Purpose To evaluate the impact of segmentation error on vessel density measurements in healthy eyes and eyes with diabetic macular oedema (DMO).
Methods In this prospective, comparative, non-interventional study, enface optical coherence tomography angiography (OCTA) images of the macula from healthy eyes and eyes with DMO were acquired. Two expert graders assessed and corrected the segmentation error. The rate of segmentation error and the changes in vessel density and inner retinal thickness after correction of the segmentation error were recorded and compared between the two groups.
Results 20 eyes with DMO and 24 healthy eyes were evaluated. Intergrader agreement was excellent (intraclass correlation coefficient ≥0.9) for all parameters in both groups. The rate of segmentation error was 33% and 100% in healthy and diabetic eyes, respectively (p<0.001). Nine healthy eyes (37.5%) and all eyes with DMO (100%) were noted to exhibit a change in at least one of the foveal or parafoveal vessel density measurements. The rate of any change in foveal and parafoveal vessel densities in both the superficial and deep capillary plexus was statistically significantly higher in the diabetic group (all p<0.001). No statistically significant change was observed in mean vessel density (superficial and deep capillary plexuses) after correction of the segmentation error in healthy and DMO eyes (All p>0.05). However, the mean absolute change in the vessel density measurements was statistically significantly higher in the diabetic group (all p<0.05). The mean absolute change in superficial and deep inner retinal thickness was statistically significantly higher in DMO (p=0.02 and p=0.002, respectively).
Conclusions In this study, misidentification of retinal layers and consequent vessel density measurement error occurred in all eyes with DMO and in one-third of healthy eyes. The segmentation error should be checked and manually corrected in the OCTA vessel density measurements, especially in the presence of macular oedema.
- diabetic retinopathy
- diabetic macular edema
- optical coherence tomography angiography
- segmentation error
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Contributors All the authors included in this paper fulfill the criteria of authorship. Writing the article, concept and design; data collection; analysis and interpretation; critical revision of the article; final approval of the article; provision of materials, patients or resources; literature search: KGF and PA. Concept and design; critical revision of the article; final approval of the article; literature search: DS. Data collection; provision of materials: AH, SG, MAK and HS.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests None declared.
Patient consent for publication Obtained.
Ethics approval The study was approved by the Ethics Committee of the Eye Research Center and adhered to the tenets of the Declaration of Helsinki.
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement Data are available on request.