The surgical results of all patients undergoing isolated adjustable suture vertical squint surgery for thyroid eye disease are presented for a single centre over five years to explore the predictive factors for surgical planning. This was a retrospective study in which 79 subjects were identified and 37 excluded. Of 42 patients, mean age was 63.2±9.26 years; 81% female. Twenty had previous orbital decompression surgery. All had preoperative diplopia. Mean duration of preoperative diplopia was 15.73±10.4 months. Mean near preoperative vertical deviation was 21.5±10.4PD which reduced to 3.8±4.6PD at one year postoperative. Mean distance preoperative vertical deviation was 23.2±10PD reducing to 4.1±4.9PD at one year; 57% achieved a vertical deviation <5PD at one year and 71.4% were diplopia free in primary position and downgaze. Eight required further treatment: four surgery, two botulinum toxin (BT), one prism and one steroids. Overall, the authors found a large initial undercorrection is needed to accommodate the full extent of postoperative drift in these patients and propose an undercorrection of 8PD for near fixation with appropriate preoperative counselling and long-term follow-up to one year.