Segmentation of retinal blood vessels by a novel hybrid technique- Principal Component Analysis (PCA) and Contrast Limited Adaptive Histogram Equalization (CLAHE).

Diabetic Retinopathy is a persistent disease of eyes that may lead to permanent loss of sight. In this paper, methodology is proposed to segment region of interest (ROI) i.e. new blood vessels in fundus images of retina of Diabetic Retinopathy (DR). The database of 50 fundus retinal images of healthy subjects and DR patients is fetched from Post Graduate Institute of Medical Education and Research (PGIMER), Chandigarh, India. The experimental set up consists of three set of experiments for the disease. For DR, in the first stage of automated blood vessel segmentation, gray-scale image is produced from the colored image using Principal Component Analysis (PCA) in the preprocessing step. The contrast enhancement by the Contrast Limited Adaptive Histogram Equalization (CLAHE) highlights the retinal blood vessels in the gray-scale image i.e. it unsheathed newly formed retinal blood vessels whereas PCA preserved their texture and color discrimination in DR images. The expert ophthalmologist(s) scrutiny on both internet repository and real time data acted as the gold standard for further analysis and formation of the proposed method. Further, ophthalmologists ascertained the forming of new blood vessels only on the disc region and divulging them, which were impossible with the naked eye. These operations help in extracting retinal blood vessels present on the disc and non-disc region of the image. The comparison of the results are done with the state of art methods like watershed transform. It is observed from the results that the new blood vessels are better segmented by the proposed methodology and are marked by the experienced ophthalmologist for validation. Further, for quantitative analysis, the features are extracted from new blood vessels as they are crucial for scientific interpretation. The results of the features lie in permissible limits such as no. of segments vary from 2 to 5 and length of segments varies from 49 to 164 pixels. Similarly, other features such as gray level of new blood vessels lie in 0.296-0.935 normalized range, coefficient with variations in gray level in the range of 0.658-10.10 and distance from vessel origin lie in the range of 56-82 pixels respectively. Both quantitative and qualitative results show that the methodologies proposed boosted the ophthalmic and clinical diagnosis. The developed method further handled the false detection of vessels near the optic disk boundary, under-segmentation of thin vessels, detection of pathological anomalies such as exudates, micro-aneurysms and cotton wool spots. From the numerical analysis, ophthalmologist extracted the information of number of vessels formed, length of the new vessels, observation that the new vessels appearing are less homogenous than the normal vessels. Also about the new vessels, whether they lie on the centre of disc region or towards its edges. These parameters lie as per the findings of the ophthalmologists on retinal images and automated detection helped in monitoring and comprehensive patient assessment. The experimental results show case that the proposed method has higher sensitivity, specificity and accuracy as compared to state of art methods i.e. 0.9023, 0.9610 and 0.9921, respectively. Similar results are obtained on retinal fundus images of PGIMER Chandigarh with sensitivity-0.9234, specificity-0.9955 and accuracy-0.9682.

Lunar lenses - Acquired lens colobomas.

Acquired lens colobomas secondary to ocular surgeries are scarcely described in the literature. We describe two cases of acquired lens coloboma in two infants with glaucoma who underwent ocular surgery. The coloboma in the first case was likely because of direct trauma to the lens zonules during an optical iridectomy with a vitrectomy cutter, resulting in localized loss of zonules and consequently localized lens coloboma. The coloboma in the second case was noticed during examination under anesthesia after scleral buckling and cryopexy for retinal detachment. The cause for coloboma development in this case could be disruption of the lens zonules because of stretching of the globe after scleral buckle surgery or because of injury to zonules during scleral buckling and the cryopexy procedure.

Utility of MALDI-TOF mass spectrometry in an outbreak investigation of acute endophthalmitis following intravitreal injection.

Bevacizumab, a recombinant humanized monoclonal antibody to inhibit tumour angiogenesis, is available for off-label use for treating choroidal neovascularization. Outbreaks have been reported after use of this drug, either because of contamination during manufacturing or the practice of multiple doses being administered from a single vial to different patients. In our institute we investigated one endophthalmitis outbreak following intravitreal injection of bevacizumab, rapidly identified the Stenotrophomonas maltophilia as the causative agent, and established the contaminated bevacizumab vial as the source using matrix-assisted laser desorption/ionization mass spectrometry (MALDI-TOF-MS) typing. The study emphasizes the need for early diagnosis of the source and pathogen for appropriate control measures.

Magnesium metabolism in patients with coronary heart disease.

1. The oral absorption of magnesium, its myocardial uptake and exchangeable magnesium have been studied in patients with coronary heart disease and controls using the radioactive isotope magnesium-28. 2. No significant difference in oral absorption or myocardial uptake was found between patients and controls. 3. The exchangeable magnesium per kg body weight was significantly lower in the patients than in the controls.