Introduction

The ocular examination in horses with painful eyes is limited by their physicality and powerful orbicularis oculi muscles. Ocular examination is normally facilitated by a combination of chemical restraint (sedation), topical local anaesthesia and periocular nerve blocks. For the majority of horses, blocking the auriculopalpebral nerve (CN VII) to immobilise the orbicularis oculi muscle, and supraorbital nerve (frontal n., CN V – ophthalmic branch) to desensitise the upper eyelid, will facilitate ocular examination, collection of samples from the ocular surface and placement of subpalpebral lavage systems (Labelle and Clark‐Price 2013).

The retrobulbar nerve block (RBNB) involves injecting local anaesthetic directly within the periorbita, (Fig 1), and in general practice, can be utilised for standing enucleations. In the referral setting, the RBNB is used in numerous procedures including standing corneal surgeries (keratectomies and grafting), eyelid surgeries, laser ablation of granula iridica cysts and cytophotocoagulation for management of glaucoma. The RBNB has the advantage of adding safety to a procedure by removing the requirement for general anaesthetic by facilitating standing procedures (Pollock et al. 2008), as well as impeding the cardiac changes of the oculocardiac reflex (OCR) (Raffe et al. 1986).

The periorbita is a conically‐shaped fibrous membrane that encloses the ‘intraconal’ muscles, fat, nerves and blood vessels behind the eye. It extends from the globe obliquely to the apex of the orbit. Structures enclosed by the periorbita include the extraocular muscles and their motor nerve branches (CN III, IV and VI) and the optic nerve (CN II). Sensory nerves (including branches of the ophthalmic nerve (CN V), lacrimal n., supraorbital and infratrochlear n., and maxillary nerve (CN V; zygomatic n.)) which provide sensation to the eyelids and periocular skin, are not consistently blocked by the RBNB. The branches of the ophthalmic nerve which provide innervation to the eyeball (long and short ciliary nerves) are consistently blocked by the RBNB. As a result of this inconsistent anaesthesia of the sensory branches of CN V supplying the eyelids, additional nerve blocks are required for desensitisation of the eyelids, commonly the supraorbital nerve for the upper eyelid and a line block for the lower eyelid and canthi.

Complications of the retrobulbar block have been described as intra‐meningeal injection from caudal placement of the needle, haematoma formation from placement of the needle too ventrally, globe trauma, optic neuritis and nerve penetration, prolapse of the globe secondary to extraocular muscle blockade, orbital cellulitis and abscessation, and orbital oedema (Gilger and Davidson, 2002; Tremaine 2007). Although a wide variety of complications are reported, with some being devastating, involving morbidity to the eye or mortality of the patient (Labelle and Clark‐Price 2013), these are very dependent upon the technique utilised. For this reason, this review will consider the three commonly utilised techniques separately: the four‐point block (RBNB‐FP), Peterson or modified Peterson block (RBNB‐P/MP) and blockade via the supraorbital fossa (RBNB‐SOF). This paper seeks to critically appraise the literature on recognised complications reported with the various types of RBNB used in equine practice, according to the relevant literature identified.

中文翻译：

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球后阻滞：回顾所用技术并报道并发症

介绍

眼睛疼痛的马匹的眼部检查受到其身体和强大的眼轮肌的限制。通常通过化学约束（镇静），局部麻醉和眼周神经阻滞相结合来促进眼科检查。对于大多数马匹而言，阻断耳睑神经（CN VII）以固定眼轮匝肌和眶上神经（额叶CNV –眼科）以使上眼睑脱敏，这将有助于眼部检查，并从中收集样本眼表和睑下灌洗系统的位置（Labelle and Clark‐Price 2013）。

球后神经阻滞（RBNB）涉及直接在眶周内注射局部麻醉剂（图 1），在一般实践中，可用于站立摘除术。在转诊环境中，RBNB用于许多手术中，包括常规角膜手术（角膜切开术和移植术），眼睑手术，虹膜颗粒囊肿的激光消融以及细胞光凝治疗青光眼。所述RBNB由通过促进站在程序除去用于全身麻醉的要求具有（波洛克增加安全性的过程的优点等。  2008年），以及阻碍眼心反射（OCR）（Raffe的心脏变化等人。1986年）。 

眶周是圆锥形的纤维膜，包裹着眼后的“圆锥形”肌肉，脂肪，神经和血管。它从地球仪倾斜地延伸到轨道的顶点。眶周包围的结构包括眼外肌及其运动神经分支（CN III，IV和VI）和视神经（CN II）。感觉神经（包括眼神经（CN V）的分支，泪腺，眶上和下室静脉和上颌神经（CN V；神经）的神经）并没有始终如一地被阻塞由RBNB。RBNB始终阻塞提供眼神经支配的眼神经分支（长睫状神经和短睫状神经）。由于供应眼睑的CN V感官分支的麻醉不一致，

球后阻滞的并发症已被描述为：从尾部放置针入脑膜内注射，从太后侧放置针入导致血肿，球囊外伤，视神经炎和神经穿透，眼外肌阻滞继发球囊脱垂，眼眶蜂窝组织炎和脓肿以及眼眶水肿（Gilger和Davidson，2002； Tremaine 2007）。尽管报告了各种各样的并发症，但其中一些具有破坏性，涉及眼睛发病率或患者死亡率（Labelle and Clark‐Price 2013），这很大程度上取决于所使用的技术。因此，本综述将分别考虑三种常用技术：四点阻滞（RBNB-FP），彼得森或改良彼得森阻滞（RBNB-P / MP）和通过眶上窝的阻滞（RBNB-SOF）。根据相关文献，本文力求对有关在马术中使用的各种类型RBNB报告的公认并发症的文献进行严格评估。