Purpose: To examine the outcome of the use of donor sclera as spacer material in complicated cases of strabismus surgery. Methods: A retrospective cohort study on patients with complicated thyroidassociated ophthalmopathy (TAO) (n = 42) or congenital strabismus (n = 75). Patients underwent strabismus surgery during 1994-2014. The surgical results were evaluated in terms of the reduction in the angle of deviation, the need for reoperation, complications and patient satisfaction. Results: The majority of the TAO patients underwent surgery for vertical strabismus (n = 25). The vertical angle of deviation in the primary position was significantly reduced from a median of 23 prism dioptres (PD) to 2 PD (n = 35, p < 0.001). The horizontal angle of deviation in primary position for TAO patients with esotropia was significantly reduced, from a median of 35 PD to 2 PD (n = 17, p < 0.001). The majority of the congenital cases had horizontal strabismus (esotropia = 29, exotropia = 27). The angle of deviation in esotropia was reduced from a median of 29 PD to 8 PD (n = 36, p < 0.001) and in exotropia from 30 PD to 10 PD (n = 34, p < 0.001). Most of the patients were satisfied with the outcome of surgery, and only 12% required re-operation within 2 years. Conclusion: This is the first clinical study on the use of donor sclera as spacer material in complicated cases of strabismus surgery. The surgical results were good in terms of the reduction in the angle of deviation, the need for re-operation, complications and patient satisfaction, supporting the use of donor sclera for strabismus surgery.