Abstract
Purpose :
To investigate diurnal variation in the mean values of summary measures of standard automated perimetry (SAP) and spectral domain optical coherence tomography (SD-OCT). We also investigate diurnal variations in the inter-visit test-retest variability (TRV) of those measures, arising from repeated SD-OCT and SAP tests carried out at different times of day.
Methods :
Healthy subjects had repeated SD-OCT (Topcon 3D OCT-2000) and SAP (Medmont M700) tests on both eyes carried out at three time points (8:00, 13:30 and 17:30), which occur during normal office hours. The fixed test times for the repeated testing of each of the eyes of the seven subjects were designed to minimise sources of variance other than those under investigation. Those data were compared with a finer grained temporal analysis, in which one subject completed four repeat sets of SAP tests at 8 intervals (1.5 hours apart), resulting in 32 tests in total over a 28 day period. TRV was estimated as the 95% confidence intervals (CI95) in the summary measures, as obtained from Bland-Altman plots.
Results :
The SD-OCT and SAP summary measures showed no significant diurnal variation in their mean values. The TRV (CI95) for horizontal and vertical cup/disc ratios were significantly larger at 13:30, compared to 8:00. The TRV for peripapillary retinal nerve fibre layer mean thickness was significantly larger at 13:30 (9.9 µm) compared to either 8:00 (5.2 µm) or 17:30 (3.8 µm). TRV for virtually all SAP summary measures was significantly greater at 13.30 than at both 8.00 and 17.30. The fine-grained SAP analysis agreed, showing the largest TRV at about 14:00 for three of four SAP summary measures.
Conclusions :
TRV for SD-OCT and SAP summary measures does not appear to be consistent throughout the day. This variability is independent of the mean summary measures values, which showed no significant diurnal variation in their mean values. Avoiding testing in the early afternoon may reduce the TRV of both SD-OCT and SAP testing.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.