Surgery for intermittent Divergent squint: A Comparison of Outcomes Following Two Different Surgical Techniques

INTERVENTION: Surgery for intermittent exotropia, Bilateral lateral recti recession or recession/ resection. the recession of the lateral recti muscle involves weakening the muscle by pulling it back few mm [ each mm will weaken the muscle by 3 diopters] so the amount will depend on the degree of divergent squint. e.g to correct 30 diopters of divergent squint will need to weaken each lateral recti muscle by 5 mm on each side so in total 10 mm = 30 Diopters. for the medial rectus resection means strengthening the muscle by cutting it { each mm will strengthen the muscle by 4 mm] and that is again depend on the amount of squint. the duration of each procedure will be approximately 20 min / muscle. CONDITION: Divergent squint [ intermittent exotropia] PRIMARY OUTCOME: Comparison between two techniques for intermittent exotropia.,{Bilateral lateral recti reccession or medial/ lateral rectus recession/ resection regarding the success rate. and this is measured by diopter [ the surgery considered successful if the residul squint is less than 10 Diopters SECONDARY OUTCOME: Does the patch test alter the distance measurements and therefore the surgical target the effect of patch test. ; we patch the involved eye for 20, 40 ,60 min at different intervals and do measure amount of squint in diopters INCLUSION CRITERIA: Age 3‐18 years History of intermittent exotropia intermittent at either near or distance Full eye movements Visual acuity 6/9 or better each eye best corrected with crowded test by the time of surgery Any myopic refractive error, anisometropia or astigmatism of 1 dioptre or greater or hyperopia which is reducing the vision to less than 6/9 must be treated prior to inclusion. Basic exotropia with difference between near and distance measurements <10 dioptres, or simulated divergence excess with difference between near and distance measurement <10 dioptres after +3.00 test and/or patch test. Able to obtain full informed consent from the family for randomisation Able to obtain accurate prism cover test measurements (distance and near cover test within 5^ on at least 2 visits)