Background <p>This study aimed to assess the surgical outcomes of Ahmed glaucoma valve (AGV) implantation in high myopic eyes (axial length [AL] of ≥ 26.0&#xa0;mm) and to determine whether high myopia independently poses a risk of surgical failure.</p> Methods <p>We retrospectively reviewed 68 eyes from 59 patients with refractory glaucoma who underwent AGV implantation. Eyes were categorised into high myopia (23 eyes, 33.8%) and control (45 eyes, 66.2%) groups. The primary outcome was the surgical success rate, defined as postoperative intraocular pressure (IOP) of 6–21 mmHg or a ≥ 20% reduction from baseline. Surgical success was further classified into criterion A (postoperative IOP ≤ 21 mmHg) and criterion B (postoperative IOP ≤ 15 mmHg). Surgical success rates were estimated using Kaplan–Meier analysis, and risk factors for surgical failure were identified via Cox proportional hazards modelling.</p> Results <p>At 1 and 2 years, surgical success was significantly higher in the control group according to criterion A (<i>p</i> = 0.013 and 0.043, respectively). Based on criterion B, the control group also showed better surgical success, although the difference did not reach statistical significance. (<i>p</i> = 0.051). Postoperative IOP was lower in the control eyes throughout all postoperative periods, and the difference reached statistical significance at 6 months (<i>p</i> = 0.017). An AL ≥ 26&#xa0;mm was a significant risk factor for surgical failure under both criterion A (hazard ratio [HR] = 8.30, <i>p</i> = 0.026) and criterion B (HR = 6.26, <i>p</i> = 0.009).</p> Conclusions <p>AGV implantation in glaucoma eyes with high myopia showed lower surgical success compared to those without high myopia. Longer AL is a significant risk factor for surgical failure, underscoring the importance of careful monitoring after AGV implantation in such cases.</p>