Influence of orthostasis and daytime on retinal thickness in uveitis-associated cystoid macular edema

To identify influence of orthostasis and daytime on retinal-thickness in cystoid-macular-edema (CME) using SD-OCT.

In this cross-sectional study 18 eyes with uveitis-associated CME (uvCME) were included. Orthostatic-changes of retinal-thickness were analyzed using a Cirrus™ 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™ OCT between 8 AM and 8 PM.

Approximately 20 s elapsed between position-change and the following OCT-measurement. In horizontal-position, the mean central retinal thickness (CRT) was 496 ± 37 µm, in upright position, the mean CRT was reduced to 412 ± 43 µm (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 (p>0.05). In the second experiment, diurnal-CRT decreased over time, whereas the main decrease happened in the morning (8 a.m. 559 ± 35 µm, 12 p.m. 533 ± 36 µm, 4 p.m. 538 ± 32 µm, 8 p.m.551 ± 38 µm, p=0.01). Thicknesses in all other ETDRS-subgrids did not decrease statistically significantly.

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.