Abstract
Purpose: :
To evaluate the relationship between intraocular pressure (IOP) and rate of visual field (VF) progression in glaucoma.
Methods: :
In a clinic-based, retrospective study, we analyzed the data of 484 eyes of 290 consecutive primary glaucoma patients who had > 5 VFs between 1989 and 2008. IOP measurements during the VF examination visits of all these patients were recorded. IOP parameters analyzed were the mean IOP, IOP fluctuation (standard deviation of all IOP measurements) and the maximum IOP during the follow-up period. Guided Progression Analysis software which provides the rate of progression (ROP) of Visual Field Index per year was used to assess the rate of visual field progression. Relationship between IOP parameters and ROP was analyzed in multivariate regression models which also included other risk factors known to be associated with progression namely age, sex, follow-up duration, presence of systemic hypertension and diabetes, type of primary glaucoma and severity of visual field loss at presentation.
Results: :
The median duration of follow-up was 6.8 years. The median ROP in this cohort was -0.3% per year (25th and 75th quartile being -1.4 and 0.1 respectively). The only IOP parameter associated significantly with ROP was IOP fluctuation. ROP worsened by 0.3% per year for every 1 mm Hg fluctuation of IOP (p=0.03). Mean IOP (β=-0.04, p=0.65) as well as the maximum IOP (β=0.01, p=0.84) during follow-up were not related to ROP. ROP also worsened by 0.27% per year for every decade increase in age (p=0.006). ROP was not significantly related to any other predictors. Results were the same when eyes which underwent trabeculectomy during the follow-up (89 eyes) were excluded. IOP fluctuation was also the only IOP parameter significantly associated with ROP in low (β=-0.78, p=0.01) and high mean IOP (β=-0.40, p=0.05) tertiles.
Conclusions: :
Long term IOP fluctuation was significantly associated with the rate of VF progression in glaucoma. Mean and maximum IOP during follow-up were not associated with ROP in our study.
Keywords: intraocular pressure • visual fields