The purpose of this study was to assess the difference in outcome between the first-operated eye and the second-operated eye following non-penetrating deep sclerectomy (DS), and to identify potential success predictors for the second eye. Methods: This single-surgeon, retrospective study analyzed the outcomes of all bilateral nonsimultaneous DS with at least 24 months of follow-up. Its main outcome measure was surgical success, defined as unmedicated intraocular pressure (IOP) ≤ 15 mmHg associated with a relative reduction ≥20%. Results: In all, 104 eyes of 52 patients who underwent bilateral (standalone or combined) DS, within a mean of 344.3 ± 526.3 days of each other, were analysed. Post-operatively, mean medicated IOP decreased from 20.7 ± 7.9 (first-operated) and 19.3 ± 6.6 mmHg (second) at baseline (p = 0.107) to 13.8 ± 4.8 ([-33.3%; p < 0.001] first-operated eyes) and 12.7 ± 3.8 mmHg ([-34.2%; p < 0.001] second eyes) after 2 years (p = 0.619). Post-operative IOP and treatments reduction respectively showed fair (r = 0.53) and good (r = 0.71) levels of correlation between fellow eyes. Rates of complete success were comparable between first-operated and second-operated eyes (32.7% and 40.4%, respectively; p = 0.364). At 2 years, among patients whose firstoperated eyes were considered a success, 82.4% of surgeries in second eyes were successful (p=0.001). The odd ratio of a second-operated eye experiencing complete success were 6.32 (p = 0.011) if the first operated eye experienced complete success. Conclusion: The present study demonstrates a strong association between first-operated eyes and secondoperated eyes following DS, in terms of surgical outcomes and IOP reduction. In effect, surgical success in the first-operated eye increases the odds of success in the second eye by 6 folds.