Complications following ophthalmic regional anaesthesia are rare but are reported during both needle (intraconal and extraconal blocks) and blunt cannula (sub-Tenon’s block) techniques. At present there is no perfect technique of ophthalmic regional anaesthesia. This article reports on the complications, treatment and prevention of commonly used ophthalmic regional blocks. Thorough knowledge of the measures required to deal with complications when they occur are of paramount importance for safe clinical practice.

Newcastle SUMMARYOphthalmia nodosa is a well-documented condition. We present a case in which a live caterpillar was rubbed into a patient's eye and, after relentless penetration of the hairs into the globe, vitrectomy was required. We discuss the differing clinical features of these injuries, the mode of penetration and the treatment options. CASE REPORTA 15-year-old male was referred from a general casualty department with a 2 day history of a foreign body sensa tion in his left eye. On examination he had mUltiple con junctival, and superficial and deep corneal foreign bodies (Fig. 1). Closer questioning revealed that he had been on a school field trip at which time a live caterpillar had been rubbed into his left eye and the irritation had continued since then. On the same day, 150-250 of these caterpi liar hairs (or setae) were removed under general anaesthetic; one of these setae was later examined under the electron microscope (Fig. 2).Despite setae being removed on numerous occasions over the next month, a number remained embedded in the cornea and some gradually migrated posteriorly. Four weeks after the initial event, four setae were found in the anterior chamber and a further two were seen in the anterior vitreous. It was noted at the time that the corneal setae had a marked infiltrate around them and there was a mild but persistent iritis.Because of continuing discomfort, the anterior chamber setae were removed via a superior corneal section 6 weeks after presentation. Initially the anterior chamber remained quiet, with visual acuity at 6/5. One month after the oper ation, anterior chamber activity had increased with a reduction in visual acuity to 6/9. The situation remained

In a prospective survey, 121 patients received sub-Tenon's block and were interviewed on the same day after their phacoemulsification cataract surgery regarding their visual experience in the operated eye during surgery. Majority of patients (81%) reported that they could see some light during surgery and various colours were seen by 56%. Movements of various descriptions were also reported by 40% of patients. The majority of patients (93%) found the visual experience acceptable but 4% thought it to be unpleasant and 3% found it frightening. Patients undergoing phacoemulsification surgery under subTenon's block experience a variety of visual sensations and some patients may be frightened. All patients should receive appropriate preoperative warning.

At present, there is no absolutely safe ophthalmic regional block. It is imperative therefore to have a basic knowledge of anatomy and technique which reduce complications.

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