Purpose: To investigate diurnal fluctuations in retinal thickness using spectral domain optical coherence tomography (SD-OCT).
Methods: Spectralis SD-OCT was used to obtain data from the right eye of 21 healthy subjects (mean age, 31.3 years) at 7 AM, 1 PM, and 7 PM. For each eye, a full peripapillary retinal nerve fiber layer circular scan and a 19-line horizontal raster scan (6- by 6-mm area) centered on the fovea were performed.
Results: Retinal nerve fiber layer thickness was greater at 7 AM or 1 PM than at 7 PM for nasal (79.1 μm [1 PM] vs. 77.6 [7 PM]; p = 0.024), inferior (134.1 [7 AM] vs. 131.9 [7 PM]; p = 0.009), and inferonasal (115.2 [7 AM] vs. 115.6 [1 PM] vs. 112.4 [7 PM]; p < 0.001) subfields. Macular thickness was greater at 7 AM than at 7 PM for inferior 6 mm (290.2 μm [7 AM] vs. 287.8 [7 PM]; p < 0.001) ETDRS (Early Treatment Diabetic Retinopathy Study) subfield. Macular volume was greater at 7 AM than at 7 PM for nasal 3 mm (0.541 mm3 vs. 0.538; p = 0.028) and inferior 6 mm (1.538 vs. 1.525; p < 0.001) ETDRS subfields. The remaining studied areas did not show any significant change throughout the day.
Conclusions: The Spectralis SD-OCT retinal thickness measurements showed a small but statistically significant diurnal variation in nasal and inferior subfields toward smaller values in the evening. However, the overall change is close to the instrument’s resolution and repeatability.