Abstract
Purpose: :
To investigate spontaneous diurnal variation of central macular thickness (CMT) and its relation to glucose and blood pressure changes in diabetic patients with macular edema.
Methods: :
Prospective observational study in type 1 or 2 diabetic patients with macular edemainvolving the centre of the macula. Baseline patient characteristics, type and treatment of diabetes and hypertension medications were recorded. Optical Coherence Tomography (Carl Zeiss, Meditec, Inc, Dublin, CA) scans, capillary blood glucose (Accu-check®, Roche Diagnostics, Germany), systolic and diastolic blood pressure measurements were performed at 9am, 12am, 3pm, 7pm and the day after at 9am. During the same day, study protocol included ambulatory 24h-blood pressure (NOVACOR type Diasys Integra II) and simultaneously glucose monitoring (CGMS, Medtronic, Northridge, CA) recording glucose values on average every 5 min over a 24-hour period. Analyses were performed using SPPS software version 14.0 for Windows (SPSS, Chicago, IL).
Results: :
Twenty-two patients with type 1 (n=4) or type 2 (n=18) diabetes were included in the study (mean age: 60±12 yrs and duration of diabetes: 18±13 yrs). CMT decreased consistently from 9am to 7pm in ten patients (374 to 337 µm) and increased or remained steady in twelve (383 to 390 µm), with a significant difference in CMT diurnal change between the two groups (p<0.001). The lower the mean diurnal blood glucose (CGMS data) was, the smaller the CMT decreased during the day (p=0.027). Moreover, patients with no CMT decrease had significantly lower mean diurnal blood glucose (p=0.021) and 8 (67%) experimented a morning or an afternoon hypoglycaemic event (<60 mg/dl) reported from CGMS data whereas none with CMT decrease had hypoglycaemia (p=0.002). Furthermore, hypoglycaemic episodes were associated with a 27% increase (from 119±19 to 151±26 mm Hg) of mean systolic blood pressure.
Conclusions: :
Hypoglycaemic events and their secondary blood pressure increases could explain the lack of diurnal CMT decrease in diabetic patients with macular edema. Further studies should be conducted in order to evaluate if this lack of diurnal CMT decrease is associated to poorer visual prognosis and can be modify by a better glucose control.
Keywords: diabetes • macula/fovea • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound)