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Editors Selection IGR 7-1

Examination methods: 24-hours IOP

Comment by Anastasios Konstas on:

11896 Correlation between office and peak nocturnal intraocular pressures in healthy subjects and glaucoma patients, Mosaed S; Liu JH; Weinreb RN, American Journal of Ophthalmology, 2005; 139: 320-324

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The current day-to-day management of glaucoma often ignores the biological rhythm inherent in the only parameter we can currently treat, the intraocular pressure (IOP) and its clinical implications. Since glaucoma is a 24-hour disease, it is logical that we should aim to determine and control the IOP throughout the 24-hour cycle. Sadly though, we generally assess IOP control by a single, daytime office measurement. Although the detection and follow-up of glaucoma patients with single IOP measurements is quick and convenient, this strategy may provide inadequate, or even misleading information and may not reflect the pattern of IOP characteristics before and during therapy. It is now well established that peak IOP is often missed, and of course IOP fluctuation cannot be determined with a single IOP measurement. It is thus important to investigate the correlation between office-hour IOP readings and 24-hr IOP parameters. In an interesting and clinically relevant paper Mosaed et al. (104) employ a retrospective review of records from a sleep laboratory to determine the correlation between office-hour IOP (four readings between 9:30 and 15:30) and peak nocturnal IOP in untreated healthy and glaucomatous eyes. Overall Mosaed et al. find a strong correlation between supine IOP during office hours and peak nocturnal IOP.

A strong correlation between supine IOP during office hours and peak nocturnal IOP was found

There was no correlation between office-hour IOP and peak nocturnal IOP in young healthy subjects, highlighting the greater unpredictability of 24-hr IOP characteristics in younger patients. On the other hand, the correlation between mean office-hour sitting IOP and peak nocturnal IOP was strong in older untreated glaucoma patients (r = 0.601, P < 0.001). In the same group, a strong correlation existed between mean supine IOP readings during office hours and peak nocturnal IOP (r = 0.713, P < 0.001). In these patients there was only a small mean difference (0,4 mmHg) between office supine IOP and peak nocturnal IOP. These data may help the clinician in estimating the nocturnal IOP peak in their untreated glaucoma patients. The study reiterates once again that the mean IOP from several readings during office hours is far superior to a single reading and suggests that employing an IOP reading in the supine position may be helpful. Similar to other studies in this field the question remains how relevant are these data to the day-to-day clinical practice and how accurately the sleep laboratory setting reflects real life glaucoma? Clearly, it will be important to determine in the future whether these correlations apply in other clinical settings and, as the authors point out, we need to determine whether these relationships are also applicable to glaucoma patients receiving medical or other forms of therapy.

The duration and homogeneity of 24-hour IOP lowering effect is a key characteristic of successful therapy. It may be important to develop (just like our medical colleagues have done in the management of arterial hypertension), suitable IOP indices such as the trough to peak ratio, the morning to evening IOP ratio and the smoothness index in assessing the features of antiglaucoma therapy. This study helps in that direction. Nevertheless, much remains to be elucidated in this important area.

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