A One-Year Follow-Up of Two Ahmed Glaucoma Valve Models (S2 and FP7) for Refractory Glaucoma: A Prospective Randomized Trial

Abstract

Aim: To compare a range of clinical outcome variables (intraocular pressure, glaucoma medications, visual acuity, and complications) between two Ahmed glaucoma valve (AGV) models (S2 and FP7).

Methods: This was a prospective and randomized clinical trial. Fifty-six patients with refractory glaucoma were randomly assigned to be implanted with either a polypropylene (S2) or silicone (FP7) Ahmed glaucoma valve. The primary outcome measure was a surgical success, defined as an IOP ≤ 16 mm Hg (without medication), and guarded success, defined as a controlled IOP ≤ 16 mmHg (with medication). Failure was defined as when the IOP lay outside of the successful range on two consecutive visits (>16 mmHg, despite medication).

Results: Mean follow-up period was 398.42 ± 12.34 days (range, 380-420 days) for the S2 group and 401.75 ± 9.78 days (range, 385-420 days) for the FP7 group; these values were not significantly different (P = 0.27). After 12 months of follow-up, the baseline IOP (45.42 mmHg) fell significantly to 16.14 mmHg in the S2 group (p < 0.000); there was also a significant reduction in IOP in the FP7 group (from 44.17 mmHg to 15.18 mmHg in FP7 group, p < 0.000). At the last follow-up examination, the mean IOP in the S2 group was 16.14 ± 3.18 mmHg, while that of the FP7 group was 15.18 ± 2.75 mmHg; there was no significant difference between the two groups with this respect (p = 0.23). The mean number of medications used by patients in the S2 and FP7 groups was 2.92 ± 1.27 and 2.75 ± 1.43, respectively; there was no significant difference between the two groups with this respect (p = 0.32). There was no significant difference between the FP7 and S2 groups with regard to their relative success rate (17.89% [5/28] versus 10.7% [3/28], respectively; p = 0.38).

Conclusion: Our data show that the S2 and FP7 models of AGV were both effective in lowering IOP and reducing the need for glaucoma medications. Although these two AGV models had similar dimensions, they were constructed from different materials. However, there were no significant clinical differences between the S2 and FP7 AGV groups after 12 months of follow-up. Furthermore, our data indicate that bleb encapsulation was the primary factor responsible for failure rate and the need for glaucoma medication in both the S2 and FP7 groups. Our analysis further indicates that the S2 and FP7 Ahmed valves are associated with a high risk of failure when considered as a first-line therapy for cases experiencing trabeculectomy.

Clinical trial registration: NCT04214847.

Keywords: Ahmed glaucoma valve; FP7; IOP; S2; encapsulation.

Conflict of interest statement

None of the authors have any conflicts of interests to declare.

© 2020 Elbaklish and Gomaa.

Figures

Figure 1

Mean (± SD) IOP for the 56 participants in the S2 and FP7 groups. P = 0.005 and P = 0.044 at 1- and 6-month post-surgery, respectively. The mean preoperative IOP fell from 45.42 ± 6.93 mmHg and 44.17 ± 5.98 mmHg before surgery to 16.14 ± 3.18 mmHg and 15.18 ±2.75 mmHg at the one-year follow-up, in the S2 and FP7 groups, respectively (P = 0.23).

Figure 2

Mean (± SD) IOP in the adults assigned to the S2 and FP7 groups. P = 0.004 and 0.024 at 1- and 6-month post-surgery. The mean preoperative IOP fell from 45.33 ± 6.49 mmHg and 43.92 ± 5.94 mmHg before surgery to 16.25 ± 3.18 mmHg and 15.29 ±2.72 mmHg at the one-year follow-up, in the S2 and FP7 groups, respectively (P = 0.24).

Figure 3

Mean number (± SD) of glaucoma medications administered in the 56 participants in the S2 and Fp7 groups. P = 0.000 and p = 0.005 at 1- and 9-month post-surgery. The mean number of medications administered fell from 3.92 ± 0.26 and 3.89± 0.31 before surgery to 2.92 ± 1.27 and 2.75±1.43 at the one-year follow-up, in the S2 and FP7 groups, respectively (P = 0.316).

Figure 4

Mean number (± SD) of glaucoma medications administered in the adult cohort of the S2 and Fp7 groups. P = 0.000 at 1 month after surgery. The mean number of medications administered fell from 3.92 ± 0.26 and 3.89± 0.31 before surgery to 2.96 ± 1.26 and 2.7±1.41, at the one-year follow-up, in the S2 and FP7 groups, respectively (P = 0.256).

Figure 5

Survival curves for the S2 (blue line) and FP7 (green line) groups. Success rates were 89% and 82% at 12 months for the FP7 group and the S2 group, respectively. The S2 curve began to fail at approximately 270 days. Mean survival times for the S2 group and FP7 group were 394.76 days (95% CI, 381.23–408.28) and 402.54 days (95% CI, 396.70–408.37), respectively. The differences between the S2 and FP7 curves for the 2 groups were not statistically significant (0.414).

Figure 6

Comparison of log MAR visual acuity before and after surgery involving stable log MAR (21 versus 22 participants), improved log MAR (2 versus 3 participants), and deteriorated log MAR (5 versus 3 participants), in the S2 and FP7 groups at the one-year follow-up (P = 0.653 and P = 0.691).