Macular Migration toward the Optic Disc after Inner Limiting Membrane Peeling

Yoshikawa and colleagues are to be congratulated for their study on a shortened papillofoveal distance after vitrectomy for diabetic macular edema. ¹ Recent clinical and population-based studies have shown that the choroidal thickness decreases by approximately 32 μm for every millimeter increase in axial length in myopic eyes. ^2,3 It suggests that in high myopia, Bruch's membrane undergoes changes in its length in an amount at least as marked as the sclera does. Otherwise, the distance between sclera and Bruch's membrane (i.e., the choroid) would have enlarged with increasing axial myopia. Consequently, the hypothesis of a “sliding Bruch's membrane theory” was formulated in a recent study on the patho-histology of highly myopic eyes, based on the fact that Bruch's membrane is connected with the sclera only by the spongy choroid, but not by a firm solid inflexible structure. ⁴ If now Yoshikawa and colleagues found a shortening of the distance between the fovea and the optic disc, one may wonder whether this change in position of the fovea was due to a shifting of the retina, including the retinal photoreceptors, on the sheet of the retinal pigment epithelium cells (which appear to be firmly connected to their basal lamina, which is the inner part of Bruch's membrane), or whether the change in the position of the fovea may have been due to a shifting or sliding of Bruch's membrane on the spongy choroid in the direction of the optic disc. If the latter theory is valid, one would postulate that the parapapillary region, in particular the recently defined parapapillary gamma zone, may have decreased in those eyes that experienced a translocation of the fovea in the direction of the optic nerve head. ⁵ A similar finding was recently reported for eyes after a pronounced reduction in intraocular pressure. ⁶ Yoshikawa and colleagues may be asked whether they could observe changes in the position of Bruch's membrane and in choroidal thickness, as well as changes in the appearance of the parapapillary region, parallel to changes in the position of the fovea, in the eyes after peeling of the inner limiting membrane.