The OSCAR-IB consensus criteria for retinal OCT quality assessment

Abstract

Background: Retinal optical coherence tomography (OCT) is an imaging biomarker for neurodegeneration in multiple sclerosis (MS). In order to become validated as an outcome measure in multicenter studies, reliable quality control (QC) criteria with high inter-rater agreement are required.

Methods/principal findings: A prospective multicentre study on developing consensus QC criteria for retinal OCT in MS: (1) a literature review on OCT QC criteria; (2) application of these QC criteria to a training set of 101 retinal OCT scans from patients with MS; (3) kappa statistics for inter-rater agreement; (4) identification reasons for inter-rater disagreement; (5) development of new consensus QC criteria; (6) testing of the new QC criteria on the training set and (7) prospective validation on a new set of 159 OCT scans from patients with MS. The inter-rater agreement for acceptable scans among OCT readers (n = 3) was moderate (kappa 0·45) based on the non-validated QC criteria which were entirely based on the ophthalmological literature. A new set of QC criteria was developed based on recognition of: (O) obvious problems, (S) poor signal strength, (C) centration of scan, (A) algorithm failure, (R) retinal pathology other than MS related, (I) illumination and (B) beam placement. Adhering to these OSCAR-IB QC criteria increased the inter-rater agreement to kappa from moderate to substantial (0.61 training set and 0.61 prospective validation).

Conclusions: This study presents the first validated consensus QC criteria for retinal OCT reading in MS. The high inter-rater agreement suggests the OSCAR-IB QC criteria to be considered in the context of multicentre studies and trials in MS.

Figure 1. Obvious: The left image is blurred due to poor focusing.

This results in increased noise and loss of transversal resolution in the OCT image on the right.

Figure 2. Signal: The signal strength for this image is 13 dB which is lower than the limit of 15 dB.

This results in a more noisy OCT image with a lot of speckling.

Figure 3. Decentration: The ring scan is not correctly centred as can be observed in the left image.

The edge of the optic nerve head crosses more than two circles. Therefore the ringscan is rejected.

Figure 4. Algorithm failure: The red line in the OCT image right is not clearly at the border of the RNFL.

The location corresponds to inferior of the ONH.

Figure 5. Retinal pathology: There is severe peri-papillary atrophy.

It can be seen that this affects the RNFL enormously.

Figure 6. Illumination: The OCT scan here is badly illuminated.

Also here this results in speckling and decrease of resolution.

Figure 7. Beam placement: the laser beam is not placed centrally.

This can be seen at the outer nuclear layer (ONL). The two arrows point to two regions of the ONL. The left arrow points to a light gray region whereas the other points to a darker gray region. If there is too much difference in colour of the ONL itself a scan is rejected.