eng Science and Education Publishing International Journal of Physics 2333-4576 2021-11-01 9 6 259 268 10.12691/ijp-9-6-1 IJP2021961 article Fulvio Andres Callegari fulvio.callegari@ufabc.edu.br 1 Centro de Engenharia, Modelagem, e Ci¨ºncias Sociais Aplicadas, Universidade Federal do ABC, Santo Andr¨¦, SP, Brasil. Avenida dos Estados, 5001 - Bairro Santa Terezinha Santo Andr¨¦ - CEP: 09210-580 The optical matrix formalism is applied to find optical parameters such as focal distance, back and front focal points, principal planes and the object image equation for a thick spherical lens immerse in two optical media of different indexes of refraction. Then, the formalism is applied to systems compound of two, three and N thick lenses in cascade, immersed in three, four and N+1 optical media of different indexes, respectively. It is found that a simple Gaussian equation is enough to relate object and image distances no matter the number of lenses. This formalism is validated trough a simple optical matrix model of the human eye. http://pubs.sciepub.com/ijp/9/6/1/ijp-9-6-1.pdf matrix optics thick lenses back focal length front focal length principal planes multi-lenses system human eye