The present invention relates to an optical article having anti-reflection properties and high thermal resistance, comprising a substrate having at least one main face coated with a multi-layer anti-reflection coating comprising a stack of at least one high refractive index layer and at least one low refractive index layer, wherein the ratio:.times..times..times..times..times..times..times..times..times..tim- es..times..times..times..times..times..times..times..times..times..times..- times..times..times..times..times..times..times..times..times..times..time- s..times..times..times..times..times..times..times..times..times..times..t- imes..times..times..times..times..times..times..times..times..times..times- ..times..times. ##EQU00001## is higher than 2.1. If the anti-reflection stack comprises at least one low refractive index layer having a physical thickness .gtoreq.100 nm which is not the outermost layer of the anti-reflection coating, said relatively thick layer and the underlying layers are not taken into account in R.sub.T calculation.