This retrospective study by Yang et al. is another in a series of rigorous 24-hour IOP studies originating from the Hamilton Glaucoma Center at the University of California at San Diego. In this particular study, the authors aimed to compare the correlation between office-hour IOP and peak nocturnal IOP in patients with open- angle glaucoma or ocular hypertension that were treated with any one of three prostaglandin analogues (PGAs), (Latanoprost, Bimatoprost, or Travoprost) compared to their untreated baseline correlation. Similarlydesigned studies have previously established a robust relationship between office-hour IOP and peak nocturnal IOP in both healthy untreated adults, as well as untreated patients with POAG, normal-tension glaucoma, or ocular hypertension.1-3 However, this correlation has not been reliably reproduced with patients on various topical antihypertensive treatments. In fact, published studies by other groups have failed to show a correlation in patients on beta blockers, PGAs, or carbonic anhydrase inhibitors.4-6 In this study, the investigators analyzed data from the laboratory database where PGA monotherapy was employed, and included records from both eyes of 51 patients. The authors found that while a correlation still exists between peak nocturnal IOP and average office-hour IOP, the strength of this correlation is weaker when the patients were treated with a PGA (r = 0.373) as compared to untreated baseline (r = 0.517). The study also found that the correlations (both in treated and untreated patients) are stronger when the average diurnal IOP is used as opposed to an individual reading. In the real world, the strength of these correlations is likely limited by several different factors, including baseline IOP levels, the class of medication used, whether single office- hour IOP is used versus the average of a diurnal curve, whether or not prior trabeculoplasty or other surgical intervention was previously employed, the subset/mechanism of glaucoma, the use of concomitant systemic medications with cardiovascular effects, the age of the patient, etc. The real value in this study is mainly to underscore that the formulae we have established to predict peak 24-hour IOP from office-visit data are not applicable to all patients in a typical glaucoma clinic, and that further studies are warranted analyzing individual factors that impact 24-hour IOP profiles.
The real value in this study is mainly to underscore that the formulae we have established to predict peak 24-hour IOP from office-visit data are not applicable to all patients in a typical glaucoma clinic.