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JE Morgan, NJ L Sheen, R Goyal, JM Wild, RV North; Assessment of Digital Stereoscopic Optic Disc Images Using a Z Screen . Invest. Ophthalmol. Vis. Sci. 2002;43(13):1015.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To determine the ability of digital stereoscopic optic disc analysis to identify glaucomatous optic nerve damage in eyes with early visual field loss. Methods: Simultaneous (Nidek 3Dx) and sequential (Nikon NF505) optic disc images of 56 glaucoma and 60 normal subjects of similar age were obtained. Glaucomatous field loss was categorised using a grading system modified from Hodapp et al (1993) of two consecutive Humphrey 24-2 SITA Standard fields. Optic disc appearance and intraocular pressure were not used in the diagnosis. The sequential and simultaneous optic disc images were digitised at high resolution and viewed stereoscopically using a Monitor Z screen (Stereographics Corp). Three residents in training, who were masked to the diagnosis, subjectively graded disc images as normal or glaucomatous. The residents then outlined the optic disc and cup borders using a cursor whose depth could be adjusted to match that of the scleral rim. The scaling factors for each image were determined for the calculation of neuro-retinal rim area (at 30° intervals) and total disc areas. Results: The visual field indices for the glaucoma group were MD -4.46 dB, PSD 5.28. Best subjective grading gave a sensitivity of 80.3%, and a specificity of 93.3% for the discrimination of glaucomatous optic discs. When account was taken of the optic disc area, by linear regression analysis of optic disc area and log transformed neuroretinal rim area (in 30° segments), glaucomatous optic discs could be detected with a sensitivity of 82.3% and specificity of 93.3%. Conclusion: Digital stereoscopic viewing systems, in conjunction with simultaneous stereoscopic optic disc photography, enable the discrimination of glaucomatous optic neuropathy with clinically useful sensitivity and specificity.
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