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A.-M. Oliva, D. Richards, W. Saxon; Search for Color-Dependent Nerve-Fiber-Layer Thinning in Glaucoma: A Pilot Study Using Digital Imaging Tehniques. Invest. Ophthalmol. Vis. Sci. 2007;48(13):3309. doi: https://doi.org/.
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Nerve-fiber-layer thinning in glaucoma is known to be detectable subjectively at short wavelengths, especially in the green. This pilot study was designed to develop an objective evaluation of nerve-fiber-layer thinning using short/ long wavelength ratios.
We imaged the fundi of 9 eyes of 9 glaucoma patients having hemifield loss by Zeiss-Humphrey Sita Standard (ZHSS) 24-2 testing (average difference of at least 7 db between upper and lower hemifields). Instrument used was Zeiss-Humphrey FF-450 color camera with Phase One H-5 camera back, yielding 2256x2032 pixels with 8 bits per color. Red, green, and blue components of the images were processed on a Sun Workstation using Interactive Date Language software to permit study of the three possible intensity ratios, short wavelength / long (S/L), pixel-by-pixel. Custom software was written to draw 24 rings about the optic nerve, separated in radius by at least one pixel; blood-vessels were eliminated by a custom sign-sensitive autocorrelation algorithm. Average S/L for each hemifield was plotted versus the linear average of hemifield loss by ZHSS to search for correlation. Similar plots were made between Ocular Coherence Tomography (Zeiss Humphrey Stratus 3000, Software 4.0.1, Fast RNFL Thickness 3.4) and ZHSS. The S/L giving greatest slope versus ZHSS for each patient was selected.
Overall correlation coefficient for S/L vs. ZHSS was 0.448, and for OCT vs. ZHSS was 0.424.
This pilot study suggests that digital color nerve fiber analysis yields comparable results to OCT, in terms of correlation with visual field loss.
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