[Regulating intraoperative pressure in filtering glaucoma operations with a sterilizable tonometer].

BACKGROUND

Hypotony with shallow or flat chamber and hypertony without filtration are important short-term complications of filtering procedures in glaucoma. Both reflect the difficulty to adjust the tension of the scleral flap in a way that the artificial valve opens at pressures within the therapeutic range. Our aim was to avoid these complications by improving the filling test.

PATIENTS AND METHOD

22 eyes of 21 patients with chronic glaucoma of different etiology underwent a trabeculectomy. After preliminarily fixing the sutures, the anterior chamber was filled until fluid appeared at the rim of the scleral flap. Then, the pressure was measured using a newly developed, sterilizable applanation tonometer. By tightening or loosening the sutures the opening pressure was adjusted to values between 5 and 20 mm Hg.

RESULTS

The IOP at the first postoperative day correlated well with the intraoperative flap opening pressure (correlation coefficient 0.771), but was 20% lower at the average. All cases had a sufficient filtering zone and IOP below 20 mm Hg. At the first day, all chambers were deep. After 2 to 9 days, 4 eyes developed temporarily a shallow chamber (minimum depth: 1 1/2 times corneal thickness). This complication occurred only in eyes with intraoperative pressures of 5 to 10 mm Hg.

CONCLUSION

Intraoperative pressure control during trabeculectomy allows a fairly good determination of the postoperative IOP. Choosing a suitable pressure level (15 to 20 mm Hg), hypotony and shallow chambers should be avoided. Hypertony can be hindered, as well.