Visual field progression outcomes in glaucoma subtypes

Purpose: To determine whether glaucoma subtype is an independent risk factor for visual field (VF) progression. Methods: We reviewed the charts of glaucoma suspects and glaucoma patients seen in a referral practice between 1999 and 2009. Automated pointwise linear regression analysis determined the rates of VF change. A progression endpoint was determined when two or more adjacent test locations in the same hemifield showed a threshold sensitivity decline at a rate of ≥1.0 dB/year with p < 0.01. Results: We included 841 eyes (841 patients; mean age, 64.1 ± 12.6 years; mean number of VF tests, 10.8 ± 2.8; mean follow-up, 6.4 ± 1.7 years). The glaucomatous group consisted of angle-closure glaucoma (76 eyes), juvenile primary open-angle glaucoma (37 eyes), normal-tension glaucoma (81 eyes), pigmentary glaucoma (34 eyes), primary open-angle glaucoma (275 eyes) and exfoliative glaucoma (XFG, 84 eyes). Normal-tension glaucoma eyes were more likely to present with beta-zone parapapillary atrophy and disc haemorrhage (p < 0.01). Exfoliative glaucoma eyes had the fastest rates of global VF change (-0.65 dB/year), as well as the highest mean, fluctuation, and peak intraocular pressure during follow-up (16.5, 3.0 and 22.0 mmHg, respectively) and reached a progression endpoint more frequently (40%). After adjusting for all covariates, including the glaucoma phenotype, there was no difference among groups regarding global rates of VF change and the risk of reaching a progression endpoint. Conclusions: Despite different clinical features, epidemiology and genetics, glaucoma phenotype is not an independent risk factor for VF progression. Rather, variations in well-known, reported risk factors remain important disease parameters that affect progression.