Nasal Retinoschisis Associated with Glaucoma

Introduction

Macular retinoschisis has been associated with optic disc pits and colobomas.¹ It has been characterized on ocular coherence tomography (OCT) by the accumulation of fluid at the level of the outer plexiform layer. A defect in the optic nerve head may provide a direct communication between the vitreous and intraretinal space.² Recently, 8 cases of macular schisis in patients with glaucoma have been identified.^3–5 The authors speculate that microholes may have developed in the thin temporal tissue of a glaucomatous optic disc and provided a conduit for vitreous fluid to enter into the retina, similar to the theorized etiology of macular schisis caused by an optic disc pit.⁵ Whereas all reported cases of retinoschisis in patients with glaucoma developed macular schisis alone, we report a case with both nasal and macular schisis.

Case Report

A 75-year-old woman who only had prior ocular care from an optometrist presented to our clinic for a gradual decrease of vision in both eyes. She was not using any ocular medications. Her best-corrected visual acuity was 20/100 in the right eye and 20/70 in the left with mild myopic correction in both eyes. A left afferent pupillary defect was present. On examination of both eyes, intraocular pressures were 19 mm Hg before dilation and 15 mm Hg after dilation. Gonioscopy revealed slightly narrow but not occludable angles and visual significant nuclear sclerotic cataracts were noted in both eyes. Fundus examination of her right eye was remarkable only for advanced thinning of the rim of the optic disc of both the superior and inferior quadrants and a cup-disc ratio of 0.80. A diagnosis of mixed-mechanism glaucoma was given to our patient. Fundus examination of her left eye revealed severe generalized cupping of the optic disc with cup-disc ratio of 0.95 (Fig. 1A) and macular as well as a large nasal area of retinoschisis (Fig. 1B). The nasal retinoschisis extended from the super nasal edge of the disc to the periphery of the retina. There were no areas of vitreous traction, retinal holes, or optic disc pits. Humphrey visual field testing demonstrated a dense superior arcuate scotoma and inferior temporal paracentral field defect in the left eye. Fluorescein angiography did not reveal areas of leakage in either eye. Ocular coherence tomography (Carl Zeiss, Inc. Thornwood, NY, USA) demonstrated an area of macular schisis with an area of schisis superior nasally (Figs. 1C and D).

Figure 1. (A) Color Photograph of the Left Optic Disk Demonstrating Significant Cupping in a Patient with Long Standing Open Angle Glaucoma. (B) Color Photograph of the Left Eye Revealing a Superior Nasal Schisis Cavity (arrow). Optical Coherence Tomography of the Left Eye Demonstrating (C) Macular and (D) Superior Nasal Schisis Cavities.

Discussion

Kahook and associates³ reported two cases of retinoschisis temporal to the optic nerve head in patients with acute elevations in intraocular pressure (IOP) and occludable angles (Table). These authors theorized that small changes in axial length accompanying fluctuations in IOP may have played a role in vitreous traction and the development macular schisis. Hollander and associates⁴ reported a case of macular retinoschisis in a patient with 4 weeks of symptoms secondary to an increase in IOP from angle closure. They hypothesized that a sustained rise in intraocular pressure may have led to severe optic nerve cupping and may have allowed liquid vitreous to enter the retina via the nerve fiber layer. Zumbro and associates⁵ reported 5 patients with macular schisis and glaucomatous optic discs. There was no evidence of acute elevations in IOP or changes in axial length in these patients. All authors did concede that a congenital pit masked by optic nerve cupping is unlikely, but possible.

Table: Demographic and Clinical Characteristics of Published Cases of Retinoschisis Associated with Glaucoma

Because the patient that we describe had retinoschisis nasally and a separate area of macular schisis, the etiology is unlikely to be an occult congenital pit and more likely to be related to glaucomatous changes in the optic nerve head. Congenital pits and detachments are uncommon at the nasal margin of the optic disc.^1,6 On the other hand, glaucoma related thinning and structural defects in the optic nerve head can occur at any location. Optic nerve damage sustained by a mixed-mechanism glaucoma may have predisposed our patient to microscopic holes at the areas of optic nerve head thinning, thereby explaining the location of the schisis cavities. Given that her IOP was normal, the retinoschisis cavities in our patient are likely a direct result of structural defect in the optic disk and not elevations in IOP. Furthermore, the two noncontiguous cavities in our patient suggest the presence of two separate optic nerve head defects. Multiple congenital pits on a single optic disk are extremely rare, whereas glaucoma related structural defects offer a more plausible explanation.^1,6

The presence of multiple schisis cavities and the nasal location supports the glaucoma related “microhole” theory put forth by Hollander⁴ et al. and Zumbro⁵ et al. We encourage clinicians to closely examine the retina for areas of schisis in patients with glaucoma and consider that a new visual defect may not necessarily be progression of glaucoma, but rather a manifestation of retinoschisis.