Peribulbar injection

When higher concentrations of drugs, particularly corticosteroids and antibiotics, are required in the eye than can be delivered by topical administration, local injections into the periocular tissues can be considered. Periocnlar drug delivery includes subconjunctival, snb-Tenon s, retrobulbar, and peribulbar administration. 

Compared with the retrobulbar technique, peribulbar anesthesia provides similar anesthesia and akinesia for both anterior segment and vitreoretinal surgical procedures, but some patients may have inadequate akinesia and require additional injections. In addition, the onset time of blockade is not as rapid as with retrobulbar injection. Nevertheless, peribulbar anesthesia reduces the potential for inadvertent globe penetration, retrobulbar hemorrhage, and direct optic nerve injury. Although serious problems with retrobulbar and peribulbar injections are uncommon, numerous complications have been reported (Box 3-3). 

Weijtens O, Vandersluijs FA, Schoemaker RC, et al. Peribulbar corticosteroid injection vitreal and serum concentrations after dexamethasone cUsocUum phosphate injection. Am J Ophthalmol 1997 123 358-363. 

One study compared vitreous and serum concentrations after 7.5-mg oral doses of dexamethasone with peribulbar injections of 5 mg dexamethasone phosphate. Peribulbar administration of the agent resulted in 3.9% higher intravitreal than vitreous concentrations, but serum dexamethasone levels were approximately equal with both routes of administration. 

A cluster of 25 cases of transient or permanent diplopia occurred after 13 retrobulbar blocks, 10 peribulbar blocks, and two unknown techniques, possibly related to the non-availability of hyaluronidase, highhghting the likely importance of hyaluronidase in preventing anesthetic-related myopathy in the extraocular muscles (290). Other reports of 21 cases of persistent postoperative diplopia following the peribulbar technique (291) and 4 cases foUowing the retrobulbar technique during the period of non-availabihty of hyaluronidase support this theory (292). Bupivacaine and lidocaine may be contraindicated for peribulbar or retrobulbar injections without hyaluronidase. 

The authors added that retinal toxicity of the local anesthetic agent did not affect the visual outcome in this patient. Scleral perforation is a well-known complication of eye blocks for ophthalmic surgery. The incidence with retrobulbar techniques is 0.075% and with peribulbar blocks 0.0002%. When recognized, ocular perforation usually requires a vitreoretinal procedure and is associated with a poor visual outcome. Risk factors include an anxious or oversedated patient, long sharp needles, superior injection, incorrect angle of needle insertion, and myopic eyes. If the intraocular pressure is increased, paracentesis may acutely reduce it, preventing retinal and optic nerve ischemia and possible permanent visual loss. 

Peribulbar anesthesia is generally considered safer than retrobulbar anesthesia, with a lower incidence of adverse effects. It avoids deep penetration of the orbit and therefore inadvertent subarachnoid injection. It also seems to be safer with regard to the risk of bulb perforation (314). 

An arteriovenous fistula of the supraorbital vessels developed in a 75-year-old man after peribulbar anesthesia with a supplementary supranasal injection. He elected to have conservative management and the lesion remained asymptomatic and static in size over 10 months follow-up. 

A 49-year-old woman had a tonic-clonic seizure about 15 minutes after a peribulbar block for left trabeculectomy (319). She recovered and surgery continued uneventfully. However, she had severe permanent visual loss in that eye, and an MRI scan at 4 weeks showed swelling of the left optic nerve. The authors suggested that some prilocaine had been injected into the nerve sheath, causing the convulsions, local optic nerve swelling, and subsequent optic nerve atrophy. 

Sensory systems When 8 ml of acetazolamide 50mg/l (pH 9.1) was accidentally injected into the peribulbar space in a 63-year-old man undergoing ocular surgery he reported pain during the injection ocular motility was globally reduced and lid edema with mild conjunctival chemosis developed. Empirical treatment included 200 ml of intravenous mannitol 20%, methylpredniso-lone 500 mg, and cefuroxime 750 mg, followed by oral prednisolone 40 mg/day for 5 days. His ocular motility normalized and the lid edema and chemosis resolved in 48 hours [2" ]. 

Wehbeh L, Mehta P, Shah P, Vohra S, Yap YC, Murray A. Management of inadvertent peribulbar injection of acetazolamide a case report. Eye (Lond) 2010 24(4) 738. 

Among the novel routes, subconjimctival injection allows circumvention of the barriers imposed by cornea and conjunctiva, resulting in higher levels in vitreous. The sub-tenon route is a good alternative to retrobulbar and peribulbar ones for administration of anesthesia due to less complications and avoidance of sharp needles. 

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