Intracameral anesthesia, an anesthetic modality involving the injection of a small volume of an amide anesthetic into the anterior chamber, is among the newest modalities in ocular surgery. It was introduced as an adjunct to topical anesthesia as a possible method for providing additional anesthetic effect by blocking the sensory nerves in the iris and ciliary body. In this way, intracameral anesthesia would reduce discomfort during iris and lens manipulation and intraocular lens (IOL) implantation in cataract surgery.
II. EFFECTIVENESS OF INTRACAMERAL ANESTHESIA
Several studies have shown significantly decreased pain and improved comfort with the addition of intracameral anesthesia to topical anesthetics. However, many reports have also demonstrated minimal pain with or without intracameral anesthesia and therefore marginal pain control benefit with this modality as an adjunct to topical anesthesia.
A. Preparing the Patient
To maximize patient comfort, careful and detailed preoperative counseling should be given to patients regarding what to expect during cataract surgery while under topical anesthesia with or without an intracameral agent. Being informed that they may be aware of tissue manipulation or the microscope light may help mitigate intraoperative anxiety experienced by patients. Patients may mistakenly interpret these experiences or sensations as pain.
B. Anesthesia in Routine and Complex Cases
It has been the authors’ experience that in over 90% of the cases, topical lidocaine 2% jelly given within 10 minutes prior to the surgery is all that is necessary in routine cases. Adjunctive sub-Tenon, intracameral, or even perior retrobulbar anesthesia may be necessary if there are more complexities in the case such as a small pupil requiring stretching maneuvers, combined glaucoma procedures, dense nuclei, Flomax (Boehringer Ingelheim Pharmaceuticals, Inc) cases, or other such issues.
III. INTRACAMERAL ANESTHETIC AGENTS
A. Volume and Method of Administration
There is no standard regarding the volume of intracameral anesthesia; however, the use of between 0.1 and 0.5 mL is reported in the literature without event.5,6 The anesthetic agent should be directed near the iris or through the pupil and under the iris to allow for diffusion around the iris tissue and ciliary body. No study has evaluated the optimal point in the procedure to administer the intracameral anesthetic. Generally, most surgeons inject the anesthetic agent through the paracentesis prior to the start of the capsulorrhexis and before the viscoelastic agent is injected. Others may inject prior to the phaco portion of the procedure or in response to the patient having discomfort with topical anesthesia alone at any point in the procedure.
B. Concentration and Corneal Toxicity
Preservative-free (PF) lidocaine 2% or more concentrated dosages are associated with corneal endothelial changes.2,7 Therefore, PF lidocaine 1% is likely the safest choice for an intracameral anesthetic agent. Bupivacaine 0.5% diluted with 1:1 glutathione bicarbonate has no associated corneal changes compared to the corneal swelling associated with bupivacaine 0.5% alone.Tetracaine hydrochloride 0.5% has been demonstrated to be without corneal toxicity; however, bupivacaine 0.75% and proparacaine hydrochloride 0.5% cause corneal thickening and opacification.
C. Retinal Toxicity
Regarding retinal toxicity, published research has demonstrated that there was no diffusion to the posterior segment by intracameral anesthetic agents.In addition, using electroretinogram (ERG) measurements, numerous reports found no significant reduction in ERG amplitudes after use of intracameral lidocaine 1%.No systemic concentration of lidocaine has been detected with intracameral use of an amide anesthetic, and cardiac and respiratory functions remain stable throughout the surgical procedure.However, long- term sequelae have not been studied and so remain unknown.
*Dikutip dari Buku Essentials of Cataract Surgery 2nd Ed, halaman 45-47