Optic disc segmentation for glaucoma screening system using fundus images.

Segmenting the optic disc (OD) is an important and essential step in creating a frame of reference for diagnosing optic nerve head pathologies such as glaucoma. Therefore, a reliable OD segmentation technique is necessary for automatic screening of optic nerve head abnormalities. The main contribution of this paper is in presenting a novel OD segmentation algorithm based on applying a level set method on a localized OD image. To prevent the blood vessels from interfering with the level set process, an inpainting technique was applied. As well an important contribution was to involve the variations in opinions among the ophthalmologists in detecting the disc boundaries and diagnosing the glaucoma. Most of the previous studies were trained and tested based on only one opinion, which can be assumed to be biased for the ophthalmologist. In addition, the accuracy was calculated based on the number of images that coincided with the ophthalmologists' agreed-upon images, and not only on the overlapping images as in previous studies. The ultimate goal of this project is to develop an automated image processing system for glaucoma screening. The disc algorithm is evaluated using a new retinal fundus image dataset called RIGA (retinal images for glaucoma analysis). In the case of low-quality images, a double level set was applied, in which the first level set was considered to be localization for the OD. Five hundred and fifty images are used to test the algorithm accuracy as well as the agreement among the manual markings of six ophthalmologists. The accuracy of the algorithm in marking the optic disc area and centroid was 83.9%, and the best agreement was observed between the results of the algorithm and manual markings in 379 images.

An Automatic Image Processing System for Glaucoma Screening.

Horizontal and vertical cup to disc ratios are the most crucial parameters used clinically to detect glaucoma or monitor its progress and are manually evaluated from retinal fundus images of the optic nerve head. Due to the rarity of the glaucoma experts as well as the increasing in glaucoma's population, an automatically calculated horizontal and vertical cup to disc ratios (HCDR and VCDR, resp.) can be useful for glaucoma screening. We report on two algorithms to calculate the HCDR and VCDR. In the algorithms, level set and inpainting techniques were developed for segmenting the disc, while thresholding using Type-II fuzzy approach was developed for segmenting the cup. The results from the algorithms were verified using the manual markings of images from a dataset of glaucomatous images (retinal fundus images for glaucoma analysis (RIGA dataset)) by six ophthalmologists. The algorithm's accuracy for HCDR and VCDR combined was 74.2%. Only the accuracy of manual markings by one ophthalmologist was higher than the algorithm's accuracy. The algorithm's best agreement was with markings by ophthalmologist number 1 in 230 images (41.8%) of the total tested images.

Optic cup segmentation: type-II fuzzy thresholding approach and blood vessel extraction.

We introduce here a new technique for segmenting optic cup using two-dimensional fundus images. Cup segmentation is the most challenging part of image processing of the optic nerve head due to the complexity of its structure. Using the blood vessels to segment the cup is important. Here, we report on blood vessel extraction using first a top-hat transform and Otsu's segmentation function to detect the curves in the blood vessels (kinks) which indicate the cup boundary. This was followed by an interval type-II fuzzy entropy procedure. Finally, the Hough transform was applied to approximate the cup boundary. The algorithm was evaluated on 550 fundus images from a large dataset, which contained three different sets of images, where the cup was manually marked by six ophthalmologists. On one side, the accuracy of the algorithm was tested on the three image sets independently. The final cup detection accuracy in terms of area and centroid was calculated to be 78.2% of 441 images. Finally, we compared the algorithm performance with manual markings done by the six ophthalmologists. The agreement was determined between the ophthalmologists as well as the algorithm. The best agreement was between ophthalmologists one, two and five in 398 of 550 images, while the algorithm agreed with them in 356 images.

Agreement among ophthalmologists in marking the optic disc and optic cup in fundus images.

The purpose of this paper was to study the agreement between six ophthalmologists who manually marked the optic nerve head using fundus images. Four different parameters were considered from the manual marking images: (1) disc (area and centroid), (2) cup (area and centroid), (3) horizontal and vertical cup-to-disc ratios, and (4) including the previous two parameters for both horizontal and vertical cup-to-disc ratios, and investigated the comprehensive agreement and accuracy among all the ophthalmologists. The best agreement percentage for all the parameters combined was between ophthalmologists number one and three for 44 % of images, and the best accuracy was for ophthalmologist number one with 77.4 % of 315 total tested images. Our analysis shows that more than half of the images in the dataset were not agreed upon when considering all the parameters together.

Combined true and pseudoexfoliation in a Saudi patient with co-existing cataract and glaucoma.

True exfoliation and pseudoexfoliation of the anterior lens capsule are different conditions, their coexistence is rare. We report a case with clinical findings of unilateral combined true exfoliation and pseudoexfoliation in a Saudi Bedouin that was confirmed histologically. We suggest that high levels of infrared radiation in the desert may have contributed to the capsular delamination.

Update on pediatric glaucoma.

Pediatric glaucomas are a group of heterogeneous diseases that can be potentially blinding. Their clinical presentation varies widely. Making the correct diagnosis in a timely manner and implementing a proper management plan are crucial in preventing visual loss. This review summarizes current concepts regarding terminology, classification, epidemiology, clinical features, medical and surgical treatment, and recent advances in basic science with an emphasis on the pathogenesis and genetics of pediatric glaucoma.

Primary and secondary congenital glaucoma: baseline features from a registry at King Khaled Eye Specialist Hospital, Riyadh, Saudi Arabia.

PURPOSE: To compare the demographic and clinical distribution of primary and secondary congenital glaucoma from a registry at King Khaled Eye Specialist Hospital. DESIGN: Registry-based cohort study. METHODS: Review of registry data that included new patients with congenital glaucoma seen between 2001 and 2003 (29 months); analysis of the demographic data and clinical features of primary and secondary congenital glaucoma at presentation. RESULTS: A total of 325 eyes of 180 patients were included. Most patients had primary congenital glaucoma (80%). The mean (± SD) age at presentation for primary congenital glaucoma was 3.8 ± 10.7 months and for secondary congenital glaucoma was 4.3 ± 7.9 months. Most primary congenital glaucoma and secondary congenital glaucoma patients had bilateral disease (82.6%; 74.3%). Primary congenital glaucoma was equally distributed by sex but secondary congenital glaucoma was 1.5-fold more common in male patients. A positive family history was elicited in 30%, and almost 60% had a history of consanguinity in both groups. The mean intraocular pressure and corneal diameter were comparable in both groups but the axial length was significantly longer in primary congenital glaucoma and cup-to-disc (C/D) ratio greater in secondary congenital glaucoma. In the primary congenital glaucoma group, corneal haze showed a significant relationship with most clinical parameters. In primary congenital glaucoma, a positive correlation was noted between age at presentation and increasing corneal diameter and axial length but a negative relationship was noted with C/D ratio and corneal haze, whereas for secondary congenital glaucoma only axial length was positively correlated. CONCLUSION: The congenital glaucoma registry provides unique baseline data on primary congenital glaucoma and secondary congenital glaucoma in Saudi Arabia that will enable us to better understand the disease in the Kingdom and region.