The glycoprotein fibrillin is the principal component of the ciliary zonule and has an important role in the strength and elasticity of ocular connective tissues. Fibrillin polymers form the structural scaffold of extensible microfibrils1-3 which are present in ocular elastic tissues and are arranged in parallel bundles to form the zonular fibres.4 These fibrillin-rich microfibrils are morphologically identical to those which provide strength and long range elastic recoil to the connective tissues of blood vessels, lung, ligament, and dermis.5 6 In these tissues, fibrillin-rich microfibrils form a scaffold for the deposition and alignment of the elastin precursor tropoelastin during elastic fibre assembly.7 8 However, the microfibrils of the ciliary zonule as well as those of kidney glomerulus, skeletal muscle, heart, and periodontal ligament do not contain significant amounts of elastin.9 Disorders which disrupt fibrillin-rich microfibril structure or function, such as Marfan's syndrome and ectopia lentis, result in a spectrum of ocular complications. This review summarises current knowledge of fibrillin and fibrillin-rich microfibrils and their role in the eye, and discusses the pathological processes which may be involved in ocular connective tissue ageing and disease. In addition to the zonules, fibrillin has been immunolocalised to the connective tissues of the anterior segment including the conjunctival, iris and ciliary body stroma, the ciliary processes, the corneal stroma and corneal epithelial basement membrane, and the endothelium of Schlemm's canal.10 In the posterior segment, fibrillin has been localised to scleral stroma, lamina cribrosa, Bruch's membrane, and choroid10; beaded microfibrils are also present in vitreous.11-13 The precise role of fibrillin-rich microfibrils in all these ocular tissues is not defined, but they may regulate development and confer strength and elasticity to connective tissues. Fibrillin present in the equatorial region of the lens capsule allows anchorage of the …