Intraoperative eye position after sub-Tenon's anesthesia for cataract surgery

Abstract

Background: To evaluate the incidence and extent of ocular deviation associated with sub-Tenon's anesthesia. Methods: Seventy-five consecutive patients undergoing routine phacoemulsification with sub-Tenon's anesthesia at the Eye Unit, Royal Gwent Hospital, were prospectively enrolled in this observational case series. The exclusion criteria were patients taking warfarin, or patients with preexisting ocular motility disorders,allergy to local anesthetics,or previous surgery for squint or retinal detachment. Eleven patients were subsequently excluded from the study group as they required additional anesthesia blocks before measurements were taken for ocular deviation. We injected 5mL of a local anesthetic mixture of 2% lignocaine and 7.5 mg/mL levobupivacaine in the sub-Tenon's space in the inferonasal quadrant. Ocular deviation was assessed objectively by means of the Krimsky test. Forced duction tests were performed before and after anesthesia. Results: Hyperdeviation was documented in 49 (77%) eyes, exodeviation in 62 (97%), and hypodeviation in 6 (9.4%). No esodeviations were documented. Only 2 patients were orthophoric after anesthesia. Mean vertical deviation was 4.4 prism dioptres (PD) (SD 4.7 PD, 95% CI 3.2–5.5 PD, range 0–14 PD). Mean horizontal deviation was 19.5 (SD 9.6, 95% CI 17–22, range 0–50) PD. Forced duction test revealed no mechanical restriction before or after anesthesia. Interpretation: This study suggests that there is an appreciable ocular deviation with sub-Tenon's anesthesia. Intraoperative ocular deviation may make certain procedures more difficult; therefore, we recommend a low threshold for an additional corrective block administered before surgery to rectify the deviation.