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H. Primack, Z. Burgansky-Eliash, D. A. Nelson, M. Neudorfer, O. Pupko, A. Grinvald; Non-Invasive Imaging of Optic Nerve Head as an Indication of Retinal Pathology. Invest. Ophthalmol. Vis. Sci. 2008;49(13):2002.
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© ARVO (1962-2015); The Authors (2016-present)
The Retinal Function Imager (RFI, Optical Imaging, Rehovot, Israel), is a fundus camera modified to deliver a fast train of flashes and process the resulting images. Recently, a novel illumination-dependent enhanced darkening signal of the optic nerve head (ONH) was observed using the RFI. We evaluated this signal quantitatively, and compared it between glaucoma and non-glaucoma subjects.
The RFI illumination consisted of train of 8 strong stroboscopic flashes (< 1 msec), 17.5 ms apart. The broadband emitted light (xenon bulb) was filtered with a 548bp75 filter. Seventeen eyes of 14 glaucoma patients, 15 eyes of 9 patients with age related macular degeneration (AMD), 8 eyes of 7 patients with diabetic retinopathy (DR), and 22 eyes of 13 healthy volunteers were recruited. All subjects had a detailed ophthalmic examination and RFI imaging of the ONH after pupil dilation. All glaucoma and healthy subjects had also a visual field test; glaucoma diagnosis was established by visual field criteria.
The first image in each train does not include any response to the retinal photic illumination, because the flash duration is shorter than 1 msec. Therefore, ratio comparisons (image #2 / image #1) reveal differences due to relative darkening of the ONH in response to the retinal photic illumination. Stronger darkening was observed in glaucoma patients compared to healthy, DR and AMD subjects. The largest quantified ONH darkening values for glaucoma patients were about 4 fold larger than the typical values observed for other subjects.
We found a new darkening signal of the ONH in response to illumination. This signal varies substantially in relation to the glaucomatous state of respective subjects' eyes.
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