Ocular Penetration/Perforation After Peribulbar Anesthesia

Having learned from the occurrence of ocular perforation (entrance and exit) in 2 patients and ocular penetration (entrance only) in 1 patient in a series of more than 33 000 blocks, mainly for cataract surgery, over the past 18 years, I would like to make the following recommendaton for the inferior injection technique, whether for retrobulbar or peribulbar placement. Rather than the traditional two-thirds/one-third entry location on the inferior orbit rim (as used in 4 patients in 2 recent articles1,2), I now routinely inject transcutaneously much farther to the temporal side, at the junction of the lateral and inferior orbit rims and close to the bony orbit rim as palpated through the skin before injection (Figure 1). 3 The rationale for going transcutaneously is to get around the tense orbicularis tone often present in the inferior eyelid or the problems created when there is a narrow palpebral fissure and a wide lateral canthal fold.Figure 1.: (Hamilton) The outline of the globe is superimposed on a template of the orbit rim. The traditional inferior-block injection site is just inside the orbit rim at “T.” The modified injection site is inferotemporal, just inside the orbit rim at “M” (reprinted with permission of Gimbel Educational Services, Calgary, Alberta, Canada).After the exact point of injection on the skin surface is chosen, the needle is advanced in a sagittal plane with 10-degree upward inflection from the transverse plane. The needle at first invaginates the skin, while being directed safely between the globe and lateral orbit wall; it soon penetrates the skin and can then be advanced to the depth of the globe equator before it is redirected according to whether one is doing an intracone or pericone block. This modified entry position provides safer access to the orbit as there is more physical space than in the traditional entry point (Figure 1). In addition, the modified technique avoids possible needle damage to the inferior rectus and inferior oblique muscles and to the motor nerve supply to the inferior oblique.4 Atypical pain during injection was a prominent symptom in all 4 patients reported.1,2 Pain experienced by patients in this situation should be taken seriously and as the sentinel to desist from further injection until the cause is investigated. Unduly deep sedation, when provided at the time of orbital local anesthetic injection, must be avoided because it can counter patients acting as their own monitor and being conscious enough to report pain. Robert C. Hamilton MB Calgary, Alberta, Canada

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