WE Gillies was a major contributor to research in glaucoma, notably pseuodexfoliation (XFS), as well as strabismus, particularly in relation to axial length (AL). The latter work involved breaking down the geometry of the eye to its basic components and using the measured AL to tailor the amount of strabismus surgery required. Similarly, the search for glaucoma genes requires us to break down glaucoma into its component measures and associated risk factors. Over the last 14 years, our data from the Glaucoma Inheritance Study in Tasmania have shown the following: that a family history is present in 60% of glaucoma cases; that 27% of members of large glaucoma families were unaware of their family history of glaucoma; and that familial glaucoma is more severe than sporadic glaucoma. Myocilin mutations account for 3% of cases of primary open angle glaucoma. Some genotype-phenotype correlations have been identified. Notably, with respect to earlier age of onset, higher maximum recorded intraocular pressure and need for surgery, the Gln368Stop mutation confers mild risk, Thr377Met and Gly252Arg mutations intermediate risk, and the Pro370Leu mutation severe risk. To identify the other genes associated with glaucoma, we have examined normal twins in the Twins Eye Study to determine the heritability of parameters that are abnormal in glaucoma - intraocular pressure and cup-to-disc ratio and confounding factors for glaucoma such as central corneal thickness, disc area, refraction and AL. We have identified high heritabilities for all of these as well as a gene locus associated with AL on chromosome 5. Recently, the LOXL1 gene was associated with XFS. Identification of further genes will improve our understanding of glaucoma and allow cascade genetic screening.