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Matin Khoshnevis, Ashwin Sampathkumar, Giancarlo A Garcia, J Sebag; Optical Sensing of Molecular Structure in Vitreous of Patients with Decreased Contrast Sensitivity. Invest. Ophthalmol. Vis. Sci. 2016;57(12):3198. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Patients complaining of floaters have decreased contrast sensitivity [CS; Sebag et al. Retina 34:1062-68, 2014], but the molecular basis of this phenomenon is poorly understood. This quantitative study of light scattering by vitreous removed from patients with clinically significant floaters sought correlations between CS and the molecular organization of vitreous, in particular the degree of polymerization of vitreous collagen and the average particle sizes scattering light.
CS was measured by Freiburg Acuity Contrast Testing (%W). Undiluted vitreous from 11 patients with clinically significant floaters was procured during vitrectomy. Light scattering measurements were performed within 4 hours of sample procurement using a customized light scattering system. The output of a 150-W tungsten halogen broadband light source was collimated to a spot of 10 mm and directed into an integrating sphere with a cuvette containing the vitreous sample. Single-strand optical fibers with 0.22 numerical aperture and 1-mm core were used to couple the light from the integrating sphere to a spectrometer that detect swavelengths from 400-1000 nm with a spectral resolution of 0.8 nm, a 50mm slit, and a signal-to-noise ratio of 300:1. Off-axis light scattering was measured with an exposure of 10ms and a boxcar average of 40. The predominant peak between 400-480nm (collagen range) was identified as an index of polymerization, and the full width half maximum (FWHM) of this peak assessed the average particle/scatter size. Results were correlated with CS using Spearman R.
All specimens exhibited a prominent light scattering peak between 455-475 nm, indicative of collagen. CS was correlated with collagen-specific wavelengths, with worse CS (higher %W) associated with increased collagen polymerization (lower predominant wavelength; Spearman R = -0.673, p=0.033). Correlation was also observed between CS and FWHM, suggesting that as scatter size increases, CS decreases (Spearman R = -0.709, p=0.022).
Increased vitreous collagen polymerization and increased scatter sizes are each correlated with decreased contrast sensitivity in patients with floaters. These results may provide a molecular explanation for the observed degradation of CS in patients with floaters. The results also suggest utility in optically characterizing vitreous molecular structures in this and other vitreo-retinal disorders.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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