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H. Chung, K.-I. Koo, S. Lee, S. H. Bae, J.-W. Ban, H.-Y. Jeong, H. Park, S.-J. Hong, J.-M. Seo, D. D. Cho; Interpretation of the Optical Coherent Tomographic Findings in the Rabbit Eye with Implanted PMMA Retinal Tack for Retinal Prosthesis. Invest. Ophthalmol. Vis. Sci. 2010;51(13):3050.
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© ARVO (1962-2015); The Authors (2016-present)
Optical coherent tomography (OCT) is a useful method to evaluate the cross-sectional morphology of the retina in vivo. However, the image processing algorithms used in OCT may not reflect the real situation from interferometric data. This paper presents OCT evaluation of the implanted poly-(methyl methacrylate) (PMMA) retinal tacks for retinal prostheses, and comparison between the acquired images and the real dimension of the implanted PMMA retinal tacks.
Two types of PMMA retinal tack, solid body with triangular barbs and square-shaped slotted body with triangular barbs, are fabricated using the microelectromechanical systems (MEMS) technology. The microfabricated PMMA retinal tacks are implanted inside of the eyes in New Zealand white rabbit (N = 3) weighing 3.0 kg by conventional 21G pars planar vitrectomy procedure. Spectral domain OCT (CirrusTM, Carl Zeiss) is taken serially for one month, and the results are compared with data from cross-sectional microscopic morphology and histology.
All the PMMA retinal tacks are implanted safely in rabbit eyes and histologic findings show no inflammatory changes of the retina. By the OCT images, the scale in shaft of the tack could be identified as numbered. However, on comparing the interval between the scale bars and the horizontal scanning length of the retina known as 6mm, the interval obtained by OCT images did not reflect the real dimension. Also horizontal misalignment of the retinal layers under the tack was found. The head and the shaft image of the retinal tack reflect the real figure as rectangular shape, but the connection angle between the head and the shaft which is actually perpendicular to each other, was distorted.
Reconstructed cross-sectional image provided by the OCT might be distorted one, and the provided scale on the OCT image also might not reflect the real dimension. It might be influenced by the refractive index of the observed materials, which can not be properly reflected on the calculation for the image reconstruction. Although OCT was a good method to show the relationship between the retina and the implanted PMMA retinal tacks, careful interpretation should be followed.
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