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Rizwan Malik, Neil O'Leary, Frederick Mikelberg, Gordon Balazsi, Raymond LeBlanc, Mark Lesk, Marcelo Nicolela, Graham Trope, Balwantray Chauhan, Canadian Glaucoma Study Group; Canadian Glaucoma Study 4: Neuroretinal Rim Area Change in Patients with Visual Field-based Endpoints and Interventions. Invest. Ophthalmol. Vis. Sci. 2013;54(15):2620.
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(1) To compare rates of neuroretinal rim area (RA) change in patients with and without a visual field (VF) endpoint in the Canadian Glaucoma Study (CGS). (2) To determine whether IOP intervention after the VF endpoint had an impact on RA change.
Patients were treated to achieve a target IOP and examined at 4-month intervals with standard automated perimetry and confocal scanning laser tomography (CSLT). Patients reaching a VF endpoint defined by repeatable progression based on total deviation change probability analysis underwent an additional ≥ 20% IOP reduction (Canadian Glaucoma Study Group. Canadian Glaucoma Study I. Can J Ophthalmol. 2006; 41: 566-75). RA rates were computed with robust linear regression only when ≥ 4 examinations were available and compared for patients with and without a VF endpoint. For patients with endpoints, the change in RA rate was computed (RA rate post-intervention - RA rate pre-intervention).
Of the 258 enrolled patients, 206 (80%) had sufficient follow-up to compute RA rates. The median (interquartile range, IQR) baseline age, follow-up and number of CSLT examinations was 68 (58, 75) years, 6 (5, 7) years, and 15 (12, 19) respectively. The median (IQR) RA rate prior to a VF endpoint of -14 (-32, 11) x 10-3 mm2/ year (n=59) was significantly worse (P=0.02, see figure), compared to that in patients with no endpoint: -5 (-14, 5) x 10-3 mm2/year (n=147). In 43 patients with sufficient follow-up before and after IOP-lowering intervention, the median change (95% CI) in RA rate was 8 (-10, 24) x 10-3 mm2/year.
Prior to the VF endpoint, patients with VF progression had a median RA rate that was nearly 3 times worse compared to those without progression. After the endpoint, IOP intervention did not have a statistically significant impact on the subsequent RA rate.
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