SEP 15, 2010
This retrospective study was conducted to determine the target intraocular pressure (IOP) in Japanese normal-tension glaucoma patients for maintaining visual field stability following trabeculectomy.
Clinical records were identified and reviewed for 40 patients (40 eyes) with glaucomatous progression despite maximally tolerated medical therapy who had undergone trabeculectomy with mitomycin C. After a mean follow-up of 12 years, IOP was reduced from 15.2 to 9.4 mmHg on average (P < 0.0001). IOP dropped by at least 20 percent from baseline in 70.0 percent of patients.
The cumulative probability of visual field stability was 92.7 percent in patients with an IOP reduction greater than 20 percent, whereas all cases with more poorly controlled IOP showed some progression (P < 0.0001). The results of patients who attained IOP values of 9, 10, 11 or 12 mmHg were also examined, with the best visual field prognosis found among those with postoperative IOP of 10 mmHg.
Based on the study's results, IOP reduction of at least 20 percent from baseline or attaining a postoperative target IOP of 10 mmHg or less is recommended in progressive normal-tension glaucoma patients. The average IOP for eyes with primary open-angle glaucoma, including normal-tension glaucoma, is rather low in Japan compared with other countries. However, this study revealed that IOP reduction is an effective therapy for Japanese low-pressure glaucoma patients.
Visual field loss progressed after IOP reduction in a minority of normal-tension glaucoma patients, raising the question as to how ophthalmologists should address these refractory cases. Since normal-tension glaucoma is presumably a multifactorial disease that may have underlying factors other than elevated IOP, such as vascular insufficiency around the optic nerve head, further studies may identify such risk factors and provide new insight into therapeutic strategies.