Reproducibility of Optic Disc Measurements with Computer Graphic Program

ABSTRACT

Computerized image analysis of simultaneous stereoscopic videographic images has been used to study structural parameters of the optic nerv head. Although these instruments are of great interest as research tools, the current economic climate and the great cost make their utility for the average ophthalmologist unlikely. Seventy unselected optic nerve heads of 44 normal subjects(22 men, 22 women, mean age 45.8) were evaluated by magnification-corrected morphometry of optic disc photographs. The radius and angle were measured by a computer graphic program(Adobe Photoshop(TM)). The mean disc area(2.48 +/- 0.46 mm2), the mean cup area(0.59 +/- 0.25mm2), and the mean rim area(1.90 +/- 0.35mm2) were evaluated. The coefficients of variation of intraobserver determination were as follows vertical disc diameter 0.92%. horizontal disc diameter 1.40%, vertical cup diameter 3.64, horizontal cup diameter 3.14%, disc area 1.33%, cup area 3.28%, and neuroretinal rim area 1.82%. The median interobserver percentage differences were as follows vertical disc diameter 0.80%, horizontal disc diameter 0.83%. vertical cup diameter 3.75%, horizontal cup diameter 1.59%, disc area 1.57%. cup area 3.03%, and neuroretinal rim area 2.53%. While it is similar to the method of measuring the manual planimetry. the measuring of optic nerve head can be done directly on the monitor of personal computer by scanning the photograph. This method of measurement can be used clinically since it has a high reproducibility.