A retrospective analysis was conducted on all patients treated in one centre with tendon elongation using bovine pericardium (BP) to examine outcomes and long-term safety. The study included 60 patients; 27 unilateral and 33 bilateral cases. Follow-up of one to four years was reported. At one day postoperatively, 51.8% had under correction but no cases of over correction. At three months postoperatively 59.3% achieved a deviation within ±10PD; three patients had horizontal over correction >10PD and 22 patients were under corrected by >10PD. Patients with deviations <40PD (unilateral) or <50PD (bilateral) showed better primary success rates (78% and 72% respectively) than those with severe esotropia. The authors conclude this surgical procedure is safe to correct severe esotropia up to 50PD, which cannot be corrected with simple medial rectus recessions. The procedure shows long-term stability and can be revised where necessary.