Effect of Partial Posterior Vitreous Detachment on Retinal Nerve Fiber Layer Thickness as Measured by Optical Coherence Tomography (OCT)

Abstract

Purpose:: To evaluate the effect of partially attached posterior vitreous detachments (pPVD) at the optic disc on retinal nerve fiber layer (RNFL) thickness, as measured by OCT.

Methods:: A retrospective study was conducted using stored OCT (Stratus III) scans of glaucoma suspect patients from 2003-2006 at Montefiore Medical Center. All scans were evaluated for vitreous attachments at the disc and were divided into control and pPVD groups. RNFL thickness was compared using the Fast RNFL protocol. Patients were defined as glaucoma suspects based on clinical findings of either elevated intraocular pressure and/or glaucomatous-appearing optic discs, with normal Humphrey visual fields.

Results:: A total of 114 eyes from 114 patients were included; 60 were in the pPVD group and 54 were controls. A prevalence rate of pPVD was found to be 39.5%. Mean RNFL thickness of eyes with pPVD was significantly increased over controls, 101.6 µm vs 95.0 µm, respectively (p<0.001). Average RNFL thickness of each quadrant was greater in the pPVD group than in the control group, with statistically significant differences only in the superior and inferior quadrants (p<0.001; p=0.001). Normotensive glaucoma suspects based on optic nerve appearance or assymmetry were also analyzed as a separate subset, with 34 patients from the pPVD group and 30 from the control group. Mean and quadrant RNFL thicknesses were greater in the pPVD group. Statistically significant differences were seen in mean RNFL thickness (p<0.001) and in average superior and inferior quadrant thicknesses (p<0.001; p=0.004).

Conclusions:: More than one-third of this population of glaucoma suspects had a partial PVD, indicating that this is a common phenomenon. The results further suggest that RNFL thickness measurements are greater in patients with partial PVD than in controls. This may indicate a limitation of using RNFL thickness as a criterion for evaluating glaucomatous damage in patients with partial PVD.

Keywords: nerve fiber layer • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • vitreous