Spatial Distribution of Choroidal Thickness and Volume at Macula and Relationship With Refractive Error
Purpose
To describe the spatial distribution of macular choroidal thickness and volume in normal eyes and their relationship with refractive error.
Methods
In a prospective, cohort and hospital-based study, spectral domain optical coherence tomography (OCT) with enhanced depth imaging was performed on 150 healthy participants of Chinese ethnicity (300 eyes) using a standardized imaging protocol. Manual segmentation of choroidal boundaries was performed by trained graders. Mean choroidal thickness and volume in the Early Treatment Diabetic Retinopathy Study (ETDRS) grid were calculated. Regression analyses were performed to determine their relationship with refractive error.
Results
The mean age of the participants is 23.0 years, of whom 83 (55.3%) are male and 67 (44.7%) are female. The mean central choroidal thickness is 324.9µm (range 123.0-566.0µm). The choroid is thickest temporally and superiorly (328.8-337.9μm) and thinnest nasally (240.9-294.0μm). Central choroidal thickness decreases by 20.0μm for every diopter increase of refractive error. The mean central choroidal volume is 0.26±0.07mm3 (range 0.10-0.45mm3). The mean volume of the outer subfields is 6.49±1.59mm3 (range 3.28-11.12mm3), and that of the inner subfields is 2.02±0.55 mm3 (range 0.91-3.49mm3). Central choroidal volume decreases by 0.016mm3 for every diopter increase of refractive error.
Conclusion
There is significant spatial distribution of choroidal thickness and volume at different regions of the macula, with progressive change of choroidal thickness and volume based on the refractive status of the eye.