Introduction
One of the most frequent surgical procedures in developed countries that involves anesthesia is ophthalmic surgery. The local and regional nerve blocks and ophthalmic anesthesia provide insights into several fundamental principles of sound anesthetic technique. Retrobulbar anesthesia (RBA), which was administered by the surgeon, was considered the gold standard for eye nerve blocks. Nevertheless, less invasive phacoemulsification (PhE) procedures have replaced previous wide-incision techniques like extra-capsular cataract extraction in cataract surgery. As a result, phacoemulsification (PhE) no longer requires absolute akinesia for the new generation of cataract surgeons.
What Is Periocular Anesthesia?
Periocular anesthesia is one of the most frequent operations requiring anesthesia in ophthalmic surgery. Together with general anesthesia, local anesthetics such as
Topical: Tetracaine, Lidocaine, Proparacaine, and Oxybuprocaine are currently the most often used topical anesthetics. Depending on their molecular composition, topical anesthetics can be categorized as amide or ester molecules. These substances reduce inflow by blocking sodium channels in the nerve cells. As a result, neuronal conduction through axons and dendrites is inhibited and the threshold potential and action potential cannot be attained. Intracameral is used as an alternative technique to topical anesthesia.
Sub-Tenon: The local anesthetic is injected into the possible area between Tenon's capsule and the sclera during Sub-anesthesia. The inferonasal conjunctival fornix is the most common location for this area, but it can potentially be accessed from any quadrant of the globe. The posterior direction of the globe is followed with a purpose-specific needle or cannula using either a surgical or nonsurgical technique. Thereafter, an injection of the local anesthetic (LA) solution may be given superficially or deeply. The LA can expand radially over the scleral section of the globe with relatively little injection volumes by performing "superficial" or more anterior injections. Larger injection volumes of about 8 to 11 ml ensure consistent akinesia. Eventually, spreading the local anesthetic solution to the extraocular muscle sheaths results in chemosis (a subconjunctival spread of LA), which requires compression to resolve intraocular pressure.
Retrobulbar Anesthesia: Retrobulbar anesthesia (RBA) is one of the standard anesthetic techniques for the eye and orbit. Typically, this procedure entails injecting a minimal amount of LA solution (3 to 5 mL) inside the ocular muscle. The superior oblique muscle typically retains function due to its extraconal motor regulation, preventing complete akinesia of the globe. The primary risk of RBA is the potential for damage to the globe or a muscle cone anatomical component. These structures are tightly clustered and fixed by the tendon of Zinn near the apex, where they cannot move away from a needle.
Peribulbar Anesthesia: It is performed by injecting the needle into the extraconal space. Two injections are used in the conventional procedure. The needle is inserted at the same spot as for an RBA injection but with a smaller up-and-in angle to approach inferior and temporal regions. The second injection is superior and nasal and is placed between the lateral two-thirds and medial third of the margin of the orbit. a higher volume of LA (6 to 12 mL) is administered. Because of the greater volume, the LA can spread over the entire corpus adipose of the orbit, including the intraconal area, which contains the nerves that need to be blocked. The anterior diffusion of LA to the lids, which provides a nerve block of the orbicular muscle and eliminates the need for a supplemental ocular nerve block, is also made possible by the enormous volume.
What Are the Indications for Periocular Anesthesia?
In the group of ophthalmologic procedures where general anesthesia is not required, local ocular anesthetic is recommended, especially for procedures involving patient cooperation. Nearly all intraocular procedures, such as
- Cataract removal.
- Corneal transplantation.
- Glaucoma surgeries.
- Vitreoretinal surgeries.
- Scleral buckling.
- Strabismus correction.
- Enucleation.
What Are the Contraindications for Periocular Anesthesia?
The major contraindications include
- Allergic reactions.
- Nystagmus (rhythmic, abnormal eye movements).
- Enoptholmus or bulging of eyes.
- Staphyloma (abnormal protrusion of the eye).
- Prolonged surgery.
- Uncooperative patient.
- Elongated eyes.
What Is the Common Agent of Periocular Anesthesia?
The most significant anesthetic agent of the ocular region involve
- Cocaine derivatives like bupivacaine, and lignocaine.
- Epinephrine: Epinephrine is indicated in patients with preexisting cerebrovascular disease because it can restrict the ophthalmic artery and result in retinal ischemia. Additionally, increases the action anesthetic, reduces bleeding, and systemic absorption.
- Hyaluronidase: It has been demonstrated that hyaluronidase injections provide more immediate and thorough anesthesia than injections lacking hyaluronidase.
- Sodium Bicarbonate: By raising the anesthetic solution's pH, sodium bicarbonate causes Bupivacaine to transition into its noncationic form, which more easily diffuses into adjacent nerves.
What Are the Pre-operative Considerations of Periocular Anesthesia?
- The preoperative condition may be influenced by patient anxiety. Direct communication between the patient and the surgeon can greatly reduce anxiety. Even while using auxiliary staff to deliver preoperative and postoperative instructions may be time-effective. Whenever surgery is decided to be performed, it is crucial to have a complete medical history.
- Psychiatric history of anxiety, panic disorders, psychosis, and equally important, how the patient feels about prior cosmetic procedure experiences, both the process and the outcome, should also be gently enquired into in addition to the usual questions about malignant hyperthermia, excessive nausea, prolonged sedation, increased bleeding, and frequent coughing. Enquire about anti-coagulant or anti-platelet medications, bleeding issues, and both. However, there is currently no suggestion for patients taking anti-platelet drugs, whereas those taking anti-coagulants may continue their medications as long as their levels are within therapeutic ranges.
- Before considering a retrobulbar block, it may be helpful to evaluate the axial length of the eye because long eyes have a higher risk of globe or optic nerve injury.
- Antibiotics, analgesics, antiemetics, and anxiolytics can be obtained earlier on, preventing the need for a fast drugstore after surgery. Those who are expected to experience substantial anxiety can take 5 to 20 mg of Diazepam one hour before surgery.
What Are the Risk Factors of Periocular Anesthesia?
- Temporary reduction in visual function as a result of conduction blockage of the optic nerve or ischemia brought on by optic nerve compression.
- Permanent vision loss due to invasion of the retina, optic nerve, or central retinal artery.
- Diplopia caused by extraocular muscle damage is frequently brought on by anesthetic injection into a muscular sheath.
- Oculocardiac reflex is a condition characterized by cardiac arrhythmias and hypotension can be brought on by exerting pressure on the globe or manipulating the extraocular muscles or conjunctiva.
- Retrobulbar venous or arterial hemorrhage since arterials tend to expand quickly, which can lead to rapid orbital edema and an increase in IOP (intraocular pressure).
- Signs of breathing problems, dysphasia, hypertension, tachycardia, acute trembling, agitation, confusion, or unconsciousness typically appear minutes after the anesthetic has been administered.
Conclusion:
Whether a patient thinks about the surgical outcome and their surgeon is likely to be significantly influenced by their experiences leading up to, during, and following any treatment. Positive impression-makers are more likely to be patient with the healing process and accepting of nature's little flaws. The actual surgical procedure, which is intricately entwined with the accompanying anesthesia, is crucial to this process. For enucleation, periocular anesthesia combined with closely managed intravenous sedation is less expensive than general anesthesia and decreases early postoperative morbidity.
