24-hour/diurnal IOP monitoring for glaucoma

Should 24-hour intraocular pressure (IOP) monitoring be the basis for treatment decisions in some glaucomatous eyes? Professor Anastasios G. Konstas MD, PhD said that IOP fluctuates widely in glaucomatous eyes. Therefore it is impossible to know from a single, random IOP measurement the real mean, peak, trough IOP over 24 hours in a particular patient with glaucoma. “We often underestimate the true level of IOP with a single pressure reading every few months, so 24-hour, or at least daytime measurements would provide greater insight into the real pressure characteristics and demonstrate how successful we are in controlling the pressure- the only parameter that we can currently modify,” said Professor Konstas, Aristotle University, Thessaloniki, Greece. He noted that in the Baltimore Eye Survey only half of all glaucomatous eyes had a pressure less than 21 mm Hg after a single measurement. But after two, or more IOP measurements the proportion with that pressure rose to 75 per cent. He also cited two studies which he said illustrate the ways that 24-hour monitoring can impact daily management of glaucoma. In these two 24-hour studies, 36 per cent and 79 per cent of glaucoma patients, respectively, had a change in treatment consequently to 24-hour IOP monitoring.

There is now comprehensive evidence that single pressure readings every few months are not sufficient for the management of many glaucoma patients

In the first study the peak pressure was found to be almost 5 mm Hg higher over 24 hours than that recorded in the clinic with single random pressure measurements. In the second study both fluctuation and peak IOP was significantly greater than previously detected in the clinic. (Hughes et al J Glaucoma 2003; 12: 232-236; Barkana et al, Archives Ophthalmol 2006;124:793-797) “So there is now comprehensive evidence that single pressure readings every few months are not sufficient for the management of many glaucoma patients. IOP fluctuates widely and thus a single pressure measurement will miss a lot of IOP related disease,” Professor Konstas said. He added that the argument in favour of 24-hour, or at least daytime, IOP monitoring is particularly strong in certain types of glaucoma with worse and more unpredictable 24-hour IOP characteristics, such as exfoliative glaucoma and angle closure glaucoma. The same goes for younger glaucoma cases, progressive glaucoma, and patients with advanced glaucoma on maximal medical therapy who often demonstrate peak pressure outside office hours. konstas@med.auth.gr