Impact of Optic Media Opacities and Image Compression on Quantitative Analysis of Optical Coherence Tomography

Abstract

To analyze the impact of opacities in the optical pathway and image compression of 32-bit raw data to 8-bit jpg images on quantified optical coherence tomography (OCT) image analysis. METHODS: In 18 eyes of nine healthy subjects, OCT images were acquired from the central macula.To simulate opacities in the optical system, neutral-density (ND) filters with linear absorption spectra were placed between the OCT device and examined eyes. Light reflection profiles (LRPs) of images acquired with various ND filters were compared. LRPs of the 32-bit raw data were compared with those obtained from the 8-bit jpg compressed images. RESULTS: ND filters induced a linear decrease of reflectivity in OCT images, depending on initial signal intensity. Quantitative OCT analysis showed no significant difference between 32-bit raw data and 8-bit jpg files (P > 0.05). CONCLUSIONS: Quantitative OCT analysis is not significantly influenced by data compression. A mathematical model can correct for optical opacities to improve OCT images.

Comparison of retinal thickness by Fourier-domain optical coherence tomography and OCT retinal image analysis software segmentation analysis derived from Stratus optical coherence tomography images

“…Taking into consideration that image quality could be affected by media opacities, 16,17 we included elderly subjects each of whom underwent uneventful phacoemulsification surgery with posterior chamber lens implantation 6-12 months prior to enrollment. The mean patient age was 70 ± 7 years (range, 65-88 years).…”

“…As a matter of fact, one of the disadvantages of TD over FD-OCT is the potential occurrence of decentration artifacts, 8 which are common in StratusOCT images in elderly patients 8 because of the poor fixation cooperation. Thus, taking into account that image quality could be affected by media opacities, 16,17 it is important to consider the effect of dense optical media, such as cataracts, on thickness measurements and segmentation performance when comparing OCT data.…”

A Comprehensive Model for Correcting RNFL Readings of Varying Signal Strengths in Cirrus Optical Coherence Tomography

“…To better characterize this relationship, researchers have artificially changed the SS in patients by defocusing the image, 9 by placing contact lenses during scans, 10 and through introduction of optical filters in between the subject and the OCT machine. 9,11,12 Simple formulas correcting for SS changes in average RNFL measurements have, at this time, shown limited predictive capability, in part due to not accounting for testretest variability and being applied in unstable testing conditions. 11 Although not specifically looking at RNFL values, more complex formulas analyzing reflectivity peaks in the macula have been developed to correct for changes due to SS 12 and show potential, but as of now are too complicated and are not commercially available.…”

Individual A-Scan Signal Normalization Between Two Spectral Domain Optical Coherence Tomography Devices

“…For image processing performance, a majority of the image processing techniques used in computer vision or computer graphics focuses on 8-bit data format images, and it has been proved that 8-bit data format is sufficient to provide satisfactory and reliable processing and segmentation results. 21 Finally, data size is smaller by converting OCT data to 8-bit data format, which would save memory space, and accelerate the processing time of image analysis and data transfer.…”