A snake has just spat its venom in your eyes. Will you go blind or suffer from permanent damage to your eye? There is a lot of false information and urban legends surrounding these incidents. Even medically, there is little detailed information on how the venom affects the eyes and vision, how long symptoms will last, how effective treatment is, and what treatment should be initiated in the event of snake venom entering the eye. Before we get to the venom let us first discuss the responsible snakes and how accurate their aim really is!
Which snakes can spit their venom in South Africa?
In South Africa, there are 3 snake species that are capable of spitting their venom. Two are cobra species that have fangs adapted for spitting their venom namely the Mozambique Spitting Cobra (Naja mossambica) and the Black Spitting Cobra (Naja nigricollis woodi). The third species being the Rinkhals (Hemachatus haemachatus) which is not a true cobra. These 3 species of snakes have fangs with smaller openings that have been adapted for spitting. The venom that is spat is exactly the same venom that you are envenomated with in the event of a bite from one of these species. When threatened, these snakes will spit their venom at intruders in an attempt to keep predators at bay, should you go closer, the snake may try to bite. Unless you have open wounds or are hypersensitive to venom, the eyes are the only real part of the body that is affected by venom spat at a human. The venom will cause an inflammatory response in the anterior part of the eyeball with common complications to include hyperaemia (blood build up inside the vessels), uveitis (inflammation of the middle layer of the eye), and corrosion of the cornea (Chu, et al. 2010).
How accurate are spitting snakes at hitting their targets?
In a study done by Westhoff, G et al in 2005 it was found that cobras do not just spit venom in the general direction of the intruder and that they actually aim at the eyes where the venom will have an effect. The two species of snakes used for the study were Black Spitting Cobras and Red Spitting Cobras (Naja pallida) and they found that these animals would quickly and accurately spit at the eyes of moving pictures of human faces but would hardly ever spit at pictures of human hands. When the pictures were held stationary no spitting was triggered. What was also interesting was that the animals performed quick rising and falling head movements when spitting their venom which leads to a target hit area of 5.5cm wide and 11cm high on average. This behavior would obviously increase the probability of hitting at least 1 of the harasser’s eyes.
In another study done by Berthé, R et al in 2009 it was found that the spray pattern is not fixed per species but instead the snake matches the spray pattern according to the size of the intruder. From these two studies, we can conclude that spitting cobras and Rinkhals are accurate spitters, aiming for your eyes when they feel threatened.
Is damage to the eye after a venom spray permanent?
Neurotoxins in snake venom cause neurological disorders in the eye which can include paralysis of the ocular muscles, ptosis (droopy upper eyelid), and diplopia (double vision). Cytotoxins in the snake venom cause corneal oedema (swelling) and inflammation. Without immediate treatment, patients can be left with permanent tissue damage and blindness. Based on case studies it was found that Black Spitting Cobras and Mozambique Spitting Cobras’ venom penetrates the cornea better than the Rinkhals and therefore have worse symptoms and outcomes if treatment is delayed.
What is the correct treatment for venom in the eyes?
Immediately rinsing your eyes with a bland liquid (water or saline is preferred) after getting venom in your eye/s will alleviate or completely remove the complications of eye damage by up to 77% (Tsai, T. et al. 2020). The venom of the Black Spitting Cobra is more commonly associated with permanent eye damage due to its quick absorption by the cornea even with quick irrigation of the affected eye/s. Topical corticosteroids, antibiotics, antihistamine and anaesthetic eye drops have been reported as appropriate treatments for snake venom-induced inflammation of the eye (Chu, R. et al. 2010). Antivenom is not necessary nor recommended as there is no evidence to show that it assists in the reversal of inflammation or more severe damage to the eyes.
Should you receive venom in the eyes immediately rinse the affected eye/s with a bland liquid in an attempt to rinse as much venom from the eyes as possible. It is always advisable to go and see a medical professional for advise and possible further treatment in severe cases.
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References
Berthé, R. de Pury, S. Bleckmann, H. Westhoff, G. Spitting cobras adjust their venom distribution to target distance. Journal of Comparative Physiology A. 2009. 195: 753-757.
Chu, E.R.; Weinstein, S.A.; White, J.; Warrell, D.A. Venom ophthalmia caused by venoms of spitting elapid and other snakes: Report of ten cases with review of epidemiology, clinical features, pathophysiology, and management. Toxicon. 2010. 56: 259–272.
Tsai, T. Lin, C. Mao, Y. Hung, C. Yang, Y. Yang, C. Jeng, M. Naja atra venom-spit opthalmia in Taiwan: An epidemiology survey from 1990 to 2016. Journal of Chinese Medical Association. 2020. 83: 77-83.
Westhoff, G. Tzschätzsch, K. Bleckmann, H. The spitting behavior of two species of spitting cobra. Journal of Comparative Physiology A. 2005. 191: 873-881.