Simplifying "target" intraocular pressure for different stages of primary open-angle glaucoma and primary angle-closure glaucoma

Abstract

Lowering of intraocular pressure is currently the only therapeutic measure for Glaucoma management. Many longterm, randomized trials have shown the efficacy of lowering IOP, either by a percentage of baseline, or to a specified level. This has lead to the concept of 'Target" IOP, a range of IOP on therapy, that would stabilize the Glaucoma/prevent further visual field loss, without significantly affecting a patient's quality of life. A clinical staging of Glaucoma by optic nerve head evaluation and perimetric parameters, allows a patient's eye to be categorized as having - mild, moderate or severe Glaucomatous damage. An initial attempt should be made to achieve the following IOP range for both POAG or PACG after an iridotomy. In mild glaucoma the initial target IOP range could be kept as 15-17 mmHg, for moderate glaucoma 12-15 mmHg and in the severe stage of glaucomatous damage 10-12 mmHg. Factoring in baseline IOP, age, vascular perfusion parameters, and change on perimetry or imaging during follow up, this range may be reassessed over 6 months to a year. "Target" IOP requires further lowering when the patient continues to progress or develops a systemic disease such as a TIA. Conversely, in the event of a very elderly or sick patient with stable nerve and visual field over time, the target IOP could be raised and medications reduced. An appropriate use of medications/laser/surgery to achieve such a "Target" IOP range in POAG or PACG can maintain visual fields and quality of life, preventing Glaucoma blindness.

Keywords: Advanced Glaucoma Intervention Study; Collaborative Initial Glaucoma Treatment Study; Collaborative Normal-Tension Glaucoma Study; Early Manifest Glaucoma Trial; glaucoma; long-term glaucoma; primary open-angle glaucoma/primary angle-closure glaucoma; randomized control trials; success in glaucoma; target intraocular pressure.

Figure 1

A normal optic nerve head functions at an average intraocular pressure of 14–17 mmHg (left), while an eye having glaucomatous optic neuropathy is damaged by high intraocular pressures, which need to be lowered so that the remaining nerve fibers can function as best as possible (right)

Figure 2

Suggested “target” range of intraocular pressures at three stages of glaucomatous damage as determined by optic nerve head and perimetric evaluation

Figure 3

Staging glaucoma by a careful examination of the neuroretinal rim. Rim loss generally starts inferiorly, and then superiorly, finally extending around the disc. The inner edge of the neuroretinal rim should be identified by the bending of the blood vessels onto the surface of the neuroretinal rim, as shown by the arrows

Figure 4

Representative visual field defects that could be classified as early, moderate, or severe glaucoma

Figure 5

Achieving target intraocular pressure based on initial baseline intraocular pressure