Comparison between Early Treatment Diabetic Retinopathy Study 7-field retinal photos and non-mydriatic, mydriatic and mydriatic steered widefield scanning laser ophthalmoscopy for assessment of diabetic retinopathy
Introduction
Early Treatment of Diabetic Retinopathy Study (ETDRS) 7-field retinal images have remained the gold standard in diabetic retinopathy (DR) detection for many years (ETDRS, 1991a). However, it is a time-consuming process which requires trained photographers and highly cooperative patients and is therefore not suitable for DR-screening. With the increasing number of patients with diabetes (Federation ID, 2013) and the subsequently growing demand for DR-screening, a fast and efficient photography-system is desired. Studies have shown that capturing fewer fields might be non-inferior to the ETDRS 7-field in grading DR (Aldington et al., 1995, Aptel et al., 2008, Boucher et al., 2003, Kuo et al., 2005, Lin et al., 2002, Moller et al., 2001, Stellingwerf et al., 2001). However, DR is a disease with a substantial peripheral retinal activity (Niki et al., 1984, Shimizu et al., 1981), and lesions are likely to be missed if only images of the posterior retina are included (Kuo et al., 2005, Moller et al., 2001).
Consequently the development of widefield cameras could optimize photography for DR-screening (Kernt et al., 2012, Liegl et al., 2014, Neubauer et al., 2008, Silva et al., 2012, Silva et al., 2013, Soliman et al., 2012, Wilson et al., 2010). The widefield scanning laser ophthalmoscopy (SLO) by Optos (Optos plc, Dunfermline, Scotland, United Kingdom) can in one single image cover 200° or approximately 80% of the retina (Soliman et al., 2012) (Fig. 1). Only needing one photo of each eye and a possibility of non-mydriatic images will make this a time-saving screening method for the clinicians as well as for the patients, who will also be able to drive right after the examination (Goel et al., 2003, Jude et al., 1998, Kernt et al., 2012, Silva et al., 2012).
However, when scaling the widefield image of the spherical eye into a two-dimensional flat image, distortion may occur and lesions might be missed. Furthermore, eyelids and eyelashes may cover varying parts of the superior and especially the inferior periphery. The Optos widefield SLO has an inherent steering function, capturing the superior, inferior, nasal and temporal periphery, which might maximize the quality of the images taken in the periphery and as such enhance the accuracy of lesion identification in the periphery (Fig. 1). This has, to our knowledge, not been tested in a clinical trial.
The aim of this study was to investigate if widefield SLO was non-inferior in grading DR compared to 7-field photography and to compare non-mydriatic and mydriatic widefield images. Secondary aim was to investigate the added value of mydriatic steered widefield images in lesion identification at the far periphery.
Section snippets
Subjects
Participants were patients with type 1 diabetes mellitus recruited from the Danish Cohort of Pediatric Diabetes 1987 (DCPD1987). The DCPD1987 is a cohort of young patients with type 1 diabetes established in 1987. The cohort has been described in detail elsewhere (Broe et al., 2014, Olsen et al., 1999, Olsen et al., 2000). Patients from the cohort were invited to participate in an examination with image-capturing by widefield and ETDRS 7-field photography and were seen during a period of 6
Image capturing
Seven mydriatic digital 45° color fundus photos, taken in accordance with the ETDRS standards (ETDRS, 1985), were captured on a 3D Spectral Domain Optical Coherence Tomography (3D OCT-2000, Topcon, Tokyo, Japan).
Optos 200Tx widefield SLO (Optos plc, Dunfermline, Scotland, United Kingdom) was used for widefield images. One non-mydriatic image and one mydriatic image were taken on each eye. Additionally 4 mydriatic steered images (superior, inferior, nasal and temporal periphery) were taken on
Characteristics
We included 95 patients (190 eyes). Of these, 49.5% were male. Mean age and duration of diabetes were 37.6 years (range 29–42 years) and 30.4 years (range 25–41 years), respectively. Mean BCVA was 85.0 (range 40–98).
Based on ETDRS 7-field images, DR was distributed as follows: no DR (ETDRS 10): 4 eyes [2.1%], mild non-proliferative DR (NPDR; ETDRS 20–35): 95 eyes [50.0%], moderate NPDR (ETDRS 43–47): 29 eyes [15.3%], severe NPDR (ETDRS 53): 5 eyes [2.6%], and proliferative DR (ETDRS 61 +): 57 eyes
Discussion
We compared 200° widefield SLO (non-mydriatic, mydriatic and mydriatic steered) to ETDRS 7-field 45° photography and found a substantial agreement between the different image-capturing modalities in grading DR. This is in agreement with the findings of others (Kernt et al., 2012, Liegl et al., 2014, Neubauer et al., 2008, Silva et al., 2012, Silva et al., 2013, Wilson et al., 2010).
Some areas of discrepancies should, however, be enhanced. A great proportion of the images graded as level 20
Disclosures
None.
Acknowledgments
This work was supported by grants from Fight for Sight, Denmark, Merchant Christian Andersen and wife Ingeborg Ovidia Signe Andersen, born Schmidt’s grant, The Foundation of AJ. Andersen and Wife, The Foundation of Carl and Nicoline Larsen, The Memorial-grant of Alice Rasmussen, The Foundation of Teacher Karen Svankjaer Yde, The Memorial-grant of Else Poulsen, The Foundation of Goldsmith AL. & D. Rasmussen, Lykfeldt’s Grant, The Foundation of the Kjaersgaard,Sunds Family, The Foundation of June
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Conflict of Interest Statement: none.