Macular retinoschisis in highly myopic eyes

To describe the characteristics and evolution of macular retinoschisis in high myopia observed by optical coherence tomography (OCT).

A consecutive, retrospective, observational case series.

Twenty-one highly myopic eyes (mean refractive error, -15.2, range -6 to -25) of 17 patients presenting with the unusual feature of macular thickening without a macular hole and associated with a posterior staphyloma were examined by biomicroscopy and OCT. Ten patients (13 eyes) were followed up for 12 months or more.

On biomicroscopy, the macula of all 21 eyes had a microcystic appearance without macular hole. In all eyes, OCT showed that retinal thickening was mainly due to an extensive hyporeflective space splitting the neuroretina into a thick inner layer and a thin outer layer. We called this condition outer retinoschisis. In six cases, inner splitting, termed inner retinoschisis, was also present. The macular profile exhibited a foveal cyst in 10 eyes, a lamellar hole in six, and a foveal detachment in six. In four of the 21 eyes, a hyperreflective preretinal structure resembling the posterior hyaloid was stretched over the retinoschisis, causing foveal traction. Two of these four eyes subsequently evolved into a full-thickness macular hole.

Macular retinoschisis is not uncommon in highly myopic eyes with staphyloma and is better characterized by OCT than by biomicroscopy. Intraretinal splitting occurs in both the outer and inner layers of the retina, leading to the formation of cystoid spaces. In most cases, the condition is fairly stable in terms of visual acuity and retinal thickness and change occurs slowly over time. However, a macular hole may occur when the retinoschisis is associated with tangential traction of the posterior hyaloid.