Retrobulbar block
Encyclopedia
A retrobulbar block is a regional anesthetic
nerve block
into the retrobulbar space, the area located behind the globe of the eye
. Injection of local anesthetic into this space constitutes the retrobulbar block. This injection provides akinesia of the extraocular muscles by blocking cranial nerves II
, III
, and VI
, thereby preventing movement of the globe. Cranial nerve IV
is not affected since it lies outside the muscle cone. It also provides sensory anesthesia of the conjunctiva
, cornea
and uvea
by blocking the ciliary nerves
. This block is most commonly employed for cataract surgery
, but also provides anesthesia for other intraocular surgeries.
formation, optic nerve
damage and perforation of the globe with possible blindness. Systemic complications include local anesthetic toxicity
, 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.
(Xylocaine) and 0.5% to 0.75% bupivicaine (Marcaine) are two commonly used agents. Avoid epinephrine, commonly mixed in with local anesthetics for vasconstriction, 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 required supplemental facial nerve block. Retrobulbar block can block levator palpebrea muscle but not orbucularis oculi. Several techniques for facial nerve block can be used in conjunction with retrobulbar block.
Regional anaesthesia
Regional anaesthesia is anaesthesia affecting only a large part of the body, such as a limb or the lower half of the body. Regional anaesthetic techniques can be divided into central and peripheral techniques. The central techniques include so called neuraxial blocks...
nerve block
Nerve block
Regional nerve blockade, or more commonly nerve block, is a general term used to refer to the injection of local anesthetic onto or near nerves for temporary control of pain. It can also be used as a diagnostic tool to identify specific nerves as pain generators...
into the retrobulbar space, the area located behind the globe of the eye
Human eye
The human eye is an organ which reacts to light for several purposes. As a conscious sense organ, the eye allows vision. Rod and cone cells in the retina allow conscious light perception and vision including color differentiation and the perception of depth...
. Injection of local anesthetic into this space constitutes the retrobulbar block. This injection provides akinesia of the extraocular muscles by blocking cranial nerves II
Optic nerve
The optic nerve, also called cranial nerve 2, transmits visual information from the retina to the brain. Derived from the embryonic retinal ganglion cell, a diverticulum located in the diencephalon, the optic nerve doesn't regenerate after transection.-Anatomy:The optic nerve is the second of...
, III
Oculomotor nerve
The oculomotor nerve is the 3rd of 12 paired cranial nerves. It enters the orbit via the superior orbital fissure and controls most of the eye's movements, including constriction of the pupil and maintaining an open eyelid by innervating the Levator palpebrae superiors muscle. The optic nerve is...
, and VI
Abducent nerve
The abducens nerve or abducent nerve is a somatic efferent nerve that controls the movement of a single muscle, the lateral rectus muscle of the eye, in humans. In most other mammals it also innervates the musculus retractor bulbi, which can retract the eye for protection...
, thereby preventing movement of the globe. Cranial nerve IV
Trochlear nerve
The trochlear nerve is a motor nerve that innervates a single muscle: the superior oblique muscle of the eye....
is not affected since it lies outside the muscle cone. It also provides sensory anesthesia of the conjunctiva
Conjunctiva
The conjunctiva covers the sclera and lines the inside of the eyelids. It is composed of rare stratified columnar epithelium.-Function:...
, cornea
Cornea
The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. Together with the lens, the cornea refracts light, with the cornea accounting for approximately two-thirds of the eye's total optical power. In humans, the refractive power of the cornea is...
and uvea
Uvea
The uvea , also called the uveal layer, uveal coat, uveal tract, or vascular tunic, is the pigmented middle of the three concentric layers that make up an eye. The name is possibly a reference to its reddish-blue or almost black colour, wrinkled appearance and grape-like size and shape when...
by blocking the ciliary nerves
Ciliary nerves
Ciliary nerves can refer to:* Short ciliary nerves* Long ciliary nerves...
. This block is most commonly employed for cataract surgery
Cataract surgery
Cataract surgery is the removal of the natural lens of the eye that has developed an opacification, which is referred to as a cataract. Metabolic changes of the crystalline lens fibers over time lead to the development of the cataract and loss of transparency, causing impairment or loss of vision...
, 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 hematomaHematoma
A hematoma, or haematoma, is a localized collection of blood outside the blood vessels, usually in liquid form within the tissue. This distinguishes it from an ecchymosis, which is the spread of blood under the skin in a thin layer, commonly called a bruise...
formation, optic nerve
Optic nerve
The optic nerve, also called cranial nerve 2, transmits visual information from the retina to the brain. Derived from the embryonic retinal ganglion cell, a diverticulum located in the diencephalon, the optic nerve doesn't regenerate after transection.-Anatomy:The optic nerve is the second of...
damage and perforation of the globe with possible blindness. Systemic complications include local anesthetic toxicity
Local anesthetic toxicity
While generally safe, local anesthetic agents can be toxic if used in excessive doses or administered improperly. Even when administered properly, patients may still experience unintended reactions to local anesthetics....
, brainstem anesthesia, and stimulation of the oculocardiac reflex
Oculocardiac reflex
The oculocardiac reflex, also known as Aschner phenomenon, Aschner reflex, or Aschner-Dagnini reflex, is a decrease in pulse rate associated with traction applied to extraocular muscles and/or compression of the eyeball. The reflex is mediated by nerve connections between the trigeminal cranial...
. 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, 3cm 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, 2-4mls of local anesthetic solution is injected and the needle is withdrawn. 2% LidocaineLidocaine
Lidocaine , Xylocaine, or lignocaine is a common local anesthetic and antiarrhythmic drug. Lidocaine is used topically to relieve itching, burning and pain from skin inflammations, injected as a dental anesthetic or as a local anesthetic for minor surgery.- History :Lidocaine, the first amino...
(Xylocaine) and 0.5% to 0.75% bupivicaine (Marcaine) are two commonly used agents. Avoid epinephrine, commonly mixed in with local anesthetics for vasconstriction, in seeing eyes as this can cause a central retinal artery occlusion. An enzyme, hyaluronidase
Hyaluronidase
The hyaluronidases are a family of enzymes that degrade hyaluronic acid.In humans, there are six associated genes, including HYAL1, HYAL2, HYAL3, and PH-20/SPAM1.-Use as a drug:...
, 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 required supplemental facial nerve block. Retrobulbar block can block levator palpebrea muscle but not orbucularis oculi. Several techniques for facial nerve block can be used in conjunction with retrobulbar block.