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Xiang-Run Huang, Ye Zhou Spector, Jianzhong Qiao; Reduced Temporal Change of Retinal Nerve Fiber Layer Reflectance Speckle in Retinas with Ocular Hypertensive Damage. Invest. Ophthalmol. Vis. Sci. 2019;60(9):5546. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Temporal change of the retinal nerve fiber layer (RNFL) reflectance speckle is associated with axonal activity. This study investigated temporal change of the RNFL reflectance speckle in normal retinas and retinas with ocular hypertensive (OHT) damage.
Normal rat retinas, retinas with OHT damage and contralateral control retinas were used in this study. Isolated retinas were perfused in a warm oxygenated physiologic solution. A series of reflectance images was collected with monochromatic illumination at 660 nm. Areas containing speckled texture were selected on bundles. Reflectance per unit thickness (σ) of the areas was measured. Correlation coefficients (CC) of the areas between a reference and subsequent images were calculated and plotted as a function of the time intervals between images. The CC time course was fitted with an exponential function characterized by a time constant τ, which evaluated temporal change of speckles. τ is associated with axonal activity. Increase of τ indicates reduced axonal activity; τ near to zero suggests no detectable dynamic activity within the RNFL.
RNFL reflectance speckles were high contrast in normal (Fig. A) and contralateral control retinas, while speckles were low contrast in retinas with OHT damage (Fig. B). Typical time courses and their exponential function fitting are shown in Fig. C and D. In the control retinas σ was within the normal range, while τ increased significantly, suggesting reduced axonal activity. In OHT retinas σ was lower than the normal, whereas τ could be within the normal, greater or lower than the normal (Table). The result suggests that OHT reduced RNFL reflectance and impaired axonal activity.
Unilateral OHT treatment results in reduced axonal activity in both treated and contralateral untreated eyes. Measurements of temporal change of RNFL reflectance speckle may offer a non-invasive method for detecting functional abnormality of the RNFL.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
RNFL reflectance speckles. A and B: speckle patterns randomly distribute within bundles; high contrast in normal (A) and low contrast in OHT (B) retinas; C and D: speckles are not stationary, rather change over time. CC time courses of the areas defined on A and B describe temporal change of the speckles. The exponential decay is related to axonal dynamics.
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