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B. C. Chauhan, Canadian Glaucoma Study Group; Rates of Visual Field Progression in the Canadian Glaucoma Study. Invest. Ophthalmol. Vis. Sci. 2010;51(13):2051.
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The Canadian Glaucoma Study (CGS) is a multi-centred clinical trial on the risk factors for the progression of open-angle glaucoma. The purpose of this research was to determine how the identified risk factors for progression (positive baseline anticardiolipin antibody level, baseline age, female gender and higher mean intraocular pressure) impacted the rates of visual field change.
Two-hundred and fifty eight patients were recruited to the CGS. Patients had visual field examinations (full threshold 30-2, Humphrey Field Analyser) at 4-month intervals. Visual field progression was identified with total deviation probability analysis. Suspected progression required confirmation in the next or following examination. The median follow-up time was 5.3 years with 167 patients (65%) completing ≥ 5 years and 67 (26%) completing ≥ 7 years. In this analysis all observations after confirmed progression were censored. Global rates of change were determined by regression of Mean Deviation (MD) with time.
The mean MD rate in patients prior to reaching an endpoint was significantly faster than in patients not reaching an endpoint (-0.64 dB/yr compared to 0.05 dB/yr respectively (P < 0.01). Patients with a positive baseline anticardiolipin antibody level had a significantly faster rate of change compared to those with a negative result (-1.30 dB/yr and -0.11 dB/yr respectively, P < 0.01). Women had a non-significantly faster progression rate compared to men (-0.19 dB/yr and -0.10 dB/yr respectively, P = 0.50). Finally, the mean follow-up intraocular pressure was not related to MD rate (r = 0.05, P = 0.50) while increasing age was (r = 0.19, P < 0.01).
Progression endpoints based on localised visual field change are preceded by global change while patients who did not reach an endpoint had remarkably stable visual fields. Patients with a positive anticardiolipin antibody had a 10-fold faster rate of visual field change compared to those with a negative result. Rate-based estimates quantify the extent risk factors affect visual field progression.
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