April 2007

 

OPHTHALMOLOGY NEWS

 

Corneal bee stings can cause a host of problems


by Matt Young EyeWorld Contributing Editor

 

 

Reported cases debate when to remove the stinger and which antibiotic to use

Day 1: Acute injury with large epithelial defect and hazy cornea.

Two months: Corneal scarring, intumescent cataract, with depigmented iris & posterior synechiae but no epithelial defect. Bee sting is still in-situ within corneal stroma.

Source: Stephen Teoh, M.B.B.S

Corneal bee stings must rank among the rarest dangers to eye health, but when they do occur, surgeons with experience treating them say their complications are extremely sight-threatening. Yet, little guidance can be provided other than general guidelines as to how to treat these patients since cases are so variable, said Stephen Teoh, M.B.B.S., F.R.C.S. Ed(UK), associate consultant, The Eye Institute, Tan Tock Seng Hospital, Singapore.

“The complications range from corneal decompensation, cataract, glaucoma, persistent uveitis to retinal toxicity,” Dr. Teoh said. Nonetheless, EyeWorld took a look at several cases of bee stings to glean helpful tips from those who have treated this rare ocular condition first-hand.

Remove the stinger?

The October 2006 issue of the Journal of The Medical Association of Thailand reported the case of a three-year-old boy attacked by a swarm of bees. Two stingers were found lodged in his right eye. He possessed corneal epithelial defect, corneal edema, secondary bacterial keratitis, heterochromia iridis, and internal ophthalmoplegia.

The stingers were removed with jeweler forceps. The patient was also treated with topical antibiotics and steroids. No optic neuropathy resulted, but he did have a central corneal scar at one month post-op as well as anterior subcapsular cataract. In the study, investigators noted that there is some controversy surrounding the removal of the stinger in such cases.

Some have said, they noted, that stingers should be removed as soon as possible because otherwise patients may keep receiving venom. “However, there is a controversial risk–benefit regarding the removal of a bee stinger,” wrote lead study author Siriwan Chinwattanakul, M.D., Department of Ophthalmology, Siriraj Hospital, Mahidol University, Bangkok, Thailand. “If a decision is made to get rid of it, it must be done neatly and completely. Contrarily, letting it remain may not affect the wound healing. Once the venom is inactivated, the chitinous stinger is believed to be inert and can be retained in situ without any untoward effect.”

In other words, the stinger can be entirely reabsorbed, the researchers pointed out. Nonetheless, in their own case, they said removing the stingers—even five days after the sting—improved the cornea’s reaction in just three days.

Which antibiotic?

Coagulase-negative Staphylococcus aureus appears to be the most common bacteria associated with ocular foreign bodies. Nonetheless, Pseudomonas infection has occurred as well. As a result, the Thai researchers advised choosing a broad-spectrum antibiotic to deal with both gram-positive and gram–negative organisms. Therefore, gentamycin or one of the fluoroquinolones are good choices to deal with these infections. The researchers mentioned that ophthalmologists should be on the lookout for toxic optic neuritis, which can occur 24 hours to two weeks after the actual sting. While the mechanism is not known for this condition, early treatment with pulsed steroids seems to prevent visual loss, they said. Another study, published in a poster by the Indiana University School of Optometry, Bloomington, reviewed eight cases of optic neuritis resulting from bee stings. Researchers, led by Steve Petkovich, O.D., clinical assistant professor, Indiana University School of Medicine, found that seven patients did end up improving to 20/50 or better. The one patient who did not improve was stung directly in the cornea. But the study showed that optic neuritis can also occur in patients that are not stung directly in the eye, but rather in other parts of the face and even the neck.

Lessons learned

The case that Dr. Teoh and his team handled involved a 67-year-old man who developed toxic optic neuropathy and retinal toxicity after he was stung in the cornea. It was published in the August 2005 issue of the Canadian Journal of Ophthalmology. The patient’s severe inflammation was controlled with intensive topical steroids, and he underwent combined phacoemulsification and trabeculectomy with mitomycin C (MMC) for uncontrolled uveitic glaucoma complicated by cataract. But the toxic retinopathy and optic neuropathy did not resolve. From his experience, Dr. Teoh garnered several lessons he wanted to share with colleagues that run into the same rare but dangerous eye condition in the future. First, he said: “Like all conditions, first of all, do no harm. But treatment, when instituted, needs to be swift and aggressive. This is because many of the complications are related to sting venom toxicity, so any form of management should be targeted at minimizing this damage.”

Second, he suggested ophthalmologists be especially cautious when taking out the stinger to reduce the risk of envenomization from the sting. In his own case, removal of the barbed stinger was only partially successful. Third, he said that the corneal bee sting can be sight-threatening. But it also depends on what tissues are penetrated and how deeply. Once the venom has been injected, much of the damage to the tissues is already done. So what causes severe complications then is the toxicity rather than infection, he said.

Editors’ note: Drs. Chinwattanakul, Petkovich, and Teoh have no financial interests related to their studies. Dr. Teoh also has no financial interests related to his comments.

Contact Information

Chinwattanakul: 0-2411-2006, piaja833@yahoo.com

Petkovich:  317-554-0053, steve.petkovich@med.va.gov

Teoh: +65 6357-7726, Stephen_Teoh@ttsh.com.sg

Corneal bee stings can cause a host of problems Corneal bee stings can cause a host of problems
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