Comparison of digital and film stereo photography of the optic nerve in the evaluation of patients with glaucoma.

The aim of this study was to validate a digital simultaneous stereo photography system against film in the assessment of optic nerve head features in patients with glaucoma. Fifteen digital and 15 corresponding film simultaneous stereo photographs (SSP) of the optic nerve from patients with glaucoma were graded by two glaucoma specialists. Assessed parameters included the vertical and horizontal cup-to-disc ratios (VCD and HCD, respectively), and the image quality score (1 = worse, 5 = best) for each image. Digital and film SSP were presented in random order, two times to each grader. A total of 60 evaluations (30 digital and 30 film) per grader were collected. A Nidek 3-Dx simultaneous stereo disc camera (Gamagori, Japan) was used with both a standard 35-mm-film camera back, and with a 6.1 mega pixel camera (Nikon D1x, Tokyo, Japan) for capture of digital images. All digital images were stored on a computer and reviewed using the Navis Screener software (proprietary software from Nidek). Digital image pairs were evaluated directly on an ADVAN 27-inch Liquid Crystal Display computer monitor (Taipei, Taiwan) with resolution comparable to that of the digital camera, using the screen-vu stereo viewer held at a fixed angle to the monitor. Film image pairs were evaluated using a Pentax stereo slide viewer (Asahi Optical Co., Tokyo, Japan) illuminated by a light box over a neutral density filter to match the luminance between the computer screen and the light box. The mean difference between digital and film was near zero for all three evaluated outcomes (VCD, HCD, and quality score), and there was no significant grader effect for any of the outcomes. Digital images correlated well with film for SSP of the optic nerve in glaucoma.