Bilamellar tarsal rotation has been a key component of the WHO SAFE approach to blindness from trichiaisis (surgery, antibiotics, facial hygiene, environment). The World Health Organisation (WHO) manual describes the procedure as a full thickness blepharotomy placed 3.0mm above and parallel to the eyelid margin and then rotated and reattached with mattress sutures. However, the recurrence rate of trichiasis following this procedure is 30-40% after one year - an unacceptably high level. For this reason this multinational team stratified surgical success by postoperative scar height. One hundred and forty-five sequential patients were reviewed one year following their surgery and their scar height measured externally and on tarsal conjunctiva at three locations in the upper eyelid. Seventy-seven lids (31%) had postoperative recurrence of trichiasis - most often centrally. There was an indirect correlation between scar height and recurrence rate, until 4.5mm height, at which point the rate levelled off. Using multivariate analysis severe disease and scar <4.5mm were both associated with postoperative trichiasis. The authors tentatively suggest that perhaps the WHO guidance of 3.0mm blepharotomy height be reviewed as this could offer significant cost-savings and patient benefit.