Influence of pulse pressure and spontaneous variations of macular thickness in patients with diabetic macular oedema

Purpose: To study spontaneous variations of central macular thickness (CMT) and its relation to blood pressure (BP) in patients with diabetic macular oedema (DME). Methods: 23 diabetic patients presenting with DME with a CMT >= 260 mu m on optical coherence tomography (OCT-3, Carl Zeiss Meditec, CA) were followed every 2 weeks for 3 months. At baseline, ambulatory 24H-BP monitoring (ABPM) was performed, as well as five CMT measurements (9 am, 12 am, 3 pm, 6 pm and 9 am the day after). During follow-up, BP and CMT were simultaneously measured at 9 am. Results: Significant spontaneous variations in CMT (at least one change in CMT greater than 11% compared to the median CMT value) were observed over 3 months in 48% of patients. Mean CMT decreased over the day and increased during the night, but not significantly (p = 0.1). During the 6 visits, the CMT at 9 am positively correlated with the pulse pressure (PP) measured at the same time (r = 0.29, p = 0.0008). In addition, the mean 24H-CMT was positively correlated with the mean 24H-PP (r = 0.48, p = 0.02). Conclusion: Significant spontaneous changes in CMT of patients with DME were observed in nearly half of cases over 3 months. Retinal thickness was correlated to PP levels (patients with higher CMT had higher PP levels). This high variability of macular oedema, and the influence of BP on retinal thickness, should be taken into consideration by practitioners when evaluating the benefit of a therapy in DME.