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Invited Commentary
March 12, 2020

Implications of Analysis Unit on Epidemiology of Multimodal Imaging–Defined Reticular Pseudodrusen: When 2 Eyes Are Better Than 1

Author Affiliations
  • 1Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, Melbourne, Australia
  • 2Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, University of Melbourne, Melbourne, Australia
  • 3Ophthalmology, Department of Surgery, University of Melbourne, Melbourne, Australia
JAMA Ophthalmol. 2020;138(5):477-478. doi:10.1001/jamaophthalmol.2020.0262

Ophthalmic epidemiology plays an important role in developing our understanding of the complex interactions between genetics, demographic characteristics, and lifestyle that are associated with ocular disease. In this issue of JAMA Ophthalmology, Dutheil et al1 present their findings on the incidence of multimodal imaging–defined reticular pseudodrusen (RPD) among an older French population. Given the unknown cause of RPD and the relatively recent understanding of its prognostic value for the progression of age-related macular degeneration, the epidemiologic profile of RPD is of great interest. In the ALIENOR (Antioxydants, Lipides Essentiels, Nutrition et Maladies Oculaires) Study, the eye (rather than participant) has been used as the primary unit of analysis, and appropriate statistical methods have been used to account for within-participant correlation (ie, Cox proportional hazards regression with robust SEs for time-to-event outcomes, Poisson generalized linear mixed models to estimate incidence, and logistic generalized estimating equations to compare characteristics between included and excluded participants).1 However, in many epidemiologic analyses, the outcome is defined according to bilateral status for each participant (ie, whether the condition is present in neither vs either eye, or the number of eyes in which the condition is present).2-4 This raises the question of whether the eye or the person is the most appropriate unit of analysis to answer research questions in this setting.

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