Bow-Tie Cupping: A New Sign of Chiasmal Compression

The classic ophthalmoscopic¹ and histologic² pattern of band or bow-tie atrophy in retrograde degeneration of decussating axonal ganglion fibers is well recognized now. Herein, we describe a further sign of chiasmal compression, which may be called bow-tie cupping or horizontal band cupping.

A 12-year-old boy with a longstanding suprasellar craniopharyngioma compressing the optic chiasm and right optic nerve was examined. Despite debulking surgery, radiotherapy, and repeated aspirations of the cystic component, his vision had deteriorated further. The right eye showed no light perception and a right relative afferent pupillary defect. The left eye had a visual acuity of −0.16 logMAR (about 20/14) for distance and N4.5 for near. He correctly identified 16 of 17 Ishihara color plates. Goldmann kinetic perimetry of the left eye confirmed a dense temporal hemianopia.

On fundus examination, the left optic disc head showed segmental bow-tie atrophy nasally and temporally, accompanied by an abnormally high horizontal cup-disc ratio of 0.8 (vertical cup-disc ratio = 0.5) (Figure, A). The nasal rim was particularly thinned and showed complete loss of the nerve fiber layer. In contrast, the superior and inferior disc rim segments appeared comparably thick and pink with clearly visible superior and inferior nerve fiber layers and striations. Likewise, the right optic disc showed an increased horizontal cup-disc ratio of 0.8, although the vertical cup-disc ratio was also increased (0.65), giving rise to a more concentric cup compared with the horizontal oval cup of the left eye (Figure, B). As in the left eye, the right optic rim was thinnest nasally. His intraocular pressures have never been elevated on repeated measurements during more than 2 years, ranging between 13 and 17 mm Hg on Pulsair tonometry (Keeler Ltd, Windsor, England) and 10 mm Hg on Goldmann applanation tonometry in each eye.

In fewer than 10% of patients, compressive lesions of the anterior visual pathway result in nonglaucomatous pathological cupping.^3-5 This case illustrates bow-tie or horizontal band cupping with pathological nasal and temporal cupping in addition to band atrophy due to compression of the decussating nasal axonal fibers of the chiasm. As the temporal retinal ganglion fibers do not decussate into the chiasm, they are therefore relatively spared by chiasmal compression, accounting for the relative preservation of the vertical optic disc poles and nerve fiber layer segments and the preservation of the remaining left nasal visual hemifield.^1,2,6 Compared with the purely horizontal cupping and segmental bow-tie atrophy seen in the left eye, the generalized optic disc pallor, the rounder cup, and the loss of all discernible nerve fiber striations in the right eye reflect the additional loss of the temporal ganglion fibers in the right eye as a result of right optic nerve compression, being superimposed on the effect of the pure chiasmal compression seen in the left eye.

In summary, we describe a further sign of chiasmal compressive disease and expand the phenomenon of bow-tie atrophy and nonglaucomatous optic disc cupping seen in conditions with retrograde degeneration of decussating axonal ganglion fibers.

Correspondence: Dr Hildebrand, Department of Paediatric Ophthalmology, Bristol Eye Hospital, University Hospitals Bristol NHS Foundation Trust, Lower Maudlin Street, Bristol BS1 2LX, England (dariushildebrand@yahoo.co.uk).

Financial Disclosure: None reported.