Research supports that 24-hour IOP control is critical to minimizing glaucoma progression. Practitioners are encouraged to review the choices for primary and adjunctive medical therapy based on the ability to control pressures during both the day and nocturnal periods.
Why is it that visual fields reportedly continue to deteriorate in some patients with glaucoma, despite the fact that daytime IOP values indicated a controlled ocular condition? Investigators suggest that the progressive visual field damage may be related to IOP fluctuation not detected by ophthalmologists during regular clinic hours.1
Minimizing IOP fluctuation
Research has shown that IOP fluctuation appears to be linked with glaucoma progression. Bergea and colleagues reported that visual field stability was better in patients with small IOP variations who had newly diagnosed disease and who completed the 2-year follow-up period.13 In particular, a greater correlation existed between visual field decay and IOP variation and mean IOP than between decay and baseline IOP or degree of IOP reduction. Asrani and colleagues also noted the risk associated with diurnal variations in IOP in patients with open-angle glaucoma.1 They found the diurnal range and range of IOP over several days were significant risk factors for progressive visual field deterioration.
Other investigators have observed similar findings. Nouri-Mahdavi et al.14 found that greater IOP fluctuation increased the odds of visual field progression by 30% (for each 5-year increment in age and 1-mm Hg increase in IOP fluctuation). The higher risk conferred by IOP fluctuation was observed consistently in eyes with and without a history of cataract extraction.
Further, Hughes and colleagues noted in an evaluation of 24-hour IOP monitoring that high IOP and wide diurnal IOP variation were major risk factors for glaucoma progression, and standard clinic follow-up evaluations failed to identify these phenomena.15 In concert, these trials all support the importance of managing IOP to minimize pressure fluctuations, avoid unnecessary progression of vision failure, and possibly prevent glaucomatous damage. Thus, selection of medical therapies capable of properly controlling IOP throughout the 24-hour period may be an essential component in effectively managing glaucoma.