Eye colour or, more accurately, iris colour is one of the most obvious physical characteristics of a person. European parents frequently ask the colour of their newborn's eyes, only to see the iris change dramatically during their child's first year of life. Genetic and epidemiological findings have uncovered further details about the basis for iris colour, which may have important implications for further research and treatment of some eye diseases and ocular characteristics. Surprisingly there is no widely recognized classification system for eye colour. An added difficulty when trying to devise an international system is that subtle differences in colour description exist between languages (e.g. hazel vs. auburn). We reviewed the recent and very early literature pertaining to eye colour classification. Recent genetic investigations of eye colour have tended to either use simple (three-category grading systems) or more complex digital colour grading. We present a nine-category grading system. Categories in this novel schema include: (i) light blue; (ii) darker blue; (iii) blue with brown peripupillary ring; (iv) green; (v) green with brown iris ring; (vi) peripheral green central brown; (vii) brown with some peripheral green; (viii) brown; and (ix) dark brown. Although different observers may categorize a person's eye colour differently, it is generally only by an adjacent category. We also describe a continuum of iris pigmentation from a small ring of brown around the pupil to almost complete brown with small peripheral flecks. Digital publishing and assessment of iris colour will result in more standardized classification of iris colour and investigation of its role in eye disease.

The Glaucoma Inheritance Study in Tasmania (GIST) is a population survey of Australia's island state, Tasmania (population 450,000). Its aim is to find families with autosomal dominant, adult-onset, primary open angle glaucoma (POAG) suitable for genetic linkage analysis. POAG is relatively common, affecting around 3% of the Australian population. By finding the large families with POAG and identifying all the descendants in a captive population, it is possible that there may be overlap of different glaucoma pedigrees. Three of the first thirteen families in the study were composed of overlapping pedigrees. In one GIST family, GTas3, there has been intermarriage with other pedigrees with glaucoma on five occasions. The possibility of multiple genotypes was also reinforced by the inability to determine a single glaucoma phenotype in this family. When finding large families of POAG for linkage analysis, researchers must be aware of the risk of affected individuals inheriting their gene from the alternate parent. Thus, the alternate parents or their families must be examined, especially if the phenotype is atypical for the rest of the family.

This study suggests that predictive glaucoma testing in appropriate circumstances is acceptable to patients and their families.

Aim:To describe the recruitment, ophthalmic examination methods and distribution of ocular biometry of participants in the Norfolk Island Eye Study, who were individuals descended from the English Bounty mutineers and their Polynesian wives.Methods:All 1,275 permanent residents of Norfolk Island aged over 15 years were invited to participate, including 602 individuals involved in a 2001 cardiovascular disease study. Participants completed a detailed questionnaire and underwent a comprehensive eye assessment including stereo disc and retinal photography, ocular coherence topography and conjunctival autofluorescence assessment. Additionally, blood or saliva was taken for DNA testing.Results:781 participants aged over 15 years were seen (54% female), comprising 61% of the permanent Island population. 343 people (43.9%) could trace their family history to the Pitcairn Islanders (Norfolk Island Pitcairn Pedigree). Mean anterior chamber depth was 3.32mm, mean axial length (AL) was 23.5mm, and mean central corneal thickness was 546 microns. There were no statistically significant differences in these characteristics between persons with and without Pitcairn Island ancestry. Mean intra-ocular pressure was lower in people with Pitcairn Island ancestry: 15.89mmHg compared to those without Pitcairn Island ancestry 16.49mmHg (P= .007). The mean keratometry value was lower in people with Pitcairn Island ancestry (43.22 vs. 43.52,P= .007). The corneas were flatter in people of Pitcairn ancestry but there was no corresponding difference in AL or refraction.Conclusion:Our study population is highly representative of the permanent population of Norfolk Island. Ocular biometry was similar to that of other white populations. Heritability estimates, linkage analysis and genome-wide studies will further elucidate the genetic determinants of chronic ocular diseases in this genetic isolate.