Establishing target IOP an essential element in glaucoma management

São Paulo, Brazil-A target IOP should be set for each patient as soon as the diagnosis of ocular hypertension or glaucoma is made, and it should be continually re-evaluated to assess whether existing treatment is achieving its goal for stopping visual field progression and protecting the optic nerve, said Curt Hartleben, MD, at the World Congress of Ophthalmology.

"There are numerous patient- and disease-related factors to consider when establishing a target IOP, but it is also important to remember that medications have effects on quality of life and that adding more medications to achieve the target can reduce quality of life and compliance," said Dr. Hartleben, chief of glaucoma, Instituto de Oftalmologia, Mexico City, Mexico.

Dr. Hartleben credited Paul Palmberg, MD, PhD, Bascom Palmer Eye Institute, Miami, with introducing the concept of target IOP as a means toward protecting the optic nerve. Since then, results from the large, randomized glaucoma trials have helped to identify what that target should be for various patients.

The Early Manifest Glaucoma Trial also provided important data relating to target IOP. Participants in that trial had early glaucoma (baseline median mean deviation –4 dB) and were randomly assigned to laser trabeculoplasty plus topical betaxolol or no initial treatment. In that study, 62% of patients who received no initial treatment showed evidence of progression in 6 years of follow-up.

Treatment had a benefit, but progression still occurred among 45% of the patients assigned to immediate treatment.

However, it is important to note there was no target IOP set in the study protocol, Dr. Hartleben noted.

The Collaborative Initial Glaucoma Treatment Study enrolled patients with mild glaucomatous visual field damage at baseline and randomly assigned them to initial treatment with medication or filtration surgery. A target IOP of 17.5 mm Hg was set for patients assigned to medical treatment and stepped treatment was allowed to achieve that goal. Patients who underwent filtering surgery achieved a mean 52% reduction from baseline IOP to 14 mm Hg.

The Advanced Glaucoma Intervention Study (AGIS) enrolled patients with more advanced disease (baseline median mean deviation –10.5 dB) and randomly assigned them to one of two surgical intervention sequences with supplemental medications allowed to achieve a target IOP below 18 mm Hg. In a subgroup of patients whose IOP was 12 mm Hg or less, there was no net progression after 8 years.

"This study also provided the important finding that IOP variation adversely affects outcome and that it is critical to keep IOP below 18 mm Hg," Dr. Hartleben said.

Implications for clinical practice

These studies reinforce the idea that target IOP varies depending in part on the presenting disease. Based on the collective results, Dr. Hartleben offered some suggestions. For patients with ocular hypertension, the target might aim to achieve a 20% to 35% reduction from baseline IOP, while a more aggressive goal of a 30% to 35% reduction or to at least between 15 and 17 mm Hg might be set for individuals with mild initial POAG.

In eyes with advanced POAG or normal-tension glaucoma, available evidence suggests an even lower IOP range of 11 to 13 mm Hg should be the goal, while in eyes with normal-tension glaucoma and very excavated optic nerves, a target of 8 to 10 mm Hg is recommended.

"Remember, glaucoma is an optic nerve neuropathy and the target should be lowered for eyes with more damage," Dr. Hartleben said.

Age of onset is another feature to take into account when setting a target IOP because of its relationship with life expectancy. Younger patients may need a more aggressive IOP target than their older counterparts.

In addition, a more aggressive target may be set for patients with a family history of blindness from glaucoma.