Characteristics of secondary epiretinal membrane due to peripheral break

Abstract

This study aimed to investigate morphological differences between idiopathic epiretinal membrane (ERM) and secondary ERM due to peripheral break (SEPB) and to identify clinical characteristics in eyes with SEPB to facilitate peripheral retinal examination. The retrospective cross-sectional study involved 93 consecutive eyes in 91 patients who underwent ERM removal surgery. Eyes were divided into two groups: the macular pucker group and the idiopathic ERM group. En-face Optical Coherence Tomography (OCT) images, fundus photographs, severity of metamorphopsia (M-score) and clinical characteristics of each group were compared. ERM extent and eccentricity (ratio of the shortest and longest distances from the foveal center to the boundary) were obtained through en-face OCT imaging. Fundus photographs were used to judge whether the membrane was turbid or not. Patients with SEPB were younger than patients with idiopathic ERM (61.3 ± 7.5 vs. 66.6 ± 8.3 years; p < 0.05). Preoperative M-score and myopic refractive error, axial length were also significantly higher in the macular pucker group than in the idiopathic ERM group (all p < 0.05). There was no difference in ERM extent between the two groups. The incidence of ERM eccentricity was 23 of the 34 eyes (67.6%) in the SEPB group and 26 of the 59 eyes (44.1%) in the idiopathic ERM group (p < 0.05). The incidence of turbid ERM was 18 of the 34 eyes (52.9%) in the SEPB group and 10 of the 59 eyes (16.9%) in the idiopathic ERM group (p < 0.01). The SEPB group, compared with the idiopathic ERM group, tended to have eccentric, turbid ERM at a younger age and with more severe metamorphopsia and myopic refractive error.

Figure 1

Measurement of epiretinal membrane extent and eccentricity in an en-face OCT image. Epiretinal membrane extent was defined as the area of homogenous grayish discoloration with irregular boundaries that is distinguishable from the surrounding retinal tissue on en-face OCT imaging. ERM eccentricity was measured by calculating the ratio between the longest straight distance (R1) and the shortest straight distance (R2) from the foveal center to the outer boundary of the ERM. When the ratio was equal to one (R1/R2 = 1) then the ERM was considered concentric (A; extent = 19mm², R1/R2 = 1.6). If the ratio exceeded the median of the entire group (median = 3.2), then the ERM was considered eccentric (B; extent = 12.3 mm², R1/R2 = 4.1).

Figure 2

Representative cases from macular pucker (A) and idiopathic ERM (B) groups. A patient of macular pucker group (A) with a history of barrier laser in the past due to a retinal break showed turbidity on fundus photography and eccentricity on the en-face OCT image. R1/R2 ratio was 6.7 and ERM extent was 12.8 mm². A patient of idiopathic ERM with no remarkable history showed a clear ERM on fundus photography. However, an ERM was confirmed in the OCT and a concentric appearance was seen on the en-face OCT image. R1/R2 ratio was 1.9 and ERM extent was 1.8 mm².