Fluctuations depending on time of day in measurements of the optic disc using confocal laser canning tomography

Abstract

The aim of this study was to evaluate whether confocal laser scanning tomographic measurements of the optic nerve head depend on the time of day when the examinations are performed. Thirty-two eyes of 20 subjects repeatedly underwent optic disc confocal laser scanning tomography using the Heidelberg Retina Tomograph I. Operated by a single examiner, measurements were performed at 10 a.m. and 4 p.m. on the same day. Comparing both measurements, differences in optic cup area (0.119+/-0.126 mm(2); p=0.89), neuroretinal rim area (0.120+/-0.131 mm(2); p=0.86), cup volume (0.069+/-0.086 mm(3); p=0.86), rim volume (0.083+/-0.090 mm(3); p=0.51), and retinal nerve fiber layer thickness (0.075+/-0.063 mm; p=0.31) were statistically not significant. Intraocular pressure differences between morning and afternoon ranged between 0 and 14 mmHg. Confocal laser scanning tomographic measurements of the optic nerve head are not markedly influenced by the time of day.