A clinical comparison study of two planimery methods: conventional versus digital planimetry of optic disc photograph

Background: The optic disc size is an important parameter for the diagnosis of glaucomatous and non-glaucomatous optic nerve damage. The aim of this s tudy was to compare quantitative measurements of the optic disc with the es tablished conventional planimetry and a new digital method using Soft imagi ng system analySIS(TM) for Ophthalmology and to determine the reproducibili ty of this new method. Patients and Methods: Fifty color stereo optic disc photographs of 50 patie nts (mean age 41.7 +/- 13.4 y) were included in the retrospective, comparat ive study. Conventional and digital planimetry was taken from one skilled e xaminer in a masked fashion. According to patient's number measurement valu es obtained with both methods were matched. Digital planimetric measurement s of 10 optic disc photographs were repeated on day 7 and day 14. Statistic al analysis was done using linear regression analysis, reliability coeffici ent and U-test. Results: The planimetric values did not vary significantly between the two methods for optic disc area (3.19 +/- 0.65 mm(2) vs. 3.03 +/- 0.64 mm(2), p = 0.96), for cup area (1.36 +/- 0.62 mm(2) vs. 1.21 +/- 0.63 mm(2), p = 0. 96) or for neuroretinal rim area (1.83 +/- 0.39 vs. 1.82 +/- 0.41 mm(2), p = 0.98). There was also no significant difference of horizontal and vertica l diameter of optic disc and cup as well as the diameter of the superior te mporal and inferior temporal retinal artery and vein at the optic disc bord er between both methods (p < 0.5). Differences between measured values for optic disc, optic cup area and neuroretinal rim area obtained with both met hods were 0.16 +/- 0.10 mm(2) (range -0.05 to 0.24), 0.15 +/- 0.10 mm(2) (r ange -0.12 to 0.26) and 0.014 +/- 0.11 mm(2) (range -0.26 to 0.26). A high correlation of all planimetric values was observed between both methods (r = 0.9, p < 0.0001). Using digital planimetry differences between day 1, day 7 and day 14 were 0.05 +/- 0.03 (range 0.02 to 0.10 mm(2)) for optic disc, 0.05 +/- 0.04 (range 0.0 to 0.13 mm(2)) for optic cup area and 0.05 +/- 0. 05 (range 0.01 to 0.14 mm(2)) for the neuroretinal rim area. The reliabilit y coefficient of digital planimetry was 0.9 for optic disc parameters. Conclusions: The comparable results between both methods and a high reprodu cibility suggest that the digital planimetry could be used either for clini cal routine or scientific evaluation of the optic nerve.