Three–dimensional analysis to detect glaucomatous optic discs by using the Heidelberg Retina Tomograph

Abstract

Abstract: : Purpose: : To evaluate the potential ability of a confocal scanning laser ophthalmoscope to differentiate subjects with normal visual field from patients with abnormal visual field using an optic nerve head (ONH) topographic map. Methods:Forty glaucomatous patients with an abnormal visual field and/or optic disc and an open angle, and 40 normal eyes with a normal visual field, an IOP of less than 22 mm Hg and no history of glaucoma in their family were selected. One eye was chosen randomly from all the subjects. All ONHs were examined with the Heidelberg Retina Tomograph (HRT, Heidelberg Engineering GMBH, Heidelberg, Germany) and visual fields were assessed by Humphrey Perimeter, program 30–2 (Humphrey Instrument, Inc, San Leandro, CA, USA). HRT topographic maps were analyzed using an analytic–geometric analysis method. Three–dimensional images were sectioned into 30 different contour lines obtained by the intersections of n equidistant planes with the surface f(x,y). Each contour line is constituted of a different number of points of the same height that shape a polygon and their areas were calculated. Results: This analysis had a sensitivity, specificity and diagnostic precision of 80%, 75% and 77.5%, respectively. Conclusions:Using this technique, the HRT capacity to differentiate normal ONH from those with glaucoma was similar to previous studies, but without drawing the optic nerve head outline which is actually too subjective.

Keywords: imaging/image analysis: clinical • optic disc • image processing