Choroidal thickness measured with swept source optical coherence tomography before and after vitrectomy with internal limiting membrane peeling for idiopathic epiretinal membranes.

Purpose: In eyes with epiretinal membranes (ERMs), retinal arteries become dilated and tortuous. This may correlate with the hemodynamics of the affected areas and possibly with choroidal thickness. The aim of this study was to estimate choroidal thickness before and after vitrectomy for idiopathic ERM in the operated eye and in the unaffected fellow eye.

Methods: A prospective study of 21 patients with idiopathic ERMs. We obtained swept source optical coherence tomography images that simultaneously evaluated the vitreous, retina, and choroid. We performed choroidal thickness measurements before pars plana vitrectomy with ERM removal and internal limiting membrane peeling. We took subsequent images 10 days and then 3 months after surgery. We compared the images with patients' fellow eyes. In each eye, we performed 256 horizontal scans, 12 mm in length and centered on the fovea. We manually calculated choroidal thickness from the posterior edge of the retinal pigment epithelium to the choroidoscleral boundary with the built-in caliper and additionally measured it automatically using DRI-OCT mapping software. We evaluated the outer choroidoscleral boundary and performed statistical analysis.

Results: We observed an ERM in 50% of fellow eyes. Mean choroidal thickness did not differ between study and fellow eyes (P = 0.67). Choroidal thickness decreased from 200 μm to 173 μm (P = 0.034) 3 months after vitrectomy and internal limiting membrane peeling. In all but two cases, the outer choroidoscleral boundary was irregular. Additionally, we observed that the suprachoroidal layer consists of two bands in four cases, an inner hyperreflective band and an outer hyporeflective one. We speculate the latter correlates with the suprachoroidal space.

Conclusion: Normalization of choroidal thickness after surgery suggests that there is some relationship between choroidal thickness and structure and the presence of idiopathic ERMs.