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BACKGROUND: Retrobulbar haemorrhage may occur due to retrobulbar block. Immediate pressure bandage after instilling one drop of 2% pilocarpine and postpone of operation for a week is advised.


What is the rationale for instilling pilocarpine incase of retrobulbar haemorrhage?

Does its miotic action prevent expulsion of the lens and vitreous due to retrobulbar pressure (from blood)? How is it helping?

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Retrobulbar hemorrhage (RH) is (Johnson et al., 2009).

an ocular emergency resulting from arterial bleeding in the orbital cavity behind the eye. Because the orbit is a relatively fixed space, increasing volume will increase orbital and intra-ocular pressure, resulting in compression of orbital structures and ischemia of the eyeball and optic nerve (Ord, 1981).

I am not sure about postponing surgery by one week when Johnson et al. (2009) also points out that prompt recognition of RH is imperative, given that a delay in surgery of as little as 90 to 120 minutes can result in permanent vision loss. Hwang et al. (2015) points out, it is crucial to decompress the orbit and relieve pressure to prevent compartment syndrome and permanent vision loss.

Pilocarpine can be used for reduction of intra-ocular pressure (IOP) and protection of the lens by causing miosis prior to surgery (McEvoy, 2003) although Johnson et al. (2009) says

Medical treatment should be initiated immediately and typically involves an osmotic agent, a carbonic anhydrase inhibitor, and a high-dose steroid. Osmotic agents, such as intravenous mannitol, shrink the vitreous body and reduce orbital volume; carbonic anhydrase inhibitors, such as intravenous acetazolamide, reduce intraocular pressure by inhibiting aqueous production; and steroids decrease inflammation.

Surgery for retrobulbar haemorrhage involves lateral canthotomy and inferior cantholysis. This can be performed under local or general anesthesia and might involve evacuating the haematoma and decompressing the orbit (Winterton et al., 2007).

References

Hwang, F. S., Patel, A. S., Murchison, A., Feldman, B. H., Burkat, C. N., & Akkara, J. D. (2015). Retrobulbar hemorrhage. In American Academy of Opthalmology EyeWiki. Retrieved from: https://eyewiki.org/w/index.php?title=Retrobulbar_hemorrhage&oldid=47711

Johnson, D., Schweitzer, K., & Sharma, S. (2009). Answer: Can you identify this condition?. Canadian Family Physician, 55(6), 607. pmcid: PMC2694085

McEvoy, G. K. (2003). AHFS Drug information 2003. Bethesda, MD: American Society of Health-System Pharmacists. ISBN: 1585280399

Ord, R. A. (1981). Post-operative retrobulbar haemorrhage and blindness complicating trauma surgery. British Journal of Oral Surgery, 19(3), 202-207. doi: 10.1016/0007-117X(81)90005-6 pmid: 6945123

Winterton, J. V., Patel, K., & Mizen, K. D. (2007). Review of management options for a retrobulbar hemorrhage. Journal of oral and maxillofacial surgery, 65(2), 296-299. doi: 10.1016/j.joms.2005.11.089 pmid: 17236937

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    The surgery in this question means cataract surgery. Thanks for answer. – JM97 Feb 2 at 13:14

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