Effectiveness of intraocular pressure phasing

Purpose: To investigate the value of intraocular pressure phasing during normal working hours in patients with and without anti-glaucoma treatment. Methods: This study is a retrospective case note review of 61 patients referred for intraocular pressure phasing (every 2 hours from 8.00am to 4.00pm). Comparison between pre-phasing intraocular pressure measurements (mean and range) taken during earlier routine visits (5 measurements) and phasing intraocular pressure (mean and range) for each eye was performed using paired t-test. Scatter plots were used to display the relationship of pre-phasing and phasing intraocular pressure. Subgroup analysis of 119 eyes into untreated and medically treated groups was performed. Results: Eyes in the untreated group (51 eyes) showed no difference between the mean intraocular pressure at pre-phasing and phasing (p value=0.8) but a significant difference between the intraocular pressure range (p value=0.007). For the medically treated group (68 eyes), there was no significant difference between the mean intraocular pressure at pre-phasing and phasing (p value=0.9) and no significant difference between the intraocular pressure range (p value=0.66). In the total 119 eyes the peak intraocular pressure was found to occur at 10-11am. Conclusions: Intraocular pressure phasing is most useful on untreated patients. Intraocular pressure phasing is less likely to give much additional data, compared to pre-phasing intraocular pressure measurements, in treated patients. If a clinician wanted to identify the peak intraocular pressure the best time is between 10-11 am.