Purpose: To explore genetic determinants specific to reticular pseudodrusen (RPD), and to compare these with genetic associations for drusen. Setting: Participants with RPD, drusen, or controls from the UK Biobank (UKBB), a large, multisite, community-based cohort study. Methods: A previously validated deep learning framework was deployed on 169,370 optical coherence tomography (OCT) volumes from the UKBB to identify cases with RPD and/or drusen and controls without these phenotypes. Cases were included if they were 60 years or older, with at least 5 lesions. Five retina specialists manually validated the cohorts using OCT and color fundus photographs. Quantifications of RPD and drusen derived by the framework were used as variables. Two primary genome-wide association study (GWAS) analyses were performed to explore potential genetic associations with number of RPD and drusen within "pure" cases, where only RPD or drusen were present in either eye. A candidate approach was furthermore adopted to assess 46 previously known AMD loci. Secondary GWAS were undertaken for number of RPD and drusen in mixed cases, as well as binary case-control analyses for pure RPD and pure drusen. Genome-wide significance was defined as p<5e-8. Results: A total of 1,787 participants were identified and analysed, including 1,037 controls, 361 pure drusen, 66 pure RPD and 323 mixed cases. The primary pure RPD GWAS yielded four genome-wide significant loci: rs11200630/ARMS2-HTRA1 (p=1.9e-09), rs79641866/PARD3B on chromosome 2 (p=1.3e-08), rs143184903/ITPR1 on chromosome 3 (p=8.1e-09), and rs76377757/SLN on chromosome 11 (p=4.3e-08). The latter three are all uncommon variants (minor allele frequency <5%). A significant association at CFH was also observed adopting a candidate approach (p=1.8e-04). Two loci reached genome-wide significance for the primary pure drusen GWAS: rs10801555/CFH on chromosome 1 (p=6.0e-33) and rs61871744/ARMS2-HTRA1 on chromosome 10 (p=4.2e-20). For the mixed RPD and drusen secondary analyses, lead variants at both the CFH and ARMS2-HTRA1 loci reached genome-wide significance, with C2-CFB-SKIV2L additionally associated for mixed drusen alone. Findings from the binary case-control GWAS for drusen mirrored those of the primary drusen analysis, however no variants reached genome-wide significance in the case-control RPD GWAS. Conclusions: Our findings indicate a clear association between the ARMS2-HTRA1 locus with higher RPD load. Although the association at the CFH locus did not reach genome-wide significance, we observed a suggestive link. We furthermore identified three novel associations that are unique to RPD, albeit for uncommon genetic variants. These findings were only observable when quantifying RPD load as a continuous trait, which increased the statistical power of the study. Further studies with larger sample sizes are now required to explore the relative contributions of AMRS2- HTRA1 and CFH to RPD development, and to explore the validity of these newly presented RPD-specific genetic associations.

The authors have declared no competing interest.

Sponsored by the EURETINA Retinal Medicine Clinical Research Grant. R.S., C.E., and A.T. received a proportion of their financial support from the UK Department of Health through an award made by the National Institute for Health Research to Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology for a Biomedical Research Centre for Ophthalmology. A.P.K is supported by a UK Research and Innovation Future Leaders Fellowship, an Alcon Research Institute Young Investigator Award and a Lister Institute for Preventive Medicine Award. This research was supported by the NIHR Biomedical Research Centre at Moorfields Eye Hospital and the UCL Institute of Ophthalmology. This work was supported in part by the Said Foundation

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The study was approved by the North West Multi-centre Research Ethics Committee (REC reference number: 06/MRE08/65, UKBB project ID 60078), adhering to the principles of the Declaration of Helsinki (www.ukbiobank.ac.uk).

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