Quantification of residual ellipsoid zone and its correlation with visual functions in patients with cone-rod dystrophy

Abstract

Cone-rod dystrophy (CORD) is one of the inherited retinal diseases that result in central visual field deterioration and decreased visual acuity (VA). In CORD patients, impaired photoreceptor cells are observed as the disruption of ellipsoid zone (EZ) on optical coherence tomography (OCT) images. In the present study, we calculated the index of residual EZ (rEZ) to quantify the function of photoreceptor cells and investigated the correlation between rEZ index and visual functions. Twenty-six eyes of 13 patients with clinical suspicion of CORD were examined. Visual field was tested with the Humphrey Visual Field Analyzer (HFA 10-2 program). We simultaneously obtained OCT images and calculated the area of decreased EZ intensity (EZa). Using the binarized OCT images, the percentage of the rEZ in a 3 × 3 mm area surrounding the macula was analyzed. To clarify interrator reproducibility, intraclass correlation coefficient (ICC) was calculated. Moreover, we investigated the association between OCT parameters and VA as well as the mean deviation (MD) value measured with HFA. The mean age of the patients was 48.5 ± 16.9 years. The mean central retinal thickness was 122.7 ± 73.2 μm. The mean EZa and rEZ were 22.2 ± 23.6 μm2 and 0.35 ± 0.31, respectively. The ICC of each rEZ index was 0.91 (95% CI: 0.89 < ICC < 0.93). Multivariate analysis indicated rEZ was significantly related to logMAR VA ( p = 0.05) and rEZ and EZa were associated with the MD value ( p = 0.014 and p = 0.009, linear mixed model). Furthermore, rEZ was also associated with photopic a- and b-wave amplitudes ( p = 0.027 and p = 0.0024, respectively, linear mixed model). Taken together, the current results suggested the usefulness of rEZ quantification for predicting visual functions in CORD patients.

Retinal sensitivity and fundus autofluorescence in adult-onset foveomacular vitelliform dystrophy

“…Freund and associates recently reported that BCVA was correlated with the degree of EZ integrity in patients with acquired vitelliform lesions [9]. We have reported a novel method for quantifying residual EZ index in macular diseases, such as CSC or cone-rod dystrophy [10,11]. It would be of interest to further investigate the relationships between the EZ integrity and visual function in AOFVD eyes.…”

Retinal sensitivity and fundus autofluorescence in adult-onset foveomacular vitelliform dystrophy

“…Freund and associates recently reported that BCVA was correlated with the degree of EZ integrity in patients with acquired vitelliform lesions 9 . We have reported a novel method for quantifying residual EZ index in macular diseases, such as CSC or cone-rod dystrophy 10 , 11 . It would be of interest to further investigate the relationships between the EZ integrity and visual function in AOFVD eyes.…”

Peripapillary vessel density in eyes with cone-rod dystrophy

“…CORD patients present with decreased visual acuity (VA), impaired retinal sensitivity and color vision loss and sometimes demonstrate peripheral visual field loss at the end stage, followed by rod photoreceptor impairments [ 4 ]. Several studies have revealed a structure-function relationship in eyes with CORD, such as the correlation between VA and residual EZ and between retinal sensitivity and the abnormal autofluorescent area [ 5 , 6 ].…”