|Year : 1997 | Volume
| Issue : 4 | Page : 236-237
Optic neuritis following snake bite
V Menon, R Tandon, T Sharma, A Gupta
Dr. Rajendra Prasad Centre for Ophthalmic Sciences, All Institute of Medical Sciences, New Delhi, India
Dr. Rajendra Prasad Centre for Ophthalmic Sciences, All Institute of Medical Sciences, New Delhi
|How to cite this article:|
Menon V, Tandon R, Sharma T, Gupta A. Optic neuritis following snake bite. Indian J Ophthalmol 1997;45:236-7
Snake bite is an important health problem in the Indian subcontinent with nearly 60,000 people being bitten every year. Though ocular complications are not uncommon, optic neuritis is rare and only a few case reports are available in the literature.
The present case describes the development of bilateral retrobulbar neuritis following a bite by the Indian black cobra.
| Case|| |
A 50 year old male farmer was bitten on the right foot by an Indian black cobra while working in the fields. He was given first aid treatment: a tourniquet and local incision at the site of the bite by the local people and taken to a hospital where he was received in an unconscious state. Hospital records show his blood pressure was 100/70 mm Hg and pulse 100 /min, regular in rhythm. There was no evidence of any spontaneous internal or external bleeding. There was a wound on the right foot. He was in respiratory paralysis and was intubated and put on a ventilator. He was also given 10 vials of antisnake venom (ASV, 10 ml per vial) after sensitivity testing, and started on systemic antibiotics.
On regaining consciousness the next day, the patient noticed diminished vision in both eyes which improved gradually over the next few days. On the 6th day there was a sudden fall in vision which was recorded as finger counting at 2 meters in the right eye and 6/36 in the left eye with accurate projection of rays in both eyes. He was noted to have bilaterally sluggishly reacting pupils and a normal fundus, and was diagnosed as having bilateral retrobulbar neuritis and referrred to our centre two weeks after snake bite.
His systemic condition was stable. On the right foot there was a 3x4 cm wound with necrotic slough. Pupillary reactions to light were bilaterally sluggish and ill-sustained. The best corrected vision was finger counting close to face in both eyes and the fundus was normal in both eyes. Visually evoked responses (flash VER) showed increased latency and decreased amplitude.
The patient was given 100 mg dexamethasone sodium phosphate in one bottle of 5% dextrose intravenously over 1-2 hours daily for 3 days along with oral ciprofloxacin 500 mg twice a day and daily wound dressing. On the 3rd day the vision improved to finger counting at 2 meters. He was then maintained on tapering oral prednisolone over 3 weeks. The vision continued to improve and was 6/ 18 both eyes at 8 weeks follow-up and the disc showed early pallor.
| Discussion|| |
We were able to find only 7 case reports of optic neuritis following snake bite (Table). Interestingly, in three of them the fall in vision was reported on the 6th day. All these patients had received ASV.
The possible causes of optic neuritis following snake bite have been postulated to be snake venom, allergy to ASV, extensive haemorrhages and capillary damage.There is indirect evidence for each theory. Mathurreported a case of non-poisonous snake bite which developed optic neuritis following administration of ASV. He attributed is to ASV. In 1981, Rao reported immediate development of blindness following a cobra bite and attributed it to the toxic influence of the venom itself. In the present case, we attribute the immediate fall in vision to the effect of the snake venom, and the subsequent decrease on the 6th day to allergic reaction developing after ASV administration.
Steroids have been used to treat optic neuritis following snake bite in all except two previously reported cases. The vision was reported to improve in all but took longer in the cases which were not given any steroids. Pulse steroid therapy, which has been given for the first time in such a situation, appears to be effective.
Though treatment by ASV still forms the mainstay of treatment of a poisonous snake bite we should be aware of its possible reactions. Some newer, less allergenic substitutes are being developed, namely more purified ASV using polyacryalamide gel affinity chromatography, purified Fab fragments of TgG,monoclonal antibodies (cobra venom), and highly refined purified antivenom from sheep or chicken. This case highlights that optic neuritis following snake bite is a rare but distinct entity. Visual prognosis is fairly good and steroids have a definite role in hastening recovery.
| References|| |
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