A retrobulbar block is a regional anesthetic

nerve block Nerve block or regional nerve blockade is any deliberate interruption of signals traveling along a nerve, often for the purpose of pain relief. Local anesthetic nerve block (sometimes referred to as simply "nerve block") is a short-term block, ...

in the retrobulbar space, the area located behind the globe of the

eye Eyes are organs of the visual system. They provide living organisms with vision, the ability to receive and process visual detail, as well as enabling several photo response functions that are independent of vision. Eyes detect light and conv ...

. Injection of local anesthetic into this space constitutes the retrobulbar block. This injection provides akinesia of the

extraocular muscle The extraocular muscles (extrinsic ocular muscles), are the seven extrinsic muscles of the human eye. Six of the extraocular muscles, the four recti muscles, and the superior and inferior oblique muscles, control movement of the eye and the o ...

s by blocking

cranial nerve Cranial nerves are the nerves that emerge directly from the brain (including the brainstem), of which there are conventionally considered twelve pairs. Cranial nerves relay information between the brain and parts of the body, primarily to and f ...

s II,

III III or iii may refer to: Companies * Information International, Inc., a computer technology company * Innovative Interfaces, Inc., a library-software company * 3i, formerly Investors in Industry, a British investment company Other uses * Ins ...

, and VI, thereby preventing movement of the globe. Cranial nerve IV lies outside the muscle cone, and therefore is not affected by the local anesthesia. As a result, intorsion of the eye is still possible. It also provides sensory anesthesia of the

conjunctiva The conjunctiva is a thin mucous membrane that lines the inside of the eyelids and covers the sclera (the white of the eye). It is composed of non-keratinized, stratified squamous epithelium with goblet cells, stratified columnar epitheli ...

cornea The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. Along with the anterior chamber and lens, the cornea refracts light, accounting for approximately two-thirds of the eye's total optical ...

and uvea by blocking the ciliary nerves. This block is most commonly employed for

cataract surgery Cataract surgery, also called lens replacement surgery, is the removal of the natural lens of the eye (also called "crystalline lens") that has developed an opacification, which is referred to as a cataract, and its replacement with an intraocul ...

, but also provides anesthesia for other intraocular surgeries.

Side effects and complications

Complications associated with this block are either ocular or systemic. Local ocular complications include

hematoma A hematoma, also spelled haematoma, or blood suffusion is a localized bleeding outside of blood vessels, due to either disease or trauma including injury or surgery and may involve blood continuing to seep from broken capillaries. A hematoma is ...

formation,

optic nerve In neuroanatomy, the optic nerve, also known as the second cranial nerve, cranial nerve II, or simply CN II, is a paired cranial nerve that transmits visual information from the retina to the brain. In humans, the optic nerve is derived fro ...

damage and perforation of the globe with possible blindness. Systemic complications include

local anesthetic toxicity A local anesthetic (LA) is a medication that causes absence of pain sensation. In the context of surgery, a local anesthetic creates an absence of pain in a specific location of the body without a loss of consciousness, as opposed to a general a ...

, brainstem anesthesia, and stimulation of the oculocardiac reflex. Most commonly, patients will report discomfort during the performance of the block, such as the sensation of the needle during insertion and/or pressure behind the eye during injection. In recent years, peribulbar block has become increasingly used because of its lower incidence of complications.

Technique

Resuscitative equipment, monitoring and personnel must be immediately available prior to performance of this block. The retrobulbar block is performed with the patient either seated or supine and looking straight ahead. The head should be maintained in a neutral position. A needle (22–27 Gauge, 3 cm long) is inserted at the inferolateral border of the bony orbit and directed straight back until it has passed the equator of the globe. It is then directed medially and cephalad toward the apex of the orbit. Occasionally a 'pop' is felt as the needle tip passes through the muscle cone delineating the retrobulbar space. Following a negative aspiration for blood, 2–4 mLs of local anesthetic solution is injected and the needle is withdrawn. 2%

Lidocaine Lidocaine, also known as lignocaine and sold under the brand name Xylocaine among others, is a local anesthetic of the amino amide type. It is also used to treat ventricular tachycardia. When used for local anaesthesia or in nerve blocks, li ...

(Xylocaine) and 0.5% to 0.75%

bupivicaine Bupivacaine, marketed under the brand name Marcaine among others, is a medication used to decrease feeling in a specific area. In nerve blocks, it is injected around a nerve that supplies the area, or into the spinal canal's epidural space. It ...

(Marcaine) are two commonly used agents. Epinephrine, commonly mixed in with local anesthetics for vasoconstriction, is not used in seeing eyes as this can cause a central retinal artery occlusion. An enzyme, hyaluronidase, is frequently a component of the anaesthetic solution, as it accelerates and improves dispersal of the agent. Akinesia and anesthesia quickly ensue within minutes with a successful retrobulbar injection. Retrobulbar block can be used successfully for corneal transplantation but may require a supplemental facial nerve block. Retrobulbar block can block levator palpebrae muscle but not orbicularis oculi. Several techniques for facial nerve block can be used in conjunction with retrobulbar block.

References

* Cousins, MJ; Bridenbaugh, PO (1998). ''Neural Blockade in Clinical Anesthesia and Management of Pain.'' {{ISBN, 0-397-51159-0 * Anesthesiology Inf
AnesthesiologyInfo.com is for sale
Regional anesthesia Eye procedures Ophthalmic drug administration

Side effects and complications

Technique

See also

References