• Treatment medical
• epidemiology
• clinical trial
• treatment surgery
• medical education
• field of vision
• treatment other
• optic nerve
• intraocular pressure
• angle
• treatment lasers
• aqueous humour
• macula
• imaging
• diagnostic tests/investigation
• anatomy

We thank Schiefer and colleagues for their interest in our recent publication and their comments regarding our conclusions.

This study was not a prospective study but was a retrospective review of patients who had had intraocular pressure (IOP) phasing at our hospital. Although a non-randomised retrospective approach may introduce bias, we believe that bias should be minimised in this study as decisions to undertake either 24-hour or daytime phasing were based on clinician preference (rather than patient-specific factors outside our inclusion criteria): one of the referring clinicians always chose 24-hour phasing and the other chose daytime phasing to be performed on this group of patients who were progressing with apparently normal, in clinic IOP readings. Although the criteria were not defined specifically, referral was based on evidence of visual field progression with normal IOP measurement in the judgement of a consultant glaucoma clinician.

The article clearly states ‘The study included all patients undergoing phasing for progressive disease (defined …