August 03, 2020
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Early management of snake venom ophthalmia leads to fast recovery

Melanin pigmentation may be a triggering factor for early pupil involvement.

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Venom ophthalmia is a rare ocular condition caused by exposure of the eye to venom of a spitting cobra.

It is the nature of the cobra to spit venom at predators or prey, and humans are accidentally affected. These cases are more common in the African subcontinent as it is home to a wide species of this snake.

Amar Agarwal
Amar Agarwal

Corneal and ocular surface damage is predominant after exposure to snake spitting. Prompt diagnosis and immediate medical management prevent permanent vision loss due to corneal opacity in such cases. Emergency service ophthalmologists and residents should be well equipped in managing venom ophthalmia. We report a case of acute onset corneal edema and mydriasis following snake venom spit showing recovery with conservative management.

diffuse severe corneal edema with Descemet’s membrane folds
Figure 1. Clinical picture of the patient with diffuse severe corneal edema with Descemet’s membrane folds with pupil dilated. Note the orange glow through the dilated pupil (a). Two weeks after treatment, showing clear cornea and a normal pupil (b).

Source: Amelia Buque, MD, Shana Sood, MBBS, DNB, Dhivya Ashok Kumar, MD, FRCS, FAICO, FICO, and Amar Agarwal, MS, FRCS, FRCOphth

Case history

A 65-year-old male patient presented to us with pain, watering and decreased vision immediately after experiencing snake spit in his left eye. On examination, uncorrected visual acuity in the left eye was 20/800 and did not improve with pinhole. Slit lamp examination revealed conjunctival congestion, chemosis and diffuse corneal stromal edema with Descemet’s membrane folds (Figure 1a). The pupil was mydriatic with a limited view of the fundus but with red glow present. A single drop of topical proparacaine 0.5% was instilled, and the conjunctival sac was washed with copious amount of normal saline. The patient was advised to use 1% hydroxypropyl methylcellulose twice hourly and 0.5% moxifloxacin four times a day, with follow-up on days 1, 7 and 14. At the last follow-up, the cornea was clear and Descemet’s membrane folds resolved (Figure 1b) with uncorrected visual acuity of 20/20. The pupil also regained its normal size and reaction on day 14 without any additional medication.

Venom ophthalmia

Venom ophthalmia is an ocular condition caused by exposure of the eye to venom of the spitting cobra. Snakes of these species have characteristic fangs with anteriorly faced openings (Figure 2), which allow a spray of venom up to a distance of 2 m as a defense mechanism. Although spitting is the primary route of venom transfer, these snakes can also directly transfer venom via bite.

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Schematic diagram
Figure 2. Schematic diagram of snake spitting with fangs.

Patients of venom ophthalmia usually present with photophobia, watering, pain and blurred vision. These symptoms are attributed to epithelial breakdown and corneal edema induced by the cytotoxic properties of the venom. In a study performed on rabbit eyes, high-resolution OCT images showed disorganization of corneal lamellae after exposure to venom. In a comparison between pigmented and albino rabbits, pupils of pigmented rabbits showed earlier onset in mydriasis that lasted longer, which was attributed to differential corneal penetration through the stroma of pigmented rabbits vs. albino rabbits. Our patient was dark skinned with brown irides, and he presented with early mydriasis that lasted for a short period. The melanin pigmentation may be the triggering factor for early pupil involvement, as noted in animal studies. Management included copious irrigation to wash out the venom, lubricants and prophylactic antibiotics. It is important to counsel such patients about the risks associated with traditional medications such as lime juice and potash. Topical steroids are contraindicated to avoid further melt of the cornea and risk for infection.

The most important prognostic factor is the duration of exposure to venom in the conjunctival sac. Delay in washout and increased exposure can cause scarring of the cornea and loss of vision. The venom of the spitting cobra when sprayed on the body causes blistering and excoriation of the skin; however, fatal injuries can result from intravenous and intramuscular spread of venom directly via bite.

Early treatment for fast recovery

In cases of venom ophthalmia, duration of exposure to the venom is the most important prognostic factor. Increased awareness among people and field health care workers is a must to prevent a delay in diagnosis. Copious irrigation of the eye with sterile distilled water or saline can be given as a first aid measure at primary health care setups with immediate referral to tertiary eye center. Early onset and longer duration of mydriasis may be seen in dark-skinned individuals, similar to the differential penetration of venom through the cornea in pigmented vs. albino rabbit eyes. However, this needs comparative studies and further investigation with a larger sample size. We share this case as it establishes the possibility of complete cure in early diagnosis and treatment.

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