Relationship between the Peripapillary Choroidal Thickness and Retinal Nerve Fiber Layer Thickness: A Population-based Study

Abstract

Purpose: Peripapillary choroidal thickness (PPCT) may be another imaging measure of early glaucoma damage since vascular factors have been suggested to play a role in glaucoma development. This study describes the relationship between PPCT and retinal nerve fiber layer (RNFL) thickness in a population-based sample of non-glaucomatous subjects.

Methods: Subjects were recruited from the Singapore Malay Eye Study during their follow-up examination and underwent standardized ophthalmic examination, including RNFL and peripapillary choroidal imaging using spectral domain optical coherence tomography (SD-OCT). RNFL thicknesses (average, and quadrants) were measured using Cirrus OCT (Carl Zeiss Meditec, Dublin, USA). PPCT (average and quadrants) were measured using Spectralis SD-OCT with enhanced depth imaging (Heidelberg Engineering, Heidelberg, Germany), and derived by a customized automated choroidal segmentation software. Of a total of 478 subjects (904 eyes) recruited, 61 eyes were excluded because of clinical features compatible with glaucoma and other factors, leaving 435 subjects (843 eyes) for analysis. Associations between PPCT and RNFL thickness were assessed using linear regression models with generalized estimating equations to account for the inter-eye correlations.

Results: Of the 435 included subjects (843 non-glaucomatous eyes), 39% were men, and the mean (SD) age was 66.7 (10.5) years. The mean PPCT was 135.59 ± 56.74 µm and the mean RNFL thickness was 92.92 ± 11.41 µm. Peripapillary choroid was thickest (150.04 ± 59.72 µm) at superior and thinnest (110.71 ± 51.61 µm) at inferior quadrant, whereas RNFL was thickest (118.60 ± 19.83 µm) at inferior and thinnest (67.36 ± 11.36 µm) at temporal quadrant. We found that thicker PPCT was independently associated with thicker RNFL thickness globally (regression coefficient [β] = 0.24 µm for one µm increase in PPCT, p = 0.002), and in the inferior (β = 0.05, p = 0.001) and superior (β = 0.04, p<0.001) quadrants, after adjusting for age, gender, axial length and variables with p≤0.05 in univariate models.

Conclusions: There is an independent positive association between inferior, superior and average PPCT and RNFL thickness. This structure-structure relationship may provide an additional diagnostic tool in glaucoma risk assessment in clinical settings.