Conjunctival dysfunction and mitomycin C-induced hypotony.

PURPOSE

To determine the role of a physically intact conjunctiva in the development of chronic hypotony after mitomycin C-enhanced trabeculectomy.

METHOD

Three patients with mitomycin C-related hypotonic maculopathy, but without a leak on Siedel test, had a thorough evaluation of the bleb area and an anterior segment fluorescein angiography. The bleb was excised and a pedicle flap, rotated from the temporal conjunctiva, was sutured to cover the defect superiorly. The scleral flap and its sutures were not disturbed. The excised bleb was subjected to light and electron microscopy.

RESULTS

The Seidel test result was negative in all patients, but late phases of the anterior segment angiography showed a generalized seepage of aqueous from the bleb. After revision of the bleb, there was a gradual increase in the intraocular pressure, a reversal of the hypotonic maculopathy, and consequent improvement in visual acuity in all three patients, stable up to a minimum follow-up of 18 months. On histopathologic examination, the basement membrane was thickest under thin areas of the epithelium and thinnest below thicker epithelial layers.

CONCLUSION

A dysfunctional conjunctival barrier, as evidenced by the "sweating" of the bleb and histopathologic alterations in the epithelial barrier, could be responsible for the hypotonic maculopathy in these patients. Excision of the conjunctiva alone and replacement by a pedicle conjunctival graft offers a safe and effective method of treating chronic hypotony after mitomycin C-augmented trabeculectomy in such patients.