Purchase this article with an account.
Michael J. Girard, Nicholas G. Strouthidis, Jean Martial Mari, C R. Ethier; Shadow Removal, Contrast And Connective Tissue Visibility Enhancement In Optical Coherence Tomography Images Of The Human Optic Nerve Head. Invest. Ophthalmol. Vis. Sci. 2011;52(14):1333.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
To improve the quality of optical coherence tomography (OCT) images of the optic nerve head (ONH).
Two algorithms were developed, one to compensate light attenuation and the other to enhance contrast in OCT images. We developed the former by introducing light attenuation into the standard OCT equations, and correcting its effects by adapting a methodology developed for ultrasound imaging. We developed the latter through direct application of pixel intensity exponentiation. The performances of these two algorithms were tested using spectral-domain OCT images of a patient’s ONH.
Application of the compensation algorithm reduced the intra-layer contrast (a measure of shadow visibility between 0 and 1, with 0 indicating a shadow free layer) in all ONH tissue layers. On average, the intra-layer contrast significantly decreased from 0.77 ± 0.13 to 0.16 ± 0.14 (p < 0.001), which indicated successful shadow removal. Moreover, this algorithm dramatically improved the visibility of deeper ONH connective tissues, such as the sclera and lamina cribrosa (Figure). Application of the contrast enhancement algorithm increased the inter-layer contrast (a measure of boundary visibility between 0 and 1, with 1 indicating a highly-detectable boundary) across all ONH tissue boundaries. On average, the inter-layer contrast significantly increased from 0.49 ± 0.23 to 0.91 ± 0.05 (p < 0.001) and thus allowed a better differentiation of tissue boundaries (Figure). Contrast enhancement was proven robust only when compensation was considered.
The proposed algorithms are simple and can significantly improve the quality of ONH images clinically captured with either time- or spectral-domain OCT. This study has important implications, as it will help: 1) improve our ability to perform automated segmentation of the ONH tissues; 2) quantify the morphometry and biomechanics of the ONH tissues in vivo; 3) identify potential risk indicators for glaucoma.
This PDF is available to Subscribers Only