The use of RADAAR (ratio of rim area to disc area asymmetry) in detecting glaucoma and its severity

BACKGROUND: In a previous study it was shown that the asymmetry of rim area and disc area of fellow eyes expressed as a ratio (rim area to disc area asymmetry ratio [RADAAR]) was associated with the diagnosis of glaucoma in patients with highly asymmetric disease. Furthermore, this ratio was able to distinguish these patients from groups of glaucoma suspects and subjects without glaucoma. The purpose of this study was to investigate whether the RADAAR correlates with the diagnosis and severity of glaucoma in a large glaucomatous population. METHODS: We reviewed the records of 140 randomly selected patients with open-angle, normal-tension or pseudoexfoliative glaucoma evaluated at the glaucoma service of a tertiary care centre in Philadelphia between January 1996 and April 2000. Heidelberg Retina Tomograph (HRT) disc area, rim area, cup-to-disc area ratio, pattern-standard deviation and mean deviation as well as maximum intraocular pressure (IOP) were recorded. Disc staging and visual fields determined severity of glaucoma, and fellow eyes were classified as "better" or "worse." RESULTS: The RADAAR was significantly correlated with IOP (r = 0.23, p < 0.03), mean deviation (r = -0.22, p < 0.02), cup-to-disc area ratio (r = 0.19, p < 0.03) and disc stage of glaucomatous optic nerve damage (r = 0.17, p < 0.05) in "worse" eyes. RADAAR groups were also correlated with fellow-eye differences in mean deviation (p < 0.05) and cup-to-disc area ratio (p < 0.02). INTERPRETATION: The RADAAR, a new HRT-derived measure of asymmetry in fellow eyes, is associated with the diagnosis of glaucoma and its severity.