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Editors Selection IGR 16-4
Surgical Treatment: Ahmed Valve and Mitomycin C
Comment by Simon Law on:
69941 Effect of mitomycin c and 5-flurouracil adjuvant therapy on the outcomes of Ahmed glaucoma valve implantation, Cui QN; Hsia YC; Lin SC et al., Clinical and Experimental Ophthalmology, 2017; 45: 128-134
Although intraoperative antifibrotic adjunctive therapy in Ahmed glaucoma valve (AGV) implantation was ineffective in enhancing the long-term IOP control as it is in trabeculectomy, the effect of additional injection of antifibrotic agents during early postoperative period has not been fully investigated. In this retrospective consecutive case series compared 26 patients (eyes) that had resident-performed AGV surgeries without any adjunctive antifibrotic therapy supervised by one author prior to 2011 (-INJECTION group) with 24 patients (eyes) with intraoperative mitomycin- C (MMC) injection and postoperative MMC and/or 5-fluorouracil (5-FU) injection supervised by another author in 2011 and thereafter (+INJECTION group), the +INJECTION group has a lower rate of hypertensive phase (3.8% vs. 54%) and lower IOP in one year (12.7 ± 0.9 vs. 16.6 ± 1.4 mmHg). Although the result seems promising, it should be interpreted with caution. Besides the small sample size, retrospective design, and short follow-up, patient selection based on a change of attending in the Veterans Administration Hospital may not be able to eliminate the bias. For instance, the two attendings might approve surgery based on different criteria (preoperative visual acuity of the -INJECTION group was significantly worse than that of the +INJECTION group) or have different details of surgical technique (such as modification to prevent postoperative hypotony associated with the FP7 model AGV) and postoperative management (such as the timing of initiating medical therapy). In addition, the timing and dosage of antifibrotic injection might not be strictly followed in a retrospective study as it is difficult to predict the postoperative IOP. For instance, though patients of the +INJECTION group were supposed to have three scheduled postoperative injection visits, they received an average of 4.3 injections postoperatively. Besides a possible antifibrotic effect resulting in a low rate of hypertensive phase, the +INJECTION group also had more frequent postoperative monitoring and therefore might have earlier intervention with ocular hypotensive agents.
It seems reassuring that despite the frequent postoperative antifibrotic injection (mean of 4.3 injections including 1.4 injections of MMC [50 mcg] and 2.9 injections of 5FU [5mcg]), complication rates of the two groups were comparable. However, longer follow-up is required to conclude on the safety as the MMC dosage was rather high. Future verification with a prospective study randomizing patients into two arms based on the use of postoperative antifibrotic may clarify the safety concern. Anyhow, authors are to be commended for attempting to enhance the results with the Ahmed glaucoma valve by using a more aggressive antifibrotic regimen. This study demonstrates the feasibility in designing a postoperative antifibrotic regimen to improve the results of glaucoma tube shunt procedure.
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