Ophthalmic surgery is one of the most common procedures requiring anesthesia. Since Knapp first used cocaine for ocular anesthesia in 1884, anesthetic techniques have greatly advanced.
Current main anesthetic options include local anesthesia methods such as topical anesthesia, sub-Tenon’s anesthesia, peribulbar anesthesia, and retrobulbar anesthesia, as well as general anesthesia. In recent years, with the spread of small-incision surgery, local anesthesia has become mainstream. With the increase in outpatient and day surgeries, ambulatory anesthesia is becoming standardized. 1)
Target surgeries include almost all intraocular procedures such as cataract extraction, corneal transplantation, glaucoma surgery, vitreoretinal surgery, scleral buckling, strabismus correction, and enucleation. In Japan, topical anesthesia and sub-Tenon’s anesthesia are widely used for cataract surgery, while sub-Tenon’s and retrobulbar anesthesia are used for glaucoma and vitreous surgery.
In recent years, local anesthesia (especially topical eye drops) has become mainstream. General anesthesia is considered when surgery under local anesthesia is difficult, such as in uncooperative patients, children, or those with cognitive decline.
In ophthalmic surgery under local anesthesia, the patient may experience the following sensations.
Topical Anesthesia
Target area: Suppresses somatic pain in the cornea, conjunctiva, and sclera. Visceral pain in the iris and ciliary body cannot be suppressed.
Characteristics: 0.4% oxybuprocaine (Benoxil®) takes effect approximately 16 seconds after instillation, with an average recovery time of 13 minutes. For surgery, 4% Xylocaine® eye drops are used.
Limitations: Eye movement cannot be suppressed, and akinesia is not achievable.
Intracameral Anesthesia
Purpose: Used as an adjunct to topical anesthesia.
Method: Inject 0.5 mL of preservative-free 1% lidocaine into the anterior chamber. Duration of action is approximately 10 minutes.
Caution: If 1% lidocaine remains in the anterior chamber for more than 3 minutes, transient changes in the corneal endothelium may occur. Therefore, administer within 3 minutes before starting phacoemulsification.
Sub-Tenon's Anesthesia
Characteristics: A relatively new anesthesia method introduced in 1990. Sensory and pain control are equivalent to retrobulbar anesthesia. Serious complications such as globe perforation are rare.
Technique: A small incision is made in the inferonasal conjunctiva with a 27G blunt needle, and the anesthetic is injected into the sub-Tenon’s space (a favorable site without oblique muscles).
Dosage: For short procedures, 1 mL of 2% lidocaine alone (duration about 1 hour). For longer procedures such as vitrectomy, 3–4 mL (mixture of lidocaine and a long-acting agent).
Retrobulbar and Peribulbar Anesthesia
Retrobulbar anesthesia: Anesthetic is injected into the muscle cone. It blocks the oculomotor, trochlear, abducens, optic, and trigeminal nerves, as well as the ciliary ganglion. It provides the highest degree of akinesia. Use 4–6 mL of anesthetic and a needle no longer than 32 mm.
Peribulbar anesthesia: A short needle (≤25 mm) is advanced horizontally beneath the globe. A larger volume of anesthetic (6–10 mL) is required. The risk of globe perforation is low, but the theoretical risk of brainstem anesthesia is higher.
The order of akinesia efficacy is: retrobulbar anesthesia > sub-Tenon’s anesthesia > topical anesthesia, while the ease of technique is the reverse.
A Cochrane review found no difference in pain scores between peribulbar and retrobulbar anesthesia (MD −0.03), and no difference in akinesia (RR 0.98). Peribulbar anesthesia is associated with more chemosis (RR 2.11), while retrobulbar anesthesia is associated with more eyelid hematoma (RR 0.36).
Sub-Tenon’s anesthesia has fewer serious complications and can be used for many intraocular surgeries including cataract, glaucoma, and vitrectomy. Retrobulbar anesthesia provides better akinesia but carries risks of globe perforation and optic nerve injury. In highly myopic eyes (long axial length), the risk of complications with retrobulbar anesthesia is increased, so sub-Tenon’s anesthesia may be recommended.
The choice of anesthesia method should comprehensively consider the patient’s general condition, ocular condition, and type of surgery.
Absolute contraindications for local anesthesia:
Relative contraindications for retrobulbar and peribulbar anesthesia:
The presence of posterior scleral staphyloma is more decisive than simple axial elongation as a risk factor for globe perforation. The reported rate of ocular injury is 0.007% for retrobulbar block and 0.022% for peribulbar block.
When general anesthesia is considered:
Other precautions: anticoagulants can be continued if within therapeutic range. There are no clear recommendations for antiplatelet drugs. It is also important to check systemic diseases (hypertension, arrhythmia, thyroid disease, diabetes). The use of adrenaline is generally contraindicated in diabetes, hyperthyroidism, and hypertension.
High axial myopia is a relative contraindication for retrobulbar and peribulbar anesthesia. In particular, posterior scleral staphyloma is a definitive risk factor for globe perforation, so sub-Tenon’s anesthesia or topical anesthesia is preferred.
Preoperative evaluation is important for selecting the appropriate anesthesia method and ensuring safe surgery.
The ESCRS guidelines recommend refraction, visual acuity, slit-lamp examination, axial length measurement, and intraocular pressure measurement as preoperative assessments for cataract surgery (GRADE ++).
The characteristics of the main local anesthetics used in ophthalmology are shown below.
| Drug name | Classification | Main uses |
|---|---|---|
| Lidocaine (Xylocaine®) | Amide type | Topical, infiltration, and conduction anesthesia |
| Bupivacaine (Marcaine®) | Amide type | Conduction anesthesia for long surgeries |
| Ropivacaine (Naropin®) | Amide type | Conduction anesthesia for long surgeries |
| Oxybuprocaine (Benoxil®) | Ester type | Eye drops for examination/pre-treatment |
Details of each drug are shown below.
Ester-type anesthetics are rapidly broken down by blood esterases, but have a high risk of anaphylaxis and are not used for infiltration or conduction anesthesia in ophthalmology. Amide-type anesthetics are metabolized in the liver and have a high safety profile.
According to a Cochrane review, when comparing sub-Tenon anesthesia with topical anesthesia, intraoperative pain is less with sub-Tenon anesthesia (SMD 0.64), and pain at 24 hours postoperatively tends to be less with topical anesthesia, but the difference is not statistically significant (SMD −0.20).
In cataract surgery, needle-free topical anesthesia is the mainstream, and in most cases there is little to no pain. Furthermore, adding intracameral lidocaine further reduces intraoperative pain. A Cochrane review has confirmed the effectiveness of this combination.
Amide-type local anesthetics, such as lidocaine, block sodium channels in the nerve membrane, inactivating action potentials and interrupting nerve transmission.
Ocular pain is classified into the following two types.
The progressive stages of local anesthetic toxicity and their management are shown below.
| Stage | Symptoms | Management |
|---|---|---|
| Early stage | Tingling of mouth and tongue, dizziness, tinnitus | Discontinue administration, observe |
| Middle stage | Agitation, anxiety, talkativeness | Administer oxygen, enhance monitoring |
| Late | Loss of consciousness, seizures | Airway management, diazepam administration |
| Severe | Respiratory arrest, circulatory collapse | Cardiopulmonary resuscitation, lipid emulsion administration |
Initial symptoms include tingling of the mouth and tongue, dizziness, and tinnitus, which progressively lead to loss of consciousness and circulatory collapse. After injection, it is important to carefully observe the patient’s verbal responses and vital signs to avoid missing early symptoms.
The following are trends in new drugs and technologies reported in the latest narrative review. 1)
New sedatives and general anesthetics
Remimazolam is an ultra-short-acting benzodiazepine that is attracting attention in MAC and general anesthesia. Animal experimental data suggest that the inhaled formulation significantly enhances analgesic effects when combined with remifentanil (without adverse pulmonary events). 1)
ADV6209 (a novel oral midazolam formulation) is characterized by prolonged duration of action and improved taste, and its pharmacokinetic parameters are reported to be equivalent to those of conventional formulations. 1)
JM1232 (MR04A3) is a non-benzodiazepine GABAA modulator. It is antagonizable by flumazenil, and a 1% aqueous solution shows rapid onset and minimal hemodynamic effects. 1)
Alphaxalone (Phaxan™) is injection pain-free, with rapid onset, short duration, minimal hemodynamic effects, and expected early cognitive recovery. 1)
AZD3043 is a water-insoluble formulation that does not cause injection pain and is characterized by rapid induction and elimination. However, side effects such as erythema, dyspnea, and involuntary movements have been reported. 1)
Novel local anesthesia and adjunctive techniques
DTFNB (deep topical fornix nerve block) is a technique that integrates the safety of topical anesthesia with the extensive anatomical distribution of retrobulbar anesthesia. Ropivacaine 0.2% is considered superior to bupivacaine (due to vasoconstrictive effect and longer duration of action). 1)
Mydrane® (tropicamide/phenylephrine/lidocaine combination) is the first fixed-dose mydriatic and anesthetic combination approved for intracameral use in adult cataract surgery, with promising results reported in phase 3 trials. 1)
Ultrasound-guided ophthalmic regional anesthesia is being studied for T-sign evaluation in sub-Tenon’s block, color Doppler monitoring of ocular blood flow, and application of ultrasound biomicroscopy (UBM) and B-probe with ultra-high-speed 3D scanning. 1)
BIS monitoring and opioid issues
A BIS value of 40–60 with appropriate muscle relaxation is predicted to achieve favorable eye position, potentially contributing to improved safety in ophthalmic surgery under general anesthesia. 1)
Due to issues of postoperative opioid dependence and abuse, the development of standardized prescribing guidelines has been proposed. A trial of opioid substitution with dexmedetomidine was discontinued early due to severe bradycardia and hypoxemia. 1)
