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 Table of Contents  
CLINICAL CHALLENGE
Year : 2020  |  Volume : 32  |  Issue : 1  |  Page : 89-90

Commentary on Concerns in the Surgical Treatment of Intermittent Exotropia


Department of Ophthalmology, The Eye Foundation, Coimbatore, Tamil Nadu, India

Date of Web Publication17-Apr-2020

Correspondence Address:
Dr. R Muralidhar
Department of Ophthalmology, The Eye Foundation, Coimbatore, Tamil Nadu
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0976-6677.282655

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How to cite this article:
Muralidhar R. Commentary on Concerns in the Surgical Treatment of Intermittent Exotropia. Kerala J Ophthalmol 2020;32:89-90

How to cite this URL:
Muralidhar R. Commentary on Concerns in the Surgical Treatment of Intermittent Exotropia. Kerala J Ophthalmol [serial online] 2020 [cited 2020 Aug 12];32:89-90. Available from: http://www.kjophthal.com/text.asp?2020/32/1/89/282655



The management of intermittent exotropia has been mired in controversy and hotly debated. This is because of the low success rates with surgical/conservative management. While nonsurgical management has abysmally low success rates of 12%, it was noted that some patients resolved spontaneously without the need for further intervention.[1] The reported success with surgery has varied from 38% to 81%. This variability is partly because of varied follow-ups. It is a well-known fact that the success of intermittent exotropia drops over time especially 4 years or more after surgery. There are very few studies with such long-term follow-ups. Another reason is the varied criteria for success used by authors and also because many did not factor the sensory status in defining success.[2],[3] A study that followed up these patients for more than 10 years reported a success of 38% when rigid motor and sensory success criteria were employed and 64% when only motor criteria were employed. It may be noted that 60% of the patients in this study needed more than one surgery.[3] The difficulty in managing these patients stems from the sensory status. Patients with intermittent exotropia have temporal hemi-suppression that is active even when the eyes are aligned. This serves as a mechanism to suppress diplopia and thereby hinders the impetus for binocularity. Attempts to treat this with alternate eye patching and surgical overcorrection have met with limited success.[4],[5],[6]

This calls for guidelines in choosing patients for surgical management. Dr. Sanitha succinctly sums up various criteria for surgical management including the Newcastle control score.[7] In general, we decide on surgery if the deviation is noted more than 50% of waking hours and if the control for near is poor. It must be remembered that a constant exotropia is highly detrimental to binocularity and surgery may not fully restore stereopsis. A decline in distance (and of course near) stereopsis has been suggested as a reliable indicator in deciding for surgery.[8],[9] Another topic of debate is the age for surgery. I believe that young patients may be taken up for surgery when reliable measurements can be obtained. Overcorrections must be avoided in children <6 years as the risk of microtropia and subnormal stereopsis is very much present. A conservative approach to surgery is desirable in children under 6 years of age for the same reason.[6]

Various approaches have been tried to measure the deviation angle to be corrected. These include various periods of patching, measuring for far distance. It has been shown that it is safe to operate for the maximum angle of deviation noted on measurements.[10]

There is little consensus on the target angle for intermittent exotropia. Most studies seem to indicate that a small initial overcorrection is desirable. It was believed that overcorrection would make up for any exotropic drift.[11] Exotropic drift is known to reduce the success over time and is maximum in the first 4 years after surgery.[2] Higher exotropic drift is noted in patients with larger angles of deviations preoperatively and in patients with larger overcorrections.[12] Another suggested mechanism include the induction of diplopia that would stimulate fusional vergences and move the image out of the temporal suppression scotoma. However, there is no consensus regarding the quantum of overcorrection needed.[11] It is impossible to induce overcorrection of the desired magnitude reliably without the use of adjustable sutures.[6] One study did not show any advantage of using adjustable sutures.[13] Another study showed remarkably low success rates with the use of hang-back recession.[14] These studies, however, were limited by a small patient number, and the surgeon must use his/her experience in formulating a surgical plan. It must also be remembered that some patients develop permanent overcorrections with subnormal stereopsis, and these are resistant to treatment.[15]

In general, I prefer a unilateral recess, resect procedure for basic exodeviations. The resected medial rectus (MR) is believed to act as a mechanical tether reducing the exotropic drift.[16] The management of divergence-excess exotropia is difficult. Bilateral lateral rectus (LR) recession with MR pulley fixation holds promise, but some patients may need bifocals/further surgery.[17] Various approaches have been described for convergence insufficiency exotropia, including slanting bilateral LR recession, bimedial resection, and improved recess resect (LR recession based on the distance deviation and MR resection based on the near deviation).[18],[19] I have generally preferred the improved R and R procedure described by Kraft et al.[20]

The management of large angle exotropia merits mention here. There are very few studies that detail on the same. I have conventionally preferred a single-stage adjustable approach under intravenous sedation, and my success rates parallel that reported by Yang et al. (77.5% motor success).[21]

To sum up, as Dr. Sanitha puts it, the management of intermittent exotropia poses many challenges.[7] A frank discussion with the patient and his/her attenders would go a long way in clearing any future misunderstandings. The surgeon needs to take a decision based on the clinical evaluation and his/her experience.



 
  References Top

1.
Hatt SR, Leske DA, Holmes JM. Long-term success in surgically and nonsurgically managed intermittent exotropia. Journal of American Association for Pediatric Ophthalmology and Strabismus {JAAPOS}. 2015;19:e25.  Back to cited text no. 1
    
2.
Lee JY, Ko SJ, Baek SU. Survival analysis following early surgical success in intermittent exotropia surgery. Int J Ophthalmol 2014;7:528-33.  Back to cited text no. 2
    
3.
Pineles SL, Ela-Dalman N, Zvansky AG, Yu F, Rosenbaum AL. Long-term results of the surgical management of intermittent exotropia. J AAPOS 2010;14:298-304.  Back to cited text no. 3
    
4.
Jampolsky A. Characteristics of suppression in strabismus. AMA Arch Ophthalmol 1955;54:683-96.  Back to cited text no. 4
    
5.
Serrano-Pedraza I, Manjunath V, Osunkunle O, Clarke MP, Read JC. Visual suppression in intermittent exotropia during binocular alignment. Invest Ophthalmol Vis Sci 2011;52:2352-64.  Back to cited text no. 5
    
6.
Von Noorden GK. Exodeviations. In: Von Noorden GK, Campos EC, editors. Binocular Vision and Ocular Motility. St. Louis:Mosby; 2002. p. 356-76.  Back to cited text no. 6
    
7.
Haggerty H, Richardson S, Hrisos S, Strong NP, Clarke MP. The Newcastle Control Score: A new method of grading the severity of intermittent distance exotropia. Br J Ophthalmol 2004;88:233-5.  Back to cited text no. 7
    
8.
Sharma P. The pursuit of stereopsis. J AAPOS 2018;22:2.e1-2.e5.  Back to cited text no. 8
    
9.
Sharma P, Saxena R, Narvekar M, Gadia R, Menon V. Evaluation of distance and near stereoacuity and fusional vergence in intermittent exotropia. Indian J Ophthalmol 2008;56:121-5.  Back to cited text no. 9
[PUBMED]  [Full text]  
10.
Kim C, Hwang JM. 'Largest angle to target' in surgery for intermittent exotropia. Eye (Lond) 2005;19:637-42.  Back to cited text no. 10
    
11.
Cho YA, Kim SH. Postoperative minimal overcorrection in the surgical management of intermittent exotropia. Br J Ophthalmol 2013;97:866-9.  Back to cited text no. 11
    
12.
Yam JC, Chong GS, Wu PK, Wong US, Chan CW, Ko ST. Predictive factors affecting the short term and long term exodrift in patients with intermittent exotropia after bilateral rectus muscle recession and its effect on surgical outcome. Biomed Res Int 2014;2014:482093.  Back to cited text no. 12
    
13.
Babu S, Goel Y, Chaudhary RB, Rastogi A, Agarwal R, Dhiman S, et al. Comparison of adjustable sutures versus nonadjustable sutures in intermittent exotropia. Eur J Ophthalmol 2018;28:264-7.  Back to cited text no. 13
    
14.
Mohan K, Sharma A. A comparison of ocular alignment success of hang-back versus conventional bilateral lateral rectus muscle recession for true divergence excess intermittent exotropia. J AAPOS 2013;17:29-33.  Back to cited text no. 14
    
15.
Lee JY, Lee GI, Park KA, Oh SY. Long-term evaluation of two reoperation groups for intermittent exotropia. J AAPOS 2017;21:349-53.  Back to cited text no. 15
    
16.
Lee YB, Choi DG. Comparison of outcomes of unilateral recession-resection as primary surgery and reoperation for intermittent exotropia. BMC Ophthalmol 2017;17:117.  Back to cited text no. 16
    
17.
Choi HY, Jung JH. Bilateral lateral rectus muscle recession with medial rectus pulley fixation for divergence excess intermittent exotropia with high AC/A ratio. J AAPOS 2013;17:266-8.  Back to cited text no. 17
    
18.
Farid MF, Abdelbaset EA. Surgical outcomes of three different surgical techniques for treatment of convergence insufficiency intermittent exotropia. Eye (Lond) 2018;32:693-700.  Back to cited text no. 18
    
19.
Wang B, Wang L, Wang Q, Ren M. Comparison of different surgery procedures for convergence insufficiency-type intermittent exotropia in children. Br J Ophthalmol 2014;98:1409-13.  Back to cited text no. 19
    
20.
Kraft SP, Levin AV, Enzenauer RW. Unilateral surgery for exotropia with convergence weakness. J Pediatr Ophthalmol Strabismus 1995;32:183-7.  Back to cited text no. 20
    
21.
Yang M, Chen J, Shen T, Kang Y, Deng D, Lin X, et al. Single stage surgical outcomes for large angle intermittent exotropia. PLoS One 2016;11:e0150508.  Back to cited text no. 21
    




 

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