Investigation of the effects of mitomycin C (MMC) and cyclosporin A (CsA) on experimentally induced glaucoma filtration surgery (GFS) in rabbits

The patency of glaucoma filtration surgery (GFS) fistula performed for treatment purpose on the glaucomatous patients totally depends on the duration of inhibition of the granulation tissue proliferation. The present study aimed at inhibiting the granulation tissue playing a primary role on the obstruction process of the GFS tunnel induced experimentally on a total of 18 New Zealand bred rabbits divided into control, MMC and MMC+CsA groups of 6 animals in each, with topical administration of MMC and MMC+CsA combination. Clinical alterations and complications in the GFS tunnel region were evaluated using ophthalmoscope, tear tests, tonometer and gonioscope 7 times at predetermined intervals, between the 0-35th days. No complication related to the surgery was determined in the groups used in the study. The right eyes of experimental subjects euthanized at the end of the study were obtained and histopathologically evaluated. According to clinical and histopahtholgical findings, the GFS tunnel remained open in all experimental animals of MMC and MMC+CsA groups during the study with no a marked difference between both groups. It was observed that a meaningful degrease in initial IOP values in all groups conformed to the clinical and histopathological findings, whereas an increase in IOP values toward the end of the study was contrast with those findings mentioned. The reasons for marked IOP decrease after the surgery are thought to be suppressive effect of operation stress on the production of humor aqueous and excessive drainage of this fluid via the new tunnel performed. On the other hand, an increase in IOP toward the end of the study despite the maintenance of the patency of the tunnel is considered to be result from the compensation action of the normal functioning of trabecular angle of the experimental subjects used. The tear production rate parameters in MMC+CsA compared to control and MMC groups showed more stabile fluctuation which is believed to result partially from the modulator effects of CsA on tear production. In conclusion, MMC and MMC+CsA combination were determined to have successfully prevented the obstruction of the tunnel with granulation tissue accordingly no a marked difference between them. It is suggested that the possible difference assumed to present between these two groups can only be understood with a prolonged study established with inclusion of another group containing just CsA.