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O. Tan, Y. Li, D. Huang; Measurement of Ganglion Cell Layer and Inner Plexiform Layer Thickness with Optical Coherence Tomography . Invest. Ophthalmol. Vis. Sci. 2003;44(13):4926.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To investigate direct measurement of the retinal ganglion cell layer (GCL) and inner plexiform layer (IPL) thickness with the commercial available optical coherence tomography (OCT). Method: The OCT3 system (Carl Zeiss, OCT3000, Dublin, CA) was capable of acquiring 400 axial-scans (A-scan) per second with axial resolution of 10 micron in tissue. 2, 2.5, 3, 3.5, and 4 mm diameter circular retinal scans (centered at fovea) were obtained from normal volunteers with an OCT3 system. Each circular scan comprised 256 A-scans. An automatic computer algorithm was developed to process the resulting OCT images. Firstly, A-scans in each image were aligned according to the vitreo-retinal boundary. Second, a Gaussian low-pass filtering was used to smooth the image and suppress the speckle noise. Then a progressive segmentation was performed to detect the boundaries based on the gradient of the filtered OCT image. Result: The thickness of the retinal layers were measured from each of the images and statistical analysis was performed. As expected, the GCL thickness decreases with increasing distance from the fovea. The thickness of the IPL is relatively constant in the area centralis. The SD of the combined GCL+IPL thickness is smaller (3-5 microns) than that of the GCL alone (4-6 microns). Conclusion: This is the first demonstration of the direct GCL and IPL thickness measurements on a clinical OCT3 system. The only other report of segmentation of these retinal sublayers are based on images from an ultrahigh resolution (1-3 microns FWHM) OCT system that uses femtosecond laser light source, which is too bulky and expensive for routine clinical use. We have achieved the same desirable end result by image processing on moderately high-resolution images.
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