Association of Longitudinal Changes in Drusen Characteristics and Retinal Layer Volumes with Subsequent Subtype of Choroidal Neovascularisation.

AIM

To investigate the longitudinal correlation between drusen characteristics and retinal layer volumes pre conversion and subsequent type of choroidal neovascularisation (CNV).

METHODS

This was a single-centre retrospective study. The study participants were patients with wet age-related macular degeneration (AMD) in one eye who developed wet AMD in the contralateral eye, with at least 2 years of follow-up prior to conversion. The Moorfields Eye Hospital database was searched for eligible patients and their data were recorded. Eyes were classified as occult or classic based on fundus fluorescein angiography. Optical coherence tomography (OCT) images were analysed for drusen characteristics and retinal layer volumes were analysed over time using automated software (Topcon 3D OCT-2000 and Orion, Voxeleron LLC, respectively). All values were obtained at baseline as well as year 1 and year 2 before conversion to wet AMD.

RESULTS

Fifty-one eyes with bilateral CNV showed high correlation of type of CNV between eyes (kappa statistic 0.89). A total of 49 wet AMD eyes (29 occult, 20 classic) were analysed for drusen parameters. Two patients with retinal angiomatous proliferation were excluded. Drusen count, area, and volume did not differ by CNV type, but the rates of change of drusen area (p = 0.046) and drusen volume (0.022) were higher in the occult group in the year preceding CNV development. Of the 49 eyes, 17 (10 occult, 7 classic) with available good quality OCT were analysed for retinal layer volumes. There was a progressive reduction in outer nuclear layer (ONL) volume (p = 0.002) and an expansion in outer plexiform layer volume (p = 0.015) in eyes that developed occult CNV.

CONCLUSION

Our study shows that rate of increase in drusen load and reduction in ONL are significant features seen in eyes developing occult CNV, highlighting new imaging markers that need to be replicated in larger studies. These markers provide insight into the pathogenesis of CNV and may serve as prognostic indicators, as classic CNV carries a poorer prognosis compared to occult CNV.