Automated measurements of human cone photoreceptor density in healthy and degenerative retina by region-based segmentation
Received 23 January 2017
Accepted for publication 18 March 2017
Published 24 April 2017 Volume 2017:11 Pages 781—790
Checked for plagiarism Yes
Review by Single-blind
Peer reviewer comments 3
Editor who approved publication: Dr Scott Fraser
Suguru Miyagawa,1,2 Hisashi Fukuyama,3 Masakazu Hirota,1 Tatsuo Yamaguchi,4 Kazuo Kitamura,4 Takao Endo,3 Hiroyuki Kanda,1 Takeshi Morimoto,1 Takashi Fujikado1
1Department of Applied Visual Science, Osaka University Graduate School of Medicine, Suita, Osaka, 2Technology Development Department Research and Development Section, Topcon Corporation, Itabashi, Tokyo, 3Department of Ophthalmology, Osaka University Graduate School of Medicine, Suita, Osaka, 4Eye Care Technology Development Department, Product Technology Section, Topcon Corporation, Itabashi, Tokyo, Japan
Purpose: The purpose of this study was to develop an algorithm based on region-based segmentation for automated calculations of human cone photoreceptor density of en face images obtained by an adaptive optics scanning laser ophthalmoscope (AOSLO).
Subjects and methods: Cone mosaics of 15 eyes of 15 healthy subjects were photographed by a custom-built AOSLO. The cone density was calculated at 0.5, 1.0, and 1.5 mm temporal from the fovea using a region-based segmentation method (RSM) developed in our laboratory. The cone density was also determined by a manual identification method (MIM) and a conventional spatial filtering method (SFM). The cone densities of three eyes of three patients with retinal degeneration were calculated by the three methods and compared to the results from normal eyes.
Results: The cone densities in healthy retinas determined by the RSM at 0.5, 1.0, and 1.5 mm temporal from the fovea were 28,436, 21,233, and 13,620 cells/mm2, respectively. These densities were in good agreement with a histological study and with in vivo AOSLO studies. The cone densities determined by RSM were different from those determined by MIM with a difference of 5% in healthy eyes. In eyes with retinal degeneration, with the appropriate threshold-level settings or spatial frequency bandwidth, the cone density measured by MIM was significantly closer to that measured by RSM than by SFM.
Conclusion: These results suggest that our method is more stable than conventional methods in cases of non-periodical photoreceptor structures such as the affected retinal area. Our method can be used in the longitudinal follow-up of retinal degenerative diseases and to determine the effect of therapy.
Keywords: AOSLO, adaptive optics, cone photoreceptor, photoreceptor density, retinal imaging, image processing
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