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Kirsten G Locke, Kelly I Locke-Reddin, Donald Charles Hood, David G Birch; Inner Retinal Thickness in Late Stage Retinitis Pigmentosa. Invest. Ophthalmol. Vis. Sci. 2016;57(12):143.
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© ARVO (1962-2015); The Authors (2016-present)
With emerging new technologies for vision restoration, such as epiretinal implants and optogenetic approaches, the integrity of the inner retinal [retinal nerve fiber layer (RNFL), ganglion cell (GC) and inner plexiform (IP)] layers in patients with retinitis pigmentosa (RP) is critical. Here we use SDOCT to assess GCIPL (GC and IP layers combined) in patients with RP where the ellipsoid zone (EZ) has disappeared and visual acuity is down to 20/400 (logMAR 1.3) or worse.
OCT 9x9 mm volume scans (Spectralis, Heidelberg, Germany) consisting of 31 B-scans were collected from a single eye in 25 patients (mean age: 48.6 ±15.7 yrs) with late stage RP. Using manual correction of the segmentation lines within the Spectralis software, the total retina (TR), RNFL and GCIPL mean thicknesses were measured over the 9 ETDRS macula grid locations. All measurements were compared to 25 age-similar normal subjects (mean age: 45.4 ±19.5 yrs).
The mean TR thickness was 229.7 ±20.3 microns (norm: 303.0 ±13.1 microns; p<0.0001). All but one patient was below the normal 95% range (277-329 microns). The mean RNFL was 45.3 ±7.6 microns (norm: 28.6 ±3.0 microns; p<0.0001). All patients but one were above the normal 95% range (23-34 microns). The mean thickness of the GCIPL in patients was 68.2 ±10.1 microns, comparable to normal (70.6 ±7.5 microns; p=0.26). Four patients were outside the normal 95% range (56-85 microns); two thinner and two thicker than normal.
The majority of patients with late-stage RP had reduced TR due to loss of the outer retinal layers. As reported previously (Hood et al., IOVS, 2009), most patients had thickened RNFL. The mechanism of the RNFL thickening is unknown at this time and may or may not pose a challenge for vision restoration. GCIPL for most patients remained within normal limits in the central macula regardless of visual acuity. Patients with preserved GCIPL may be suitable candidates for vision restoration targeting the inner retina.
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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