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Higher peak, final IOP portends progression in average-pressure glaucoma
Risk of progression also correlated with a higher final cup-to-disc ratio.
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Average-pressure glaucoma requires keen surveillance and monitoring of IOP, central corneal thickness and disc hemorrhage, according to a study.
“Average-pressure glaucoma is a chronic open-angle glaucoma with progressive optic nerve damage despite the intraocular pressure always remaining below 21 mm Hg,” Sarah Driscoll Kuchar, MD, said at the Wills Eye Annual Conference in Philadelphia. “While we didn’t come up with any new factors, this longer-term analysis does give credence to the idea that tighter intraocular pressure control in patients with average-pressure glaucoma potentially allows them to ward off progression and remain stable for longer.”
In an earlier analysis, the Collaborative Normal Tension Glaucoma Study Group found a significantly lower rate of progression in patients who achieved a 30% or greater reduction in IOP, Kuchar said. In addition, glaucoma did not progress in more than half of untreated eyes within the 5-year follow-up period.
“Does this represent true disease stability? Or is it that there’s at least a subset of average-pressure glaucoma patients that have a chronic, more slowly progressive disease and that a time period of 5 years is insufficient to demonstrate progression?” Kuchar asked.
Sarah Driscoll Kuchar
In a study published in Acta Ophthalmologica, Kim and colleagues followed patients for a mean of 12 years and found a correlation between progression and the amount of IOP reduction that could be achieved, and they identified disc hemorrhage as an independent risk factor, she said.
Methods and measures
The retrospective study included 49 eyes with average-pressure glaucoma followed for an average of 9 years. Patients underwent evaluation of the optic nerve, visual fields and IOP. Progression was defined as worsening optic nerve damage and progressive visual field loss.
“The purpose of our study was to consider this subset of average-pressure glaucoma patients that may have a chronic, more slowly progressive course and perform a longer-term analysis to identify clinical characteristics that may contribute to long-term stability among patients being treated,” Kuchar said. “An awareness of these clinical characteristics may help a physician tailor their treatment plans, knowing if their patient had certain risk factors for progression.”
Structural progression was defined as worsening of the optic disc based on three consecutive drawings, with or without photographs. Functional progression required losses seen across three consecutive reliable visual fields.
“The outcome criteria for functional progression were quite specific,” Kuchar said.
Twenty-five eyes met the definition of progression, and 24 eyes remained stable.
Outcomes and observations
Eyes with progressive glaucoma had higher peak and final IOP. Cup-to-disc ratio also correlated with progression.
“What we did find was that progression was significantly associated with both a high peak intraocular pressure and a higher final intraocular pressure, as well as a higher final cup-to-disc ratio and a greater change in ratio overall,” Kuchar said. “Additionally, there was a higher percentage of more severe visual field loss at baseline as defined by being grade 3 or grade 4 among the group that progressed.”
Glaucomatous damage worsened on treatment in about half of the cases.
“Based on our definitions of progression, it stands to reason that a higher final cup-to-disc ratio and a greater change in the cup-to-disc ratio would be associated with progression,” Kuchar said. “But the baseline cup-to-disc ratio was not [associated with progression], which suggests that the baseline optic nerve assessment may be a poor predictive marker for progression or stability.” – by Matt Hasson