Purpose: Previous studies have documented good pressure control with combined cataract and filtering surgery. However, relatively high incidences of iridocapsular synechiae (ICS) and cell precipitates on the optic (CPO) were found. Corneal valve incisions preclude intraoperative chamber flattening and iris injury or prolapse. Rigid one-piece PMMA lenses with a small optic maintain a pronounced optic-iris clearance. In a prospective series, the effect of this approach was studied with special regard to the morphological results.
Methods: A temporary corneal lip was created in the clear cornea beneath the scleral flap to serve as a temporary valve during cataract extraction. The lip was then widened and a rigid one-piece 5-mm PMMA lens implanted. Lip and trabeculum were finally excised en bloc at a width of 3 mm. Two years' functional and morphological results were evaluated.
Results: Fifty-four eyes were available for evaluation. After the mean follow-up of 21 months, mean IOP had dropped from 21.6+/-3 mm Hg preoperatively to 13.9+/-2.4 mm Hg, with a mean pressure reduction of 7.7+/-3.4 mm Hg. IOP was 18 mm Hg or less in all cases. The mean medication index dropped from 2.7 to 1.0. Eyes with a preoperative IOP of 21 mm Hg or more showed a significantly greater IOP reduction than eyes with an IOP of 20 mm Hg or less (-9.2+/-3.0 vs. -6.1+/-2.9 mm Hg, p = 0.0003). Intraoperatively, the temporary valve effectively prevented chamber flattening and iris injury or prolapse. Postoperatively, 9 eyes or 6% showed hyphemas, 1 undergoing lavage. Two eyes developed a capsular hematoma, 1 requiring YAG capsulotomy. Ten eyes or 19% developed mild and 2 eyes severe but transient fibrin exudation following hypotony or iridoplasty. One eye showed grade I anterior chamber flattening, 1 developed a ciliolenticular block requiring surgery. Postoperative pressure spikes of 30-35 mm Hg were noted in 4 eyes. Three eyes showed prolonged hypotony associated with transient choroidal effusion. A pronounced optic-iris clearance was found in 87% of the eyes. Iris-optic touch developed in 1 eye with prolonged postoperative anterior chamber flattening and in 3 of the 4 eyes that had undergone intraoperative iridoplasty. Three of the latter developed extensive ICS followed by CPO. The mean optic-iris distance was 1.2 mm and the anterior chamber depth 4.2 mm.
Conclusion: Apart from effectively lowering IOP, the surgical approach used significantly reduced the incidence of ICS and CPO.