Cup shape measurement may be helpful in evaluating optic disc

Measurement of the cup shape seems to be a “promising parameter in evaluation and comparison of the optic discs of normal subjects,” a group of Turkish researchers reported. The cup shape was the only disc parameter independent of variable factors such as age, sex and disc area, the researchers found.

A. Hakan Durukan, MD, and colleagues at Gulhane Military Medical Academy in Ankara conducted optic nerve head topographic analysis using the Heidelberg Retinal Tomograph II bilaterally in 551 healthy subjects between ages 11 and 75. Subjects were divided into three groups: those under 30 years old, those 30 to 60 years old and those older than 60. They were also divided into three groups based on disc area: under 2 mm², between 2 and 2.25 mm² and greater than 2.25 mm².

Disc area, topography standard deviation and a total of 12 topographic parameters were calculated for each subject using the HRT II. The mean disc area for the 543 subjects included in the study was 2.12 mm². The mean refractive error was –0.58 D with a range of –4.75 D to +4.25 D. The mean cup shape as determined by HRT II was –0.21.

The study authors found that disc area was significantly correlated with all of the topographic parameters but two: the cup shape measure and the height variation contour. Significant age-related differences were detected in four parameters and significant sex-related differences were detected in three parameters. There were no significant differences in any of the parameters for laterality and refractive error.

The cup shape measure was the only parameter that did not correlate with any of the variables measured.

The study is published in the June issue of Clinical & Experimental Ophthalmology.