Visual field decline in glaucoma patient is due to variant eye pressure according to the according to a report in the August issue of Archives of Ophthalmology, one of the JAMA/Archives journals. Even if the eye pressure remains low there is still a decline in the peripheral field of vision.
Glaucoma therapy is done in order to prevent further decline of the visual filed. According to the author "Previous studies reported that lowering intraocular pressure (IOP) slowed the advancement of visual field damage in patients with glaucoma. However, even if the IOP can be substantially lowered, reduction of mean [average] and peak IOP does not always prevent progressive visual field deterioration".
Samin Hong, M.D., and colleagues at the Yonsei University College of Medicine, Seoul, Korea, studied 408 eyes of patients (average age 66.5 years) who had undergone a triple procedure to treat glaucoma: phacoemulsification, that involves dissolving and removing the lens; posterior chamber intraocular lens implantation; and trabeculectomy, also known as filtration surgery.
All patients had a low IOP after surgery (below 18 milligrams of mercury). Measurements of IOP and visual field were taken for an average of 9.2 years following surgery. Based on the standard deviation (difference from the average) in IOP, the eyes were split into two groups, one with greater fluctuation and one with less.
Throughout the follow-up period, the two groups had the same average IOP, and their visual fields were the same after three months. However, after the last follow-up examination—13 years later—the visual field was significantly worse in the group with greater fluctuation in IOP. The number of patients with progressive visual field loss was significantly larger in the group with more fluctuation.
"Our results suggest that glaucomatous visual field damage cannot be stabilized by only lowering the postoperative IOP but also requires reducing the long-term fluctuation of the post-operative IOP," the authors conclude.