Dr. Divya Kishore, D17623, Dr. Pramod Kumar Pandey, Dr. Divya Kishore, Dr. Annu Joon
Abstract
Purpose:Sensory exotropia (XT) constitutes a sizeable chunk of exodeviations. Large deviations, associated vertical/pattern strabismus, DVD may pose formidable surgical challenges. Supramaximal horizontal surgery may cause side gaze incomitance and undercorrection.
Methods:Ten patients with sensory XT >50 PD were studied. Visual acuity (VA),ocular deviation,oblique muscle action,pattern strabismus were evaluated. LR recession 10 mm, MR resection 6mm, IO recession 10mm and temporal SO tenotomy were done in the affected eye .Results were evaluated at 12 weeks and success defined as final alignment within 8 PD.
Results– Correction achieved was 70 PD with SD of 14. No vertical deviation was induced,no side gaze incomitance or palpebral aperture narrowing noted.
Conclusion Adjunctive simultaneous weakening of both oblique muscles with horizontal recti surgery works well for large sensory XT (>50 PD).Obliques weakening may produce an additional correction of 20 PD or more over isolated horizontal surgery.
Introduction
Sensory exotropia (XT) constitutes a sizeable chunk of exodeviations. Large deviations, associated vertical/pattern strabismus, DVD may pose formidable surgical challenges. Supramaximal horizontal surgery may cause side gaze incomitance and undercorrection. This study was undertaken for the purpose of evaluating the outcome of simultaneous weakening of both obliques with horizontal recti in large angle sensory deviations.
Material and Methods
This study was approved by the institutional Ethics Committee and followed the tenets of the Declaration of Helsinki. Ten consecutive patients aged >18 years with sensory large angle exotropia >50PD attending the Squint clinic at Guru Nanak Eye centre, New Delhi Eye from Jan 2016 to April 2017 were included. Patients with paralytic strabismus,Dissociated vertical deviation (DVD), a history of prior strabismus surgery and restrictive strabismus were excluded. The best corrected visual acuity (BCVA) was recorded. The angle of deviation was measured by the alternate cover andKrimsky’s test at near and distance fixation whenever possible.Ductions, versions and vergences were evaluated, oblique muscle under/overaction and pattern strabismus were recorded. Any concomitant vertical deviation, HeimannBielschowsky phenomenon, concomitant co morbidities were recorded. Fundus torsion,Forced duction test (FDT) and Guyton’s exaggerated traction test for obliques was performed in all patients before surgery for all patients
All patients were operated under localperibulbaranaesthesia by a single surgeon (PKP).Lateral rectus (LR) and Inferior oblique (IO) were approached by the inferotemporal fornix incision and both were recessed 10mm. superior oblique (SO) and medial rectus (MR) were approached by the superonasal fornix incision and MR resection 6mmand temporal SO tenotomy close to temporal border of SR were done. On table FDT was done. Conjunctiva was closed by 8-0 vicryl sutures.
Patients were given antibiotic steroid eye drops six times a day for the first week, tapered weekly over six weeks. They were followed up on post op day 1, week 1, 3, 6 and 12.
Results were evaluated at the end of 12 weeks. Postoperative BCVA, deviation, obliques action, pattern, induced vertical, lid fissure changes, abduction deficits, palpebral fissure narrowing on adduction and fundus torsion. Success was defined as alignment within 8 PD.
Results:
6 female and 4 male patients were included in the study. The mean age of the patients was 31± 12 years. BCVA in the affected eye was less than 6/60 in all patients and the unaffected eye was 6/12 or better.Etiology was post traumatic in four patients, anisometric amblyopia in two, typical coloboma in two and old RD with cataract in one.Preoperative deviation was 65±18 PD.X pattern was seen in 6 patients. Associated DVD and HeinmannBeilschowsky were not noted in any patient. Some limitation of adduction was noted in 6 patients. On FDT, LR was found to be tight in 4 patientsand both obliques tight in 2, which was relieved post-surgery.Fundus torsion could be evaluated in 6 patients and was within normal limits. Postoperative correction achieved was70± 14 PD. No vertical deviation, palpebral narrowing, fundus torsion was induced by this procedure.
Discussion
Sensory exodeviation constitute a significant proportion of exodeviations in our country. Large deviation more than 50 PD pose surgical challenge as doing unconventionally large recession and resection has adverse effects on motility and palpebral fissure.
Alternatives to supramaximal surgery is recession of the conjunctiva and Tenon’s capsule overlying the receded muscle(1), closing the conjunctiva Horizontally after a vertical incision, recession combined with marginal myotomy.(2),
Patients often suffer psychological problems like low self-esteem(3) due to the apparent large angle squint. Hence they want quick results and surgeons are compelled to align the eyes with a single stage procedure. This is all the more challenging as only one eye can be operated which limits the number of muscles that can be operated. Also, Supramaximal surgery causes limitation of motility due to decrease in the arc of contact. (4)For example, the functional equator lies 4mm posterior to the anatomic equator laterally, making recessions beyond 11mm for the LR ineffective.
In large recessions, there may be induced errors while measuring from calipers which are designed to measure a linear surface, not a curved globe.(4). This factor would overestimate the actual amount of recession achieved.
Raab(5) operated eight patients with conventional maximum horizontal rectus recession/resection plus weakening of both obliques of the poorly seeing eye and believed it to be superior to “supermaximal” recession/resection procedures, as it probably releases additional sites of contracture in the obliques and also avoids surgery in the “good” eye which is invariably required in large angle deviations.
He performed 7-8mm recession of LR and 6mm resection of MR and variable recessions of 8-10 mm on the inferior obliques. He performed nasal tenotomy of the SO whereas we performed temporal tenotomy close to SR.
Mean deviation in our series was less than that reported by Raab who had deviations of upto 100 PD, whereas we had deviation of 65±18 PD. He achieved correction of upto 20 PD in 6 patients and larger deviation of 100 PD were corrected in the range of 25-30 PD. Our success criteria was more stringent than this study in the form of 8 PD and was achieved in all.
Raab also had vertical deviation induced probably due to the nasal approach for SO tenotomy. We approached temporally and had no case of postoperative hypotropia. Temporal SO tenotomy with 10mm IO recession seems to cancel out vertical vectors and likely correction of 20PD in PP and improvement in X pattern.
He had utilised a limbal incision but we used the fornix incision. We feel it is faster and causes less inflammation as muscles can be approach with the same incision rather than multiple incisions
The drawback of our study was small sample size and no control group. Studies taking larger sample size and control group need to be undertaken. Also, longer follow up to see the outcome of the procedure is required.
Conclusion
Adjunctive simultaneous weakening of both oblique muscles with horizontal recti surgery works well for large sensory XT (>50 PD).Obliques weakening may produce an additional correction of 20 PD or more over horizontal recession/ resection surgery.
Temporal SO tenotomy may be preferable over nasal tenotomyas vertical tropia is less likely to be induced.
REFERENCES
- Rayner JW, Jampolsky A: Management of adult patients with large angle amblyopic exotropia. Ann Ophthalmol 5: 95-99, 1973.
- Helveston EM, Cofield DD: Indication for marginal myotomy and technique. Am J Ophthalmol 70:574-578, 1970.
- Burke J, Leach CM, Davis H. Psychosocial implications of strabismus surgery in adults. J Pediatr Ophthalmol Strabismus 1997;35:159-64.
- Livir-Rallatos G, Gunton KB, Calhoun JH. Surgical results in large-angle exotropia. J Am Assoc Pediatr Ophthalmol Strabismus. 2002 Apr;6(2):77–80.
- Raab EL. Unilateral four-muscle surgery for large-angle exotropia. Ophthalmology. 1979 Aug;86(8):1441–50.
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