A new study shows that patients with glaucoma or ocular hypertension (OHT) and recurrent anterior uveitis have a reduced tonographic outflow—lower than patients without glaucoma or OHT—but an actual aqueous flow that is not statistically any different from patients without glaucoma or OHT.

Researchers from St. Thomas Hospital in London divided 92 patients into three groups. Group one had patients with recurrent anterior uveitis (three or more attacks) and were being treated for glaucoma or OHT. Group two patients had experienced previous recurrent anterior uveitis without glaucoma or OHT. The third group, the controls, had no ocular problems and IOP less than 21mm Hg.

They found that the tonographic outflow facility was approximately 0.18 in group one, 0.25 in group two and 0.27 in the control group. However, the aqueous flow rate in group one was 2.47μl/min, in group two it was 2.13μl/min and 2.25μl/min in the control.

The investigators say this demonstrates that the elevated IOP seen in the uveitic glaucoma or OHT eyes was due to reduced tonographic outflow facility. “The aqueous humor flow rate was not detectibly different nor did the calculated uveoscleral outflow demonstrate any discernible difference. However, the exact mechanism remains to be elucidated.”