Purpose: The authors studied the effects of trabeculectomy on the time course of central 30 degrees visual field performances in progressive normal-tension glaucoma (NTG).
Methods: Patients with NTG who had clear ocular media and were adequate performers on the 30-2 program of Humphrey Perimeter were prospectively followed with periodic field testing. Trabeculectomy using an antimetabolite was indicated when the slope of a line fitted to the time course of the mean deviation (MD), MD slope, was significantly negative. The time courses of MD and mean of total deviations (mean TD) in four subfields, superior and inferior arcuate and superior and inferior cecocentral fields, were analyzed using the mixed linear model.
Results: In progressive NTG, 21 eyes of 21 cases with postoperative follow-up of 2 years or more, intraocular pressure averaged 16 mmHg, MD averaged -13.5 dB, and MD slope averaged -1.48 dB/year preoperatively; 2 years after surgery, they averaged 9.2 mmHg, -13.6 dB, and +0.13 dB/year, respectively. Trabeculectomy had a significant beneficial effect on the time course of MD and mean TD in the superior and inferior arcuate and superior cecocentral fields, which showed significant preoperative deterioration. The mean TD in the inferior cecocentral field showed no significant time change during the period studied.
Conclusion: For patients with NTG in whom the MD slope is significantly negative, trabeculectomy may have beneficial and diffuse effects on further deterioration of the visual field.