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C. F. Lanzillo, III, A. Syed, U. Mian; The Classification of High versus Low Partial Posterior Vitreous Detachments and Effects on Retinal Nerve Fiber Layer Thickness as Measured by OCT. Invest. Ophthalmol. Vis. Sci. 2008;49(13):914.
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© ARVO (1962-2015); The Authors (2016-present)
To objectively assess the relative degrees of partial posterior vitreous detachments (pPVD) at the optic disc and the differing effects of each type of detachment on RNFL thickness via OCT.
This is a retrospective study, employing stored OCT scans (Stratus OCT II) of glaucoma suspects at Montefiore Medical Center from 2003-2006. Subjects were culled from an earlier study at the same institution demonstrating elevation of RNFL thickness in these patients as compared to controls. Scans with pPVDs were subjectively assigned to a High or Low group based on appearance, the degree of elevation above the retinal plane, and the concurrence in opinion of three experienced observers. Using the Fast RNFL protocol, RNFL measurements by quadrant were assessed and compared between the two groups as were the relative rates of resolution or complete detachment.
72 eyes from 72 patients were studied, with 36 eyes in the Low pPVD group and 36 eyes in the High group. Our study found that average RNFL thicknesses between the High and Low groups were not statistically different. However, in the inferior quadrant maximum values, the difference in thickness between the two groups approached significance (152.5 µm vs. 162.5 µm respectively, p < .06). Additionally, while there was not a significant difference in the superior quadrant max, the ratio of Imax/Smax between the high and low groups also approached statistical significance (0.96 µm vs. 1.01 µm respectively, p=.06). There was a tendency of the pPVDs in the High group to proceed to complete detachment versus those in the Low group (3 vs. 2), as well as a tendency for Low pPVDs to resolve more often than High pPVDs (3 vs. 1), but these findings were suggestive rather than statistically significant.
While our study confirmed the earlier finding that the presence of a partial PVD elevates RNFL thickness in glaucoma suspects, a statistically significant difference was not found in average RNFL thickness between subjectively classified High and Low pPVDs. Rather, differences approaching significance in the inferior quadrant maximums were found between the two groups. Additionally, Imax/Smax ratios between the two groups approached significance, and there was a relative trend of High pPVDs to detach and Low pPVDs to resolve. With a greater study population, it is likely that these differences would become statistically significant, allowing both better classification of pPVDs in glaucoma suspects and ultimately aiding in the prognosis of pPVDs in patients based on objective classification parameters.
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