Strabismus surgery outcomes are frequently unpredictable, especially when surgery is performed under general anesthesia; conversely, topical anesthesia is a non-akinetic procedure that leads to more precise results, but is generally reserved for adults.1
The use of the adjustable suture technique, described by Bielschowsky in 1907,2 Claude Worth in 1908,3 and diffused by Jampolsky in the 1970s,4,5 theoretically allows the reduction of the postoperative residual angle of deviation and reoperation rate. Most surgeons perform adjustable suture surgery using a two-stage approach: muscle reattachment with the use of the bow-tie or sliding-noose technique under general anesthesia followed, postoperatively, when the anesthetic effect has worn off, by the adjustment of sutures under topical anesthesia and conversion into a permanent knot.6,7 This adjustable suture technique is used in both adults and children8,9 in whom the adjustment may require additional anesthesia (either topical or intravenous),10 often meeting resistance from anesthesiologists to perform it in the recovery room.
Published studies on adjustable sutures show controversial results. Some studies have demonstrated their utility,7,11,12 whereas the last two Cochrane reviews highlight how “no reliable conclusions could be reached regarding which technique (adjustable or non-adjustable sutures) produces a more accurate long-term ocular alignment following strabismus surgery or in which specific situations one technique is of greater benefit than the other.”13,14
On the other hand, a one-stage intraoperative adjustment of strabismus surgery, either with or without adjustable sutures, allows customization of the surgical procedure for each patient with intra-operative orthoptic evaluation based on the alternate prism cover test (APCT) that plays a key role in this type of approach.15 The benefits and safety of topical anesthesia with intraoperative adjustment in strabismus surgery are known,16,17 but this technique is generally reserved for adults, due to their better collaboration compared to children.
We present 19 cases of strabismus surgery performing this technique in selected children, with encouraging outcomes and without intraoperative or postoperative complications.
Patients and Methods
Nineteen children with horizontal deviation were operated on between February 2015 and October 2017 at the Ophthalmology Unit of St. Anna University Hospital of Ferrara, Ferrara, Italy. Each patient underwent a complete eye examination with assessment of visual acuity, tonometry, slit-lamp biomicroscopy, fundus examination, and orthoptic evaluation to measure the angle of deviation for distance and near vision with the APCT, ocular motility evaluation in the nine cardinal positions of gaze, fusional convergence amplitude in intermittent strabismus, and stereopsis measurement with TNO and Frisby stereo tests.
During preoperative examination, it is fundamental to accurately select a suitable candidate. Selection criteria were: horizontal strabismus, at least 8 or 9 years of age, cooperative character, curious and relaxed attitude, and ability to work together and respond well and confidently to questions asked during the visit. Exclusion criteria were: prior operation on the muscle undergoing surgery, insecure and fearful child, anxious attitude, and child apparently dependent on parents and not responding to verbal instructions.
Surgery was performed by the same surgeon (FF) and included unilateral or bilateral recession/ resection of horizontal muscles or medial or lateral rectus, with intraoperative adjustment of sutures under topical anesthesia. The surgical technique consisted of a limbal incision approach to reach and isolate the muscle, proceeding thereafter with recession, resection, or adjustable sutures. Adjustable sutures were performed with the sliding-noose technique using a double-armed 6-0 polyglactin 910 suture. After detaching the muscle and suturing it to the sclera at its original insertion, the noose knot was created with a separate piece of suture around the scleral suture. Sliding the knot allows regulation of the suture according to the estimated amount of surgery needed based on intraoperative orthoptic evaluation. The APCT was performed during surgery after muscle recession/resection, by an orthoptist under the surgeon's supervision, while the patient was sitting on the operating table. Residual deviation angles were measured in primary position with the patient fixating on a light target for near (33 cm) and distance (5 meters away). Patients with lens prescription underwent the APCT wearing their own glasses, which had been previously gas sterilized.
The adjustment target was to leave patients with esotropia within 4 prism diopters (PD) of straight in cases of fusion potential and undercorrect by +8 to +10 PD at distance in cases of no fusion potential, whereas patients with exotropia were overcorrected (esotropia) in distance by +2 to +6 PD. The amount of surgery was adjusted until target correction was reached and no diplopia was present on the APCT in primary position and down gaze.
Our topical anesthesia protocol consisted of sublingual or intranasal midazolam 0.25 mg/kg from 20 to 30 minutes before the child entered the operating room, followed by instillation of lidocaine 4% eye drops in the conjunctival sac before beginning surgery. The use of topical benoxinate 4 mg/mL eye drops before lidocaine can reduce or avoid a burning sensation, whereas additional lidocaine 4% eye drops were instilled if the patient complained of discomfort during surgery. Pain was assessed using the 4-point Verbal Rating Scale (0 = no pain, 1 = mild, 2 = moderate, 3 = severe). In cases of severe pain, intravenous injection of propofol 1 to 3 mg/kg was used as an additional sedative. After propofol use, we waited at least 10 minutes for muscle relaxation before orthoptic evaluation.18 Patients were continuously monitored during surgery with electrocardiography, systemic arterial blood pressure measurement, and pulse oxymetry.
Follow-up was performed 1 day and 1, 3, and 6 months postoperatively. Surgical success was defined as a postoperative residual angle of deviation of ±8 PD or less at 6 months and presence of single binocular vision in primary position in patients with preoperative diplopia.
The study and data collection conformed to the principles of the Declaration of Helsinki and were approved by the local ethics committee. Written informed consent was provided by both parents of all patients.
Nineteen children (14 boys and 5 girls, mean age: 12.68 ± 2.50 years [range: 8 to 16 years]) underwent surgery. All patients were affected by horizontal deviations: 5 with esotropia and 14 with exotropia.
The overall mean preoperative horizontal angle of deviation (absolute values) was 24.21 ± 11.20 PD (range: −50 to +30 PD) at distance and 22.11 ± 11.05 PD (range: −50 to +30 PD) at near. The average pre-operative angle of deviation was +23.80 ± 5.89 PD (range: +14 to +30 PD) at distance and +23.40 ± 6.73 PD (range: +12 to +30 PD) at near in patients with esotropia and −24.36 ± 12.76 PD (range: −50 to −8 PD) at distance and −21.64 ± 12.42 PD (range: −50 to −2 PD) at near in patients with exotropia. Five patients underwent previous strabismus surgery under general anesthesia; in those patients, surgery did not involve previously operated muscles.
Seventeen of 19 patients (89%) remained comfortable during surgery, whereas in two patients intravenous injection of propofol was necessary.
The overall mean postoperative angle of deviation (absolute values) at 6 months was 4.11 ± 2.87 PD (range: −10 to +10 PD) at distance and 3.58 ± 2.95 PD (range: −10 to +10 PD) at near. At 6 months, the average residual angle of horizontal deviation was +4.80 ± 3.35 PD (range: +2 to +10 PD) at distance and +4.00 ± 3.46 PD (range: +2 to +10 PD) at near in patients with esotropia and −3.86 ± 2.77 PD (range: −10 to +2 PD) at distance and −3.43 ± 2.87 PD (range: −10 to +2 PD) at near in patients with exotropia.
Fourteen of 19 patients (74%) required an intraoperative adjustment and the mean adjustment angle was 4.5 PD (absolute value).
Patients showed variation in the residual angle of deviation, which remained substantially stable from 1 month during the subsequent follow-up (Figure 1).
Preoperative and postoperative horizontal angle of deviation. ET = esotropia; XT = exotropia
Seventeen patients (89%) reached the target angle, one patient with exotropia was overcorrected with a following exoshift, and one patient with esotropia was undercorrected and no shift occurred. None of them required further surgery during the 6 months of follow-up.
The success rate, defined as a postoperative residual angle of deviation ±8 PD or less, was 89% at 6 months, with achievement of a small horizontal deviation and single binocular vision in the 4 patients with preoperative diplopia. No patient reported diplopia after surgery.
All patients reported no pain during conjunctival limbal incision and tissue dissection. Greater discomfort was reported during muscle isolation due to the hooking maneuver. No pain was reported during muscle reattachment or suture adjustment. Intraoperative cardiac monitoring did not record positive oculocardiac reflex in any patients. No patients experienced side effects after sublingual administration of midazolam or after intravenous injection of propofol, when provided.
Strabismus surgery with intraoperative suture adjustment has several advantages, such as immediate postoperative eye alignment, increased accuracy of strabismus correction, and decreased frequency of reoperation.19 Generally, indications for this technique include restrictive strabismus (Graves' disease20 or scleral buckle), orbital blow-out fractures, incomitant deviations (Duane syndrome, Moebius syndrome, myasthenia gravis, or paralytic strabismus), slipped, lost, or disinserted muscles, and combined horizontal, vertical, and torsional deviations.7 Some studies have demonstrated the utility of adjustable suture strabismus surgery in adults, whereas there are only a few reports on the use of adjustable sutures in children.8,9,12 Most surgeons perform the adjustable suture technique using a two-stage approach.6,7 This method has the disadvantage of extending the surgical time by waiting before suture adjustment, which is generally performed within 8 to 24 hours after surgery.21 Some authors showed that intraoperative adjustment of sutures is useful for comitant horizontal strabismus surgery to avoid a large overcorrection, especially in cases of moderate angle horizontal muscle surgery.22 For these reasons, we evaluated a one-stage intraoperative adjustment of sutures under topical anesthesia. Therefore, even if intraoperative adjustment of sutures under topical anesthesia is less commonly used in children,23 it may overcome the disadvantages of postoperative adjustment, being a single surgical procedure. Furthermore, intraoperative adjustment of sutures is a safer technique that allows manipulation of the muscles in sterile conditions and under the supervision of an anesthetist.17,22
We commonly use topical anesthesia in adult strabismus surgery with satisfactory results and excellent patient comfort,17 so it would be advantageous to extend the indication to eligible children. Topical anesthesia does not have the potential complications of retrobulbar anesthesia (eg, hemorrhage, eyeball perforation, and optic nerve damage) and general anesthesia (eg, nausea, vomiting, and other adverse effects).24 Postoperative nausea and vomiting is a possible complication in pediatric anesthesia.25 Excessive manipulation of extraocular muscles increases the risk of stimulating oculocardiac reflex, a vagal overstimulation that can manifest with profound bradycardia and hypotension, especially in children.26 In our study, no intraoperative or postoperative complications (eg, postoperative nausea and vomiting) were encountered during topical anesthesia and no patients had any cardiac arrhythmias. When administered, intravenous propofol was not associated with notable side effects. There are no clear studies on the relationship between propofol and midazolam with the angle of strabismus. Although in clinical practice we may notice a variation in the angle of deviation, there are studies with good outcomes.27
In adults, patient selection for topical anesthesia is generally easier than in children, due to their cooperation and consciousness of surgery and topical anesthesia. For children, evaluation criteria are different because they are not often fully aware of the type of surgery and consent for topical anesthesia is given by parents who can have an overprotective attitude that can be counterproductive. The pre-operative examination with parents and children analyzing their character and attitude is crucial in understanding whether children may be eligible for this type of anesthesia.
The success rate of this study was 89% at 6 months after surgery and no patients required further surgical intervention. Furthermore, this technique could reduce time, costs, and risks related to general anesthesia, but it is always appropriate to be prepared to perform general anesthesia to complete surgery.
Despite the advantages described above, there are some disadvantages. First, it would be better to limit surgery to two muscles in each eye because the patient may have difficulty tolerating an overly long procedure. Second, in patients who underwent previous surgery, tissue dissection can be more difficult due to the presence of adhesions and scarring, making surgery longer and more painful; so far, we have no experience using topical anesthesia during reoperation on previously operated muscles.
Strabismus surgery with intraoperative suture adjustment under topical anesthesia in children is a tolerable procedure with encouraging outcomes, representing an alternative to general anesthesia in well-selected children. Clinical evaluation of both the child and parents is fundamental in predicting a likely poor collaboration of the child during surgery, which, if present, would require surgery under general anesthesia. The limitations of this study are the relatively small number of patients, the short postoperative observation period, the non-masked observer for preoperative and postoperative examination, the need for an orthoptist in the operating room, and the effect of midazolam and propofol on deviation. Studies are needed to elucidate further the patients who are eligible for this procedure and to compare this procedure with conventional techniques.
- Sharma P, Julka A, Gadia R, Chhabra A, Dehran M. Evaluation of single-stage adjustable strabismus surgery under conscious sedation. Indian J Ophthalmol. 2009;57:121–125. doi:10.4103/0301-4738.45501 [CrossRef]
- Bielschowsky A. The newer views on the nature and treatment of strabismus [article in German]. Med Klin. 1907:335–337.
- George NDL. Adjustable sutures: who needs them?Eye (Lond). 2003;17:683–684. doi:10.1038/sj.eye.6700466 [CrossRef]
- Jampolsky A. Strabismus reoperation technique. Trans Am Acad Ophthalmol Otolaryngol. 1975;79:704–717.
- Jampolsky A. Current techniques of adjustable strabismus surgery. Am J Ophthalmol. 1979;88:406–418. doi:10.1016/0002-9394(79)90641-X [CrossRef]
- Hunter DG, Dingeman RS, Nihalani B. Adjustable suture in strabismus surgery. In: Edward WM, Saunders RA, Trivedi RH, eds. Pediatric Ophthalmology: Current Thought and A Practical Guide. 2009:213–226. doi:10.1007/978-3-540-68632-3_16 [CrossRef]
- Nihalani B, Hunter D. Adjustable suture strabismus surgery. Eye (Lond). 2011;25:1262–1276. doi:10.1038/eye.2011.167 [CrossRef]
- Awadein A, Sharma M, Bazemore MG, Saeed HA, Guyton DL. Adjustable suture strabismus surgery in infants and children. J AAPOS. 2008;12:585–590. doi:10.1016/j.jaapos.2008.06.005 [CrossRef]
- Engel JM, Guyton DL, Hunter DG. Adjustable sutures in children. J AAPOS. 2014;18:278–284. doi:10.1016/j.jaapos.2013.12.015 [CrossRef]
- Cogen MS, Guthrie ME, Vinik HR. The immediate postoperative adjustment of sutures in strabismus surgery with comaintenance of anesthesia using propofol and midazolam. J AAPOS. 2002;6:241–245. doi:10.1067/mpa.2002.123398 [CrossRef]
- Tripathi A, Haslett R, Marsh IB. Strabismus surgery: adjustable sutures—Good for all?Eye (Lond). 2003;17:739–742. doi:10.1038/sj.eye.6700465 [CrossRef]
- Kamal AM, Abozeid D, Seif Y, Hassan M. A comparative study of adjustable and non-adjustable sutures in primary horizontal muscle surgery in children. Eye (Lond). 2016;30:1447–1451. doi:10.1038/eye.2016.144 [CrossRef]
- Haridas A, Sundaram V. Adjustable versus non-adjustable sutures for strabismus. Cochrane Database Syst Rev. 2013;7(12):CD004240.
- Hassan S, Haridas A, Sundaram V. Adjustable versus non-adjustable sutures for strabismus. Cochrane Database Syst Rev. 2018;3:CD004240.
- Joo KS, Koo H, Moon NJ. Measurement of strabismic angle using the distance Krimsky test. Korean J Ophthal. 2013;27:276–281. doi:10.3341/kjo.2013.27.4.276 [CrossRef]
- Chow PC. Stability of one-stage adjustable suture for the correction of horizontal strabismus. Br J Ophthalmol. 1989;73:541–546. doi:10.1136/bjo.73.7.541 [CrossRef]
- Chang YH, Ryu IH, Han SH, Lee SJ, Lee JB. Intraoperative adjustment in strabismus surgery under topical anesthesia. Yonsei Med J. 2006;47:667–671. doi:10.3349/ymj.2006.47.5.667 [CrossRef]
- Lundström S, Twycross R, Mihalyo M, Wilcock A. Propofol. J Pain Symptom Manage. 2010;40:466–470. doi:10.1016/j.jpainsymman.2010.07.001 [CrossRef]
- Wisnicki HJ, Repka MX, Guyton DL. Reoperation rate in adjustable strabismus surgery. J Pediatr Ophthalmol Strabismus. 1988;25:112–114.
- Imburgia A, Elia G, Franco F, et al. Treatment of exophthalmos and strabismus surgery in thyroid-associated orbitopathy. Int J Oral Maxillofac Surg. 2016;45:743–749. doi:10.1016/j.ijom.2015.12.002 [CrossRef]
- Spierer A. Adjustment of sutures 8 hours vs 24 hours after strabismus surgery. Am J Ophthalmol. 2000;129:521–524. doi:10.1016/S0002-9394(99)00406-7 [CrossRef]
- Yi JH, Chung SA, Chang YH, Lee JB. Practical aspects and efficacy of intraoperative adjustment in concomitant horizontal strabismus surgery. J Pediatr Ophthalmol Strabismus. 2011;48:85–89. doi:10.3928/01913913-20100518-06 [CrossRef]
- He X, Chen L, Pan X, Hu H, Shi Z. Application value of topical aneasthesia in children strabismus surgery. Eye Sci. 2012;27:134–137.
- Coats DK, Olitsky SE. Anesthesia-related complications. In: Strabismus Surgery and Its Complications. 2007:285–290.
- Höhne C. Postoperative nausea and vomiting in pediatric anesthesia. Curr Opin Anaesthesiol. 2014;27:303–308. doi:10.1097/ACO.0000000000000073 [CrossRef]
- Coats DK, Olitsky SE. Anesthesia considerations. In: Strabismus Surgery and Its Complications. 2007:47–55.
- Spinelli C, Pedrotti E, Fasolo A, et al. Strabismus surgery under topical or general anesthesia: a comparative retrospective study. Invest Ophthalmol Vis Sci. 2014;55:2591.