Snakebite remains a significant public-health problem in several parts of India, particularly in rural and agricultural regions. While the life-threatening effects of venom on the nervous system, blood coagulation, and kidneys are well documented, eye-related complications are rarely discussed. A clinically significant case highlights how viper envenomation can unexpectedly lead to sudden and irreversible vision loss through a condition known as central retinal artery occlusion (CRAO).
Background: Snakebite and Its Systemic Effects
Venomous snakebites, especially from vipers, typically cause haemostatic disturbances rather than neurotoxicity. Viper venom is a complex mix of enzymes and proteins that simultaneously promote and disrupt blood clotting. This paradox often results in consumption coagulopathy, disseminated intravascular coagulation (DIC), and ischemic damage to vital organs such as the kidneys, lungs, and brain. Ocular involvement, however, is uncommon and therefore often overlooked in early clinical evaluation.
The Case: From Snakebite to Sudden Vision Loss
A 60-year-old farmer from rural Bengaluru was bitten on his right index finger while working in his field. The snake, identified as a saw-scaled viper, caused localized swelling and pain but no immediate systemic symptoms. He reached the hospital 24 hours later and was admitted for close monitoring and treatment.
Initial examination revealed:
- Fang marks with extensive hand swelling
- Severely deranged coagulation parameters
- Elevated white blood cell count
- Early kidney dysfunction
- No neurological deficits at presentation
He was treated with anti-snake venom (ASV), antibiotics, and supportive care. Due to worsening cellulitis, an emergency fasciotomy was performed under fresh frozen plasma cover.
Sudden Ocular Complication
On the second day of hospitalization, the patient reported sudden loss of vision in the left eye. Ophthalmic examination and fundoscopy showed classical signs of central retinal artery occlusion, a condition caused by abrupt interruption of blood flow to the retina. Intraocular pressure was also elevated.
Despite prompt treatment with acetazolamide and ocular massage, vision did not improve. Over the following days, the patient’s condition deteriorated further with:
- Progressive renal failure requiring dialysis
- Hematuria and worsening coagulopathy
- Drop in hemoglobin and platelet counts
- Development of alveolar hemorrhage and respiratory failure
Despite aggressive supportive care, the patient succumbed to multi-organ failure on the tenth day of admission.
Why Can Viper Bites Affect Vision?
CRAO following snakebite is extremely rare but biologically plausible. Several mechanisms may be involved:
- Microthrombus formation due to venom-induced coagulopathy
- Direct endothelial damage to retinal vessels
- Severe vascular spasm triggered by toxic vasculitis
- Disseminated intravascular coagulation causing retinal ischemia
Previous reports suggest that even with timely ophthalmic intervention, visual recovery in CRAO is often poor, particularly when systemic envenomation is severe.
Key Takeaways
- Viper envenomation can cause rare but devastating ocular complications, including permanent vision loss.
- Sudden visual symptoms after snakebite should be treated as a medical emergency.
- CRAO likely results from a combination of haemostatic dysfunction and direct vascular toxicity.
- Overall prognosis depends not only on eye involvement but on the extent of multi-organ damage.
Conclusion
This case underscores the need for heightened awareness among clinicians regarding rare complications of snakebite. While saving life remains the immediate priority, early recognition of ocular symptoms may help prevent irreversible blindness. In regions where snakebite is endemic, a multidisciplinary approach, including ophthalmic evaluation, is essential for comprehensive patient care.
Reference: Rajappa, G.C., Asuti, S., Gupta, C.N. and Sudhir, U., 2014. Central retinal artery occlusion: a rare complication of viperine snake bite. JIACM, 15(2), pp.160-1.
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