Ординатура / Офтальмология / Английские материалы / Strabismus Surgery and Its Complications_Coats, Olitsky_2007

The primary objective of the surgical management of strabismus is to achieve the desired result while avoiding complications. Preoperative and postoperative care of the strabismus patient are important components of surgical management. Individual practice patterns that evolve to help achieve these goals often do not have firm scientific rationale. A definitive answer for many important questions is often not available in the literature. This may be because adequate prospective or even retrospective analyses of complications is difficult due to the relative rarity of a complication or the fact that more compelling studies are only indirectly related to the particular complication. For example, data confirming that preoperative antibiotics administration reduces conjunctival flora are sometimes used to justify their use in an attempt to decrease the incidence of postoperative infection, though there is no sound scientific evidence that this is the case.

Faced with anecdotal evidence, long-term retrospective data with great procedural variability, indirect conclusions, or in many cases simply a lack of data, it is not surprising that preoperative and postoperative management protocols vary significantly among strabismus surgeons. Olitsky and coworkers [1] surveyed a large number of strabismus surgeons on this issue. They found that some trends exist, but they did not find enough agreement among survey respondents to indicate that specific and accepted “standards of care” exist. Specific recommendations and the data to support them, where available, are provided in detail throughout this textbook. This chapter will briefly summarize some of the common concerns regarding the perioperative care of the strabismus patient based upon our personal practice patterns, discussions with other strabismus surgeons and scientific data, where available. The reader will be directed to the appropriate chapter for further information when indicated.

5.1 Scheduling Surgery

Opinions differ with regard to the timing of surgical scheduling. Some strabismus surgeons prefer to wait to schedule surgery until they have had a chance to examine the patient at least twice and have collected similar measurements on each of these visits. Other surgeons believe that more than a single visit is helpful to develop a rapport with the patient and/or family,

which may be beneficial in the event of an unexpected or undesirable outcome following surgery. While these concerns seem reasonable, we generally feel comfortable offering surgery to a patient after the first visit if there is no need for refractive error correction, treatment of amblyopia or other conditions, and if reliable strabismus measurement can be obtained. In the absence of such factors, additional visits seem to provide little, if any, supplementary information, and require more time away from home, school and/or work for the patients and family involved. Such visits seem to us to represent inefficient use of office time and are generally a waste of scarce healthcare resources. There is little evidence that short-term fluctuations exist in the degree of strabismus that is measured from one visit to another. Ing [2] followed 41 patients with congenital esotropia. Approximately 50% of these children demonstrated an increase in their deviation by an average of 20 prism diopters. However, these patients were followed for an average of 3 months. We generally operate on patients shortly after they have been scheduled and will obtain new measurements if surgery is delayed. A small majority (56%) of strabismus surgeons who responded to our survey reported that they will schedule surgery after the initial visit [1].

Once surgery is scheduled, an informational handout written layman’s language can be very helpful in further educating patients and parents. Information that may be helpful to include in a handout includes the place, time and date of surgery, the time and date of the preoperative visit (if needed), and the time to arrive for surgery. Fasting instructions can also be included as a reference (>Fig. 5.1).

5.2 Preparation for Surgery

Prior to surgery, several important procedures need to take place. The patient must sign a consent or request for surgery form after a discussion with the surgeon and his/her staff. It is expected that the physician has provided informed consent regarding the planned procedure at the time surgery was discussed. Some surgeons will obtain consent at the time that the surgery is recommended, while others will wait until the day of surgery to obtain formal consent for surgery. The medicolegal aspects of informed and written consent are discussed in Chap. 32.

Fig. 5.1. Preoperative surgical handout

The patient must also be evaluated and prepared for anesthesia. This includes providing instructions on preoperative fasting. The need and procedural protocols for preanesthesia consultation vary according to regional and individual practice patterns. Anesthesia considerations are covered in detail in Chap. 6.

In most institutions, the operative site must be marked by a member of the operating team before the patient can be brought into the operating room. We choose to mark the surgical site with the surgeon’s initials and sometimes indicate what type of surgery is to be performed in order to provide an additional measure of safety to protect against wrong-site surgery or the wrong procedure being performed.

5.3 Arrival in the Operating Room

Once the patient arrives in the operating room, the patient identity and the planned procedure are confirmed among the operating room staff in a time out. We will often verify the procedure again just prior to initiation of surgery. Following induction of anesthesia, we place a drop of 2.5% phenylephrine hydrochloride in each eye. This constricts the conjunctiva blood vessels and helps to minimize bleeding from the conjunctiva during surgery. It also dilates the pupil to allow prompt examination of the fundus should a deep needle pass or perforation be suspected during surgery. The patient is then prepped and draped in a sterile fashion (Chap. 7). During this preparation, a drop of 5% povidone-iodine is instilled in both eyes (see below).

5.4 Care of the Patient Following Surgery

Many patients undergoing strabismus surgery will experience at least some nausea following their procedure. While no single medication or treatment protocol has been shown to be universally effective in reducing the incidence of nausea and vomiting following strabismus surgery, some measures may be useful. These measures are covered in detail in chapters on anesthesia considerations (Chap. 6) and anesthesia complications (Chap. 28).

5.5 Timing of the First Postsurgical Visit

No consensus exists as to the best timing for the first postsurgical evaluation of the strabismus patient. When asked when they perform the first postoperative exam, 353 strabismus surgeons replied as follows: day 1 (39.1%), days 2–4 (36.4%), 1 week (20.4%), 3–4 weeks (3.2%) and greater than 1 month (0.9%). The two important issues that are evaluated during this time are the initial surgical result and an assessment for postoperative complications, such as slipped muscles, cellulitis, abscess formation, and endophthalmitis. Although endophthalmitis typically is not noted until the second to fourth postoperative day, the range of onset of serious infections is impressively wide, and has been reported as early as 1 day and as late as 30 days after surgery [3, 4] (Chap. 22). Thus there is not an optimal time to for the first postoperative examination that will allow detection of all cases of endophthalmitis. Furthermore, since most surgeons do not make decisions regarding further treatment of overand under-corrections immediately after surgery, an examination during the early days after

Instead, the timing of the first postoperative examination should be tailored to the individual patient and the surgery performed. More important than the timing of this examination is careful review of the signs and symptoms of potential postoperative complications and availability of the operating surgeon, or their designate, during this time period. This information should be provided to the patient and/or family prior to discharge from the surgery unit (>Figs. 5.2, 5.3).

5.6 Preoperative and Postoperative Drops

Olitsky and co-workers [1] found the use of preoperative and postoperative medications to be highly variable. In their survey, 5% of respondents reported that they used antibiotic drops before the day of surgery, while 6.7% instilled an antibiotic at the time of surgery, and 54.7% placed topical 5% povidoneiodine solution in the conjunctival fornices during surgical preparation. Postoperatively, 74.2% of respondents instilled an antibiotic at the end of the case and 64.7% had the patient use antibiotic drops at home. Among those who used antibiotics, 93.5% added a topical steroid, usually in a combination preparation. Oral antibiotics were used routinely by only 5.6%.

We utilize 5% povidone-iodine solution as part of our routine surgical preparation and place a drop of this solution in the conjunctival fornices during the sterile preparation of the eyes for surgery. We instill a second drop of this solution at the conclusion of the procedure. The literature supports the effectiveness of this agent in considerably reducing the normal conjunctival bacterial flora [5–7]. It has also been shown to reduce the incidence of endophthalmitis in patients undergoing cataract surgery [8]. Although extrapolating these data to include strabismus surgery may not be accurate, we feel that the cost

References

1.Olitsky SE, Awner S, Reynolds JD (1997) Perioperative care of the strabismus patient. J Pediatr Ophthalmol Strabismus 34:126–128

2.Ing MR (1996) Progressive increase in the quantity of deviation in congenital esotropia. Ophthalmic Surg Lasers 27:612–617

3.Kivlin JD, Wilson ME Jr. (1995) Periocular infection after strabismus surgery. The Periocular Infection Study Group. J Pediatr Ophthalmol Strabismus 32:42–49

Chapter 5

5.Isenberg SJ, Apt L, Yoshimori R, Khwarg S (1985) Chemical preparation of the eye in ophthalmic surgery. IV. Comparison of povidone-iodine on the conjunctiva with a prophylactic antibiotic. Arch Ophthalmol 103:1340–1342

6.Apt L, Isenberg S, Yoshimori R, Paez JH (1984) Chemical preparation of the eye in ophthalmic surgery. III. Effect of povidoneiodine on the conjunctiva. Arch Ophthalmol 102:728–729

7.Apt L, Isenberg SJ, Yoshimori R (1985) Antimicrobial preparation of the eye for surgery. J Hosp Infect 6 [Suppl A]:163–172

8.Speaker MG, Menikoff JA (1991) Prophylaxis of endophthalmitis with topical povidone-iodine. Ophthalmology 98:1769–1775

tine postoperative care: a survey of 25 strabismus surgeons. Binocular Vision Eye Muscle Surg Q 5:7

(1990) Are antibiotic-steroid drops necessary following strabismus surgery? A prospective, randomized, masked trial. J Pediatr Ophthalmol Strabismus 27:205–207

Most strabismus surgery is performed in an outpatient setting. The choice of anesthesia modality is dependent upon one or more of the following factors: patient preference, surgeon preferences, nature of the operation planned, health of the patient, and the recommendations of the anesthesiologist. No single anesthesia modality universally applies to all patients in all situations. In our experience, all children, and even most young adults require general anesthesia, because they usually are unable to tolerate surgical manipulation under local anesthesia. The anesthesia modalities that will be discussed in this chapter include general anesthesia, retrobulbar and peribulbar anesthesia, and topical anesthesia.

The final decisions on the anesthesia modality to be used and indeed on evaluation of the patient’s general health, and the decision on proceeding with surgery are, in the final analysis, made by the anesthesiologist. We have made it a policy never to argue or disagree with an anesthesiologist who feels our patient is not healthy enough to undergo a procedure, recognizing that the anesthesiologist often has a far more complex situation on his/her hands in maintaining cardiopulmonary function than does the strabismus surgeon.

6.1 Preoperative Preparation

6.1.1 Laboratory Testing

Some centers require a separate preoperative visit with the anesthesiologist prior to the day of surgery, while others utilize telephone screening and day of surgery evaluation by the surgical staff and anesthesiologist satisfactorily. Preoperative laboratory and other testing may be indicated for several reasons, including: (1) identifying a disorder that may affect perioperative anesthetic care, (2) determining the status of an already known disorder, disease, or therapy which may affect perioperative anesthetic care, and (3) formulation of plans and alternatives for perioperative anesthetic care. Routine laboratory testing diagnostic screening is not necessary for preanesthetic

tion of patients undergoing strabismus surgery. Identification of specific clinical indicators such as age, pre-existing

and magnitude of the surgical procedure planned helps termine the need for presurgical testing in selected

(Source: American Society of Anesthesiologists http://www. asahq.org/publicationsAndServices/standards/28.pdf accessed 14 April, 2006.)

6.1.2 Fasting Recommendations

One of the most serious complications of general anesthesia is aspiration of particulate matter from the stomach into the pulmonary system. To reduce the risk of aspiration, patients are asked to fast for a period of time prior to surgery. One exception is that vital medications may be taken on the morning of surgery with a small sip of water. Children who must take medications with applesauce or some other semisolid food should generally avoid taking the medications, if possible. When practical, medication should be given 6 hours preoperatively or held until the patient is in the recovery room. These suggestions do not apply to nonessential medications such as vitamins and nutritional supplements, which should not be taken. Fasting for adult patients is generally recommended for 6–8 h prior to surgery. Gastric emptying times in infants and children suggest emptying half-times of 50–70 min for formula and 25–50 min for breast milk. A simple rule to remember is 2 h (for clear liquids), 4 h (for breast milk), and 6 h (for everything else, including formula). An 8-h fast should be considered following meals that contain substantial amounts of fried or fatty foods or meats, as these items can prolong gastric emptying. Table 6.1 summarizes these fasting recommendations for children. (Source: American Society of Anesthesiologists http://www.asahq.org/publicationsAndServices/NPO.pdf, accessed 14 April, 2006.)

6.1.3 Preoperative Medications

Routine use of preoperative sedatives is not necessary. Preoperative medications are reasonable, however, for the child or adult patient who is particularly apprehensive prior to surgery. Children who need preoperative sedation may be given midazolam orally as a flavored cocktail. This preparation is administered 10–15 min prior to surgery. Apprehensive adult patients can be premedicated with agents such as midazolam or diazepam.

6.2 General Anesthesia

General endotracheal anesthesia is probably still the most common anesthesia modality used to facilitate strabismus surgery. It is used for virtually all children and for many adult patients undergoing strabismus surgery. Induction of general anesthesia can be achieved through inhalation of inhalational agents such as nitrous oxide or sevoflurane or through intravenous administration of agents such as propofol. An anesthesiologist or certified nurse anesthetist should be present throughout the procedure.

Many patients and families fear complications of general anesthesia more than they fear strabismus surgery itself. In a healthy patient undergoing routine strabismus surgery, excessive fears of complications associated general anesthesia are unfounded. While complications, even serious complications, can occur in association with general anesthesia, serious complications are exceedingly rare. A discussion with the ophthalmologist and anesthesiologist can have an important calming effect on patients and families preoperatively.

Chapter 6

While some anesthesiologists prefer to initiate an intravenous line prior to induction of anesthesia in children, we find this practice to be so distressing to children that our standard protocol involves induction of anesthesia with an inhalational agent followed by placement of an intravenous line. Once venous access has been obtained, the patient then undergoes endotracheal intubation or placement of a laryngeal mask for continuation of inhalational anesthesia. The techniques of induction, maintenance, and reversal of anesthesia are left entirely to the discretion of the anesthesiologist.

In some centers, parents are encouraged to be in the operating room during anesthesia induction. In others this practice is discouraged. In general, we find this to be unnecessary for the child undergoing anesthesia. However, we have found that many times this process is calming to anxious parents.

6.2.1 Induction of Anesthesia

Once in the operating suite, anesthesia can be induced through administration of an inhalational or intravenous agent. In adult patients, an intravenous line is usually started preoperatively, typically in a preoperative holding area. This facilitates administration of anesthetic agents intravenously with rapid induction of anesthesia followed by endotracheal intubation or placement of a laryngeal mask (>Fig. 6.1) to administer oxygen and additional inhalational agents as needed to accomplish surgery. Preformed tracheal tubes are an excellent alternative during strabismus surgery. Preformed tracheal tubes (>Fig. 6.2) direct the tube away from the surgical field, reducing the risk that the tube will be dislodged during surgery and improving access to the tube by the anesthesiologist. A laryngeal mask can be advantageous in children with difficult airways. They are especially useful for short procedures and have the added advantage of being less stimulating to the airway and requiring lower concentrations of halogenated agents for insertion compared to endotracheal tubes [1]. Additionally, muscle relaxants can be avoided, extubation is usually less stressful, and the airway more comfortable following extubation.

Fig. 6.1. Laryngeal mask airway, cuffed endotracheal tube, and uncuffed endotracheal tube

Fig. 6.2. A preformed endotracheal tube has the advantage of being directed away from the surgical field

6.3 Retrobulbar and Peribulbar Anesthesia

It is important from the point of view of strabismus surgery to have an understanding of the anatomy relevant to ophthalmic anesthesia. This allows the surgeon to target the block to the most essential areas of the eye and/or orbit. Sensory fibers from the globe and orbit are carried by the trigeminal nerve, which has three divisions: ophthalmic, maxillary, and mandibular. The majority of the sensory fibers from the eye and ocular adnexa are carried by the ophthalmic division. The ophthalmic nerve has three divisions of its own: frontal, lacrimal, and nasociliary. The frontal nerve has at least two subdivisions which include the supraorbital nerve (carrying sensation from the conjunctiva and skin of the central upper lid) and the supratrochlear nerve, which carries sensation from the medial onethird of the upper lid. The lacrimal subdivision carries sensory fibers from the skin and conjunctiva of the lateral portion of the upper eyelid. The nasociliary nerve carries sensory fibers from the cornea, iris, ciliary body, peribulbar conjunctiva, and the optic nerve sheath. Its fibers pass through the ciliary ganglion. The infratrochlear branch of the nasociliary nerve is responsible for sensation from the medial canthus, medial portion of the lower skin, conjunctiva, caruncle, lacrimal sac, and canaliculi.

Motor input to the extraocular muscles comes from the oculomotor, trochlear, and abducens nerves. The oculomotor nerve supplies motor fibers to the superior rectus, medial rectus, inferior rectus, inferior oblique muscles and the levator palpebrae superioris muscle in the upper eyelid. It enters the orbit through the superior orbital fissure and splits into a superior and inferior division. The superior division innervates the superior rectus and the levator muscles. The trochlear nerve supplies motor fibers to the superior oblique muscle. It enters through the superior orbital fissure above the annulus of Zinn. Anesthetic delivered into the muscle cone would therefore not be expected to provide significant akinesia of the superior oblique muscle. The abducens nerve enters the orbit through the superior orbital fissure to innervate the lateral rectus muscle.

Retrobulbar and/or peribulbar anesthesia is an excellent option for cooperative adult patients who feel that they can comfortably tolerate surgery under local anesthesia with or without concurrent sedation. The term retrobulbar anesthesia is used here to refer to both retrobulbar and peribulbar anesthesia. It is often a preferred modality of anesthesia administration for the adult patient undergoing routine monocular strabismus surgery because of its safety, simplicity, and speed of recovery. Patients who have undergone strabismus surgery under retrobulbar anesthesia have very few systemic complaints following surgery and are generally very comfortable. Retrobulbar anesthesia may also be utilized in a patient who is undergoing bilateral surgery in which the eye undergoing the most complex procedure receives a retrobulbar block and the eye undergoing the less complex procedure receives topical anesthesia as described below.

Effective use of retrobulbar anesthesia requires several prerequisites, including a physician proficient in the administration of retrobulbar anesthesia, a skilled surgeon, and a care-

fully planned procedure. An inadequate retrobulbar block can be associated with significant residual pain and discomfort during surgery that may be intolerable to the patient. Even an excellent retrobulbar block may be associated with a sensation of deep pressure during traction on the extraocular muscle. A less experienced strabismus surgeon may wish to consider strabismus surgery under general anesthesia in appropriate patients to avoid these problems. Surgery on the inferior oblique muscle is often associated with intraoperative discomfort despite an excellent retrobulbar block and surgeons not proficient in the techniques of inferior oblique surgery may wish to consider general anesthesia as an alternative.

One disadvantage of retrobulbar anesthesia is tissue distortion that can occur as the anesthetic agent migrates anteriorly, hydrating the anterior Tenon’s capsule, with resultant swelling of this tissue. While relatively easy to manage for the experienced surgeon, tissue and landmark distortion can confuse less experienced surgeons. Retrobulbar anesthesia may be supplemented with intravenous sedation administered by the anesthesiologist as deemed necessary during the case, titrated by continuous communication between the operative team and the patient. Topical anesthetic drops can be a useful adjunct to supplement retrobulbar anesthesia especially during the latter stages of the case when the effect of retrobulbar anesthesia on the conjunctiva often begins to wane.

A variety of anesthetic agents can be used. A common combination is bupivacaine 0.5%–0.75% and lidocaine 2% without epinephrine in a 50/50 mixture. Using a retrobulbar needle, 3–5 ml of this mixture is injected into the retrobulbar or peribulbar space. Because retrobulbar injection of an anesthetic agent can be very painful, brief administration of intravenous sedatives can facilitate administration of retrobulbar anesthesia. Potential complications of retrobulbar anesthesia, reviewed in Chap. 28, include retrobulbar hemorrhage, penetration of the globe, intramuscular injection, trauma to the optic nerve, and stimulation of the oculocardiac reflex.

6.4 Sub-Tenon’s Anesthesia

Tenon’s capsule is an anterior extension of the dura covering the optic nerve. Mein and Woodcock [2] described the use of sub-Tenon’s anesthesia for use in cataract and vitreoretinal surgery. Capo and Munoz [3] later described its use in strabismus surgery. Anesthesia develops rapidly after administration of the anesthetic agent and akinesia follows after 4–5 min. The technique results in blockage of all three branches of the ophthalmic division of the trigeminal nerve providing an excellent superior sensory block. We have found the technique to be an excellent alternative for both routine and complicated strabismus cases.

6.5 Topical Anesthesia

The concept of topical anesthesia for strabismus surgery is a misnomer. While an occasional patient can tolerate strabismus

surgery with topical anesthesia alone, such patients are uncommon and most require at least mild to moderate sedation in order to comfortably tolerate surgery. The prerequisites for using topical anesthesia with intravenous sedation include a skilled, gentle surgeon, and an anesthesiologist who is skilled at assessing both the patient’s moment-to-moment needs during the procedure and the surgical needs of the surgeon. A comfortable patient is needed during the procedure, but a relatively awake and alert patient is needed near the end of the procedure to facilitate adjustment. Thus careful coordination between the anesthesiologist and surgeon is required in order to effectively manage a patient using topical anesthesia approaches.

The indications for strabismus surgery under topical anesthesia are dependent on the judgment and experience of the surgeon and include the desire to assess alignment and make adjustments to the ocular alignment intraoperatively, and the ability to accomplish bilateral surgery on a patient who is not a good candidate for general anesthesia when a sequential retrobulbar injection on different days is not feasible. Complex strabismus surgery and surgery on oblique muscles is not easy to perform under topical anesthesia because it is often associated with significant patient discomfort, and therefore is rarely done. Exposure of the surgical site can be so compromised by modifications in surgical technique required because of use of topical anesthesia that the technique is not universally applicable to all patients.

Concurrent sedation that is administered to supplement topical anesthesia is directed by the anesthesiologist and guided by the ophthalmologist in conjunction with the patient. Effective use of the technique requires careful coordination between the ophthalmologist and anesthesiologist to effectively time the administration and withdrawal of the sedative agents and requires careful and detailed explanation to the patient preoperatively with continuous intraoperative communication. The surgeon should have a backup plan to manage the occasional patient who, despite favorable assessment preoperatively, turns out not to be able tolerate surgery under topical anesthesia. Options include conversion to retrobulbar or sub-Tenon’s anesthesia, conversion to general anesthesia, or deferring surgery to another day. The preoperative systemic evaluation should be tailored to the backup plan, unless the surgeon is willing to postpone surgery to another day. For example, if general anesthesia is the backup plan for a patient undergoing planned strabismus surgery under topical anesthesia, preoperative assessment should be sufficient to clear the patient for general anesthesia.

Fig. 6.3a,b. Operating “in the hole” with less exposure is often required for surgery performed under topical anesthesia with sedation (a), compared to the greater exposure allowed under general anesthesia (b)

6.5.1Modification of Surgical Technique for Topical Anesthesia

The surgeon must be willing and able to significantly modify his/her usual surgical technique in order to comfortably perform strabismus surgery under topical anesthesia. The procedure must be done with less exposure of the surgical site, minimization of cautery, and minimized traction on the extraocular muscles. It is often necessary to operate “in the hole” (>Fig. 6.3). Exposure of the muscle is facilitated by retropulsion of the globe and mild traction compared to the more direct traction and anterior displacement of the globe that is used during standard strabismus surgery.

Surgery under local anesthesia can be stressful to some patients. Conversation in the operating room often must be kept to a minimum to reduce patient anxiety. The operating team should control conversation and avoid such terms as “oops,” “oh no,” and similar phrases that can have a negative connotation and be alarming to patients. Additionally, avoiding open discussion about scissors, knives, hooks, and other surgical tools is recommended. Referring to surgical equipment by its name rather than function may reduce patient anxiety. A request for the “Westcott’s” rather “Westcott scissors,” for example, may be less of a concern to the patient undergoing surgery.