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

6.6 Postoperative Nausea and Vomiting

The most common problems that occur in the recovery room following pediatric anesthesia include nausea, vomiting, restlessness, and pain [4]. The incidence of postoperative nausea and vomiting following strabismus surgery is high, affecting as many as 30%–70% of patients [5–8]. Nausea and vomiting frequently occur on the way home from the operating suite or several hours following surgery after the patient has returned home. Postoperative nausea and vomiting is usually limited in duration, but can occasionally be prolonged, extending to the following day.

Eberhart and coworkers [9] identified four risk factors among 1257 children undergoing a variety of different surgical procedures in a prospective study. Those four factors included duration of surgery greater than or equal to 30 min, age ≥3 years, strabismus surgery, and a positive history of postoperative nausea and vomiting in the patient or primary

Velez and coworkers [10] reported that nausea and was more common in the first 24 h after surgery in

who underwent manipulation of adjustable sutures on the

of surgery compared with patients who underwent adjustment the following day.

Despite many attempts to reduce the frequency of and vomiting after strabismus surgery, it remains a

Many techniques have been used, sometimes with conflicting results. Chhabra and coworkers [11] reported that peribulbar block with propofol-based anesthesia resulted in a low dence of nausea and vomiting, reporting that only 2.9% of dren undergoing strabismus surgery in their prospective experienced nausea and vomiting, considerably lower with other anesthesia techniques they investigated. prospective study showed no significant difference in the

of postoperative nausea and vomiting following strabismus surgery performed with retrobulbar anesthesia compared use of general anesthesia [12].

There are a number of reports in the literature suggesting variety of preoperative medications to reduce the incidence postoperative nausea and vomiting. No single pharmacologic agent has been proven to be a panacea. We do not administer antiemetic medications prior to strabismus

but instead leave this decision to the anesthesia team.

dration administered through perioperative fluid administra tion was shown in one study to significantly reduce postopera tive nausea and vomiting in children undergoing strabismus surgery [13]. Madan and coworkers [14] reported that istration of intravenous dexamethasone (0.25 mg/kg) diately after induction of anesthesia was effective in postoperative nausea and vomiting in pediatric patients dergoing strabismus surgery. Propofol was shown to

the incidence of vomiting following strabismus surgery pared to thiopental/isoflurane anesthesia in one study [15] was shown in another study to have no significant advantages over halothane/thiopental [16]. Wennstrom and Reinsfelt reported a reduction in postoperative nausea and vomiting children who received diclofenac administered rectally pared to administration of morphine. In a study by

and coworkers [18] children treated with ondansetron had less than half the risk of vomiting compared to those given placebo. Ketorolac was not shown to offer an advantage compared to placebo in one study [19]. Hand acupressure was reported to reduce postoperative nausea and vomiting after strabismus surgery in one study [20]. The benefits of prophylactic antiemetic therapy have been challenged on the grounds that there are insufficient data available to draw conclusions [21]. A list of possible agents that may be used to prevent and/or reduce postoperative nausea and vomiting is included in Table 6.2.

We attempt to reduce the occurrence of postoperative nausea and vomiting through specific measures. We generally try

to avoid use of narcotics for analgesia because of their potential to stimulate nausea and vomiting, instead utilizing ketorolac, a prostaglandin synthesis inhibitor, administered intraoperatively if significant postoperative pain is anticipated. Ondansetron, a selective 5-HT3 receptor antagonist, may be administered intraoperatively as an antiemetic agent in patients most susceptible to postoperative nausea and vomiting.

We find that postoperative nausea and vomiting is much more likely to occur in children than adults patients following strabismus surgery. We routinely offer healthy children greater than 2 years of age a postoperative prescription for oral or rectal promethazine at a dose of 0.25–1 mg/kg (not to exceed 25 mg) every 4–6 h as needed for nausea. We recommend that parents fill the prescription if excessive nausea and vomiting occurs in the postoperative period and we ask that the family contact us if nausea and vomiting persists. We do not use promethazine in children less than 2 years of age because of a significant risk of severe respiratory depression. If anti-nausea medication is indicated in this younger age group, we prefer a telephone call from the parent and make a determination at the time of the call if anti-nausea medication is warranted. Most commonly, a child will have a few episodes of vomiting, but is able to continue drinking small amounts of fluid either through eating ice chips or sips of water and we encourage parents to continue to observe the child without treatment. It is also important to remind parents that their child has received adequate intravenous fluid replacement both before and after surgery. Overly aggressive encouragement of oral fluids may only exacerbate postoperative nausea and vomiting ultimately leading to dehydration. Rarely does a child under 2 years of age require anti-nausea medicines after surgery. However, small children can become dehydrated rapidly. If dehydration is a concern, consultation with the child’s pediatrician and/or evaluation in the emergency room for intravenous fluid replacement may be warranted.

6.7 The Oculocardiac Reflex

Profound bradycardia during strabismus surgery is a rare but potentially serious event. The trigeminal-vagal or oculocardiac reflex can be elicited by tension on the extraocular muscles, manipulation of the globe, and by an increase in intraorbital pressure. Some studies have suggested that the medial rectus muscle may be more reflexogenic than the other extraocular muscles [22] while others have not demonstrated this finding [23]. Gradual traction on an extraocular muscles is less likely to produce the reflex than is more abrupt traction on a muscle [23, 24].

The neural pathway responsible for the oculocardiac reflex is initiated by peripheral mechanoreceptors and stretch receptors. Afferent fibers travel with the long and short ciliary nerves to the Gasserian ganglion to project to the trigeminal nucleus. Internuclear fibers project to the motor nucleus of the vagus nerve and efferent fibers then travel in the vagus nerve to muscarinic receptors in the heart (>Fig. 6.4).

Chapter 6

The oculocardiac reflex may occur more frequently in children. The reflex results in slowing of the heart rate, which can be profound, occasionally inducing asystole and other dysrhythmias in rare cases. In rare cases, intraoperative death has been attributed, in part, to bradycardia produced by the oculocardiac reflex [25]. It is presently not possible to predict, with any certainty, which patients will develop a significant oculocardiac reflex during strabismus surgery [26]. In contrast to previous reports that iris color could help to predict which patients might develop the oculocardiac reflex, Stump and Arnold [27] found that iris color was not predictive.

Arnold and coworkers [28] reported that, in the absence of anti-cholinergic blockade, rapidly acting narcotics act to enhance the degree of bradycardia produced by the oculocardiac reflex. The occurrence of the reflex can be altered through several techniques. The reflex may be less likely to occur when sevoflurane is used as the inhalational agent compared to halothane [29]. Pretreatment with atropine can significantly reduce the occurrence and severity of the oculocardiac reflex [30–32]. Topically administered lignocaine was shown in one study to reduce the severity of the oculocardiac reflex during strabismus surgery [33]. Rocuronium has been shown to reduce the frequency of the oculocardiac reflex by reducing the incidence of supraventricular and ventricular premature beats [34].

The occurrence of significant bradycardia due to the oculocardiac reflex can usually be minimized through alteration of surgical technique, avoiding excessive traction on the extraocular muscles. However, even with traction on the rectus muscles minimized, the oculocardiac reflex can still occur. The surgeon can easily recognize the onset of the oculocardiac reflex by listening to the sound of the cardiac monitors intraoperatively. We typically ask that the anesthesiologist keep the signal audible during surgery for this purpose. As soon as the oculocardiac reflex is recognized, the surgeon should relieve traction on the rectus muscle(s) that is being manipulated. It is not necessary to remove the hook and other instruments that are engaging the muscle, but merely to release the traction on the instruments until the episode subsides and the heart rate increases. The reflex is usually fatigued following repeated manipulation of the extraocular muscles. If the reflex recurs and shows no sign of abating as the surgery continues, the anesthesiologist can administer intravenous atropine to block the reflex. Tramer and coworkers [31] reported that adult patients rarely experienced the oculocardiac reflex regardless of the anesthetic technique used if they were prophylactically treated with atropine. Rarely, the reflex may continue despite anti-cho- linergic blockade through atropine administration. In this rare situation, administration of a retrobulbar block should eliminate the oculocardiac reflex through its inhibitory effect on the trigeminal nerve, the afferent component of the reflex.

The treatment required for bradycardia and other dysrhythmias stimulated by the oculocardiac reflex depends on severity. Small reductions in the heart rate may be tolerable provided they are not accompanied by significant hypotension. When severe bradycardia or hypotension develops, surgery must be discontinued until these parameters have returned to normal. Atropine can be administered, if needed, prior to resuming

surgery. Administration of atropine during a cardiac dysrhythmia that has been produced by the oculocardiac reflex should be done with caution because dangerous dysrhythmias may be produced in this setting.

The oculocardiac reflex can also be stimulated during manipulation of adjustable sutures [35], and surgeons who utilize adjustable sutures should be aware of this potential. The occurrence of an intraoperative oculocardiac reflex while under general anesthesia is highly predictive of a postoperative vasovagal response during manipulation of adjustable sutures postoperatively [36].

6.8 The Ocular Respiratory Reflex

The ocular respiratory reflex is also elicited by ocular stimulation [37]. This reflex produces bradypnea, irregular respirations, and can produce apnea. The afferent pathway for this reflex is similar to that for the oculocardiac reflex. The afferent

fibers project to the respiratory centers while the efferent fibers course along with the phrenic and other respiratory nerves. Unlike the oculocardiac reflex, this reflex is not inhibited by atropine.

6.9 Postoperative Pain

Fortunately, most patients who undergo strabismus surgery have only mild to moderate pain and severe pain is present only in very unusual cases. For pediatric patients, significant pain seems to be even less of a problem than for adult patients, in our experience. Some children will awake from anesthesia in a frightened or confused state crying aggressively. This behavior may be misinterpreted as pain, at which time narcotics are then given resulting in further sedation of the child and increasing the risk of nausea and vomiting. Our postoperative pain regimen for the pediatric patient involves the use of acetaminophen formulated for children, administered only if the

child appears to be in pain. We advise parents to contact us should the child appear to be in pain despite the use of pediatric doses of acetaminophen. In this case acetaminophen with codeine elixir is our treatment of choice. Though codeine has the potential to exacerbate postoperative nausea and vomiting, we continue to use this agent when needed because it is well tolerated and has a high margin of safety. We rarely find it necessary to recommend anything more than pediatric doses of acetaminophen.

Postoperative pain is generally mild for adult patients also. In a prospective study of 103 adult patients undergoing strabismus surgery, only 23 of the patients rated their level of pain during the first week after surgery as above 5 on a 10-point scale and 66 (64%) of the patients rated their pain as mild, in the range of 1–3 on this 10-point scale (unpublished data). Our standard regimen involves prescription of propoxyphene and acetaminophen (Darvocet-N® 100) every 4–6 h as needed for pain. Most adult patients will use pain medications for 1–2 days after surgery and thereafter are comfortable enough that they do not usually require further pain management. An occasional patient will complain of intense, long-lasting pain following surgery. It is rare that such patients have a serious complication, but this is always of concern and it is probably wise to examine such patients postoperatively to assure that a serious complication has not developed.

References

1.Taguchi M, Watanabe S, Asakura N, Inomata S (1994) Endtidal sevoflurane concentrations for laryngeal mask airway insertion and for tracheal intubation in children. Anesthesiology 81:628–631

2.Mein CE, Woodcock MG (1990) Local anesthesia for vitreoretinal surgery. Retina 10:47–49

3.Capo H, Munoz M (1992) Sub-Tenon’s lidocaine irrigation for strabismus surgery. Ophthalmic Surg 23:145

4.Patel RI, Hannallah RS (1988) Anesthetic complications following pediatric ambulatory surgery: a 3-yr study. Anesthesiology 69:1009–1012

5.Kuhn I, Scheifler G, Wissing H (1999) Incidence of nausea and vomiting in children after strabismus surgery following desflurane anaesthesia. Paediatr Anaesth 9:521–526

6.Baines D (1996) Postoperative nausea and vomiting in children. Paediatr Anaesth 6:7–14

Chapter 6

10.Velez FG, Chan TK, Vives T et al (2001) Timing of postoperative adjustment in adjustable suture strabismus surgery. J AAPOS 5:178–183

11.Chhabra A, Pandey R, Khandelwal M, Subramaniam R, Gupta S (2005) Anesthetic techniques and postoperative emesis in pediatric strabismus surgery. Reg Anesth Pain Med 30:43–47

12.Cheng KP, Larson CE, Biglan AW, D’Antonio JA (1992) A prospective, randomized, controlled comparison of retrobulbar and general anesthesia for strabismus surgery. Ophthalmic Surg 23:585–590

13.Goodarzi M, Matar MM, Shafa M, Townsend JE, Gonzalez I (2006) A prospective randomized blinded study of the effect of intravenous fluid therapy on postoperative nausea and vomiting in children undergoing strabismus surgery. Paediatr Anaesth 16:49–53

14.Madan R, Bhatia A, Chakithandy S et al (2005) Prophylactic dexamethasone for postoperative nausea and vomiting in pediatric strabismus surgery: a dose ranging and safety evaluation study. Anesth Analg 100:1622–1626

15.Hamunen K, Vaalamo MO, Maunuksela EL (1997) Does propofol reduce vomiting after strabismus surgery in children? Acta Anaesthesiol Scand 41:973–977

16.Serin S, Elibol O, Sungurtekin H, Gonullu M (1999) Comparison of halothane/thiopental and propofol anesthesia for strabismus surgery. Ophthalmologica 213:224–227

17.Wennstrom B, Reinsfelt B (2002) Rectally administered diclofenac (Voltaren) reduces vomiting compared with opioid (morphine) after strabismus surgery in children. Acta Anaesthesiol Scand 46:430–434

18.Bowhay AR, May HA, Rudnicka AR, Booker PD (2001) A randomized controlled trial of the antiemetic effect of three doses of ondansetron after strabismus surgery in children. Paediatr Anaesth 11:215–221

19.Bridge HS, Montgomery CJ, Kennedy RA, Merrick PM (2000) Analgesic efficacy of ketorolac 0.5% ophthalmic solution (Accular) in paediatric strabismus surgery. Paediatr Anaesth 10:521–526

20.Cummings M (2001) Hand acupressure reduces postoperative vomiting after strabismus surgery (n = 50). Acupunct Med 19:53–54

21.Tramer M, Moore A, McQuay H (1995) Prevention of vomiting after paediatric strabismus surgery: a systematic review using the numbers-needed-to-treat method. Br J Anaesth 75:556–561

22.Blanc VF, Hardy JF, Milot J, Jacob JL (1983) The oculocardiac reflex: a graphic and statistical analysis in infants and children. Can Anaesth Soc J 30:360–369

Management of post-strabismus nausea and vomiting in children using ondansetron: a value-based comparison of outcomes. Br J Anaesth 89:473–478

8.Treschan TA, Zimmer C, Nass C, Stegen B, Esser J, Peters J (2005) Inspired oxygen fraction of 0.8 does not attenuate postoperative nausea and vomiting after strabismus surgery. Anesthesiology 103:6–10

9.Eberhart LH, Geldner G, Kranke P et al (2004) The development and validation of a risk score to predict the probability of postoperative vomiting in pediatric patients. Anesth Analg 99:1630– 1637 (table of contents)

reflex in strabismus surgery. Can J Ophthalmol 18:314–317

24.Machida CJ, Arnold RW (2003) The effect of induced muscle tension and fatigue on the oculocardiac reflex. Binocul Vis Strabismus Q 18:81–66

25.Fayon M, Gauthier M, Blanc VF, Ahronheim GA, Michaud J (1995) Intraoperative cardiac arrest due to the oculocardiac reflex and subsequent death in a child with occult Epstein-Barr virus myocarditis. Anesthesiology 83:622–624

26.Arnold RW, Gould AB, MacKenzie R, Dyer JA, Low PA (1994) Lack of global vagal propensity in patients with oculocardiac reflex. Ophthalmology 101:1347–1352

27.Stump M, Arnold RW (1999) Iris color alone does not predict susceptibility to the oculocardiac reflex in strabismus surgery. Binocul Vis Strabismus Q 14:111–116

28.Arnold RW, Jensen PA, Kovtoun TA, Maurer SA, Schultz JA (2004) The profound augmentation of the oculocardiac reflex by fast acting opioids. Binocul Vis Strabismus Q 19:215–222

29.Allison CE, De Lange JJ, Koole FD, Zuurmond WW, Ros HH, van Schagen NT (2000) A comparison of the incidence of the oculocardiac and oculorespiratory reflexes during sevoflurane or halothane anesthesia for strabismus surgery in children. Anesth Analg 90:306–310

30.Arnold RW, Farah RF, Monroe G (2002) The attenuating effect of intraglossal atropine on the oculocardiac reflex. Binocul Vis Strabismus Q 17:313–318

31.Tramer MR, Fuchs-Buder T, Sansonetti A, Rifat K (1997) Low incidence of the oculocardiac reflex and postoperative nausea and vomiting in adults undergoing strabismus surgery. Can J Anaesth 44:830–835

32.Misurya VK, Singh SP, Kulshrestha VK (1990) Prevention of oculocardiac reflex (O.C.R) during extraocular muscle surgery. Indian J Ophthalmol 38:85–87

33.Ruta U, Mollhoff T, Markodimitrakis H, Brodner G (1996) Attenuation of the oculocardiac reflex after topically applied lignocaine during surgery for strabismus in children. Eur J Anaesthesiol 13:11–15

34.Karanovic N, Jukic M, Carev M, Kardum G, Dogas Z (2004) Rocuronium attenuates oculocardiac reflex during squint surgery in children anesthetized with halothane and nitrous oxide. Acta Anaesthesiol Scand 48:1301–1305

35.Eustis HS, Eiswirth CC, Smith DR (1992) Vagal responses to adjustable sutures in strabismus correction. Am J Ophthalmol 114:307–310

36.Hertle RW, Granet DB, Zylan S (1993) The intraoperative oculocardiac reflex as a predictor of postoperative vaso-vagal responses during adjustable suture surgery. J Pediatr Ophthalmol Strabismus 30:306–311

37.Blanc VF, Jacob JL, Milot J, Cyrenne L (1988) The oculorespiratory reflex revisited. Can J Anaesth 35:468–472

7.1 Preoperative Patient Preparation

The patient’s skin, lid margins, and conjunctiva are the most common source of bacterial contamination that can result in serious postoperative infection following eye surgery [1]. Thus cleansing these structures with an antimicrobial solution prior to surgery is among the most important methods available to reduce the risk of postoperative infection. The use of preoperative antibiotic drops is optional for strabismus surgery, at the discretion of the operating surgeon. Most strabismus surgeons do not recommend preoperative antibiotic drops. Available evidence does suggest that administration of topical antibiotic drops for 3 days prior to surgery combined with chemical preparation prior to surgery is very effective in reducing bacterial flora on the conjunctiva [2]. While many ophthalmologists have extrapolated these results to mean that the risk of infection can be reduced with these preparations, this has not been proven to be true. We recommend cleaning the area around both eyes of all patients undergoing strabismus surgery and draping both eyes, even for patients undergoing monocular surgery because it is often necessary to perform traction testing on both eyes.

Skin preparation is accomplished with 5%–10% povidoneiodine solution for 3–5 min using several applications, extending from the lid margin to the forehead superiorly, across the bridge of the nose, and for approximately 3 cm below the lower eyelid margin. The area generally prepared in this manner is shown in Fig. 7.1. Irrigation of the conjunctival fornices with saline does not significantly reduce bacterial flora of the conjunctiva [3]. Irrigation of the conjunctiva with half-strength (5%) povidone-iodine solution prior to surgery has been shown to be effective in reducing bacterial flora of the conjunctiva. Apt and coworkers [4] reported the number of colonies that could be grown decreased by 91% and the number of species decreased by 50%. These authors recommended that a half-strength (5%) povidone-iodine solution be used as part of the chemical preparation of the eye for surgery. Furthermore, the use of 5% povidone-iodine has been proven to decrease the incidence of endophthalmitis in patients undergoing cataract surgery [1]. For these reasons, we recommend its use prior to strabismus surgery. The use of Hibiclens® (chlorhexidine 4% and detergent) should be avoided for skin preparation around the eyes because of the potential corneal toxicity (Chap. 19).

Fig. 7.1. Recommended facial preparation for patients undergoing strabismus surgery

7.2 Draping the Patient

The exact method utilized to drape the patient with sterile drapes is not critical. Draping should sufficiently overlap the cleansed area of the skin, while allowing easy access to the operative site. In the United States, it is widely recommended that the surgeon mark the operative site preoperatively on patients undergoing unilateral surgery. It is helpful to place this mark within the area to be cleansed so that it is visible after the patient has been draped, adding an extra measure of safety to the procedure (>Fig. 7.2).

The decision to isolate the eyelashes with an adhesive drape is dependent on the preference of the surgeon. The argument for isolation of the lashes with an adhesive drape (>Fig. 7.3) is that the lid margins and lashes are often a source of bacterial contamination in patients who develop postoperative infections such as endophthalmitis following ophthalmologic surgery [1]. Thus, it seems logical to consider this technique for isolation of the lashes prior to strabismus surgery. On the other

hand, infection following strabismus surgery is extremely rare, and adhesive drapes covering the eyelashes and ocular adnexa can reduce access to the surgical site, making surgery more difficult. In the absence of an evidence-based recommendation regarding the management of eyelashes with draping for strabismus surgery, the preference of the surgeon in this regard seems reasonable. Lash trimming was common practice prior to ophthalmologic surgery in previous decades in the belief that it reduced bacterial flora and the risk of postoperative infection. This practice has been shown to be ineffective and is unnecessary [5].

One extremely important point to remember when removing surgical drapes is to exercise caution to avoid displacing the endotracheal tube, which sometimes becomes adherent to the adhesive edges of surgical drapes. A patient, particularly a child with an uncuffed endotracheal tube or laryngeal mask, can be inadvertently extubated, complicating the job of the anesthesiologist and putting the patient at risk of a serious complication.

Chapter 7

7.3Arrangement of the Operating Room Space

Arrangement of the operating room space for strabismus surgery will depend in large part on the configuration of the operating room and local customs. Basic room set up is shown in Fig. 7.4. Two aspects of room set up may be universally applicable. First, the instrument stand is best placed above the patient’s chest, rather than at other locations around the operative site. Second, care should be taken to avoid the positioning of electrical cords, fiberoptic light cables and other devices in such a way as to impede movement within the room. Entanglement of operating room personnel in a poorly placed cable can result in harm to both the patient and operating room personnel.

Lighting is particularly important for strabismus surgery, especially for oblique muscle surgery and for operations where surgery may be performed in the posterior portion of the orbit. We have found that the use of a single overhead light positioned directly above the patient’s chest, well above the surgeon’s head and angled so that the projected light is centered on the bridge of the patient’s nose, provides excellent lighting for almost all standard strabismus operations (>Fig. 7.5). Placement of the overhead light in this position also avoids inadvertent obstruction of the light path by operating room personnel and by observers who may block the light source when it is placed in other orientations. Standard operating room lights may be insufficient for some procedures. A fiberoptic light source delivered through a headset worn by the surgeon is often useful when performing surgery in the deeper aspects of the orbit such as when performing surgery on oblique muscles, repair of slipped and lost muscles, placement of a posterior fixation suture, and other procedures that require surgical manipulation in the posterior orbit.

Fig. 7.2. The surgical site mark can be easily identified within the surgical site after drapes have been applied

Fig. 7.3. Isolation of the lashes preoperatively with an adhesive drape

7.4 Surgical Instruments

Simplicity can go a long way to facilitate strabismus surgery. While there is a wide variety of instruments of various shapes and sizes available for strabismus surgery, the reality is that strabismus surgery can usually be performed perfectly well with a small set of basic instruments. Only in occasional cases are more exotic instruments required. Ready access to all possible instruments that might be needed for a particular case should be assured, but there is no need for all instruments that might be used in an operation to be opened and on the instrument table during surgery. Rather, infrequently used items should be sterile and available in the vicinity of the operating room.

One possible scenario is to organize instruments into an A-list, B-list, and C-list format. A-list instruments might include all of the commonly used hooks, scissors, lid speculums, and other devices that allow the vast majority of surgeries to be performed. These instruments are placed on the instrument stand (>Fig. 7.6). B-list instruments might include instruments used occasionally, perhaps in 10% of cases. Rather than

have B-list instruments crowd the instrument stand, they can be kept on the back table where they are readily available, if needed (>Fig. 7.7). Generally, they do not need to be removed from their storage container unless they are used during surgery. Finally, C-list instruments represent rarely used instruments. These instruments will vary from surgeon to surgeon and may include malleable retractor, special hooks, and special scissors (>Fig. 7.7). These instruments may be kept sterilized in peel packs and other sterile containers in the instrument storage area near the operating room where they can be readily retrieved, if needed.

Specific instruments that comprise the list of instruments commonly and uncommonly used by a particular surgeon are based on personal preference and availability. One surgeon’s favorite instrument might be another surgeon’s least favorite instrument and in most cases there is no clear reason to choose one particular instrument over another. In our experience three instruments are so unique in their design and function that they offer significant advantages not offered by comparable instruments and thus are worth specific elaboration.

Fig. 7.6. A-list instruments that should be available for every case on the instrument stand. This list will vary depending on the personal preferences of the surgeon. From left to right: Green hook (2), Jamison

hook (2), Stevens hook (2), 0.5-mm curved locking forceps (2), Thorpe forceps (2), needle holder, Wescott scissors, caliper, hemostat, and lid speculum (above)

Fig. 7.7. Instruments that might be considered for inclusion on the B-list of occasionally used instruments or the C-list of rarely used instruments. From left to right: malleable retractors (2), #3 knife handle,

double hook, Gass hook, Bishop hook with plate, Scobee hook, Demarres retractor, Conway lid retractor, Birch tendon tucker, Jameson muscle clamp, Fink tendon tucker, Scott ruler, Serrefine clamps (2)

Locking 0.5-mm forceps are available in a straight and curved design. Both may be used during several important steps in strabismus surgery. The most important application is placement of these forceps on the muscle stump following detachment of the muscle to help manipulate and position the eye and to help with identification of the muscle insertion after the muscle has been detached. The curved version of these forceps offers distinct advantages in that they extend over, rather than rest on, the cornea (>Fig. 7.8). Because of this design feature, these forceps are unlikely to result in damage to the corneal epithelium and they may be allowed to rest on the orbital bones without the need for constant manipulation by the assistant surgeon.

Many surgeons prefer to place a traction suture around the lateral rectus muscle for use in positioning the eye during surgery on the inferior oblique muscle. This step has traditionally required blind passage of a large needle between the lateral rectus muscle and sclera, a maneuver that can be dangerous (>Fig. 7.9). A Gass muscle hook has a hole in its toe (>Fig. 7.9) that both simplifies placement of a lateral rectus muscle traction suture and makes the procedure safer. As shown in Fig. 7.9, after passing the Gass muscle hook beneath the lateral rectus muscle, the suture can be passed transconjunctivally through the perforation in the toe of the hook. The hook is then withdrawn, pulling the traction suture around the lateral rectus muscle insertion and avoiding the blind passage of a large needle beneath the lateral rectus muscle.