Abstract
Purpose :
Historically, disease progression in patients with an inherited retinal dystrophy is monitored using standard automated perimetry (SAP) and electrophysiology. With ocular coherence tomography (OCT) we have access to objective quantitative structural information, which has promise in monitoring degenerative retinal changes characteristic of dystrophies such as retinitis pigmentosa (RP). This retrospective, observational clinical study aims to evaluate the correlation between a measurement of the ellipsoid zone (EZ) band derived from OCT scans and visual field (VF) characteristics in a cohort of RP patients.
Methods :
Nineteen participants diagnosed with RP were identified. Nine participants were excluded due to unavailable data. A further seven eyes from four participants were excluded as foveal pit unidentifiable. An IR+OCT 30* ART scan for each eye was analysed using Heidelberg Eye Explorer v. 1.8.6.0. The plane containing the foveal pit was identified, and the point at which the EZ band, defined as the second hyper-reflective band, disappeared was identified. The distance (um), temporally and nasally from the foveal pit, was measured using the calliper tool. The extent of preserved VF, represented on Zeiss Humphrey Field Analyser 3 plots, defined as <10dB total deviation from the age-matched normal database, was recorded both temporally and nasally from the fovea.
Results :
Thirteen eyes from seven participants (4 male 3 female, mean age 52 years, range 28-71 years) were analysed using descriptive statistics. The mean distance from the fovea at which the EZ band terminated was 473μm (SD=519μm) temporally and 445μm (SD=566μm) nasally. The mean VF preserved was 2 degrees (SD= 2) from the fovea both temporally and nasally. There is a moderate correlation between the length of the EZ band and the degrees VF preserved (Spearman’s Coefficient (ρ) 0.42 P=0.01 temporally, and (ρ) 0.54 P=0.01 nasally).
Conclusions :
The measurement of the EZ band length appears to demonstrate a reliable indicator of VF size in patients with RP, and utilises objective clinical data, potentially negating the need to perform VF analysis. The large spread in data is due to wide age range and disease duration. Further research is needed on a larger sample to determine whether the disappearance of the EZ band is a reliable predictor for VF loss across a broad spectrum of disease and whether change over time correlates with loss of VF and indeed functionality.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.