The interesting article by Wang et al (1) seeks to explain the mechanism of bitemporal hemianopia due to chiasmal compression. Our case is a reminder that bitemporal hemianopia may be secondary to refractive optical effects and mechanical effects on the optic chiasm. A 68-year-old woman with an 18-month history of a generalized headache was noted to have a bitemporal visual field defect by her optometrist and was referred urgently to the Ophthalmology Department. Her visual acuities were 20/30 in each eye when corrected for myopia and astigmatism (right eye: −6.25+2.00 × 77; left eye: −5.75+1.50 × 97). Intraocular pressures were normal in each eye. Ophthalmoscopy showed tilted optic discs with peripapillary atrophy but healthy neuroretinal rims and pale nasal retinas bilaterally (Fig. 1). Automated visual field testing (24-2) with the patient's reading prescription (right eye: −3.00+1.75 × 76 left eye: −2.50+1.50 × 95) confirmed a bitemporal visual field defect (Fig. 2A). However, confrontation visual fields were full. Brain magnetic resonance imaging revealed no abnormalities along the visual pathways but did demonstrate “ovoid” globes (Fig. 3). Optical coherence tomography and B-scan ultrasonography confirmed nasal staphylomata in both eyes and showed the eyes to be longer from front to back nasally (29.06 mm, right eye, and 31.40 mm, left eye) than temporally (27.74 mm, right eye, and 29.04 mm, left eye) The diagnosis of refractive bitemporal visual field defects due to staphylomata was confirmed by repeating the examination with the patient wearing her distance refraction, which abolished the field defects (Fig. 2B).FIG. 1: Both optic discs are tilted with less pigmentation of the nasal retina bilaterally.FIG. 2: Automated visual fields. A. Bitemporal field loss is present with the patient wearing her reading prescription. B. Visual fields are full with the patient wearing her distance prescription.FIG. 3: T2 axial magnetic resonance imaging reveals ovoid globes nasally.A posterior staphyloma is a protrusion of the posterior wall of the eye (2), commonly associated with high myopia (3), and is known to give rise to visual field defects (4,5). One possible explanation is that nerve fibres are under mechanical tension in the area of the staphyloma which reduces axonal flow impairing optic nerve function (5). An alternate explanation is that the field defects are due to a differing refractive error in the location of the staphyloma caused by increased axial length (6). Our findings support the latter possibility; we repeated visual field testing with a higher power of the correcting lens, compensating for the staphylomatous refractive error. Light previously defocussed over the staphyloma was now in focus and therefore perceived by the patient (Fig. 4).FIG. 4: A. The black line indicates an emmetropic eye, where parallel light is focused onto the retina. The dashed line indicates a myopic eye, where light is focused anterior to the retina. B. In a myopic eye, with use of a concave lens, parallel light is focused onto the retina. In a patient with no staphyloma, the curvature of the eye is spherical. Light falling onto all parts of the retina will be focused through the concave lens. C. In a patient with staphyloma, light is focused on the macula (solid line) but with increased axial length in the staphylomatous segment, light is not focused on the retina (dashed line) causing blurred vision in the corresponding visual field. P, principal plane of the eye. Modified from Elkington AR, Frank HJ, Greaney MJ (6).Although a rare cause, bilateral nasal staphylomata should be included in the differential diagnosis of bitemporal hemianopia. Unnecessary imaging to rule out compressive lesions of the optic chiasm could have been avoided by retesting fields with a different refractive correction. Clues to diagnosis were bilateral nasal retinal pallor, visual field defects crossing the vertical midline, and the presence of full fields to confrontation. ACKNOWLEDGMENTS The authors thank Dr Raveesh Hanasoge, MD, DNB, FRCR, for help with MRI images.