Introduction
The appropriate choice of local and regional anesthesia in ocular surgery is determined by the intended method, the required length, and the patient factors. Because sensory innervation to the face is highly redundant, a combination of anesthetic procedures is frequently required to produce the best outcomes. In addition, the growing senior population means that an increasing number of older individuals may seek eye surgery. Therefore, administrators will seek cooperation from anesthesia providers in implementing techniques that improve operating room efficiency to manage rising patient numbers while also satisfying organizational goals aimed at budgetary austerity.
Cataract surgery is the most frequent ocular surgical treatment, and a local anesthetic method is usually recommended. However, anesthesia supply differs globally in terms of resources and experience. Therefore, intraconal and extraconal needle blocks are routinely utilized. Even though the techniques are generally safe, severe rare sight and life-threatening problems have occurred due to incorrect needle placement. Unfortunately, most practicing anesthesiologists are reluctant to conduct regional ocular blocks because of a lack of formal training.
An intraconal (retrobulbar) block is performed by injecting local anesthesia into the region of the orbital cavity (the muscle cone) behind the globe produced by the four recti muscles and the superior and inferior oblique muscles. The extraconal (peribulbar) block was created as a safer alternative to the retrobulbar block in which the needle tip was kept outside the muscle cone.
What Is the Anatomy and Physiology of the Eye?
The trigeminal nerve has three branches:
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Ophthalmic nerve (V1).
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Maxillary nerve (V2).
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Mandibular nerve (V3).
The first division (V1) and the second division (V2) innervate the brow and midface. The ophthalmic division (V1) passes along the lateral wall of the cavernous sinus and enters the orbit through the superior orbital fissure. The nerve is divided into the supraorbital and supratrochlear nerves inside the orbit.
The maxillary division (V2) leaves the foramen rotundum after traveling along the inferolateral wall of the cavernous sinus. The zygomatic nerve arises from the pterygopalatine fossa and enters the orbit through the inferior orbital fissure, dividing it into the zygomaticofacial and zygomaticotemporal nerves. V2 becomes the infraorbital nerve after entering the orbit through the inferior orbital fissure. The anterior superior alveolar nerve gives branches before the infraorbital nerve exits the infraorbital canal. The skin of the nose, eyelids, and face receive sensory innervation from the terminal nasal, labial, and palpebral branches.
What Are the Indications of Ophthalmic Nerve Block?
When deciding on the best anesthetic route, anatomical location and length of the surgery are taken into account.
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Surgeries of the eye- Intraocular and periocular surgeries.
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Management of sinus, oculoplastic, and lacrimal surgery.
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Reconstruction of the face.
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For the management and treatment of headaches caused due to migraine.
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Neuralgias of the face, both primary and secondary.
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Dermatologic treatments.
What Are the Contraindications of Ophthalmic Nerve Block?
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Absolute Contraindications: Refusal of the patient, pre-existing anesthetic allergy
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Relative Contraindications: Infection at the injection site, anatomic distortions (traumatic, post-surgical, or due to underlying disease), coagulation or bleeding disorders, and inadequate patient cooperation.
What Are the Targeted Nerve Blocks?
1. Retrobulbar Block:
An alcohol swab or povidone-iodine is used to prepare the inferior lid. The rim of the lower orbit is then palpated, and the globe is superiorly shifted to increase the gap between the orbital floor and the globe. Next, the needle is placed into the skin at or just superior to the level of the inferior orbital rim with the needle bevel-up (to limit the possibility of globe perforation). Next, the needle is moved along the orbital floor until the first "pop" is felt, indicating that the needle has passed through the orbital septum. The needle is then turned 45 degrees medially and superiorly and progresses through the second "pop," which indicates passing through the muscle cone and access into the intraconal area.
2. Supraorbital Block:
The supraorbital nerve is a branch of the ophthalmic division of the trigeminal nerve. It divides into a superficial medial branch and a deep lateral branch after passing through a supraorbital notch (73.8 percent) or foramen (26.2 percent). The notch is usually felt and identifying this location aids in precise placement and targeted blockage. The needle is placed from an inferolateral location 0.19 inches below the supraorbital foramen or notch and progresses cautiously to avoid foramen penetration. The superior eyelid, brow, forehead, and anterior region of the scalp are all anesthetized by regional supraorbital blocking. Compared to local tissue infiltration, it has the advantage of anesthetizing a greater area with a lesser volume of anesthetic.
3. Supratrochlear Block:
Another branch of V1 leaves the supraorbital border medially to the supraorbital nerve. This placement is estimated by locating the supraorbital margins three millimeters medial to a vertical line drawn from the medial canthus. The block is given by inserting a needle into the place where the supratrochlear nerve comes out at the supraorbital border and gently extending along the direction of the nerve. This block is frequently used in combination with the supraorbital block to optimize anesthesia of the forehead.
4. Nasociliary Block:
Inside the orbit, the nasociliary nerve gives branches off the ophthalmic nerve. The sphenoid, ethmoid, frontal sinuses, anterior septum, lateral nasal cavity, ala of the nose, and nose tip are all supplied by branches of the nerve. Anesthetic blocks are best directed at the anterior and posterior ethmoidal foramina, providing anesthetic to the infratrochlear nerve. Because epinephrine is rarely administered to lessen the risk of retinal artery spasms, the duration of action of this block is shortened.
5. Infratrochlear Block:
Another branch of V1 is the infratrochlear nerve. The infratrochlear nerve, a branch of the ophthalmic nerve, passes into the orbit alongside the medial rectus muscle. It supplies the medial canthus's inferior part, the nose's lateral part, the medial conjunctiva, and the caruncle. This nerve's external position, which is felt below the trochlea, allows for targeted blocking through infiltration at the superomedial orbit. This block is frequently used in the anatomic regions during nose surgery or skin laceration repairs.
6. Anterior Ethmoid Block:
The anterior ethmoid nerve is divided into internal and external nasal branches that innervate the anterior septum, the lateral wall of the nasal cavity, the nasal bone, and skin up to the tip of the nose. The anterior ethmoidal foramen is 1.5 cm deep and placed medially from the midway point between the posterior palpebral fold and the forehead. A tiny gauge needle (25 to 27 gauge) is used for this block, accomplishing a continuous injection while withdrawing the needle. A needle inserted nine mm above the medial canthal tendon's superior border will prevent damage to the lacrimal sac.
7. Infraorbital Block:
The maxillary branch runs along the inferior orbital rim inside the infraorbital groove before coming out of the infraorbital foramen, which is about one centimeter below the lower rim of the orbit. The infraorbital nerve and its branches provide a sensory supply to the lower eyelid, lateral nose, upper lip, and maxillary teeth with sensory information. As a result, this nerve block can be used for several lower eyelid and maxillofacial surgeries. The block can be executed intraorally but requires accurate landmark identification. The intraoral approach is performed by inserting a needle superiorly parallel to the upper second premolar and moving it toward the foramen. To avoid injection into the foramen, careful palpation is required. The extraoral method is simple to understand. However, supplementary vasoconstrictive medicine is not advised because of the closeness of the facial nerve.
8. Zygomaticofacial and Zygomaticotemporal Nerve Blocks:
The zygomatic nerve arises from the maxillary nerve as it passes out of the pterygopalatine fossa. The zygomaticofacial branch extends from the zygomatic bone onto the face, innervates the surrounding skin, and can be anesthetized laterally at the inferolateral orbital rim.
The zygomaticotemporal branch enters the temporal fossa through a foramen, innervates the temporal skin, and gives secretomotor fibers to the lacrimal nerve.
The zygomaticotemporal branch will be targeted by an anesthetic applied to the concave surface of the posterolateral orbital rim and progress inferiorly to the level of the lateral canthus.
9. Facial Nerve Blocks:
The facial nerve block anesthetizes the periocular branches of the facial nerve during ocular surgery to minimize excessive blinking during surgery by orbicular muscle akinesia. The three traditional approaches are O'Brien's block, Atkinson block, and Van Lint block. In various ocular surgeries, including cataract surgery, pterygium excision, keratoplasty, dacryocystorhinostomy, glaucoma operations, and minor oculoplastic treatments, using a facial nerve block as a local anesthetic approach may be desirable.
What Are the Complications of the Ophthalmic Nerve Block?
Complications differ widely based on the method used. Retrobulbar blockage increases the chances of retrobulbar bleeding, globe damage, optic nerve or extraocular muscle injury, and central spread accompanied by depression in the brain stem. Other periocular local and regional blocks provide the following risks:
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Ecchymosis (a discoloration of the skin due to bleeding below the skin), hematoma, and bleeding and infection.
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Local tissue injury and swelling.
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Anesthesia is injected into the veins.
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Nerve damage, whether temporary or permanent.
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The anesthetic's systemic toxicity.
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Anesthetic-induced allergic response.
Conclusion
Eye blocks offer good anesthesia for ocular surgeries and have a high success rate. Both needle and cannula orbital injections can provide adequate anesthesia and akinesia, but they can also have significant local and systemic consequences. Knowledge of orbital anatomy and training is required to perform orbital regional anesthesia.
