Purpose:
To report a six radial scan protocol, which simply generates a topographic map of choroidal thickness and volume on a commercial SD-OCT device. We analyzed the features of the resulting choroidal maps in healthy eyes.
Methods:
Eighty eyes from 40 healthy volunteers who visited the healthcare clinic of Hanyang University Hospital from December 2010 to February 2011. All participants underwent a six radial scanning protocol using a SD-OCT. In a single session it produces six high-resolution averaging B-scan images. For segmentation of the choroid layer, the reference lines of the retinal boundary (ILM-RPE) were adjusted to the choroidal boundary (RPE-choroid/sclera junction) in each of the six radial B-scans. A topographic map of choroidal thickness and volume was automatically generated by built-in software according to the ETDRS layout. A statistical analysis was conducted to compare the choroidal thickness and volume measurements for each ETDRS subfield.
Results:
The mean time required for segmentation adjustment was 167.4 ± 15.8 seconds. The mean choroidal thickness of all ETDRS subfields was 285.9 ± 53.0µm, and the mean total choroidal volume of the entire ETDRS area was 7.72 ± 1.2 mm3. The nasal outer macula area was significantly smaller than any other ETDRS subfield (p<0.05) except for the adjacent superior and inferior outer macula subfields. Refractive error was correlated with choroidal thickness in all ETDRS subfields. Age was also correlated with choroidal thickness for almost all of the ETDRS subfields except for the temporal inner, nasal outer, and temporal outer macula areas. The total choroidal volume was correlated with the refractive error and age.
Conclusions:
A six radial scan protocol, using a commercial SD-OCT, enables us to produce reliable choroidal thickness and volume maps with an ETDRS layout. Using this protocol, more comprehensive choroidal evaluation is possible in clinical practice or research.
Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • image processing