Involvement of Inner Choroidal Layer in Choroidal Thinning during Regression of Multiple Evanescent White Dot Syndrome

Abstract

Purpose: To investigate relationships between total thickness and the thickness of inner and outer layers in the choroid during regression in patients with multiple evanescent white dot syndrome (MEWDS).

Methods: This retrospective observational case series included 15 unilaterally affected eyes and 13 unaffected fellow eyes from 15 MEWDS patients (4 men and 11 women; mean age, 37.6 ± 17.6 years). Using enhanced depth imaging optical coherence tomography, whole, inner, and outer choroidal layer thicknesses at the fovea and perifovea were manually measured at the initial visit and at 1 and 3 months after the initial visit. The mean thickness values of the layers were compared at each stage.

Results: With regression of MEWDS, the mean subfoveal whole and inner choroidal layer thicknesses significantly decreased at 1 and 3 months compared to baseline values in MEWDS eyes (P=0.01 and P < 0.0001, respectively), but not in fellow eyes. The outer layer in MEWDS eyes tended to thin. Changes in the inner and outer layers at the perifovea in MEWDS eyes also showed the same trends. Simple linear regression analysis revealed significant positive correlations in choroidal thickness changes between the whole and inner layers (R = 0.53, P=0.04) and between the whole and outer layers (R = 0.91, P < 0.0001) from baseline to 3 months. Multiple linear regression analysis revealed that choroidal thickness changes in the whole layer were significantly correlated with those in the inner (β = 0.51, P < 0.0001) and outer (β = 0.73, P < 0.0001) layers.

Conclusion: The inner choroidal layer significantly thinned with regression of MEWDS, correlating with the thinning of total choroidal thickness. These results suggest that MEWDS lesions in the choroid are likely to lie mainly in the inner layer.

Figure 1

Images of the left eye in a patient with multiple evanescent white dot syndrome (MEWDS). (a) Funduscopic photograph showing multiple subretinal white dots extending from the posterior pole to the midperiphery and foveal granularity at the initial visit. (b) Late-phase indocyanine green angiograpahy (ICGA) showing numerous hypofluorescent spots scattered more broadly than white dots. An arrowhead indicates the closest hypofluorescent spot from the fovea where choroidal thickness was measured, as shown in Figure 1(d). (c) Three months after the initial visit, the white dots spontaneously resolved. (d–f) Horizontal enhanced depth imaging optical coherence tomography images through the fovea. The outer choroidal layer thicknesses (blue lines) were measured from the inner border of the choroid-sclera junction to the innermost points of large choroidal vessels (asterisks) observed in closest proximity to the subfovea and the perifovea (identical with an arrowhead of Figure 1(b)). The inner choroidal layer thicknesses (red lines) were obtained via subtraction of the outer layers (blue lines) from the whole thicknesses (yellow lines). Diffuse loss of the ellipsoid zone at the macular area was observed at the initial visit, with subfoveal and perifoveal lesions (Fig. 1(b); yellow arrowhead) thickness values of 146, 237, and 384 µm and 111, 264, and 375 µm for the inner, outer, and whole layers, respectively (d). One month after the initial visit, the macular ellipsoid zone improved. Thickness values at the subfoveal and perifoveal lesion sites decreased to 133, 225, and 359 µm and 99, 243, and 342 µm in the inner, outer, and whole layers, respectively (e). Three months after the initial visit, thickness values at these lesions further decreased to 122, 207, and 330 µm and 95, 235, and 330 µm in the inner, outer, and whole layers, respectively, with spontaneous complete recovery of the macular ellipsoid zone (f).

Figure 2

Sequential changes in choroidal thickness of the mean whole, inner, and outer layers at the subfovea (a–c) with granular changes and the perifovea (d) with a white dot and/or a hypofluorescent spot observed on ICGA in patients with MEWDS, and correlations in choroidal thickness change from baseline to 3 months between the whole and inner layers (e) and between the whole and inner layers (f) at the subfovea in MEWDS eyes. (a) The mean whole choroidal thickness in MEWDS eyes (n=15, black line) significantly decreased at 1 and 3 months, compared to baseline (Friedman test, P < 0.0001; Scheffe's paired comparison test, P=0.01 and P < 0.0001, respectively). By contrast, there was no significant change in the whole thickness of fellow eyes (n=13, dotted line, Wilcoxon signed-rank test, P=0.08). (b) The mean inner choroidal layer thickness in MEWDS eyes significantly decreased at 1 and 3 months, compared to baseline (Friedman test, P < 0.0001; Scheffe's paired comparison test, P=0.01 and P < 0.0001, respectively). By contrast, there was no significant change in the inner layer thickness of fellow eyes (P=0.64). (c) The mean choroidal outer layer thickness in MEWDS eyes tended to reduce with no statistically significant difference during the 3-month follow-up period (Friedman test, P=0.12). There was no significant change in the outer layer thickness of fellow eyes (P=0.16). (d) Similarly, the mean whole and inner choroidal thicknesses (n=25) in MEWDS eyes significantly decreased at 1 and 3 months, compared to baseline (Friedman test, P < 0.0001 for each; Scheffe's paired comparison test, P < 0.0001 for each and P=0.0002, P < 0.0001, respectively). The outer choroidal layer thickness in MEWDS eyes tended to reduce (Friedman test, P=0.13). (e, f) There were significant positive correlations in baseline-to-3-month thickness changes between the whole and inner layers (Spearman's rank correlation coefficient, R = 0.53, P=0.04) (d) and between the whole and outer layers (R = 0.91, P < 0.0001) (e).