ASSOCIATIONS OF TYPES OF LENS OPACITIES BETWEEN AND WITHIN EYES OF INDIVIDUALS - AN APPLICATION OF 2ND-ORDER GENERALIZED ESTIMATING EQUATIONS

The lens opacity characteristics of individuals constitute multivariat e data. Our goal was to estimate the associations between the three ma in types of age-related lens opacities (nuclear, cortical, posterior s ubcapsular) both between and within eyes of individuals using cross-se ctional data from the Framingham (Massachusetts) Eye Studies. We descr ibe use of a recently proposed extension of the generalized estimating equations approach to marginal logistic models (GEE2), and we demonst rate that a variety of research problems can be investigated with this methodology. For example, in our data, there were strong associations of the same opacity types between the two eyes of individuals and wea k associations between different types of opacities. We also note that estimation of such associations may be limited in other epidemiologic settings.