Three Dimensional Imaging of Glaucomatous Optic Disc With Fourier Domain Optical Coherence Tomography

Abstract

Purpose: : To evaluate three dimensional fourier domain optical coherence tomography (FD–OCT) for glaucomatous optic disc imaing.

Methods: : We built a spectrometer–based FD–OCT system whose acquisition time is 18700 A–scan/sec, 27 ms for a single B–scan (transverse 500 A–scans), and 3.5 sec for a single OCT volume consisting 256 x 256 A–scans. This system was combined with a fundus camera for retinal monitoring in clinical use. The sensitivity of 97dB was achieved. This system employs a superluminescent diode (SLD) which has the center wavelength of 830 nm and the band width of 50 nm as a lightsource. This lightsource is resulting in 6.1 µm depth–resolution in tissue. To cancel the motion artifact of three–dimensional acquisition for investigation of patient eyes, a simple and fast correlation–based algorithm was developed.

Results: : The volume rendering of 3D data set allowed the acquisition of high contrast 3D optic disc images in which detailed interior structures were observed. Three dimensional optic disc cupping was delineated more clearly than in any other current clinical instruments. In the 3D images, highly reflective peripapillary retinal nerve fiber layer (RNFL) was seen to assemble into the optic nerve at its head. RNFL defect in glaucomatous subjects were visualized. The 3D imaging also resolved the deeper microstructures including lamina pores of the whole lamina cribrosa and scleral ring. Three dimensional and cross sectional images in orthogonal planes of optic disc were observed from everywhere at any plane within scan area.

Conclusions: : High contrast 3D images of glaucomatous optic disc by high–speed FD–OCT will be a powerful tool for precise quantitative measurements of peripapillary RNFL volume and for topographic measurements of the optic nerve head for diagnosis of glaucoma. Moreover, 3D imaging of lamina cribrosa and scleral ring by FD–OCT may open a new avenue for investigating the pathology of glaucomatous optic neuropathy.

Keywords: optic disc • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound)