Symptomatic and Morphological Differences between Choroidal Excavations

Abstract

The purpose of this report is to describe the morphological and clinical features of two patients with focal choroidal excavation in an attempt to understand more about this rare condition. Spectral-domain optical coherence tomography (SD-OCT), fluorescein angiography, and indocyanine green angiography were used to assess the morphological characteristics of the patients' choroidal excavations. Both patients showed the following features on SD-OCT: (1) the retinal pigment epithelium band and inner/outer segment junction followed the contour of the choroidal excavation, which involved the outer nuclear layers up to the outer limiting membrane; (2) the sclerochoroidal junction was smooth and undisturbed, but large choroidal vessels were present beneath each excavation. The patient with metamorphopsia showed separation between the photoreceptor outer segment and the retinal pigment epithelium as well as disturbance of the inner/outer segment junction on SD-OCT volume scans and hyperfluorescence and hypofluorescence in the foveal region on indocyanine green angiography. Symptomatic and morphological differences between focal choroidal excavations suggested anatomical alterations between the photoreceptor tips and the retinal pigment epithelium or location of choroidal excavation as the cause of metamorphopsia. We speculate that the pathogenesis of focal choroidal excavation involves outward traction on the macula caused by choroidal vascular abnormalities because of embryonic developmental failure of the choroid.