Mitomycin trabeculectomy: the microsurgical sponge difference

A reproducible method for mitomycin application during glaucoma surgery is necessary to compare clinical results among investigators. To evaluate the potential reliability in drug delivery characteristics, mitomycin absorption and release from microsurgical sponges was studied.

Four brands of commercially available sponges were compared using a 0.5 mg/ml concentration of mitomycin. First, the maximum volume each sponge could absorb was measured. Second, 0.2 ml was applied to each sponge and then the expansion width was measured. Finally, 0.2 ml was applied to each sponge, the sponge was placed on filter paper, and then the amount (by weight) each sponge released during a 31/2-min period was measured.

The volume absorbed was similar for each brand; the means ranged from 0.44 to 0.52 ml. The expansion width was variable between the brands; the means ranged from 4.0 to 10.4 mm. The amount released to filter paper was also variable between the brands; the means ranged from 19 to 54 mg.

The difference in delivery characteristics suggests that the microsurgical sponge may be an important variable in mitomycin application. In absence of a standardized method, more detailed descriptions about specific mitomycin techniques are needed.