Purpose: To assess the relationship between macular thickness and volume as characterized by optical coherence tomography (OCT) and known risk factors for diabetic retinopathy (DR) or macular edema (DME) in type 2 diabetic patients with no DME.
Methods: Seventy-four patients with type 2 diabetes without DME and no or only minimal DR (n = 67 with no DR; n = 7 with minimal DR; mean age, 59.5 years) were recruited at a tertiary eye hospital. Central subfield macular thickness (CSMT; circle of 500-μm radius) and central subfield macular volume (CSMV) were measured using spectral-domain OCT. Associations between OCT parameters and known risk factors for DR were examined using multiple linear regression models.
Results: The mean CSMT and CSMV values were 273.7 ± 17.8 μm and 0.215 ± 0.015 mm(3), respectively. After adjusting for age, sex, duration of diabetes, hemoglobin A1c, and urine protein, low-density lipoprotein (LDL) cholesterol was positively associated with CSMT and CSMV; each 1 mmol/L increase in LDL was associated with a mean increase in CSMT of 6.52 μm (95% confidence interval [CI], 1.96-11.08; P = 0.006) and a mean increase in CSMV of 0.0047 mm(3) (95% CI, 0.001-0.0085; P = 0.015).
Conclusions: A higher LDL cholesterol level was associated with increased CSMT and CSMV in diabetic patients without DME. Prospective longitudinal studies are warranted to assess whether having both elevated levels of LDL and higher CSMT or CSMV is a risk indicator for subsequent development of DME.
Keywords: diabetes; diabetic macular edema; macular edema; macular thickness; optical coherence tomography.