OCT derived measures - longitudinal

I am planning a longitudinal analysis using the TABS-derived OCT retinal layer thickness IDPs (category 100079, fields 28500–28553, and related macular/RPE fields 27800–27841). Two points are not clear from Showcase or release notes up to v20 (dispense 3 December 2025):

1. Instance 0 / Instance 1 longitudinal cohort. For fields 28500/28501 (average RNFL) and related layer IDPs, participants with Instance 1 values are  subset of those with Instance 0 values, i.e. a true within-participant longitudinal subset of 19,000 individuals scanned at both the 2006–2010 baseline and the 2012–2013 first repeat assessment? 

2. Instance 2 and Instance 3 derived IDPs. Field 6072 shows OCT was acquired for 4,182 participants at Instance 2 and 15,601 at Instance 3, but none of the derived IDPs in fields 27800–27841 or 28500–28553 appear populated at these instances in our application. Is this expected globally (i.e. not an artefact of our specific dispense), and is it related to the device change from Topcon 3D OCT 1000 Mk2 to Topcon Triton? Are there planned releases of equivalent tabular layer thickness IDPs for Instance 3 as part of the Repeat Imaging Project, and if so, is there an indicative timeline and any planned cross-device harmonisation with the Instance 0/1 measurements?

Thank you very much.

Best regards,

Gianmarco Bellucci