Comparison of Retinal Thickness Measures Obtained by STRATUS®-OCT and HD-OCT in Normal and Glaucoma Eyes

Abstract

 

Purpose:

 

The comparison of retinal thickness measures obtained by STRATUS®-OCT and a prototype of a 3 dimensional raster scanning spectral domain high definition OCT (HD-OCT) using a newly developed algorithm for automated retinal layer detection.

 

Methods:

 

We examined healthy volunteers and glaucoma patients using STRATUS®-OCT as well as HD-OCT. In STRATUS®-OCT a fast macular thickness scan was performed using 6 radial lines in a resolution of 256 pixels and a retinal thickness map was obtained from these scans. In HD-OCT a raster scan of 20° by 20° was performed in an axial resolution of approximately 6µm and a resolution of 512*128*1024 voxels. For the evaluation of the retinal thickness an algorithm was used which was especially designed for the detection of the different retinal layers. The central 1.5mm radius of both scans were compared and divided into 5 fields, i.e. the central 1mm area (0.5mm radius), as well as four fields in the 3mm central area (radius 1.5mm) according to the regular macular thickness map of STRATUS®-OCT. To reduce the known inter-scan fluctuation of STRATUS®-OCT the mean value of at least 3 scans for each individual was used. For HD-OCT the area of interest was divided into 5 fields and retinal thickness was defined as the distance between the ILM and IS/OS-boundary according to STRATUS®-OCT detection definition. For statistical analysis a paired t-test was performed.

 

Results:

 

The HD-OCT values were 2.2%-4.7% higher than the ones obtained by STRATUS®-OCT. This was statistically significant for all fields except for the central thickness.  

 

Conclusions:

 

With the newly developed algorithm for automated segmentation of the retinal layers it is possible to measure the retinal thickness. Although the values are significantly higher in HD-OCT by 6 to 13 µm this small difference is probably not clinically relevant.

 

Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • macula/fovea