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Y. Agoumi, P. H. Artes, M. T. Nicolela, B. C. Chauhan; Spectral Domain Optical Coherence Tomography Measurements of Laminar and Prelaminar Tissue Movement After Intraocular Pressure Elevation. Invest. Ophthalmol. Vis. Sci. 2009;50(13):4898.
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© ARVO (1962-2015); The Authors (2016-present)
To determine the effects of acute intraocular pressure (IOP) elevation on laminar and prelaminar tissue position.
Eleven healthy subjects (mean 36.2; range 13-52 years) had their right optic nerve heads scanned with spectral domain optical coherence tomography (SD-OCT, Spectralis, Heidelberg Engineering) with 24 radial scans in high-resolution mode. Each radial scan consisted of 50 A-scans per location. Baseline IOP was measured with a Tonopen and then measured again with an ophthalmodynamometer with a fixed force perpendicular to globe through the inferior lid. SD-OCT imaging was repeated with the ophthalmodynamometer in place. The software allows image acquisition in the same locations in sequential scans, hence the baseline and post-IOP elevation images were precisely registered. A line joining Bruch’s membrane/retinal pigment epithelium opening was used as reference for baseline and post-IOP elevation for each radial scan. The vertical distance from the reference line to the anterior laminar surface and prelaminar tissue surface at 9 equidistant points was measured for IOP conditions.
The mean baseline IOP was 13.8 (range; 9-19) mm Hg. Mean IOP elevation was 12.7 (range; 9-17) mm Hg, with the elevated IOP ranging 19-36 mm Hg. The overall mean shift in laminar position for the subjects was 0.06 (range; -5.29 to 3.99) microns indicating negligible net movement of the laminar surface with IOP elevation. On the other hand, the prelaminar tissue surface was displaced backwards by a mean of 26.54 (range, 14.67-25.63) microns. There was no relationship between the amount of prelaminar tissue displacement and magnitude of IOP elevation (r = -0.19, P = 0.68) or absolute IOP during elevation (r = 0.05, P = 0.92).
In normal subjects, the lamina appears to be non-compliant to acute IOP changes. Our results suggest that disc surface changes caused by acute IOP elevation are the result of compression of prelaminar tissue as opposed to a backwards displacement of the lamina.
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