A compactness based saliency approach for leakages detection in fluorescein angiogram

This study has developed a novel saliency detection method based on compactness feature for detecting three common types of leakage in retinal fluorescein angiogram: large focal, punctate focal, and vessel segment leakage. Leakage from retinal vessels occurs in a wide range of retinal diseases, such as diabetic maculopathy and paediatric malarial retinopathy. The proposed framework consists of three major steps: saliency detection, saliency refinement and leakage detection. First, the Retinex theory is adapted to address the illumination inhomogeneity problem. Then two saliency cues, intensity and compactness, are proposed for the estimation of the saliency map of each individual superpixel at each level. The saliency maps at different levels over the same cues are fused using an averaging operator. Finally, the leaking sites can be detected by masking the vessel and optic disc regions. The effectiveness of this framework has been evaluated by applying it to different types of leakage images with cerebral malaria. The sensitivity in detecting large focal, punctate focal and vessel segment leakage is 98.1, 88.2 and 82.7 %, respectively, when compared to a reference standard of manual annotations by expert human observers. The developed framework will become a new powerful tool for studying retinal conditions involving retinal leakage

Intensity and Compactness Enabled Saliency Estimation for Leakage Detection in Diabetic and Malarial Retinopathy

Leakage in retinal angiography currently is a key feature for confirming the activities of lesions in the management of a wide range of retinal diseases, such as diabetic maculopathy and paediatric malarial retinopathy. This paper proposes a new saliency-based method for the detection of leakage in fluorescein angiography. A superpixel approach is firstly employed to divide the image into meaningful patches (or superpixels) at different levels. Two saliency cues, intensity and compactness, are then proposed for the estimation of the saliency map of each individual superpixel at each level. The saliency maps at different levels over the same cues are fused using an averaging operator. The two saliency maps over different cues are fused using a pixel-wise multiplication operator. Leaking regions are finally detected by thresholding the saliency map followed by a graph-cut segmentation. The proposed method has been validated using the only two publicly available datasets: one for malarial retinopathy and the other for diabetic retinopathy. The experimental results show that it outperforms one of the latest competitors and performs as well as a human expert for leakage detection and outperforms several state-of-the-art methods for saliency detection

Optimising Visualisation of Fluorescein Dye

Purpose: The use of the excitation and emission filters in conjunction with sodium fluorescein dye to examine the anterior eye have not been studied when considering different light sources. This is despite the industry now incorporating white LED lights in slit lamps used in eye examinations in place of halogen light. Novel, cost-effective filter combinations that minimise spectral overlap are proposed, enhancing the contrast of fluorescein dye compared with traditionally used filters. Methods: The Oceanview spectrophotometer recorded the spectral distribution and intensity of light traveling through an emission and excitation filter. Several combinations of emission filter, excitation filter and light source were trailed. Following this, 50-micron aliquots of diluted fluorescein against a background were photographed for various filter combinations. Contrast was defined as the minimum visible thickness of fluorescein divided by the background illumination. Results: The combination of white LED light, the BG3 excitation filter, and Wratten No. 12 emission filter showed superior contrast when compared to similar combinations involving the Haag Streit cobalt blue excitation filter. These results did not hold for filter combinations involving halogen light. Discussion: Previous filters mentioned in the literature are no longer available, leaving either costly matched interference filters, or the traditional Wratten 12/cobalt blue filters to view the anterior eye through the slit lamp. The latter combination may produce “optical noise” and reduce image contrast. White LED light, combined with the BG3 excitation filter, and the Wratten No. 12 emission filter show relative improvements in contrast when compared with traditionally used filter combinations. Conclusions: The superior contrast is exhibited by the BG3 filter when used in combination with the Wratten No. 12 Emission filter and white LED light sources may provide stimulus for further research into its clinical use in eye exams