Quantitative assessment of outer retinal folds on enface optical coherence tomography after vitrectomy for rhegmatogenous retinal detachment

Abstract

We aimed to investigate the possible causes of metamorphopsia for rhegmatogenous retinal detachment (RRD) based on findings of enface optical coherence tomography (OCT). The study was a retrospective, consecutive case series of 33 eyes with macula-off RRD. Metamorphopsia was measured by M-CHARTS and enface OCT images covering a macular area of 6 × 6 mm square obtained at 1, 3, and 6 months postoperatively. Within the outer retinal slabs of enface OCT, multiple lines that looked like folds were delineated in all eyes at month 1, and we succeeded in extracting images of folds by subtracting retinal vessels. We calculated their density by an image-processing technique. The mean M-CHARTS scores were 0.62 ± 0.47 at month 1 and 0.30 ± 0.29 at month 6 (P < 0.001). The fold density was 8.3 ± 4.2 at month 1 and 6.1 ± 3.1 at month 6 (P = 0.0044). The M-CHARTS scores at 6 months were significantly associated with the fold density at 1 month (r = 0.515, P = 0.002). In conclusion, enface OCT visualized the outer retinal folds in eyes that had undergone successful RRD surgery, and a larger number of folds was related to the remaining metamorphopsia.

Figure 1

Findings for a 53-year-old man with rhegmatogenous retinal detachment repair. Color fundus camera before surgery showed a corrugated fundus appearance (A), and B-scan OCT showed undulation of the outer retina (B).

Figure 2

Finding for the same patient as shown in Fig. 1 with rhegmatogenous retinal detachment repair. Enface OCT of the outer retinal slab at 1 month showed several folds with dull hyporeflective lines (A). Corresponding lesions on B-scan OCT at 1 month after vitrectomy showed disrupted outer retinal bands (B). A binary image of enface OCT (C) showed extracted folds. The density of folds was 19.72 respectively. Folds on enface OCT became unclear at 6 months postoperatively (D). In the B scan OCT images at 6 months, disruption of the outer retinal bands was less apparent than at 1 month (E). The density of folds in the binary images of enface OCT decreased to 11.73 respectively (F).

Figure 3

Findings for the right eye of a 58-year-old man with rhegmatogenous retinal detachment repair. Enface OCT of the outer retinal slab at 1 month postoperatively showed several folds with sharp outlines (A). The corresponding region on cross-sectional OCT showed elevated outer retinal bands (B). Binary images of enface OCT showed folds. The density of folds was 15.71 respectively (C). At 6 months, the folds in the enface OCT images were indistinct (D), and the elevation of the outer retinal bands on B-scan OCT regressed with less reflectivity (E). The total number and density of folds in the binary images of enface OCT at 6 months decreased to 7.09 respectively (F).

Figure 4

Time course of density of folds (A) and number of folds (B) on enface OCT at 1, 3, and 6 months after vitrectomy for macula-off rhegmatogenous retinal detachment repair. Vertical bars represent mean ± standard error. ^*P < 0.05, ^†P < 0.01.

Figure 5

Method of enface OCT Image analysis of macula-off rhegmatogenous retinal detachment. Enface OCT of the outer retinal slab (A) and OCT angiography of the superficial retinal slab (B) were converted to binary images by the adaptive thresholding method. The binarized enface OCT image of the outer retinal slab showed fold-like changes, and an artifact of the blood vessels (C) and the binarized enface OCTA image of the superficial retinal slab showed blood vessels (D). The image of binarized enface OCT minus the image of binarized OCTA yielded an image that shows only the fold-like changes (E). Each fold was identified by its contours, and a bounding rectangle was drawn circumscribing each fold. The length of the long side of the rectangle was defined as the length of the fold, and that of the short side was defined the width (F). The gradient of the fold was defined as the slope of the diagonal of a rectangle (G).