Anesthesia for elective eye surgery

INTRODUCTION — The goals of anesthetic care during elective eye surgery are pain-free surgery, facilitation of the surgical procedure, rapid recovery, and minimization of risks associated with surgery and anesthesia.

This topic reviews the techniques for providing analgesia, sedation, or anesthesia during cataract, glaucoma, and vitreoretinal surgery. Other aspects of surgical management of these conditions are discussed separately:

●(See "Cataract in adults", section on 'Surgical treatment'.)

●(See "Retinal detachment".)

●(See "Open-angle glaucoma: Treatment", section on 'Types of therapy'.)

●(See "Angle-closure glaucoma", section on 'Management'.)

GENERAL CONSIDERATIONS — Cataract surgery is one of the most common procedures requiring anesthetic care [1]. Other types of elective eye surgery include intraocular glaucoma surgery, vitreoretinal surgery (eg, for retinal detachment), and strabismus repair.

Preoperative consultation — The preoperative medical evaluation includes evaluation of comorbid conditions and perioperative decisions regarding chronically administered medications. Low-value preoperative testing is avoided [2]. Further details are available in a separate topic. (See "Cataract in adults", section on 'Preoperative planning'.)

Consultation for anesthetic management emphasizes the following additional considerations [3]:

Anesthetic considerations — Most elective eye surgery is performed with a topical or regional anesthetic technique, combined with monitored anesthesia care (MAC). Regional anesthetics may be performed by anesthesiologists and certified registered nurse anesthetists or the ophthalmologist.

The preanesthetic consultation includes:

●Assessment of communication and cooperation – It is critical that the patient can lie flat comfortably during eye surgery with no movement if topical or regional anesthesia with MAC is planned [4]. Thus, it is important to confirm that the patient is willing to cooperate, and can understand instructions and communicate with the team to express discomfort. Also, the patient should be asked about claustrophobia, as this condition may impact ability to cooperate.

●Focused medical history – Performance of a focused medical history, including use of any anticoagulant or antithrombotic therapies, previous eye operations, and overall suitability for same-day surgery [5]. Although many patients with cataracts are older adults with comorbidities such as diabetes, hypertension, obesity, or chronic obstructive pulmonary disease (COPD), there are few conditions that preclude cataract surgery for those who can tolerate positioning to perform the procedure [4]. Cataract surgery incurs little risk since physiologic stress is minimal and no blood loss or fluid shifts occur. However, significant delays for indicated cataract surgery (ie, more than four months) are associated with increased morbidity due to greater likelihood of falls with hip fracture, automobile accidents, worsening cognitive impairment, and higher mortality [6]. For these reasons, we agree with the Society for Ambulatory Anesthesia position statement recommending that cataract surgery not be postponed unless the patient has an acute condition that requires time to achieve optimal medical management. Examples of such conditions include [4]:

•Recent myocardial infarction (within 30 days)

•Recent percutaneous coronary intervention (within 14 days without stenting or within 30 days with stenting)

•New onset of clinically significant arrhythmia(s)

•Decompensated heart failure

•New onset of a serious pulmonary condition (eg, upper respiratory infection, pneumonia, pulmonary embolus), or exacerbation of a severe chronic condition (eg, COPD).

•New onset of a neurologic condition (eg, stroke, transient ischemic attack, altered mental status)

•Malignant hypertension with evidence of acute end-organ damage (eg, encephalopathy, myocardial ischemia, acute kidney injury)

•Recent episode of diabetic ketoacidosis or hyperosmolar hyperglycemic nonketotic syndrome

●Focused physical examination – Standard airway assessment is always performed. Detection of relevant abnormalities on physical examination, including any conditions that interfere with the ability to lie supine comfortably (eg, severe congestive heart failure, COPD, back pain, or claustrophobia) when topical or regional anesthesia is planned.

●Preoperative testing – No benefits derive from routine testing before cataract surgery [4,7,8]. Tests are indicated only in patients with severe new or acutely exacerbated medical problems that would warrant investigation in any setting [9].

●Awareness of chronically administered oral medications and ophthalmic solutions – In addition to noting the patient's chronically administered oral medications (see "Perioperative medication management"), the anesthesiologist should be aware of potential systemic effects of chronically administered eye drops. Ophthalmic nonselective beta-adrenoreceptor antagonists such as timolol and carteolol may cause decreased heart rate and increased systemic vascular resistance, or decreased forced expiratory volume in one second (FEV₁) [10]. Relevant systemic effects of other ophthalmic solutions include an increase in heart rate or blood pressure (BP) with muscarinic agonists such as pilocarpine, increased BP with phenylephrine, decreased BP with drops that have alpha-2 adrenergic agonist effects (eg, brimonidine or apraclonidine), flushing or drowsiness with atropine, or bronchospasm with pilocarpine or nonsteroidal antiinflammatory drugs (NSAIDs) [10].

●Instructions regarding fasting – Standard preoperative fasting guidelines require that patients may not drink non-clear liquids or consume solids within six hours of elective procedures requiring anesthesia or sedation, while at least eight hours should elapse following a large or fatty meal. Patients may drink clear liquids (eg, water, juices without pulp, coffee or tea without milk, carbohydrate drinks) until two hours before elective procedures requiring anesthesia or sedation but should consume no liquids within two hours of surgery. (See "Preoperative fasting in adults", section on 'Fasting guidelines'.)

There is a lack of consensus regarding the fasting interval for patients undergoing elective eye surgery with planned regional anesthesia but with minimal or no sedation. Some clinicians use a more liberal guideline for such patients if aspiration risk is low and a need for heavy sedation or conversion to general anesthesia is unlikely, allowing consumption of a light meal (eg, tea and toast) before surgery [11]. This more liberal approach has the advantages of preventing preoperative thirst and hunger as well as enhancing patient satisfaction. Nonetheless, many (including KM) believe that more research is warranted before endorsing and adopting this more liberal approach.

Ophthalmic considerations

●Anticoagulant and antithrombotic therapies: Implications for bleeding – For patients who have a high risk of clotting and embolic complications due to cardiac or vascular pathology, administration of therapeutic doses of aspirin and warfarin are usually continued throughout the perioperative period [12,13], as noted in a review of bleeding versus thrombosis risks for various ophthalmic procedures [14]. One large retrospective study noted no higher incidence of sight-threatening bleeding complications after regional anesthesia (ie, eye block) in patients taking aspirin, warfarin, or clopidogrel before cataract surgery, compared with patients not taking these drugs [15].

There is conflicting evidence regarding bleeding risk during elective eye surgery in patients receiving dual antiplatelet therapy (eg, aspirin plus clopidogrel), and scant data for other types of eye surgery [14,16-18]. Since dual antiplatelet therapy is often used after placement of a drug-eluting coronary artery stent, and fatal stent clotting may develop if antiplatelet medications are prematurely discontinued, we suggest delaying eye surgery until after the minimum period recommended for daily administration of dual antiplatelet therapy in such patients, if possible [13,19]. (See "Cataract in adults", section on 'Management of antithrombotic agents' and "Long-term antiplatelet therapy after coronary artery stenting in stable patients".)

Studies in patients taking direct oral anticoagulants (DOACs) such as apixaban, rivaroxaban, and dabigatran have consistently shown lower intraocular bleeding risk as compared with warfarin [20]. One retrospective study noted that continuing chronically administered DOAC therapy throughout the perioperative period in 42 patients did not result in a higher incidence of bleeding complications compared with withholding these medications in 24 cases [16]. Also, a prospective case control study compared the complication rate from peribulbar anesthesia in 750 patients taking oral vitamin K antagonists with 750 patients who had never been treated with any anticoagulant [21]. Patients who continued oral anticoagulation during the perioperative period had no increased incidence of sight-threatening bleeding following regional anesthesia compared with those not taking any anticoagulant.

Taken together, these data suggest that perioperative management of patients receiving anticoagulant and antiplatelet drugs should be individualized with respect to timing of elective eye surgery [14]. Discussions and decision-making for these patients balances relative risks of bleeding during or after eye surgery versus thrombosis in the coronary arteries or other vascular sites. Such discussions involve the ophthalmologist, anesthesia provider, clinician who prescribed the drug(s), and the patient.

●Axial eye length: Implications for globe perforation during regional block – The axial length of the eye (distance from the cornea to the retina) is routinely measured by ultrasound before cataract surgery to determine the proper intraocular lens size to be implanted. It has been noted that patients with long eyes (axial length >25 mm) have an increased risk of needle injury during a retrobulbar (intraconal) block, usually due to penetration of the posterior pole of the globe [22-24]. Indications that the eye may be longer than average include a history of myopia in childhood (confirmed by an affirmative answer to the question, "Did the patient need to wear glasses as a child to see distant objects?") or the presence of globe-enveloping intraorbital hardware, such as a scleral buckle [24,25]. (See 'Retrobulbar block (intraconal block)' below.)

Also, patients with an abnormal outpouching of the eye called a staphyloma (figure 1), which is usually associated with an axial length >25 mm and is usually located in the posterior portion of the globe, are at increased risk for globe perforation by a retrobulbar needle [23,24].

In such patients, retrobulbar block is usually avoided in favor of a peribulbar (extraconal) or sub-Tenon block, topical anesthesia, or general anesthesia. (See 'Regional anesthesia' below.)

●Prior intraocular gas bubble: Implications for expansion by nitrous oxide – Patients with a previously injected intraocular gas bubble cannot receive nitrous oxide until an ophthalmologist's examination has been performed to document complete absorption of the gas bubble. There are multiple case reports describing blindness after nitrous oxide administration within a few months of gas bubble injection [26-28]. (See 'Vitreoretinal surgery' below.)

Intraoperative management — During MAC for the surgical procedure, the following considerations apply (see "Monitored anesthesia care in adults"):

Positioning considerations — Positioning of the patient on the operating table is supervised collaboratively by the anesthesiologist and the surgeon to ensure patient and surgeon comfort during the procedure and avoid potential complications. (See "Patient positioning for surgery and anesthesia in adults", section on 'General considerations' and "Patient positioning for surgery and anesthesia in adults", section on 'Supine'.)

Specific considerations for intraocular surgery include [29]:

●Position the head at the top edge of the table to avoid surgical back and neck pain due to poor posture.

●Support the head on a comfortable headrest to prevent head movement.

●Position the head above or at the level of the heart to avoid increased venous pressure in the eye that may exacerbate intraoperative hemorrhage.

●Once properly positioned, consider taping the head to the operating room table to prevent or minimize unexpected sudden movement.

●Restrain arms to the patient's side with the draw sheet or secure straps on the arm boards to prevent sudden arm movement (eg, toward the eye or dropping off the table).

●Configure surgical drapes to minimize the accumulation of oxidizers (eg, oxygen [O₂]) under the drapes. (See "Fire safety in the operating room", section on 'Drapes, towels, sponges, and gauzes'.)

Management of sedation — Sedation is minimized to reduce the risk of side effects (eg, restlessness, confusion, unresponsiveness, or airway obstruction) that may jeopardize the patient's ability to cooperate during surgery. Patient cooperation is necessary throughout the procedure to avoid any head movement. Even minor movement, which is highly magnified under a microscope, may result in eye injury.

If the patient experiences eye pain, the ophthalmologist is alerted to request administration of additional local anesthetic. Heavy sedation should not be used as a substitute for inadequate analgesia [30].

Management of oxygenation — We routinely deliver compressed medical air (ie, 21 percent O₂) under the surgical drapes, either via nasal canula at a rate less than 4 L/minute or into a face tent at 10 L/minute during the surgical procedure. If supplemental O₂ is required, we use an air/O₂ blender to deliver the lowest O₂ concentration required (ideally ≤30 percent), maintain adequate O₂ saturation as measured by pulse oximetry (SpO₂). Keeping the delivered O₂ concentration to 30 percent or less reduces risk of fire if an ignition source (eg, electrocautery) is used [31]. If a higher concentration of O₂ is temporarily required, then the surgeon should be warned preoperatively not to use a possible ignition source (eg, electrocautery) until the following measures have been taken (see "Fire safety in the operating room", section on 'Limit oxygen administration and avoid nitrous oxide'):

●The surgeon informs the anesthesia provider that electrocautery will be required

●The anesthesia provider turns off or reduces the concentration of O₂ delivered to the patient's face to allow a decrease to <30 percent

●The anesthesia provider then informs the surgeon that use of a heat source (ie, electrocautery) is now safe

We minimize O₂ buildup by flushing the field under the surgical drapes with medical air to reduce the risk of rebreathing high levels of carbon dioxide (CO₂). Some clinicians employ vacuum suctioning to scavenge the operating field and expired CO₂ [31,32]. Use of a forced air warming blanket device also reduces CO₂ accumulation under the drapes [33]. (See "Fire safety in the operating room", section on 'Management of open oxygen delivery systems'.)

Postoperative management — Patients are typically instructed not to drive a car, operate machinery, or drink alcohol until at least the day after surgery or when the effects of sedation have dissipated, the eye patch has been removed, and vision has returned to baseline or better.

ANESTHETIC TECHNIQUES

Topical anesthesia

●General principles – Topical anesthesia (typically with supplemental intracameral preservative-free lidocaine) is the most common technique for cataract and intraocular glaucoma surgery in the United States [34]. Topical anesthesia is a good choice for short, uncomplicated procedures in which the surgeon does not require complete akinesia (eg, cataract surgery with phacoemulsification through a small corneal incision), as well as in the following situations:

•Fully anticoagulated patients, due to concerns regarding the risk of bleeding during needle insertion to perform a regional technique.

•Patients with monocular vision (ie, unilateral blindness), due to concerns regarding the risk of vision loss in the remaining eye because of perforation or penetration of the globe during performance of a regional eye block.

●Technique – The anesthesiologist, ophthalmologist, or specialized nurse applies local anesthetic eye drops or gels on the cornea and conjunctiva (eg, lidocaine 2% jelly, proparacaine 0.5% solution, tetracaine 0.75% solution, or chloroprocaine 3%) [35]. Anesthetic gels produce greater levels of drug in the anterior chamber than equal doses of drops and may provide superior surface analgesia. However, gels may form a barrier to bactericidal agents; thus, they are administered after antiseptic solutions. Just before beginning surgery, the ophthalmologist may choose to supplement topical anesthesia with intracameral injection of 1% preservative-free lidocaine into the anterior chamber of the eye.

●Benefits – Topical analgesia is the simplest technique to anesthetize the anterior chamber of the eye and may be used as the sole anesthetic technique [36]. Risk of complications is low compared with other anesthetic techniques because no needle is used [37]. Vision is quickly regained in the postoperative period. (See 'Retrobulbar block (intraconal block)' below and 'Peribulbar block (extraconal block)' below and 'Sub-Tenon block' below.)

●Drawbacks – Topical analgesia cannot provide akinesia of the eye. Since the patient must voluntarily remain motionless for the entire procedure, appropriate patient selection is important. Anxious patients with a low pain threshold will likely fare better with a regional anesthetic technique or general anesthesia.

Risks of topical anesthesia are minimal, but very rarely, an allergic reaction or infection may occur.

Regional anesthesia — Profound anesthesia and akinesia of the eye are provided with a successful regional anesthesia technique (ie, eye block).

Management during needle insertion — The following considerations apply during needle insertion for a regional block:

●American Society of Anesthesiologists (ASA) standard monitors (including capnography for moderate or deep sedation) should be used during performance of the regional block, as well as during surgery [38]. The anesthesiologist must be vigilant for evidence of the oculocardiac reflex (resulting in bradycardia or asystole) or accidental injection of local anesthetic into a blood vessel (resulting in systemic toxicity) or into the central nervous system (resulting in brainstem anesthesia) [3]. Although rare, these situations might necessitate airway support or other emergency intervention. (See 'Oculocardiac reflex manifestations' below and 'Systemic complications' below.)

●Supplemental oxygen (O₂) is frequently administered at the time of initial sedation and during the block to reduce the risk of hypoxemia during sedation for the regional block.

●Sedatives (eg, midazolam) and/or opioids (eg, remifentanil) with a short duration of action are administered immediately before the regional block to reduce or eliminate the pain of needle insertion and injection of the local anesthetic. The goal of sedation is to minimize anxiety while providing the maximum degree of safety. An alternative technique is administration of small doses of propofol (eg, 10 to 20 mg increments) until the patient loses consciousness for approximately two minutes while the block is performed.

The anesthesiologist should avoid prolonged sedation, since subsequent performance of the surgical procedure requires an awake and cooperative patient. (See 'Intraoperative management' above.)

Commonly used agents — Traditionally, a combination of lidocaine 2% and bupivacaine 0.75% is used to yield a mixture of lidocaine 1% and bupivacaine 0.375%. This strategy theoretically offers the benefit of the earlier onset of lidocaine with the prolonged anesthetic from bupivacaine. Additionally, the blend reduces the associated risk of myotoxicity seen with lidocaine concentrations >2% and bupivacaine >0.5% [39]. However, the strategy of mixing local anesthetics remains controversial, and utilizing a single agent for eye blocks is a reasonable alternative [40]. Some clinicians use ropivacaine 0.75%; reported results include less pain on injection compared with other local anesthetics as well as excellent intraoperative akinesia and postoperative pain control [41,42]. If lidocaine is used alone, epinephrine may be added to prolong the duration of anesthesia.

The enzyme hyaluronidase as an ancillary agent is usually used with local anesthetics [43]. Concentrations between 1 and 7.5 units/mL are most commonly used, but concentrations as low as 0.75 units/mL may be effective [44]. The addition of hyaluronidase:

●Increases tissue permeability of the local anesthetic

●Promotes dispersion of the local anesthetic

●Reduces the increase in orbital pressure associated with the injected volume

●Enhances the quality of the block

●Reduces the risk of injury to the extraocular muscles

Peribulbar block (extraconal block)

●General principles – Peribulbar (extraconal) block was developed as a safer alternative to the retrobulbar (intraconal) block for providing anesthesia and akinesia of the eye [45]. The needle is typically shorter and is placed less deeply and at a different angle compared with placement for retrobulbar block. Theoretically, these modifications make the peribulbar block less likely to result in perforation of the globe posteriorly, injury to the optic nerve, or injection into the central nervous system with resultant brainstem anesthesia [45,46].

Also, peribulbar block produces more reliable akinesia of the orbicularis oculi, the muscle that closes the eyelids, compared with retrobulbar block [3,47]. This is due to the larger volume and distribution of local anesthetic injected (see 'Retrobulbar block (intraconal block)' below). Specifically, the patient cannot open the eyelid because cranial nerve III is blocked. Although the patient may be able to close the eyelid because cranial nerve VII is usually not completely blocked, the lid closure force is typically weak [47].

For all of these reasons, the peribulbar technique is more popular, but the retrobulbar block has not been entirely replaced [48]. (See 'Retrobulbar block (intraconal block)' below.)

●Technique – Typically, a single injection of 6 to 12 mL of local anesthetic is injected into the inferolateral quadrant. This produces an excellent block without the need for a second injection in most patients, due to spread of the injectate in all directions [49].

An alternate technique is a single injection of 5 to 6 mL of local anesthetic in the extreme inferolateral quadrant of the orbit, with additional injection of 3 to 5 mL in the medial quadrant (medial peribulbar), if necessary to produce adequate anesthesia and akinesia (figure 2) [50,51].

A needle ≤1.25 inches long is recommended to reduce the risk of injuring structures deep in the orbit. We use an Atkinson needle, which has a relatively blunt tip compared with the traditional needle used for intramuscular injections. The Atkinson needle may enhance the operator's ability to identify scleral tissue if it is encountered before perforation of the globe. However, some clinicians use sharper needles to minimize the pain of insertion and to theoretically limit the amount of damage to the globe if inadvertent perforation does occur.

●Benefits – The likelihood of inadvertent perforation of the globe or brainstem is theoretically less than with a retrobulbar (intraconal) block [45,46]. Also, peribulbar block produces more reliable akinesia of the orbicularis oculi, the muscle that closes the eyelids, compared with retrobulbar block [47]. Thus, a supplemental facial nerve block is rarely necessary. The success rate of the peribulbar (extraconal) block in producing anesthesia and akinesia of the eye is reported to be at least 84 percent, but may be higher with experience [50,52].

●Drawbacks – At least five minutes are required for the block to take effect, which is slightly longer than with a retrobulbar (intraconal) block. Conjunctival chemosis (swelling of the conjunctiva from accumulation of local anesthesia solution under it) is more common after peribulbar block, compared with retrobulbar block [48]. Globe injury is possible, although one study reported no instances of globe penetration or perforation in a series of 2000 peribulbar injections [46].

Retrobulbar block (intraconal block)

●General principles – Retrobulbar (intraconal) block produces profound analgesia and takes effect rapidly, in less than five minutes. This block was previously the predominant technique, but it is used less frequently now since theoretically safer techniques have been developed. (See 'Topical anesthesia' above and 'Peribulbar block (extraconal block)' above and 'Sub-Tenon block' below.)

●Technique – A single injection of 2 to 5 mL of local anesthetic is placed inside the muscular cone formed by the four recti muscles in the extreme inferolateral quadrant of the orbit. A needle ≤1.25 inches long is used to reduce the risk of complications (figure 3) [53]. (See 'Peribulbar block (extraconal block)' above.)

●Benefits – Retrobulbar block has a faster onset than peribulbar block and is associated with less chemosis (ie, swelling or edema of the conjunctiva). In experienced hands, it has a success rate of >85 percent [54].

●Drawbacks – Because a longer needle is often used with a retrobulbar (intraconal) block, this technique may have a higher risk of certain complications (eg, brainstem anesthesia) compared with the peribulbar (extraconal) block technique [3,24,37,45,46] (see 'Peribulbar block (extraconal block)' above and 'Management of perioperative complications' below):

•Globe perforation – The incidence of globe perforation as a result of retrobulbar block varies depending on many factors, including the skill of the operator and patient anatomy [55]. In two case series of patients receiving retrobulbar blocks, the incidence of globe penetration or perforation was 0.03 to 0.08 percent [22,56].

Patients with long axial eye length (>25 mm) have an increased risk of needle injury to the globe during performance of a retrobulbar block. One report notes a high incidence of inadvertent globe perforation in 1 out of 140 patients (0.7 percent) having an axial length ≥26 mm [57]. Thus, other regional techniques (eg, peribulbar [extraconal] block or sub-Tenon block), topical anesthesia, or general anesthesia are preferred in these patients. (See 'Ophthalmic considerations' above.)

If retrobulbar (intraconal block) is indicated to produce profound akinesia despite a long axial eye length, the approach for the needle insertion may be modified by introducing the needle less deeply and changing its angulation to reduce the risk of striking and injuring the posterior portion of the elongated globe.

Detection and management of globe perforation are discussed below. (See 'Globe or optic nerve perforation' below.)

•Brainstem anesthesia – The incidence of apparent central spread of local anesthetic into the brainstem was reported to be 16 cases in a series of 6000 patients receiving retrobulbar blocks [58]. Eight of these patients (0.13 percent) developed respiratory arrest. Brainstem anesthesia is thought to occur due to spread of local anesthesia entering the subarachnoid covering of the optic nerve sheath, and then into the midbrain [59].

•Retrobulbar hemorrhage – Retrobulbar hemorrhage manifests as rapid development of proptosis, tight orbit, and elevated intraocular pressure (IOP). This is an emergency that must be addressed with lateral canthotomy to relieve pressure. Elective surgery is usually cancelled and rescheduled for another day. This complication is thought to be less likely with peribulbar and sub-Tenon blocks since these are less likely to result in bleeding from within the cone.

•Absence of eyelid akinesia – Although akinesia of the orbit is profound, retrobulbar block may leave the orbicularis oculi muscles fully functional. Eyelid squeezing could cause extrusion of the intraocular contents during critical periods of certain procedures (eg, during corneal transplantation). Thus, a facial nerve block may occasionally be necessary to prevent squeezing of the eyelid (eg, a Van Lint block, in which local anesthesia is injected subcutaneously in a V shape above and below the orbit) [3,60].

•Eyelid hematoma – Eyelid hematoma is more common after retrobulbar block compared with peribulbar block [48].

Sub-Tenon block

●General principles – The sub-Tenon block employs a blunt cannula, rather than a needle, to induce regional anesthesia of the eye [3,61,62]. It is used in the United Kingdom and some other countries more often than in the United States. Onset of the block is rapid, but the extent of akinesia is variable and is proportional to the volume of local anesthetic injected [62,63].

Absolute contraindications to the sub-Tenon block include infection or a prior scleral buckle, while relative contraindications include prior retinal or glaucoma surgery.

●Technique – A blunt cannula is inserted through a small incision in the conjunctiva and Tenon capsule, also known as the episcleral membrane, with subsequent deposition of 3 to 5 mL of local anesthetics (figure 4) [64]. The local anesthetic reaches the posterior part of the globe, even with an anterior injection. Approximately five minutes is required for the block to take effect [3,65]. Additional infusion of 2 to 3 mL may be required if akinesia is inadequate.

Shorter (12 mm), more flexible plastic cannulae or ultrashort (6 mm) cannulae may be preferable to longer, more rigid metallic cannulae, although they are associated with a higher incidence of conjunctival hemorrhage and chemosis. Also, a newer minimally invasive technique for sub-Tenon block without incision has been developed [66].

●Benefits – The success rate for sub-Tenon block for producing anesthesia of the eye is reported to be >97 percent [63,67].

Because a blunt cannula (not a needle) is used for the block, globe perforation and other serious complications such as brainstem anesthesia can occur but are rare [68-70]. In one series of 6000 sub-Tenon blocks, there were no serious block-related complications [68].

In very myopic patients with an elongated axial eye length, there is a reduced risk of posterior pole perforation since the technique avoids needle placement in the posterior orbit.

Also, since major hemorrhage is rare with the sub-Tenon block, it may be a good choice for the anticoagulated patient at risk for retrobulbar hemorrhage [68].

●Drawbacks – Chemosis and minor subconjunctival hemorrhage occur with a higher frequency compared with needle blocks [70]. Chemosis is unlikely if small volumes are injected via a long cannula.

General anesthesia — A small percentage of adult patients undergoing cataract or other types of elective eye surgery require general anesthesia. These include patients who are unable to communicate and those who cannot cooperate due to neurocognitive dysfunction, severe anxiety, or claustrophobia. General anesthesia is also considered in patients who are unable to lie supine comfortably (eg, patients with severe and symptomatic congestive heart failure, chronic obstructive pulmonary disease [COPD], or back pain) or unable to remain motionless (eg, patients with tremor disorders such as Parkinson disease, severe anxiety, or claustrophobia). Furthermore, most children require general anesthesia because they are not able to reliably remain motionless during eye surgery. However, supplemental regional anesthesia is used for pediatric ophthalmic surgical procedures in selected cases [71].

During general anesthesia for eye surgery, a deep plane of anesthesia is maintained to avoid laryngospasm, coughing, or other movement that may cause direct eye injury and/or increase intraocular pressure (IOP) [72]. Endotracheal intubation is often used, particularly in patients at risk for aspiration during general anesthesia. If an endotracheal tube is used, a nondepolarizing neuromuscular blocking agent (eg, rocuronium or vecuronium) is administered and titrated according to monitoring of muscle relaxation with a peripheral nerve stimulator.

However, in patients without specific aspiration risk, the laryngeal mask airway (LMA) has been used with increasing frequency during elective eye surgery [73,74]. Advantages of the LMA include less risk of increasing IOP during insertion and removal due to less straining and coughing [74,75]. As with endotracheally intubated patients, a deep plane of anesthesia is maintained during eye surgery to avoid laryngospasm, coughing, or other movement. As with any facial surgery, vigilance must be maintained to detect accidental displacement of the LMA.

CONSIDERATIONS FOR SURGICAL PROCEDURES

Cataract surgery — Most cataract operations are performed with monitored anesthesia care (MAC) and a topical or regional anesthetic technique [3]. In the United States, topical analgesia is the most common technique, followed by peribulbar (extraconal) block or, less commonly, retrobulbar (intraconal) block [76,77]. Sub-Tenon blocks are most popular in the United Kingdom [68]. Typically, general anesthesia is reserved for adults who are unable to communicate, cooperate, or remain stationary during eye surgery, and for children [3].

The technical considerations, benefits, and drawbacks of each of these anesthetic techniques are described above. (See 'Anesthetic techniques' above.)

Other aspects of the surgical treatment of cataracts are presented separately. (See "Cataract in adults", section on 'Surgical treatment' and "Cataract in children", section on 'Management'.)

Intraocular glaucoma surgery — Anesthetic techniques for intraocular glaucoma surgery (eg, trabeculectomy) are the same as those for cataract surgery. (See 'General considerations' above and 'Anesthetic techniques' above.)

Topical anesthesia can be the choice for patients for glaucoma surgery to avoid any transitory increase in intraocular pressure (IOP) during injection of local anesthetic for a regional anesthetic.

Outcomes after glaucoma surgery appear to be similar regardless of the anesthetic technique used. A 2020 systematic review of 13 randomized controlled trials of 2388 phacoemulsification procedures noted less intraoperative pain perception in patients receiving topical anesthesia supplemented with intracameral lidocaine 0.5% to 1% rather than topical anesthesia alone [78]. However, there were no differences between the techniques in adverse events or other outcomes. In a randomized study of 120 consecutive glaucoma patients undergoing combined phacotrabeculectomy with either a regional technique (peribulbar local anesthesia) or topical anesthesia with 2% lidocaine jelly, there were no differences in pain control and satisfaction during or shortly after the procedure, and no differences in IOP or the incidence of bleb leakage at follow-up after one year [79]. Similarly, anesthetic technique did not influence the success of trabeculectomy surgery during a longer follow-up period (4.2 years) in 57 patients receiving either a regional or topical anesthetic technique [80].

However, some surgeons prefer general endotracheal anesthesia in patients undergoing trabeculectomy, because of specific concerns regarding increased risk of damage to the optic nerve during injections of local anesthetic in glaucoma patients, as well as concerns regarding poor healing after administration of subconjunctival lidocaine [81,82]. During induction of general anesthesia, fastidious attention is directed to avoiding increases in IOP during laryngoscopy and endotracheal intubation [72]. During the intraocular surgical procedure, complete akinesia is necessary. Therefore, a nondepolarizing neuromuscular blocking agent (eg, rocuronium or vecuronium) is administered and titrated according to monitoring of muscle relaxation with a peripheral nerve stimulator, and a deep plane of anesthesia is maintained [3]. Techniques to avoid increases in IOP and movement during general anesthesia are discussed in detail separately. (See "Anesthesia for emergency eye surgery", section on 'General anesthesia'.)

Surgical treatments for glaucoma are presented separately. (See "Open-angle glaucoma: Treatment", section on 'Laser therapy' and "Open-angle glaucoma: Treatment", section on 'Surgery' and "Angle-closure glaucoma", section on 'Laser peripheral iridotomy' and "Angle-closure glaucoma", section on 'Other surgery'.)

Vitreoretinal surgery — Patients undergoing vitreoretinal surgery (eg, a detached retina) usually receive a regional anesthetic block and/or general anesthesia (without the use of nitrous oxide), rather than topical anesthesia [83-85]. Topical anesthesia alone is avoided because surgery may be quite lengthy, and it is imperative that the patient does not move [86].

If general anesthesia is used, patients should not receive nitrous oxide when injection of gas (eg, SF₆ or C₃F₈) is planned, or when gas was previously used to create a "bubble" to internally tamponade the detached retina, unless an ophthalmologist has documented that the bubble has been completely absorbed. Although SF₆ is usually completely absorbed by 10 days, and C₃F₈ by six weeks, there are case reports of blindness due to use of nitrous oxide after 25 days for SF₆ and after 41 days for C₃F₈ [27].

Retinal detachment operations are basically extraocular, but may become intraocular if the surgeon elects to perforate and drain subretinal fluid [3]. Hence, patients are managed in the same manner as those having intraocular surgery (see 'Intraocular glaucoma surgery' above). Furthermore, rotation of the globe with traction on the extraocular muscles during retinal detachment operations may elicit the oculocardiac reflex. Thus, vigilance must be maintained to detect bradycardia and other arrhythmias. (See 'Oculocardiac reflex manifestations' below.)

Other aspects of vitrectomy for detached retina and diabetic retinopathy are discussed separately. (See "Diabetic retinopathy: Prevention and treatment", section on 'Vitrectomy'.)

MANAGEMENT OF PERIOPERATIVE COMPLICATIONS — Complications of anesthesia for ophthalmic surgery can be both vision- and life-threatening [86,87]. An abbreviation to remember the serious complications of eye surgery is OPHTS [88]. "O" stands for optic nerve perforation (very rare and extremely unlikely with needles ≤1.25 inches or less), "P" for globe perforation, "H" for hemorrhage (eg, retrobulbar hemorrhage), "T" for toxic reactions to local anesthetics (eg, injury to extraocular muscles caused by injection of these agents), and "S" for systemic adverse effects (eg, spread of local anesthetic into the central nervous system or intravascular injection with resultant cardiorespiratory depression or arrest).

In a series of 15 anesthesia-related adverse events, there were five wrong site (wrong eye) regional blocks, two retrobulbar hemorrhages, three cases of hemodynamic instability, and five globe perforations resulting in permanent loss of vision [87]. Recommendations for reducing anesthesia-related adverse events due to human errors during cataract surgery are listed in the table (table 1) [34], and are addressed in separate UpToDate topics:

●Standardizing surgical facility policies for identifying and marking the planned operative eye. (See "Patient safety in the operating room", section on 'Wrong procedure or wrong site errors'.)

●Performing a time-out before administration of any eye block. (See "Patient safety in the operating room", section on 'Timeouts, briefing, and debriefing'.)

●Ensuring that each anesthesia provider has adequate and documented training (both didactic and clinical) for anesthetic techniques used for cataract surgery, particularly regional eye blocks. (See "Patient safety in the operating room", section on 'Types of human errors'.)

●Employing the least invasive anesthetic technique appropriate for the planned procedure, considering the patient's comorbidities and preferences. (See 'Anesthetic techniques' above.)

Oculocardiac reflex manifestations — Manifestations of the oculocardiac reflex commonly occur when pressure is applied to extraocular muscles. These include bradycardia (a decrease of 10 to 20 percent in the basal heart rate), junctional rhythms, hypotension, and, rarely, asystole. This reflex can occur during injection of local anesthesia or during the surgical procedure itself.

Management includes stopping the stimulus (eg, release of traction or manipulation of the extraocular muscles). If this is ineffective, an anticholinergic medication (eg, atropine or glycopyrrolate) is administered.

The risk of inducing this reflex may be reduced by an effective regional anesthetic block or general anesthesia with adequate depth.

Ophthalmologic complications

Globe or optic nerve perforation — Globe perforation is a rare but serious complication of ocular regional anesthesia. It is more common in myopic patients with long axial eye length (>25 mm). (See 'Retrobulbar block (intraconal block)' above.)

Symptoms of ocular perforation are variable, ranging from intense ocular pain with abrupt loss of vision and hypotonus, to no signs or symptoms. The clinician performing the block may have a sense of increased resistance, particularly if a blunt needle is used.

If ocular perforation is suspected, the ophthalmologist must be notified immediately to perform ophthalmoscopy or ultrasound to assess the damage. Usually, the planned surgery must be cancelled, and the patient is referred to a retinal surgeon. Occasionally, the damage can be managed with cryosurgery, laser treatment, or mere observation. More commonly, however, proliferative vitreoretinopathy occurs, often accompanied by retinal detachment, and this is managed with vitrectomy and retinal reattachment surgery.

A devastating scenario occurs when the ocular perforation is undetected and an intraocular injection of local anesthetic occurs. Less than 2 mL of solution injected into the globe can produce an ocular explosion and permanent blindness in the affected eye.

Hemorrhage — Bleeding secondary to needle-based techniques is not uncommon. Bleeding may be superficial or deep, arterial, or venous. Superficial hemorrhage, while not vision-threatening, may produce an unsightly periorbital hematoma. By contrast, retrobulbar hemorrhage, when arterially based, may cause sudden bleeding and a palpable dramatic increase in intraocular pressure (IOP), as well as globe proptosis and upper lid entrapment. This can jeopardize the globe and optic nerve's vascular supply, with a potentially devastating effect on vision. The incidence of retrobulbar hemorrhage has been reported to be 0.03 [89] to 3 percent [90].

If retrobulbar hemorrhage is suspected, immediate consultation with an ophthalmologist is indicated, for consideration of urgent lateral canthotomy or paracentesis based on clinical examination, tonometric determination of IOP, funduscopic examination, and sometimes ultrasound assessment. Continuous electrocardiographic monitoring is necessary because the oculocardiac reflex may occur as blood extravasates from the muscle cone. (See 'Oculocardiac reflex manifestations' above.)

If the hemorrhage is mild or moderate, the decision to proceed with surgery depends on several factors, including the amount of bleeding, the nature of the proposed ophthalmic surgery, and the patient's condition. In cases of severe hemorrhage, surgery should be cancelled.

Intramuscular injection — Intramuscular injection of local anesthetics may cause injury to extraocular muscles. This is thought to be a cause of postoperative strabismus [91].

Systemic complications — Emergency equipment must be immediately available for any type of ophthalmologic surgical procedure, including resuscitation drugs and emergency airway equipment (eg, bag and mask, airways, and intubation equipment), even though serious systemic complications due to regional or general anesthetic techniques are rare during eye surgery.

Spread of local anesthetic into the central nervous system (ie, the brainstem) is possible, with resultant cardiorespiratory depression or arrest requiring airway management and cardiopulmonary resuscitation.

As with all nerve blocks, accidental intravascular injection of local anesthetic may lead to systemic toxicity. Treatment consists of intravenous (IV) administration of 20% lipid emulsion 1.5 mL/kg bolus followed by 0.25 mL/kg/minute infusion, and supportive airway and hemodynamic management. Calcium channel blockers, beta blockers, and local anesthetics (eg, lidocaine, procaine) should be avoided; vasopressin is not recommended, and initial doses of epinephrine should be small (10 to 100 mcg IV). If after 30 minutes there is no clinical improvement, the bolus dose of 1.5 mL/kg lipid emulsion should be repeated, and the continuous infusion should be increased to 0.5 mL/kg/minute. (See "Overview of peripheral nerve blocks", section on 'Local anesthetic systemic toxicity'.)

Also, there have been recent reports of a rare but potentially fatal complication of ocular venous air embolism (OVAE) when air-fluid exchange is used for retinal stabilization during vitrectomy [92].

Perioperative systemic complications are rare after most ophthalmologic procedures. In a retrospective cohort study of 36,652 Medicare beneficiaries (mean age 74.7 ± 6.1 years), the group undergoing cataract surgery had a lower incidence of systemic complications within seven days of surgery (primarily cardiac and respiratory complications) compared with those undergoing other types of elective low-risk outpatient procedures such as colonoscopy, gastrointestinal endoscopy, and cardiac catheterization (7.7 after cataract surgery versus 13 to 52 percent after other procedures) [93]. Although an anesthesia provider was present for most cataract procedures, the systemic complication rate was also low in the six percent that did not have anesthesia care (7.4 percent in this group). These data underscore the low risk of complications in patients undergoing cataract surgery, even without anesthesia care.

INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5^th to 6^th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10^th to 12^th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.

Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)

●Basics topics (see "Patient education: Anesthesia for elective eye surgery (The Basics)")

SUMMARY AND RECOMMENDATIONS

●Preoperative consultation

•Anesthetic considerations – Consultation for elective eye surgery with sedation and monitored anesthesia care (MAC) includes assessment of ability to lie supine comfortably, follow instructions to avoid all movement, and communicate regarding discomfort. (See 'Anesthetic considerations' above.)

•Ophthalmic considerations

-Patients with a high risk of clotting and embolic complications who are receiving aspirin, clopidogrel, warfarin, or direct oral anticoagulants (DOACs) in therapeutic doses usually continue these medications before cataract surgery, although such decisions are individualized. (See 'Ophthalmic considerations' above.)

-The ophthalmologist's measurement of axial eye length on the preoperative ultrasound is reviewed, since long eyes (axial length >25 mm) have an increased risk of needle injury during retrobulbar (intraconal) block. (See 'Ophthalmic considerations' above.)

●Intraoperative management

•Positioning of the patient on the operating table is supervised collaboratively by the anesthesiologist and the surgeon to ensure patient and surgeon comfort during the procedure and avoid potential complications. (See 'Positioning considerations' above.)

•Sedation is minimized during surgery to reduce the risk of side effects that may jeopardize the patient's ability to cooperate during surgery. (See 'Management of sedation' above.)

•Ideally compressed room air or an O₂ concentration <30 percent (to minimize fire risk) is delivered at a rate of 2 to 4 L/minute under the surgical drapes (to decrease rebreathing of expired carbon dioxide [CO₂]). If a higher concentration of oxygen is temporarily required, then the surgeon should be warned preoperatively not to use a possible ignition source (eg, electrocautery) until the following measures have been taken (see 'Management of oxygenation' above):

-The surgeon informs the anesthesia provider that electrocautery will be required.

-The anesthesia provider turns off or reduces the concentration of O₂ delivered to the patient's face to allow a decrease to <30 percent.

-The anesthesia provider then informs the surgeon that use of a heat source (ie, electrocautery) is now safe.

●Anesthetic techniques – (See 'Anesthetic techniques' above.)

•Topical anesthesia – Use of topical anesthetic as the sole anesthetic technique avoids the potential complications of both needle insertion and local anesthetic injection. A drawback is that topical anesthetic will not provide akinesia of the eye. (See 'Topical anesthesia' above.)

•Regional anesthesia – Regional anesthesia may be provided by peribulbar, retrobulbar, or sub-Tenon block (figure 2 and figure 3 and figure 4). Peribulbar (extraconal) regional blocks are the most common choice in the United States. (See 'Regional anesthesia' above.)

Sedatives (eg, midazolam) and opioids (eg, remifentanil) with a short duration are administered to reduce or eliminate pain during needle insertion and injection of local anesthetic for a regional block. An alternative technique is administration of 10 to 20 mg increments of propofol until the patient briefly loses consciousness while the block is performed. Supplemental oxygen (O₂) is administered to reduce the risk of hypoxemia. (See 'Management during needle insertion' above.)

•General anesthesia – General anesthesia is reserved for patients who cannot communicate or cooperate or who have severe anxiety or claustrophobia, as well as some patients who are unable to lie supine comfortably (eg, congestive heart failure, chronic obstructive pulmonary disease [COPD], or severe back pain), and also for children. Either endotracheal intubation with a nondepolarizing neuromuscular blocking agent or a laryngeal mask airway (LMA) may be used during cataract surgery. Maintenance of a deep plane of anesthesia is necessary to avoid laryngospasm, coughing, or other movement. (See 'General anesthesia' above.)

●Considerations for specific surgical procedures

•Cataract surgery – Most cataract operations are performed with MAC and a topical or regional anesthetic technique. Typically, general anesthesia is reserved for adults who are unable to communicate, cooperate, or remain stationary during eye surgery, and for children. (See 'Cataract surgery' above.)

•Glaucoma surgery – For intraocular glaucoma surgery, anesthetic techniques are the same as those for cataract surgery. Some surgeons prefer general anesthesia for trabeculectomy; in these cases, complete akinesia is ensured by titration of a nondepolarizing neuromuscular blocking agent according to monitoring of muscle relaxation with a peripheral nerve stimulator and maintenance of a deep plane of anesthesia. (See 'Intraocular glaucoma surgery' above.)

•Vitreoretinal surgery – For vitreoretinal surgery (eg, detached retina), a regional anesthetic technique or general anesthesia (without nitrous oxide) is preferred, rather than topical anesthesia. Nitrous oxide is contraindicated when injection of gas (eg, SF₆ or C₃F₈) is planned or was previously used to create a "bubble" to tamponade a detached retina, unless complete bubble absorption is documented. (See 'Vitreoretinal surgery' above.)

●Perioperative complications – Recommendations for reducing anesthesia-related adverse events due to human errors during cataract surgery are listed in the table (table 1).

•The oculocardiac reflex can occur when pressure is applied to extraocular muscles and may result in bradycardia, junctional rhythms, hypotension, or asystole. Management includes discontinuing manipulation of the extraocular muscles and administration of an anticholinergic medication (eg, atropine or glycopyrrolate). (See 'Oculocardiac reflex manifestations' above.)

•Serious ophthalmologic complications of regional blocks include globe or optic nerve perforation, and retrobulbar hemorrhage. (See 'Ophthalmologic complications' above.)

•Rare serious systemic complications include inadvertent administration of local anesthetic into a blood vessel or the central nervous system, with resultant cardiorespiratory depression or arrest. (See 'Systemic complications' above.)

ACKNOWLEDGMENTS

The UpToDate editorial staff acknowledges Jeffrey H Silverstein, MD (deceased), who contributed to earlier versions of this topic review.

The UpToDate editorial staff also acknowledges Joseph Bayes, MD, who contributed to earlier versions of this topic review.