Lumican is keratan sulfate proteoglycan of the small leucine rich proteoglycan family. Through studies in animal models lumican has been found to be critical in maintaining corneal clarity. It maintains ordered collagen fibrils which are vital in keeping the cornea transparent. It may also be important in primary open angle glaucoma influencing aqueous outflow. Lumican deficiency in mice results in increased axial length with fibromodulin deficiency and thinner sclerae. There is evidence suggesting that this characteristic may be pertinent in humans and lumican gene polymorphisms could be related to high myopia. Lumican plays a fundamental role in inflammation and wound healing. It localises macrophages to the site of corneal injury and recruits neutrophils in lipopolysaccharide-induced keratitis in mice. It has also been shown to bind lipopolysaccharide which may be critical in inflammatory diseases such as uveitis. Lumican is also important in wound healing revealing decreased synthesis in scar tissue and mediating Fas-Fas ligand interactions. It is present in human placenta and amniotic membrane suggesting that it may ensure viable amniotic membrane grafts. Lumican may also be involved in the formation of posterior capsular opacification following cataract surgery. Research into the pivotal role of lumican in the pathogenesis of ocular disease has resulted in greater understanding of the key role which proteoglycans play in human disease. 1. Introduction A normal ocular extracellular matrix is vital for ocular structure, homeostasis, and function. It is increasingly evident that it is also essential to maintain ocular immunologic status and immune privilege. A key component of the extracellular matrix is lumican, a proteoglycan that plays an important role in many structural, inflammatory, and disease processes. Animal studies in glaucoma, high myopia, inflammatory eye diseases, and wound healing indicate an important role for lumican in the pathogenesis of these common eye diseases. There are limited data from human studies. In humans the gene for lumican (lum) is located on the short arm of chromosome 12q22. Lumican is an extracellular matrix protein of the small leucine rich proteoglycans (SLRPs). Within the SLRP family there are also decorin, fibromodulin, biglycan, and keratocan [1, 2]. Lumican, as with other SLRPs, has a molecular mass of approximately 40？kDa [3, 4] and is 338 amino acid residues in length [5, 6]. It consists of four domains, namely, (1) a signal peptide, (2) a negatively charged N-terminal domain, (3) tandem leucine-rich
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