In vitro mitomycin C absorption and delivery with different sponge materials used in filtering surgery

Using a Novel, Subconjunctival, Sustained-Release Mitomycin C Formulation in a Rabbit Model of Filtration Surgery with Gel Stent Implantation

Purpose: To investigate gel stent implantation with and without intraoperative sustained-release mitomycin C (MMC SR) in a rabbit model for gel stent implantation, and to examine aqueous humor outflow (AHO) postimplantation. Methods: Four groups of rabbits were included. Group 1 was untreated (control). Groups 2, 3, and 4 received the gel stent without MMC, with MMC solution (subconjunctival injection), and with MMC SR (subconjunctival injection), respectively. Intraocular pressure (IOP) and AHO were assessed via tonometry and indocyanine green-based angiography, respectively. The main efficacy measure was change in IOP from baseline. Results: Following gel stent implantation, Groups 2, 3, and 4 maintained ≥20% IOP reduction (response) for a median duration of 1 week, 6.5 weeks, and 30 weeks, respectively. Angiography showed normal aqueous humor drainage (Group 1) beginning at the perilimbal trabecular plexus and continuing posteriorly to episcleral outflow vessels. Following implantation, drainage occurred preferentially and directly into the subconjunctival bleb. Conclusions: Gel stent implantation with MMC SR was most effective in achieving sustained, long-term IOP reduction in the rabbit model, compared with implantation with or without MMC solution. Bleb presence and the postimplantation aqueous angiography results indicated redirection of the AHO to the subconjunctival vasculature and presumed lymphatics, suggesting efficient glaucoma filtration to lower IOP in this model. This rabbit model and aqueous angiography may help refine understanding of the mechanism of action of minimally invasive glaucoma surgeries and ultimately translate to improved surgical devices and procedures for patients with glaucoma.

Short-term outcomes of Mitomycin-C augmented phaco-trabeculectomy using subconjunctival injections versus soaked sponges: a randomized controlled trial

OBJECTIVES

To determine whether subconjunctival Mitomycin-C (MMC) injections are as safe and effective as sponge-soaked MMC in phaco-trabeculectomy.

METHODS

This prospective, randomized, interventional study was conducted on consecutive patients with visually significant cataract and an uncontrolled primary open-angle glaucoma. One hundred thirty-nine patients were recruited but 15 were ineligible for analysis. The patients were randomized into a sponge/injection group. All participants received a twin-site phaco-trabeculectomy. They were followed up on days 1, 15, 30, 3 months and 6 months post-operatively. A p-value < 0.05 was considered significant.

INTERVENTIONS

Participants in the sponge group received an augmentation of their phaco-trabeculectomy with sponges soaked in a mixture of 0.04% MMC and 2% preservative-free Lignocaine in a 1:1 ratio, placed in the subconjunctival space for four minutes. Participants in the injection group received the same mixture as a subconjunctival injection, after surgical draping.

RESULTS

There were 62 patients in each group. The groups had no significant differences in their baseline characteristics. The mean IOP at 6 months was significantly lower in the injection group (14.8 ± 3.7 mm Hg) than in the sponge group (17.1 ± 6.4 mm Hg) (p = 0.02). There was no notable difference in the complications or the final post-operative visual outcome but a significantly greater number of patients in the sponge arm required removal of the releasable suture (p = 0.001) and additional anti-glaucoma medications (p = 0.04) at six months post-operatively.

CONCLUSIONS

Subconjunctival MMC achieves a lower IOP with fewer anti-glaucoma medications than sponge-soaked MMC at six months for twin-site phaco-trabeculectomy in primary open-angle glaucoma with no additional risks.

One-Year Randomized Comparison of Safety and Efficacy of Trabeculectomy with Mitomycin C Sub-Tenon Injection versus Mitomycin C-Infused Sponges

PURPOSE

To compare the safety and efficacy of sub-Tenon injection of mitomycin C (MMC) with application of MMC-infused sponges during trabeculectomy.

DESIGN

Single-center randomized clinical trial.

PARTICIPANTS

A total of 56 eyes of 49 patients with open-angle glaucoma were included in this clinical trial.

METHODS

In this single-center randomized clinical trial, 56 eyes of 49 patients underwent trabeculectomy with MMC for primary open-angle glaucoma. Patients were randomized into 2 groups. The injection group received a sub-Tenon injection of 0.15 ml of 0.01% MMC diluted with preservative free lidocaine 2% (n = 27). In the sponges group, sponges soaked in 0.02% MMC were applied under the Tenon's capsule and the scleral flap for 2 minutes (n = 29). Intraocular pressure, endothelial cell count, best-corrected visual acuity, and number of intraocular pressure (IOP)-lowering medications were assessed before surgery and 1 week; 1, 3, and 6 months; and 1 year after surgery. Complete success was defined as IOP of 14 mmHg or less without medication. Bleb morphologic features were assessed using the Indiana Bleb Appearance Grading Scale bleb grading system.

MAIN OUTCOME MEASURES

Intraocular pressure reduction was the primary outcome. Bleb morphologic features and endothelial cell counts (ECCs) were secondary outcomes.

RESULTS

Mean IOP in the sponges group decreased from 30.5 ± 7.4 mmHg at baseline to 12.6 ± 5.9 mmHg at 1 year (P < 0.001); in the injection group, IOP decreased from 29.3 ± 6.8 mmHg at baseline to 12.7 ± 4.3 mmHg at 1 year (P < 0.001). No difference in IOP between the 2 groups was noted at any visit (P < 0.001). Surgical success was 81.5% and 82.8% in the injection and sponges groups, respectively, at 1 year. Mean ECC values were unchanged from baseline to 1 year after surgery for both groups (P = 0.444). Complication rates were similar in the 2 groups. Bleb morphologic features showed differences in the appearance and grading of the blebs between the 2 groups at 1 year, showing larger extent, lower height, and less vascularization in the injection group.

CONCLUSIONS

Sub-Tenon injection of MMC during trabeculectomy seems to be as safe and as efficacious as conventional application of MMC with sponges at 1 year after surgery. Bleb morphologic features show notable differences that may suggest a better long-term outcome.

National survey of intraoperative mitomycin C use during trabeculectomy surgery in the UK

PURPOSE

Mitomycin C is a routinely used antimetabolite which effectively limits the scarring process. Conventionally, the intra-operative technique of MMC delivery during trabeculectomy is the direct application of the soaked sponges. The aim of this study is to evaluate the current practice of delivering MMC during trabeculectomy and to see the practices related to a retained MMC swab during trabeculectomy in the UK.

METHODS

An electronic questionnaire of 8 questions regarding the intraoperative use of MMC during trabeculectomy surgery was emailed to 69 ophthalmologist members of the UK and Eire glaucoma society (UKEGS) through email in July 2019.

RESULTS

97.2% of the surveyed glaucoma surgeons said they use MMC during trabeculectomy routinely, while 2.9% said they never use MMC for trabeculectomy. In reply to a question 'Have you ever had a retained MMC-soaked sponge/fragment of sponge', 11.76% replied 'yes', 88.24% said 'No'. In response to what technique was employed at the time of retained MMC sponges, all the respondents said they had employed the same technique of 'multiple individual sponges'. 47.1% surgeons said they use multiple individual sponges on being asked what technique they currently employ for delivering MMC during trabeculectomy surgery, while 14.7% surgeons use multiple sponges linked with a 'necklace suture' and 5.9% inject MMC.

CONCLUSION

Our survey suggests the intra-operative MMC use in the UK is high and that unintentional MMC-soaked swab retention does occur, albeit rarely. A preference of using the MMC-soaked swabs as a delivery method of MMC is seen in our survey.