Intraobserver Repeatability and Interobserver Reproducibility of Ellipsoid Zone Measurements in Retinitis Pigmentosa

Abstract

PurposeTo examine repeatability and reproducibility of ellipsoid zone (EZ) width measurements in patients with retinitis pigmentosa (RP) using a longitudinal reflectivity profile (LRP) analysis.MethodsWe examined Bioptigen optical coherence tomography (OCT) scans from 48 subjects with RP or Usher syndrome. Nominal scan lengths were 6, 7, or 10 mm, and the lateral scale of each scan was calculated using axial length measurements. LRPs were generated from OCT line scans, and the peak corresponding to EZ was manually identified using ImageJ. The locations at which the EZ peak disappeared were used to calculate EZ width. Each scan was analyzed twice by each of two observers, who were masked to their previous measurements and those of the other observer.ResultsOn average, horizontal width (HW) was significantly greater than vertical width (VW), and there was high interocular symmetry for both HW and VW. We observed excellent intraobserver repeatability with intraclass correlation coefficients (ICCs) ranging from 0.996 to 0.998 for HW and VW measurements. Interobserver reproducibility was also excellent for both HW (ICC = 0.989; 95% confidence interval [CI] = 0.983–0.995) and VW (ICC = 0.991; 95% CI = 0.985–0.996), with no significant bias observed between observers.ConclusionsEZ width can be measured using LRPs with excellent repeatability and reproducibility. Our observation of greater HW than VW is consistent with previous observations in RP, though the reason for this anisotropy remains unclear.Translational RelevanceWe describe repeatability and reproducibility of a method for measuring EZ width in patients with RP or Usher syndrome. This approach could facilitate measurement of retinal band thickness and/or intensity.

Ellipsoid Zone Thickness in Sporadic Adult-Onset Foveomacular Vitelliform Dystrophy

“…Measurement of photoreceptor damage is important in monitoring the disease progression. Evaluation of the EZ band has been associated with the progression of retinal disorders such as AMD, branch retinal vein occlusion, Stargardt disease, achromatopsia, retinitis pigmentosa, and others [42]. Currently, identi cation and quanti cation of the hyper-re ective EZ band alone is not routinely used for clinical purposes and is usually done manually for research purposes.…”

Relationships Between Serum Antioxidant and Oxidant Statuses and Visual Function in Retinitis Pigmentosa

“…Igarashi et al 37 also demonstrated superior test-retest repeatability with microperimetry (intraclass correlation coefficient [ICC]: 0.81); however, HFA still showed good repeatability (ICC: 0.77) in RP patients. The length of EZ was also frequently analyzed as a structural parameter to reflect the degeneration status of RP 38,39 ; however, our study did not include EZ width data because the resolution of optical coherence tomography images was not sufficiently high to precisely determine the EZ width.…”

Reliability of Spectral-Domain OCT Ellipsoid Zone Area and Shape Measurements in Retinitis Pigmentosa

“…The ΔArea is defined as the absolute difference between the areas of the two polygons. This approach has been used in prior studies of EZ area reliability,9,10,15 and is conceptually similar to the difference in widths used in reliability studies of EZ width measurements from individual b-scans 6,11,12…”

“…We also investigated, for the first time to our knowledge, EZ measurement reliability in terms of shape. Previous studies have focused on the reliability of the EZ area9,10 or EZ width11,12 values, but these quantities are not the raw measurements; instead, they are only summary indicators of extent derived from the EZ boundary measurements. Reducing the boundary measurement to simply the area contained therein discards all morphologic components of measurement variability such as shape and position.…”