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A very rare sequela to bee or wasp stings is optic neuropathy. Goldstein et al. reported the first bee-associated case in 19601 and we have found only two in connection with wasp stings.
A previously healthy woman of 74 years sustained several paper wasp (Polistes humilis) stings to her left periorbital region while gardening. She did not recall being stung before and had no ophthalmic history. Over the ensuing weeks she developed periorbital pain, a pea-sized nodule by her left lower eyelid and gradual blurring with disturbed colour vision in her left eye. On examination visual acuity was 6/6 right and 6/24 with no improvement on pinhole left; previously an optometrist had recorded acuities as 6/6 in either eye. A left relative afferent pupillary defect (RAPD) was present with reduction in colour vision of the left eye, and a central scotoma was demonstrated on confrontation fields. The anterior segment was white and quiet with normal intraocular pressure, and on dilated fundal examination the optic disc appeared normal. At 1 month follow-up, left visual acuity had improved to 6/12 with a persistent RAPD and no colour vision. A large nodule some 1.5×1.0 cm was now palpable over the inferonasal aspect of the left orbit. Electrophysiological tests revealed abnormal visual evoked potentials with both delay and decreased amplitude, consistent with an inflammatory optic neuritis.
She was reviewed after a further 3 months, at which time left visual acuity was 6/9, with improving colour vision, and the RAPD had resolved. CT of the left orbit revealed a cystic lesion arising from the inner canthal region extending posteriorly in close relation to the medial rectus. Because this mass was causing an ectropion (outturned eyelid) and secondary epiphora, it was excised; the histology was reported as fibroadipose tissue with a giant-cell reaction consistent with a panniculitis. At her last review, 24 months after the initial injury, left visual acuity remained 6/9 with full resolution of symptoms and clinical signs.
The stings of wasps, bees and hornets (Hymenoptera) are painful but usually inconsequential. Ocular complications include retained foreign body, conjunctivitis, corneal oedema or perforation, keratitis, mydriasis, optic nerve swelling and visual loss. Chen et al.2 reported chemosis, corneal oedema, hyphaema and cataract formation in a single case. Our patient developed a constellation of symptoms and signs after her stings consistent with an optic neuropathy. This is a very rare complication;3–5 moreover, no previous report describes simultaneous development of optic neuropathy and an orbital inflammatory granuloma.
With regard to the mechanism of optic nerve damage, allergic, immune and toxic phenomena have been implicated and there is probably an interplay between all three. Hymenoptera venom is known to contain histamine and dopamine, polypeptide toxins and high molecular weight enzymes such as phospholipase and hyaluronidase.6 It also possesses anticholinesterase-like activity.7 Hypersensitivity reactions to stings may be immediate (acute anaphylaxis) or delayed, involving the nervous system including the optic nerve. Song and Wray measured visual evoked potentials soon after an ocular bee sting and proposed an acute and irreversible demyelination of the optic nerve secondary to an allergic response to the venom.4 In our case, however, it was probably a delayed immune-mediated reaction that triggered both the optic neuropathy (distant effect) and development of the orbital mass (local effect at sting site). Indeed, the clinical course was typical of the demyelinating type seen in multiple sclerosis or postviral illness, in which the prognosis is good. The optic nerve pathology is likely to have been retrobulbar, since the optic disc appeared normal. If we had seen the patient earlier, we might have given prednisolone to control the inflammatory response.