Comparison of Optic Nerve Head Measurements by Optical Coherence Tomography and Confocal Scanning Laser Ophthalmoscopy

PURPOSE: To evaluate the relationship between the optic disc measurements generated by TopSS(TM) and by OCT. METHODS: Sixty-two eyes of 34 patients, 52 non-glaucomatous and 10 glaucomatous eyes, were scanned with TopSS(TM) and OCT 3000(TM). The margin of optic disc were defined automatically in OCT 3000(TM). The relationship between the optic disc variables- disc area (DA), cup area (CA), neuroretinal rim area (NRRA), and cup-disc area ratio (CDAR)- from TopSS(TM) and OCT was evaluated and the relationship between these and the tilt of disc was assessed. The horizontal (HD) and vertical diameter (VD) of the disc were measured from TopSS(TM) and OCT , then the ratio (HD/VD) were compared. RESULTS: In non-glaucomatous eyes with tilt more than 4 degrees, OCT measured DA and NRRA larger, and CDAR smaller than those measured by TopSS(TM), but the CA showed no difference. In non-glaucomatous eyes with tilt less than 4 degrees, there were no significant differences between OCT and TopSS(TM). In glaucomatous eyes, the CA measured by OCT was greater than that measured by TopSS(TM) (p=0.013). The HD/VD measured by TopSS(TM) showed no difference from HD/VD measured by OCT (p=0.849), and significant difference from HD/VD measured by OCT in eyes with tilted more than 4 degrees (p=0.003). In glaucomatous eyes, HD/VD measured by TopSS(TM) showed difference from HD/VD measured by OCT (p=0.022). CONCLUSIONS: Although measurement of disc in TopSS(TM) and OCT are correlated, the discrepancy becomes prominent in eyes with tilted disc or in glaucomatous eyes. Therefore optic disc analysis by OCT needs to be interpreted cautiously in tilted disc and in glaucomatous eyes.

Optic Disc Measurements with Topographic Scanning System

Quantitative analysis of the optic nerve head topography is important in diagnosis, differential diagnosis and follow-up of optic nerve diseases, especially in glaucoma. This study was undertaken to analyze the optic nerve head with confocal scanning laser ophthalmoscope(TopSSTM Software Version 2.2, LDT.Inc) and further to determine gender, age, refractive error and axial length-based on differences in the size and topography of the optic disc. One hundred normal human optic nerve heads of 100 subjects (42 men, 58 women, mean age 43.3+/-14.5 years) were evaluated. The men value of the parameters in TopSSTM were as follows : horizontal disc diameter 1.62+/-0.17mm, vertical disc diameter 1.77+/-0.24mm average disc diameter 1.71+/-0.15mm, disc area 2.31+/-0.43 mm2, cup area 1.01+/-0.50 mm2, horizontal cup to disc ratio 0.52+/-0.17, vertical cup to disc ratio 0.47+/-0.20, average cup to disc ratio 0.45+/-0.18, rim area 1.30+/-0.35 mm2. There were no significant correlations between these morphometric optic disc parameters and age, refractive error or axial length(p>0.05). However, male subjects had about 10% larger optic discs compared with female subjects. The optic disc size was well correlated with cup area and rim area (p<0.05).