Effect of Reclining on Retinal Thickness in Diabetes
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Purpose: Previous studies have shown diurnal variation in retinal thickness in patients with diabetic macular edema (DME) over the course of the day but the cause, presence and magnitude of this variation is controversial. This study will investigate the direct effect of reclining on retinal thickness in diabetic patients with DME using spectral domain optical coherence tomography (SD-OCT). Methods: Ten patients with DME and proliferative diabetic retinopathy (PDR) or severe non-proliferative diabetic retinopathy (NPDR) (mean age 57.4yrs, SD ±6.8yrs) and thirteen healthy controls (mean age 43yrs, SD ±13.8yrs) were recruited. Subjects reclined for two hours and retinal thickness using SD-OCT (Heidelberg Spectralis, model spec, Heidelberg, Germany) was measured at five time points; before reclining, immediately after reclining while lying on side, one hour after reclining while lying on side, two hours after reclining while lying on side, and immediately after returning back to an upright position. Results: Throughout the reclining period, there was a global trend for retinal thickness to change over time within each group (p=0.068) and a trend for there to be a greater change in retinal thickness over time in the diabetic group (p=0.104). In terms of the change analysis, a significant increase reached its maximum after two hours of reclining (+7.2 ±13.2 µm for the diabetic group compared to -0.8 ±2.4 µm for the controls, p=0.044). On resuming a sitting position, the retinal thickness significantly reduced in the diabetic group but exhibited some residual increase (+2.1 ±3.2 µm for the diabetic group compared to -0.4 ±1.4 µm for the controls, p=0.029). Of the 6 macular areas / sectors assessed, the temporal macular sector showed the greatest increase in reclining induced DME (+21.1 ±31.1 µm for diabetic group compared to +0.8 ±4.2 µm for controls, p= 0.029) Conclusion: We found a global trend for retinal thickness of the diabetic group to increase in response to reclining when compared to a control group. This increase was reversed close to baseline values immediately after returning to an upright position. Certain macular areas showed significant increase of retinal thickness, especially the temporal macula. The clinical implications of this reclining induced DME effect are discussed.