Abstract
Abstract: :
Purpose: To investigate direct measurement of the retinal ganglion cell layer (GCL) and inner plexiform layer (IPL) thickness both on normal eyes and glaucoma eyes with the commercial available optical coherence tomography (OCT). Methods: The OCT3 system (Carl Zeiss, Stratus OCT, Dublin, CA) was capable of acquiring 400 axial–scans (A–scan) per second with axial resolution of 10 micron in tissue. Fast thickness map (six radial scan centered at fovea, 6mm scan length) were obtained from normal volunteers and glaucoma patients with a Stratus OCT system. 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 nonlinear coherence diffusion 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. Results: The statistic and thickness map of normal data and glaucoma data are calculated. GCL & GCL+IPL thicknesses are less variable than overall retinal thickness in a normal population. GCL & GCL+IPL were significantly thinner (30%) in glaucoma eyes in our pilot study (non–age–matched control). Both the pooled and population SD of the combined GCL+IPL thickness (10%) is smaller than that of the GCL (20%) alone. The thickness maps of glaucoma eyes are comparable to visual function test. Conclusions:This is the first demonstration of direct GCL & IPL thickness measurements on a clinical OCT system. Combined GCL+IPL thickness measurement may be more repeatable than GCL thickness. GCL & GCL+IPL thicknesses are less variable than overall retinal thickness in a normal population. GCL & GCL+IPL were significantly thinner in glaucoma eyes in our pilot study (non–age–matched control). Further clinical testing for glaucoma diagnosis and monitoring should be planned.
Keywords: imaging/image analysis: clinical • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • macula/fovea