although the sensitivity of UWF was even lower for this diagnosis. Approximately 27% of eyes with CSMO present on SD-OCT were identified by UWF imaging alone.
ERM was detected by UWF image grading in 2.4% of eyes and by SD-OCT in 6.8% of eyes. Only 3.4% of ERMs detected on SD-OCT images were identified on UWF imaging alone. When UWF imaging alone found that ERM was absent, SD-OCT found an ERM in 6.8% of eyes. When UWF grading showed that ERM was present, however, only 10% of those cases were confirmed by SD-OCT.