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Ryosuke Tamiya, Yuki Muraoka, Shin Kadomoto, Akihito Uji, Koji Nozato, Akitaka Tsujikawa; Enhanced Visualization of the Inner Retinal Layers Using Adaptive Optics Optical Coherence Tomography. Invest. Ophthalmol. Vis. Sci. 2019;60(11):PB041.
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© ARVO (1962-2015); The Authors (2016-present)
Optical coherence tomography (OCT) has aided in elucidation of physiologic or pathological changes in the human retina in vivo. However, on conventional OCT, the contrast of the ganglion cell layer (GCL) to the inner plexiform layer (IPL) is not high enough to precisely evaluate the pathological changes in the inner retina at each layer. In this study, we have developed a prototype adaptive-optics (AO)-OCT system, and investigated whether an evaluation of each inner retinal layer could be performed using the AO-OCT.
Seven eyes of 7 healthy volunteers (mean age 36 ± 6 years, range 30-44 years) were imaged with a prototype AO-OCT system (Canon Inc., Tokyo, Japan). The AO-OCT system provides high resolution retinal imaging with an axial resolution of 3.4 μm and a transverse resolution of approximately 3 μm. A total of 400 B-scans were acquired and averaged to obtain the final images for analyses. The superior fovea, which was located 0.75 mm superiorly from the center of the foveola, was vertically scanned with the AO-OCT, and the contrast-to-noise ratio (CNR) of GCL to IPL was calculated. The CNR calculated on AO-OCT was compared to that of a conventional, non-AO-OCT (OCT HS-100, Canon Inc.). In addition, the average thicknesses of the retinal nerve fiber layer (RNFL), GCL, and IPL were measured with a width of 1.0 mm.
During OCT imaging, the developed AO system could successfully detect an ocular aberration in real time in all subjects. When the focus of AO-OCT was placed on the inner retinal layers, the contrast between the GCL and the adjacent inner retinal layers was apparently increased, and the borders between layers were more sharply demarcated than those imaged by using conventional SD-OCT. The CNR of GCL to IPL on AO-OCT (1.920±0.880) was significantly higher than that on non-AO-OCT (0.884±0.307, P=0.0365) and the ratio of CNR on AO-OCT to that on non-AO-OCT was 2.35±1.24. In AO-OCT, the average retinal thicknesses of RNFL, GCL, and IPL were 14.0 ± 2.0 μm, 56.4 ± 4.7 μm, 30.5 ± 2.6 μm, respectively. The measurement value of each retinal thickness was consistent with that of previous histological investigations (Iwasaki et al., IOVS 1986).
In AO-OCT, contrast between GCL and IPL significantly increased compared to that of conventional OCT imaging. Enhancement of GCL contrast on AO-OCT may be useful for layer-by-layer evaluation of the inner retina.
This abstract was presented at the 2019 ARVO Imaging in the Eye Conference, held in Vancouver, Canada, April 26-27, 2019.
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