a , 46-year - old indian male presented to our hospital with complaints of inward deviation of his left eye for the last 9 months , which he developed after sustaining a head injury . the deviation was associated with horizontal diplopia , which was more in the left lateral gaze . the patient was a known hypertensive and was on medication for the past 7 years . examination showed best - corrected visual acuity ( bcva ) of 20/20 in both eyes . the alternate cover test showed left esotropia of 25 pd in primary gaze [ fig . 1 ] . preoperative photograph shows left esotropia patient underwent left medial rectus recession of 5 mm from the insertion and a split - tendon transposition of the left superior and inferior rectus muscles to the lateral rectus insertion ( hummelsheim procedure ) through limbal conjunctival peritomy . on the first postoperative day , there was moderate corneal edema with anterior chamber reaction of flare 2 + and cells 2 + on slit lamp biomicroscopy . the pupil was still mid dilated and was nonreacting to light [ fig . 2 ] . one week postoperative photograph shows mild conjunctival congestion , no corneal edema and a mid - dilated pupil patient was followed up regularly . on anterior segment examination , the cornea was clear , the anterior chamber was quiet , the pupil was mid - dilated and nonreacting to light [ fig . 3a ] . visual axis was parallel and abduction of the left eye was in near normal [ fig . ( a ) one year postoperative photograph shows quite eye with mid dilated pupil , ( b ) 1-year postoperative photograph shows normal abduction range our patient developed asi following one muscle recession , and two muscle split muscle transposition , which is equivalent to two muscle surgery as the second halves of these vertical recti muscles still continue to contribute one ciliary vessel each . however , our patient was a known hypertensive , which could have been a risk factor for the development of asi . al enezi and al wayel reported asi in a 35 years old myopic patient following a similar procedure . they proposed that high myopia could also be a risk factor for asi with vertical muscle surgery . a two - staged procedure with an interval of 46 months could have prevented asi in our patient with hypertension as a risk factor as this would have allowed time for remodeling of the collateral circulation . however , limbal incisions are said to predispose to more severe ischemia compared to fornix incisions as these compromise the anterior episcleral arterial circle . microscopic surgery on recti muscle for carefully dissecting anterior ciliary vessels before disinsersion can also be considered for high - risk patients as this helps to keep the anterior ciliary vessels intact and prevent asi . anterior segment ischemia should be kept in mind during vertical muscle transposition in high risk patients during strabismus surgery .