Evaluation of Bilateral Medial Rectus Recession in Esotropia (03/04)

100 files going backwards from December 31, 2000 of bimedial recession were examined from the private office of Dr. Lionel Kowal and from the Ocular Motility Clinic (cases where Dr. Lionel Kowal was the primary surgeon).

From these 100 files, 5 were either not bimedial recession or were done with adjustable sutures and were excluded. 16 others had follow-up elsewhere (typically another Ophthalmologist) and were excluded. 3 were extreme myopes and this being such a different category of patients were also excluded. 76 files are the subject of this study. 12 month follow-up data was available on all patients.

DETAILS OF SURGICAL MANAGEMENT

Surgery was typically performed using Parks' tables. If the globe was less than 20 mm the surgical dose was reduced by 10%, if it was greater than 24 mm was increased by 10%. The technique usually used was Parks' so called fornix approach with the hangback technique. The maximal dose of bimedial recession was 6.5 mm.

For convergence excess greater than 10^: if the patient had low plus the patient had a Parks' augmentation of + 1 mm. If the patient had more than + 2.5 DS, augmentation was as described by Kushner or Guyton (up to 2 mm).

For patients who had divergence excess, prism adaptation test was performed to assess the risk of near diplopia and if there was no risk then bimedial recession was performed.

RESULTS

1. Age at surgery

. < 12 mo: 4
. 1 - 3 y: 23
. 3 - 5 y: 23
. > 5 yr: 26

2. Spread of Cycloplegic Refraction

. < +1 : 14
. +1 - + 2.25 : 23
. +2.5 - + 4 : 17
. > +4 : 19

3. Patients with Convergence Excess of 10 or more ^

Distance - Near Incomitance
Pre-op Post-op
10-52 0-30
Mean 18 7
SD 9.5 9

50 p'ile 17 2
75 p'ile 20 12
95 p'ile 41 25

4. Duration before Treatment

The mean duration between clinical onset of esotropia by history and presentation for consideration of surgery was 31.5 months with standard deviation of 43 months.

5. Overall Results

The traditional "cure" for esotropia is to have the patient aligned within 10^ of orthotropia.

We subdivided this 'cure' into three smaller subgroups:

Class 1: Distance and near orthotropia.

Class 2: One of either the distance or near measurements is orthotropic or only one measurement was taken and is orthotropic.

Class 3: Both measurements are greater than zero and less than 10.

The traditional "cure" includes all the above three classes.

Class 4: One measurement is less than 10^ and one is greater than 10^ (there were no patients in this group).

Class 5: Both measurements are greater than 10.

The results were:

Class 1: 32 patients = 44%
Class 2: 23 patients = 32%
Class 3: 3 patients = 4%
Class 5: 15 patients = 20%

Re-Operation

Re-operation was carried out in 8 (11%). There was no correlation with cycloplegic refraction or presence of distance - near incomitance.

Another 7 patients had measurements greater than 10^ for distance and for near. These would traditionally be considered for re-operation but re-operation was not sought. Presumably these patients have a positive angle kappa that enhanced their appearance.

Discussion

The "mother of all audits" was by Ciancia who had a cohort of 568 patients. 390 were included and he had a follow-up of 27 years on many of these. Of those patients who have an esotropia and are treated with bimedial recession, 91% were straight on day 1. Of these patients, 26% have developed a recurrent esotropia by year 4. 8% of the group have consecutive exotropia by year 4.

By year 15, approx 30% of these patients have developed consecutive exotropia. This suggests that the amount of bimedial recession required to give early orthotropia will, with subsequent growth of the globe muscle and orbit and subsequent changes of the muscles - sclera union results in a relative disadvantage to medial rectus function in 30% of patients, sufficient to cause an exodeviation.

Birch and Wilson have both shown in separate studies that realignment within 4 months of constant esotropia results in better sensory motor results than a longer duration of constant esotropia. The referral pattern within our group of patients did not allow for early surgery. The 25th percentile of duration from onset to presentation was 6 months.

The method of augmentation of bimedial recession for convergence excess seems to be effective.

The rate of success (Classes 1,2 3) are equal to the best published results.

Dr. LIONEL KOWAL
Practice Restricted to Strabismus and Pediatrics
Director Ocular Motility Clinic, Royal Victorian Eye and Ear Hospital
Senior Fellow, University of Melbourne Department of Ophthalmology
First Vice President, International Strabismological Association (2002-2006)

and

Dr. Ravindra Battu
Fellow, Ocular Motility Clinic, Royal Victorian Eye and Ear Hospita