Quantitative changes in the field of binocular single vision following a fadenoperation to a vertical rectus muscle.

Purpose: To quantify the effect of a fadenoperation to a vertical rectus muscle on the field of binocular single vision (BSV).
Patients and Methods: BSV was assessed quantitatively in 32 patients before and after a fadenoperation to a single vertical rectus muscle by measuring the vertical extent of single vision in the midline and a score for the total field of BSV. Patients were aged from 14 to 72 years. All patients had diplopia in either downgaze or upgaze before surgery. In 11 patients, this was due to a fourth cranial nerve palsy, and in 8 patients it followed an orbital floor fracture.
Results: The 15 patients who had an inferior rectus fadenoperation alone showed a significant mean increase in downward and total vertical extent of BSV and in their field of BSV. The 9 patients who underwent a superior rectus fadenoperation alone showed a significant increase in total vertical extent of BSV and field of BSV score. Three of the 8 who underwent a fadenoperation combined with another strabismus procedure at the same time had a substantial improvement in their score, but after the other 5 showed little change. Patients with a paretic deficit showed substantially more improvement than those with an upgaze deficit after a blowout fracture.
Conclusion: The fadenoperation to a vertical rectus muscle produced a significant functional expansion in the field of BSV in approximately two thirds of patients. The procedure was more effective in incomitant squints of paretic rather than mechanical etiology.