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

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.

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.

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.

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.