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Mitomycin helps trabeculectomy, but with high incidence of hypotony
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PITTSBURGH — Primary trabeculectomy with adjunctive mitomycin-C significantly lowers intraocular pressure at 5 years postop, a long-term study here concluded. But the treatment is associated with a high incidence of delayed hypotony, researchers said.
Rajiv Bindlish, MD, and colleagues here retrospectively evaluated 123 eyes that underwent primary trabeculectomy with mitomycin-C. Laser suture lysis (LSL) was performed for postop IOP control. Mean preoperative IOP was 25.9 mm Hg, and mean postop IOP was 9.9 mm Hg. Follow-up in all eyes was 5 years. The incidence of delayed hypotony (defined as IOP less than 6 mm Hg) and maculopathy were recorded at each follow-up visit.
The authors found three statistically significant variables for occurrence of hypotony at least once from 6 months to 5 years postop: race, LSL performed and initial IOP 1 month postop. Hypotony was less likely to occur in eyes with a higher IOP 1 month postop, they reported in the July issue of Ophthalmology.
“Hypotony was five times more prevalent in whites than blacks,” the authors said. “LSL was also performed less frequently in the hypotonus group than in the nonhypotonus group.”
The researchers found no correlation between MMC concentration or exposure time and the development of hypotony
The study included 107 eyes of white patients and 15 eyes of black patients. Of the total, 114 eyes had primary or secondary open-angle glaucoma, and nine eyes had primary or secondary angle-closure glaucoma.
The mean target IOP was 14.7 mm Hg. On day 1 postop the mean IOP was 14.6 mm Hg, and it continued to drop at each follow-up point. LSL was performed in 59 eyes.
Surgical success — defined as IOP less than target IOP with or without medications, excluding cases of bleb leak or blebitis — was 87% at year 1, 87% at year 2, 88.2% at year 3, 85% at year 4 and 83% at year 5.
The incidence of hypotony at any time after 6 months postop was 42.3%, occurring at a mean of 26 months postop. Maculopathy occurred at a mean of 34 months, and incidence was 8.9%. Eighteen eyes (14.6%) lost 4 or more lines of vision during the follow-up period. Visual loss was attributed to hypotony, hypotony with maculopathy, advanced glaucoma, macular/retinal disease, cataract and endophthalmitis.
In this study, up to 8% of new hypotony cases occurred during years 4 and 5.
“It is evident from our study that eyes with an acceptable clinical result (IOP less than target, more than 6 mm Hg) at 1 or more years postop may eventually develop hypotony after longer follow-up,” study authors conclude.