Clinical decision making based on data from GDx: One-year observations

Purpose: To determine whether information derived from the GDx scanning laser polarimeter aids in the clinical decision-making process for patients with various types of glaucoma. Methods: Over a 4-month period, 342 consecutive patients with primary open-angle glaucoma, ocular hypertension, angle-closure glaucoma, or secondary glaucomas or in whom the diagnosis of glaucoma was uncertain were evaluated with the GDx scanning laser. After 1 year, 153 patients with glaucoma underwent GDx analysis again. Chart review revealed that 42 of the 153 patients had a change in therapy as a result of the GDx evaluation combined with analysis of visual fields, optic disc cupping, and intraocular pressure (IOP). Outcomes were then compared. Results: The group who had a change in therapy had a higher average GDx number (51.5 ± 26.1 vs 37.0 ± 23.5 [P=.001]) at the initial visit and higher IOP (18.2 ± 4.6 vs 16.0 ± 3.2 mm Hg [P=.005]). In spite of a change in therapy, at an average of 344 days later, IOP was unchanged (18.3 ± 5.3 vs 15.7 ± 3.2 mm Hg [P=.001]) and GDx values in the altered therapy group were higher than at baseline (57.3 ± 27.9 vs 36.7 ± 23.4 [P=.001]), although the differences within each group did not achieve statistical significance. Conclusion: GDx analysis may be helpful in determining patients at risk for damage from glaucoma, even in eyes in which cup-disc ratio and field loss have not progressed. Changing medications without significantly reducing IOP may be insufficient to halt increases in GDx numbers and may indicate a need for more aggressive therapy.