Successful outcome of Knapp’s procedure with Foster augmentation suture in a case of monocular elevation deficiency with large primary position vertical deviation

Abstract

Abstract A 26-year-old female patient presented to us with diminution of vision, downward deviation with restriction of extraocular movements of the left eye (LE) with drooping of ipsilateral upper lid since childhood. On examination, the best corrected visual acuity in LE was 6/12 and 6/6 in the right eye (RE), restriction of adduction and elevation (−4) on duction, and limitation on dextro-elevation and levo-elevation (−4) on version with moderate ptosis was present. On Hirschberg’s test, hypotropia of 30° was seen in LE with poor Bell’s phenomenon. Prism bar reflex test showed hypotropia of 65 prism diopters (PD). She was diagnosed with LE monocular elevation deficiency (MED) with mild LE amblyopia. Forced duction testing was strongly positive for LE Inferior Rectus muscle, therefore LE IR recession 6.5 mm with conjunctival recession was done as the first procedure. There was a residual hypotropia of 50 PD after 4 months of follow-up for which LE Knapp procedure with foster augmentation suture was performed. Post-operatively, the patient was orthophoric in the primary position with significant improvement LE upgaze limitation. Through this case report, we aim to conclude that a two-step surgical approach including inferior rectus recession followed by Knapp’s procedure with foster augmentation suture is an effective procedure in a case of MED with a large primary position vertical deviation.