Purpose: We determined ocular and systemic factors influencing macular thickness measured by spectral-domain optical coherence tomography (SD-OCT) in a population-based sample of healthy eyes.
Methods: We recruited 490 healthy Chinese adults, aged 40 to 80 years, from the Singapore Chinese Eye Study, a population-based survey. All participants underwent a comprehensive eye examination and a standardized interview. The SD-OCT (Cirrus HD-OCT, software version 6.0) was used to measure a range of macular thickness parameters (central foveal subfield thickness, average inner macular thickness, average outer macular thickness, overall average macular thickness, and overall macular cube volume). Linear regression analyses were performed to examine the effects of various ocular and systemic factors on macular thickness.
Results: The mean (standard deviation) age of the subjects was 53.17 (6.14) years and 50.0% of them were male. The mean central foveal subfield, average inner, and average outer macular thicknesses were 250.38 (20.58), 319.33 (14.40), and 276.67 (11.94) μm, respectively. The overall average macular thickness was 280.25 (11.42) μm and overall macular cube volume was 10.09 (0.41) mm(3). Sex, age, and axial length (AL) are the factors that influenced macular thicknesses. Thinner overall average macular thickness was associated with female sex (4.46 μm thinner compared to males, P < 0.001), older age (0.38 μm decrease per each year increase in age, P < 0.001), and longer AL (2.34-μm decrease per each mm increase in AL, P < 0.001), whereas thinner central foveal subfield thickness was associated with female sex (13.5 μm thinner compared to males, P < 0.001) and shorter AL (3.33-μm decrease per each mm increase in AL, P < 0.001).
Conclusions: Female sex, older age, and longer AL were associated independently with thinner overall average macular thickness, whereas female sex and shorter AL were associated with thinner central foveal thickness in ethnic Chinese. These factors should be taken into consideration when interpreting macular thickness measurements with SD-OCT.
Keywords: macular thickness; population-based study; spectral-domain OCT.