Abstract
Purpose: :
To analyze the influence in the optic disk measurements of the automatically determined edge of the optic nerve head (ONH) and the manually corrected one in cases where the Optical Coherence Tomography did not identify the disc limits correctly.
Methods: :
89 eyes of 89 consecutive patients, either normal or glaucomatous, submitted to the Fast Optic Disc Stratus OCT (Carl Zeiss Meditec, Dublin, CA, USA; software 4.0) test were selected. 47 eyes in which either the manual assignment was not necessary or the signal strength was below six were excluded. OCT ONH scans are composed of six radial scans in a spokelike pattern centered on the disc and with each radial scan spaced 30 degrees from one to another. After image acquisition and processing, one expert examiner manually corrected the determination of the edge of the ONH, identified as the end of the retinal pigment epithelium/choriocapillaris layer. Disk Area, Cup Area, Rim Area and Cup/Disc Area Ratio results were compared before and after the optic disk margin manually corrected determination. Student's t-test was performed to evaluate the differences, and P<0.05 was considered statistically significant.
Results: :
42 eyes of 42 people, either normal or glaucomatous, were analyzed. No statistically significant difference (P>0.3) was found when analyzing the following parameters results obtained with automated and manual determination (mean ± SD): Disk Area (2.51 ± 0.54 mm2; 2.45 ± 0.64 mm2), Cup Area (1.19 ± 0.6 mm2; 1.20 ± 0.60 mm2) and Cup/Disc Area Ratio (0.46 ± 0.18 mm2; 0.46 ± 0.19 mm2). The Rim Area results were significantly different (P=0.03) before (1.32 ± 0.40 mm2) and after (1.25 ± 0.38 mm2) the manual correction.
Conclusions: :
The Stratus OCT Optic Nerve Head Report results were little influenced when optic disk limits were manually determined. Therefore the standard automated Stratus OCT disk margin assignment is adequate, and manual edition is not necessary.
Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • imaging/image analysis: clinical • optic disc