Mitomycin C has been applied intraoperatively, to enhance the outcomes of glaucoma filtration surgery since the 1990s. Such application is usually made topically onto the scleral and subconjunctival surfaces, though a subtenon injection during surgery has also been described¹ . The resuscitation of filtering blebs by needling them has become increasingly popular. To date good evidence as to the benefits of supplementing the needling with antimetabolites is lacking, though both 5-Fluorouracil and Mitomycin C have been used by subconjunctival injection.

We performed a retrospective case series on the long-term benefits and complications of supplement Mitomycin C injection with bleb needling. Patients received 20 mg of Mitomycin C via subconjunctival injection 30 minutes prior to the needling.

A total of 30 patients were analysed. Their mean pre-needling intraocular pressure (IOP) was 26.1 mmHg, and dropped to 11.2 mmHg immediately post-needling (p<0.03). The mean time elapsed between trabeculectomy and needling was 15.5 months (range 5—22 months). A total of 22/30 patients received supplemental 5-Fluorouracil injections within six weeks post-needling. Those patients had intraocular pressure increases greater than 5 mmHg and required massage or repeat needling to reduce the pressure again. In those circumstances supplemental 5-Fluorouracil was injected subconjunctivally. A mean of 1.6 injections of 5-FU was given.

Figure 1

Figure 1 shows after one year the mean IOP was 18.6 mmHg and this gain was maintained at two years at 18.2 mmHg and at three years with 17.9 mmHg (all at p<0.03).

Significant complications only occurred in the patients who received supplemental 5-FU injections. Those complications were bleb ischemia and subconjunctival bleb fibrosis.

Twelve of the twenty two patients showed significant bleb ischemia though still good IOP control and none of the total of 30 patients developed a blebitis.

Six of the 22 patients (with supplemental 5 FU) developed significant subconjunctival bleb fibrosis, which required surgery in four out of six cases for uncontrollable increases in IOP with maximum tolerable medications. In all four of these patients a very dense sheet of subconjunctival fibrous tissue was removed. No antimetabolites were used intraoperatively, but oral Diclofenac and Colchicine were administered for a total of two months if tolerable. They were followed for a minimum of one year and had a mean IOP of 14.5 mmHg at that point.

No patients developed any evidence of scleral melting or lost any line of best corrected visual acuity.

The amount and intensity of the subconjunctival bleb fibrosis was unusual. It could either be part of a Mitomycin-antibody or a fibrovascular ischemia response. For this reason any local antimetabolites were avoided during the re-operations. Equally disconcerting was the overall amount of bleb ischemia.

No lines of best corrected visual acuity were lost, IOP reduction maintained and no scleral melts found, however, the ischemia and fibrosis were felt to be significant. It is also noted that in a small case series from Germany, Mitomycin C subconjunctival injections just prior to trabeculectomy were found to be associated with scleral melts.²

Based on the findings of this three-year follow-up the investigators have discontinued the use of Mitomycin C as a supplement to bleb needlings and only utilize 5-FU for this purpose.

References

1. E. Lee, et al Acta Ophthalmol. 2008;86(8):866-70

2. G.Sauder, J.B. Jonas Am. J. Ophthal. 2006; 141(6):1129-30.