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C.R. Hopley, J. Crowston, P.R. Healey, A. Lee, E. Rochtchina, P. Mitchell, Blue Mountains Eye Study; Vertical Cup: Disc Ratio in a Non-glaucomatous Population-based Sample: The Blue Mountains Eye Study . Invest. Ophthalmol. Vis. Sci. 2003;44(13):3408.
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Purpose: The 97.5th percentile for vertical cup:disc ratio (VCDR) has been proposed as a useful tool to assist in the diagnosis of glaucoma in population studies. Previous population based reports of VCDR percentiles, however, have not been adjusted for optic disc diameter and the Rotterdam Study adjusted for disc area. Our aim was to describe VCDR in a large population-based sample of non-glaucomatous eyes. Methods: Data were collected from 3654 people, aged 49 years or older, living in the Blue Mountains, west of Sydney, Australia. Vertical optic disc diameter and VCDR was determined by planimetry from stereo optic disc photographs. Eyes with glaucoma and non-glaucomatous optic disc anomalies as well as pseudophakic and aphakic eyes were excluded, as a spherical equivalent-based correction factor (Bengtsson) was used in determining optic disc size. Results: A total of 6616 eyes were used for analysis. Median cup disc ratio and 95th, 97.5th and 99th percentile increased with vertical optic disc diameter in a linear fashion. The trend line for the non-grouped 97.5th percentile was y = 0.0231x + 0.5761. A 0.18 increase in median VCDR (0.35 to 0.55) was observed between small (1.1 to 1.3mm) and large (1.8 to 2.0mm) optic discs. An equivalent increase of 0.15 (0.59 to 0.74) was observed for the 97.5th percentile from small to large optic discs. The intra-group range of VCDR from the median to 97.5th percentile was 0.24 (0.35 - 0.59) for small optic discs, 0.24 (0.44 - 0.68) for medium-sized optic discs and 0.19 (0.55 - 0.74) for large optic discs. Conclusion: This study has reported the 95th, 97.5 and 99th percentiles for a "normal" population adjusted for vertical optic disc diameter. These data may assist clinical practice in defining a range of normality. Sole use of particular VCDR percentile cut-off levels to define glaucoma cases in population surveys requires further validation.
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