Aim: To identify influence of orthostasis and daytime on retinal-thickness in cystoid-macular-edema (CME) using SD-OCT. Methods: In this cross-sectional study 18 eyes with uveitis-associated CME (uvCME) were included. Orthostaticchanges of retinal-thickness were analyzed using a Cirrus TM SD-OCT. Retinal-thickness was measured with patients lying horizontally on their side, followed by a fast sitting-up and OCT-measurement in sitting-position. Diurnal-change in thicknesses were assessed by Spectralis TM OCT between 8 AM and 8 PM. Results: Approximately 20 s elapsed between position-change and the following OCT-measurement. In horizontal-position, the mean central retinal thickness (CRT) was 496 � 37mm, in upright position, the mean CRT was reduced to 412 � 43m m( p = 0.032), thus position-change led to a 17% decrease in CRT. None of the other ETDRS-subfields showed a statistically significant decrease in thicknesses (p40.05). In the second experiment, diurnal-CRT decreased over time, whereas the main decrease happened in the morning (8 a.m. 559 � 35mm, 12 p.m. 533 � 36mm, 4 p.m. 538 � 32mm, 8 p.m.551 � 38mm, p = 0.01). Thicknesses in all other ETDRS-subgrids did not decrease statistically significantly. Conclusions: Intraretinal-fluid in uvCME may show a high mobility: CRT decreases within seconds after a patient changes position, indicating that position effects retinal-thickness. Main diurnal-decrease in CRT occurs before noon, which is likely due to a position-change in the morning. Patient-population (walk-in patients versus hospitalized, lying patients) and previous waiting-position should be considered when interpreting retinal-thickness in clinical-practice.
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