Migration of retained tarsal bee stinger onto the ocular surface causing superficial keratopathy

Summary

We report a case of keratopathy due to retained stinger elements following a bee sting and envenomation of the ocular adnexa. A 48-year-old woman presented with a 2-day history of right-sided eye pain, photophobia, and reduced visual acuity. Six days prior to presentation, she had been stung on the right upper eyelid by a bee. Her usual practitioner had removed the stinger and commenced a course of oral antibiotics. Anterior segment examination revealed coarse linear abrasions and superficial punctate keratitis with associated epithelial edema. Eversion of the right upper eyelid revealed the presence of retained stinger lancets near the medial eyelid margin. The retained stinger was removed, and the patient responded well to treatment with topical antibiotics, steroids, and cycloplegia.

Introduction

Bee sting injury of the eye and ocular adnexa is a rare cause of animal-inflicted ophthalmic trauma. Stinger penetration and subsequent envenomation cause an infectious, toxic, and immunological milieu that results in tissue damage. The location and severity of ocular damage as well as the degree of subsequent visual impairment are difficult to predict following envenomation. They may be partially anticipated with identification of the bee genus.1 The ultrastructure of the stinger allows it to embed in the ocular tissues, with a propensity to cause penetrating injuries, making complete removal difficult in some instances.2,3 We report a rare case of periocular bee sting and subsequent migration of the retained stinger through the tarsus, causing superficial keratopathy.

Case Report

A 48-year-old woman presented at Gold Coast University Hospital, Southport, Australia, with a 2-day history of right-sided eye pain, photophobia, and reduced visual acuity. She was otherwise in good general health, taking no regular medications. Six days prior to presentation, she had been stung on the right upper eyelid by a bee. There was reportedly marked periorbital edema, which had improved prior to presentation, after her general practitioner presumably removed the stinger and commenced a course of oral cephalexin.

On examination, there was mild periorbital edema and no external evidence of retained stinger or cellulitis. Visual acuity was 6/18-2 improving to 6/12-1 with pinhole in the right eye and 6/12-1 improving to 6/5-2 with pinhole in the left eye. Intraocular pressure was 13 mm Hg in the right eye and 11 mm Hg in the left eye. The right cornea showed coarse linear abrasions and superficial punctate keratopathy. The corneal stroma was clear, with no stromal infiltrate (Figure 1A–B). The lens was clear, with quiet intraocular media. Posterior segment examination was unremarkable. Eversion of the right upper eyelid revealed a mild tarsal papillary reaction and the presence of a foreign body near the medial eyelid margin (Figure 1C). The lesion was removed with forceps and appeared as retained bee sting apparatus, which was confirmed with light microscopy to be two lancets (Figure 1D–E). Given that the two lancets had remained embedded in the tarsal conjunctiva, primary removal 6 days prior was incomplete, with only the stylet of the stinger removed. The patient was commenced on empiric topical antibiotics, steroids, and cycloplegia. She responded well to treatment. Final visual acuity was 6/6.

Figure 1.

A, Slit lamp photograph of the patient’s right eye showing linear corneal abrasions and epithelial edema. B, Fluorescein staining of the ocular surface. C, Everted upper eyelid showing the exposed tip of the stinger perforating through the tarsus and tarsal conjunctiva (white arrow). D, The retained tarsal stinger elements removed from the eyelid with forceps. E, Light microscopy revealed the foreign body to be two retained lancets from the bee sting.

Discussion

Complications following bee sting to the eye can result from mechanical damage due to stinger penetration as well as immunological or toxic reactions to the envenomated substances.3 These insults may be systemic (eg, anaphylaxis) or localized ocular damage, including keratitis, cataract, intractable glaucoma, anterior uveitis, panuveitis, toxic or infective endophthalmitis, ophthalmoplegia, and optic neuritis.1,3–7 Bee venom is a variable composition of multiple toxins, predominantly enzymatic and nonenzymatic biogenic amines, which are profoundly antigenic because of their high molecular weight.3 These compounds are also responsible for the pain and toxicity following envenomation. The nonenzymatic polypeptide amines cause cell membrane disruption, protein denaturation, hemolysis, platelet activation, and mast-cell degranulation, with an additional neurotransmission blockade due to potassium channel inactivation.1,3,4 This is primarily mediated by polypeptide toxins melittin and apamin. Synergistic enzymatic hydrolysis of structural phospholipids and augmented capillary permeability enhance toxin penetration and local tissue destruction.1,3

Superficial keratopathy caused by migration of retained bee sting through the eyelid is rare, with only 2 reports in the recent literature, to our knowledge.2,8 The stinger is a modified ovipositor (tubular organ for depositing eggs) commonly found in female hymenopteran insects, a large order of insects including bees. It typically consists of a chitinous outer stylet with two barbed inner lancets, which can express approximately 50 μg of venom down the poison canal into the victim. In this report, only the stylet was initially removed, and the two lancets embedded in the patients’ upper lid resulted in mechanical injury to the cornea.

Care should be taken to ensure complete removal of all stinger components, which may be challenging if the lancets are barbed and subsequently liable to fracture with manipulation.2,3 Description of relevant stinger anatomy has been previously described.2 Ophthalmologists should remain vigilant for retained stinger fragments following stings from hymenopteran insects, with a thorough inspection of the ocular structures when patients present with linear superficial keratopathy. Light microscopy is useful in identifying stinger anatomy and ensuring that all components have been completely removed.