DOCSLIB.ORG

Deep Learning Based Approach for Optic Disc and Optic Cup Semantic Segmentation for Glaucoma Analysis in Retinal Fundus Images Original Scientific Paper

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Deep Learning Based Approach for Optic Disc and Optic Cup Semantic Segmentation for Glaucoma Analysis in Retinal Fundus Images Original Scientific Paper Deep learning based approach for optic disc and optic cup semantic segmentation for glaucoma analysis in retinal fundus images Original Scientific Paper Dunja Božić-Štulić University of Split, Faculty of Electrical Engineering, Mechanical Engineering and Naval Architecture Ruđera Boškovića 32, Split, Croatia [email protected] Maja Braović University of Split, Faculty of Electrical Engineering, Mechanical Engineering and Naval Architecture Ruđera Boškovića 32, Split, Croatia [email protected] Darko Stipaničev University of Split, Faculty of Electrical Engineering, Mechanical Engineering and Naval Architecture Ruđera Boškovića 32, Split, Croatia [email protected] Abstract – Optic disc and optic cup are one of the most recognized retinal landmarks, and there are numerous methods for their automatic detection. Segmented optic disc and optic cup are useful in providing the contextual information about the retinal image that can aid in the detection of other retinal features, but it is also useful in the automatic detection and monitoring of glaucoma. This paper proposes a deep learning based approach for the automatic optic disc and optic cup semantic segmentation, but also the new model for possible glaucoma detection. The proposed method was trained on DRIVE and DIARETDB1 image datasets and evaluated on MESSIDOR dataset, where it achieved the average accuracy of 97.3% of optic disc and 88.1% of optic cup. Detection rate of glaucoma diesis is 96.75%. Keywords – optic disc, optic cup, glaucoma, deep learning 1. INTRODUCTION increased intraocular pressure that can lead to vision loss if left untreated. Medical tests for glaucoma should, Optic disc and optic cup are one of the most recog- amongst other things, include measurement of change nized retinal landmarks, alongside fovea, macula and in the cup-to-disc (CDR) ratio, and this ratio can be cal- retinal blood vessels. It is a point of convergence for culated automatically (e.g. [6, 7]) given the segmented retinal blood vessels, and in a fundus image that shows optic cup and optic disc from retinal fundus image. The no abnormalities is usually represented by the bright- focus of this paper is on the automatic optic disc seg- est region in the image, A large number of methods for mentation and optic cup segmentation. Our method its automatic detection is reported in the literature (e.g. is based on popular SegNet [8] deep neural network, [1-5]), but approaches based on deep learning, such as which is originally used for semantic segmentation of the one proposed in paper, are still relatively novel. It natural landscape images. SegNet belongs to encoder- can be used in the automatic segmentation of retinal decoder type of deep architecture for multi-class pixel- blood vessels, fovea and macula, as it can provide con- wise segmentation. textual information about the retinal image. It is also This paper is organized as follows. In Section 2. we useful in the automatic detection and monitoring of discuss related work, with special attention being given glaucoma, and eye disease usually characterized by an to optic disc segmentation methods that are based on Volume 11, Number 2, 2020 111 deep learning. In Section 3. we give an overview of the proaches can be found in [11, 13, 14, 15]. Methods that proposed method, including data preparation process are used for blood vessels removal from fundus images and network architecture description. In Section 4. we are numerous, and some examples would be morpho- present and discuss optic disc and cup segmentation logical closing [11] and local entropy thresholding and in- results obtained with the proposed method, as a glau- painting techniques [13]. Other approaches for automatic coma detection rate. In Section 5. we give a conclusion optic disc segmentation do not remove blood vessels and discuss future work. from fundus images, but rather use the fact that the optic disc is a point of convergence for retinal blood vessels in 2. RELATED WORK automatic optic disc segmentation. Examples of these ap- proaches can be found in [1, 16]. In this section of the paper we discuss existing meth- ods for optic disc segmentation and optic cup segmen- When it comes to image enhancement for optic disk tation. segmentation, various techniques can be used. For ex- ample, illumination equalization was used in [1], aniso- 2.1. OPTIC DISC SEGMENTATION tropic diffusion was used in [17], median filter of size 15x15 pixels was used in [4], and averaging filter of size Approaches for automatic optic disc segmentation 25x35 pixels was used in [18]. span a great number of categories, and since these cat- egories are usually intertwined, it makes it difficult to Methods used for automatic optic disc detection categorize these approaches into fixed categories. For encompass a wide range of different techniques that this reason, in this section of the paper we discuss vari- range from template matching (e.g. [19] (the authors ous techniques that are commonly used in automatic used histograms instead of images for templates) and optic disc segmentation. Special attention is given to [45] (the authors used template matching for optic disc novel automatic optic disc segmentation approaches centre detection)) to algorithms inspired by biological that are based on deep learning. organisms (e.g. firefly algorithm in [4] and ant colony optimization algorithm in [17]). Automatic optic disc segmentation methods usually consist of a preprocessing part and the main segmen- Methods for automatic optic disc detection that are tation part. Preprocessing part commonly encompass- based on deep learning are still relatively novel. Exist- es the selection of the appropriate color space or color ing methods that use deep learning for automatic op- channel in which to perform further analysis, removal tic disk segmentation, localization and/or detection of retinal blood vessels from fundus images, and vari- include [8, 21, 22]. ous techniques for image enhancement. The main seg- Approaches for automatic optic disc segmentation mentation part commonly consists of a combination can be trained and evaluated on various fundus image of various image processing techniques, for example datasets. In this paper we decided to train the proposed mathematical morphology, edge detection, different method on DRIVE (Digital Retinal Images for Vessel Ex- classifiers, etc. traction) [23, 24] and DIARETDB1 (Diabetic Retinopathy One of the usual first steps in the preprocessing part Database) [25, 26] image datasets. DRIVE consists of 40 of automatic optic disc detection methods is the se- fundus images equally split into training and testing cat- lection of optimal color space or color channel to use. egories. For the purposes of this paper, we used all 40 We found that various approaches use different color images for the testing purpose, as it is commonly done channels. For example, green channel from the RGB when it comes to evaluation of automatic optic disc color space was used in [9, 10], both green and red segmentation approaches. The size of the images in the channels from the RGB color space were used in [11], DRIVE dataset is 565x584 pixels. DIARETDB1 consists of and in [12] it was found that it was reliable to use lumi- 89 fundus images whose size is 1500x1152 pixels. Since nance channel from the HLS color space for optic disc there are no formal ground truth segmentations of the localization and red channel from the RGB color space optic disc for neither of these two image datasets, we to find the contours of the optic disc. From this we can created our own optic disc manual segmentations for conclude that there is no formal agreement between both of them. The proposed method was evaluated on researchers on what color space or color channel to use 200 images from the MESSIDOR image dataset [44]. in automatic optic disc segmentation. Our contributions in this work are: Another important step that is often used in the prepro- We proposed a novel fully automatic model for de- cessing part of automatic optic disc detection methods is tecting glaucoma disease based on deep learning ap- the removal of retinal blood vessels from fundus images. proach. Model preforms semantic segmentation of op- Retinal blood vessels are usually removed from fundus tic disc and optic cup respectively. images because they intersect the boundary of the op- tic disc, making it more difficult to detect it. In order to 2.2. OPTIC CUP SEGMENTATION compensate for this situation, many automatic optic disc segmentation approaches employ the removal of retinal Automatic optic cup segmentation is usually associ- blood vessels from fundus images. Examples of these ap- ated with automated glaucoma detection and analysis. 112 International Journal of Electrical and Computer Engineering Systems Image processing based glaucoma detection has been that are in the top 20% from the segmented optic disc studied in the literature (e.g. [3]), and they usually work region. Lim et al. [8] proposed a method for optic cup by calculating the CDR ratio. In this section of the paper segmentation that. In [13] authors proposed a method we will briefly discuss some of the methods used for for optic cup segmentation that includes an over-seg- automatic, image processing based optic cup segmen- mentation of the optic disc region into superpixels, ex- tation. traction of features belonging to these superpixels, and the classification procedure (by using the SVM classi- Akram et al. [3] proposed a method for optic cup seg- fier) that determines if the superpixel belongs to the mentation that selects pixels that have intensity values optic cup or not. Fig. 1. Flow chart of proposed method for detecting glaucoma 3. PROPOSED METHOD 3.1. OVEr-SEGMENTATION OF THE fUNDUS IMAGES Fig. 1. illustrates the proposed method and is com- posed of three phases. Phase one, the image is Segmentation is one of the most complex computer vision.
Load more

Recommended publications
  • Semaphorin3a/Neuropilin-1 Signaling Acts As a Molecular Switch Regulating Neural Crest Migration During Cornea Development
    Developmental Biology 336 (2009) 257–265 Contents lists available at ScienceDirect Developmental Biology journal homepage: www.elsevier.com/developmentalbiology Semaphorin3A/neuropilin-1 signaling acts as a molecular switch regulating neural crest migration during cornea development Peter Y. Lwigale a,⁎, Marianne Bronner-Fraser b a Department of Biochemistry and Cell Biology, MS 140, Rice University, P.O. Box 1892, Houston, TX 77251, USA b Division of Biology, 139-74, California Institute of Technology, Pasadena, CA 91125, USA article info abstract Article history: Cranial neural crest cells migrate into the periocular region and later contribute to various ocular tissues Received for publication 2 April 2009 including the cornea, ciliary body and iris. After reaching the eye, they initially pause before migrating over Revised 11 September 2009 the lens to form the cornea. Interestingly, removal of the lens leads to premature invasion and abnormal Accepted 6 October 2009 differentiation of the cornea. In exploring the molecular mechanisms underlying this effect, we find that Available online 13 October 2009 semaphorin3A (Sema3A) is expressed in the lens placode and epithelium continuously throughout eye development. Interestingly, neuropilin-1 (Npn-1) is expressed by periocular neural crest but down- Keywords: Semaphorin3A regulated, in a manner independent of the lens, by the subpopulation that migrates into the eye and gives Neuropilin-1 rise to the cornea endothelium and stroma. In contrast, Npn-1 expressing neural crest cells remain in the Neural crest periocular region and contribute to the anterior uvea and ocular blood vessels. Introduction of a peptide that Cornea inhibits Sema3A/Npn-1 signaling results in premature entry of neural crest cells over the lens that Lens phenocopies lens ablation.
    [Show full text]
  • Ophthalmology Ophthalmology 160.01
    Introduction to Ophthalmology Ophthalmology 160.01 Fall 2019 Tuesdays 12:10-1 pm Location: Library, Room CL220&223 University of California, San Francisco WELCOME OBJECTIVES This is a 1-unit elective designed to provide 1st and 2nd year medical students with - General understanding of eye anatomy - Knowledge of the basic components of the eye exam - Recognition of various pathological processes that impact vision - Appreciation of the clinical and surgical duties of an ophthalmologist INFORMATION This elective is composed of 11 lunchtime didactic sessions. There is no required reading, but in this packet you will find some background information on topics covered in the lectures. You also have access to Vaughan & Asbury's General Ophthalmology online through the UCSF library. AGENDA 9/10 Introduction to Ophthalmology Neeti Parikh, MD CL220&223 9/17 Oculoplastics Robert Kersten, MD CL220&223 9/24 Ocular Effects of Systemic Processes Gerami Seitzman, MD CL220&223 10/01 Refractive Surgery Stephen McLeod, MD CL220&223 10/08 Comprehensive Ophthalmology Saras Ramanathan, MD CL220&223 10/15 BREAK- AAO 10/22 The Role of the Microbiome in Eye Disease Bryan Winn, MD CL220&223 10/29 Retinal imaging in patients with hereditary retinal degenerations Jacque Duncan, MD CL220&223 11/05 Pediatric Ophthalmology Maanasa Indaram, MD CL220&223 11/12 Understanding Glaucoma from a Retina Circuit Perspective Yvonne Ou, MD CL220&223 11/19 11/26 Break - Thanksgiving 12/03 Retina/Innovation/Research Daniel Schwartz, MD CL220&223 CONTACT Course Director Course Coordinator Dr. Neeti Parikh Shelle Libberton [email protected] [email protected] ATTENDANCE Two absences are permitted.
    [Show full text]
  • Using the Ophthalmoscope: Viewing the Optic Disc and Retina
    Using the Ophthalmoscope: Viewing the Optic Disc and Retina Judith Warner, MD University of Utah THE OPHTHALMOSCOPE DIRECT OPHTHALMOSCOPY • Jan Purkinje 1823 • Hermann von Helmholtz 1851 • Hand held ophthalmoscope • Direct up-right image Dials of the Ophthalmoscope RED-FREE FILTER (GREEN LIGHT) 450 nm monochromatic light nerve fiber layer optic nerve drusen OTHER DIALS • Used for measuring lesion size • Looking for the center of fixation OTHER DIALS: SLIT BEAM The wheel has lenses of power Panoptic-ophthalmoscope Direct type Wider field of view Distance from pt greater Similar apertures Not as easy to carry Slightly dimmer light source Not as magnified view of Disc Clean the rubber cup between patients Photographs: http://panoptic.welchallyn.com/faq.html WHEN EVER POSSIBLE: DILATE THE PATIENT Steps to Direct Ophthalmoscopy • Dimly lit room • Dilating drops • Patient fixates distant target • Align yourself • Red reflex • Dial in HOW TO USE THE DIRECT Ophthalmoscope.avi ophthalmoscope.wmv THE RED REFLEX The layers you will go through to see the optic disc THE OPTIC NERVE WHAT YOU SHOULD OBSERVE IN EVERYONE RIGHT EYE AND LEFT EYE THE NORMAL DISC • The disc is 1.62 mm or 1 million fibers • Central retinal artery and vein • Lamina Cribrosa • The optic cup The Normal Disc Appearance The lamina cribrosa is an important disc structure --Means Sieve --Anatomically present in all discs --Visible in about 1/3 --Shallow in myopia Look at the Cup-to-disc ratio: WHAT IS THE CUP-TO-DISC RATIO? .7 NO CUP 0.1 CUP 0.3 CUP 0.7 CUP 0.9 CUP What is the cup
    [Show full text]
  • Ovalness* of the Optic Cup and Disc in the Normal Eye
    Br J Ophthalmol: first published as 10.1136/bjo.58.5.543 on 1 May 1974. Downloaded from Brit. J. Ophthal. (1974) 58, 543 Ovalness* of the optic cup and disc in the normal eye ALAN TOMLINSON Department of Ophthalmic Optics, University of Manchester Institute of Science and Technology AND CALBERT I. PHILLIPS Department of Ophthalmology, University ofEdinburgh Observations have been made of the horizontal extent of cupping of the optic nerve head in both normal and glaucomatous eyes in an attempt to determine the factors which influ- ence cup size in the normal eye (Armaly, I967; Armaly and Sayegh, I969; Armaly, 1969a, b; Tomlinson and Phillips, I969; Jonsas, I972) and to establish differential diagnostic criteria for glaucomatous excavation (Armaly, I969c; Armaly, I970; Becker, 1970; Kirsch and Anderson, I973a). In our series (i969) cup-disc area ratio was chosen to take account of oval or other shapes. Recently the vertical elongation of the optic cup has been considered as a possible diagnostic feature of glaucomatous cupping by Kirsch and Anderson (I973a, b) and Weisman, Asseff, Phelps, Podos, and Becker (I973). It is important, however, to consider factors which influence physiological variations of any feature before it may be utilized as http://bjo.bmj.com/ a diagnostic criterion ofany condition, e.g. it has been found (Tomlinson and Phillips, I 969) that the area of cup of the optic disc in normal eyes is related to axial length of the eyeball and that this in turn is related to intraocular pressure (Tomlinson and Phillips, 1970); similarly the degree of angulation and position of emergence of vessels at the optic disc are dependent on the area of physiological cupping present (Tomlinson and Phillips, 1977 ).
    [Show full text]
  • Bmps and Ventral Optic Cup Differentiation 3163
    Development 129, 3161-3171 (2002) 3161 Printed in Great Britain © The Company of Biologists Limited 2002 DEV1795 The role of bone morphogenetic proteins in the differentiation of the ventral optic cup Ruben Adler1 and Teri L. Belecky-Adams2,* 1The Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore, MD, USA 2Department of Biology, Indiana University Purdue University Indianapolis, Indianapolis, IN 46202, USA *Author for correspondence (e-mail: [email protected]) Accepted 20 March 2002 SUMMARY The ventral region of the chick embryo optic cup undergoes stages of development, this treatment resulted in a complex process of differentiation leading to the microphthalmia with concomitant disruption of the formation of four different structures: the neural retina, developing neural retina, RPE and lens. At optic cup the retinal pigment epithelium (RPE), the optic disk/optic stages, however, noggin overexpression caused colobomas, stalk, and the pecten oculi. Signaling molecules such as pecten agenesis, replacement of the ventral RPE by retinoic acid and sonic hedgehog have been implicated neuroepithelium-like tissue, and ectopic expression of optic in the regulation of these phenomena. We have now stalk markers in the region of the ventral retina and RPE. investigated whether the bone morphogenetic proteins This was frequently accompanied by abnormal growth of (BMPs) also regulate ventral optic cup development. Loss- ganglion cell axons, which failed to enter the optic nerve. of-function experiments were carried out in chick embryos The data suggest that endogenous BMPs have significant in ovo, by intraocular overexpression of noggin, a protein effects on the development of ventral optic cup structures. that binds several BMPs and prevents their interactions with their cognate cell surface receptors.
    [Show full text]
  • Anatomy & Physiology of The
    Anatomy & Physiology of The Eye 2017-2018 Done By: 433 Team Abdullah M. Khattab Important Doctor’s Notes Extra Abdullah AlOmair Resources: Team 433, Doctors Notes, Vaughan & Asbury’s General ophthalmology. Editing File Embryology of The Eye ............................................................................................. 2 ● Defects: ........................................................................................................................... 2 Development of The Eye After Birth .......................................................................... 3 ● Refractive power depends on two factors: ...................................................................... 3 The Orbit ................................................................................................................... 4 ● Seven bones contribute the bony orbit and surrounded by nasal sinuses. .................... 4 ● The orbital wall, pear-like shaped, formed by: ................................................................ 4 ● Structures Passing Through the Optic Openings: ........................................................... 4 Extraocular Muscles .................................................................................................. 1 ● Anatomy .......................................................................................................................... 1 ● Notes: .............................................................................................................................. 1 ● Field of action:
    [Show full text]
  • Photogrammetric Measurement of the Optic Disc Cup in Glaucoma*
    Photogrammetric Measurement of the Optic Disc Cup in Glaucoma* Takenori Takamoto, Ph .D. Assistant Professor Bernard Schwartz, M.D. Ph .D. Professor and Chairman Department of Ophthalmology New England Medical Center and Tufts University School of Medicine 171 Harrison Avenue Boston, Massachusetts 02111 ABSTRACT Cupping of the optic disc associated with the atrophy of the optic nerve is one of the earliest recognizable signs of glaucoma. Measure­ ments of the optic cup changes would provide objective evaluation in early diagnosis and therapy of glaucomatous eyes, by following the course of the patient in relation to the loss of visual field and medical or surgical control. A semi-analytical photogrammetric technique, the radial section method, has been devised to provide general references so that any differences in optic discs can be compared objectively. The coefficient of variation of the cup parameters is about 4% for cup diameter, and abour 5% for cup depth and volume . Due to the small size of the dilated pupil and refractive index of the eye , the accuracy of photogrammetric measurements of the optic disc is limited. However, optimal geometry of fundus stereophotography can be obtained by convergent stereophotography. On model experiments with 15 degrees of convergent angle, the new method improves the accuracy eight times in cup depth and more than two times in cup diameter measure­ ments over that of non-convergent method . INTROIXJCTION Eye diseases and systemic diseases with ocular manifestations have been studied by examining living vascul ar and nerve tissue under magnificat ion. The information can be recorded on photographs , which can provide a ready means of estimating changes in establi shed l esions and can be a valuable diagnostic method .
    [Show full text]
  • I. Eye Development
    Sara Thomasy DVM, PhD, DACVO Mouse Day 8 Dog Day 11 Eye Fields Mouse Day 7 Dog Day 10 Prosencephalon https://syllabus.med.unc.edu/courseware/embryo_images/unit-eye/eye_htms/eyetoc.htm Mouse Day 8 Dog Day 12 Cyclopia Cyclopia - Formation of a single median globe Synophthalmia – Two incompletely separated or fused globes Concurrent severe craniofacial defects Veratrum californicum . Day 14 of gestation in sheep Steroidal alkaloids . Cyclopamine and jervine . Inhibit sonic hedgehog signal transduction during gastrulation Affects midline neural plate Corn Lily or False Hellebore Day 15 Optic vesicle Mouse Day 9.5 Optic stalk https://syllabus.med.unc.edu/courseware/embryo_images/unit-eye/eye_htms/eyetoc.htm Mouse Day 9.5 Dog Day 15 Optic vesicle Microphthalmia Optic stalk https://syllabus.med.unc.edu/courseware/embryo_images/unit-eye/eye_htms/eyetoc.htm Optic vesicle deficiency Corresponding small palpebral fissure Failure of normal optic cup growth . Failure of fusion of the choroid fissure → colobomas . Failure to establish normal IOP Associated with a myriad of ocular defects ASD PHPV Neural plate deficiency Cataract Retinal dysplasia Colobomatous malformations Merle ocular dysgenesis Intraretinal space Mouse Day 11 Dog Day 18 https://syllabus.med.unc.edu/courseware/embryo_images/unit-eye/eye_htms/eyetoc.htm Mouse Day 11 Iris coloboma Dog Day 18 https://syllabus.med.unc.edu/courseware/embryo_images/unit-eye/eye_htms/eyetoc.htm “Defect” Failure of fusion of the choroid fissure “Typical colobomas” at the 6 o’clock position Abnormal differentiation of the outer optic cup “Atypical colobomas” at other locations Charlois Collie Collie Day 25 Mouse Day 11 https://syllabus.med.unc.edu/courseware/embryo_images/unit-eye/eye_htms/eyetoc.htm Persistent keratolenticular attachment Classic example: Peter’s anomaly Corneal opacity with stromal & DM defects (B) Persistent pupillary membrane (A) .
    [Show full text]
  • The Optic Disc in Glaucoma I: Classification
    Br J Ophthalmol: first published as 10.1136/bjo.60.11.778 on 1 November 1976. Downloaded from Brit. Y. Ophthal. (1976) 6o, 778 The optic disc in glaucoma i: Classification R. A. HITCHINGS Moorfields Eye Hospital, City Road, London AND G. L. SPAETH Wills Eye Hospital, Spring Garden Street, Philadelphia I9I30, USA The pale, cupped disc found in the final stages of deepening of the cup exposing the lamina cribrosa glaucomatous disease has been known from the (the 'laminar dots' sign (Reed and Spaeth, 1974)); time of Von Graefe (I854). Since then many and change in the course of the retinal vessel which observers have described changes that occur at the is seen as a sharp change in direction ('kinking' or optic disc in chronic, simple glaucoma. There has bayoneting (Reed and Spaeth, 1974)). In addition, been particular interest in changes which may the presence of localized regions of nerve fibre loss occur in the early stages of the disease. or 'gutters' has been demonstrated in some cases Studies of the normal population have shown of early glaucoma by Hoyt, Frisen, and Neuman that while there is a wide diversity in the appearance (1973). copyright. of the normal optic disc, in a single subject (Armaly, The aim of this paper was to assess systematically I969; Fishman, I970; Kolker and Hetherington, glaucomatous discs and look for those features that 1970; Portnoy, 1973) the two discs are remarkably are commonly associated. As a result, five different similar (Witsiuk, I966; Kronfeld, 1970; Woodruff, types of optic disc appearance are described. 1970; Portnoy, I973).
    [Show full text]
  • Ratio of Optic Cup to Optic Disc in Relation to Axial Length of Eyeball and Refraction
    Br J Ophthalmol: first published as 10.1136/bjo.53.11.765 on 1 November 1969. Downloaded from Brit. J. Ophthal. (I969) 53, 765 Ratio of optic cup to optic disc In relation to axial length of eyeball and refraction A. TOMLINSON AND C. I. PHILLIPS Department of Ophthalmology, University of Manchester Armaly (I967) found that the ratio of the horizontal diameter of the optic cup to that of the optic disc, in three samples offirst degree relatives, varied directly and similarly between parents and offsprings, and between siblings. The frequency distribution of the ratio did not differ in the three samples and was not influenced by age or sex. He concluded that the ratio was determined genetically in a multifactorial pattern. On the basis of his valuable and interesting observations, he also pointed out that cup-to-disc diameter ratio is not a good criterion of glaucomatous cupping, although inequality between the cups in two eyes may give rise to suspicion. In the present survey, not only the horizontal diameters of the optic cup and disc have been measured, but also their areas, because the area ratio seemed likely to be a better parameter than diameter ratio. These ratios will be considered in relation to axial length and refraction of eyeballs. Subjects and method SUBJECTS The survey was conducted on 75 adult students in the Department of Ophthalmic Optics, University of Manchester Institute of Science and Technology. Their ages were between i8 and 27 years; http://bjo.bmj.com/ 26 were females and 49 males. Ocular tensions, measured by applanation tonometry, ranged from Io to I9 mm.
    [Show full text]
  • Your Glaucoma Eye Examination: Part 2 Your Optic Disc
    Your Glaucoma Eye Examination: Part 2 Your Optic Disc In the last issue of Eyelights we discussed What happens in glaucoma? the significance of eye pressure measurement Glaucoma causes damage to the nerve fibres in glaucoma care. This time we look at the and although the exact mechanism is still importance of examining the optic disc. unknown, there are two main theories that may explain glaucoma damage. What is the optic disc? The optic disc or optic nerve head is the The mechanical theory proposes it is the portion of the optic nerve which can be seen effect of eye pressure that damages the on examination of your eye. nerve fibres. It is thought that the nerve fibres are compressed at their exit point and The optic nerve begins in the eye and is continued, long-term damage causes the composed of 1,200,000 tiny nerve fibres that nerve fibres to atrophy or slowly die. send signals from the eye to the brain. It is these nerve fibres that can be seen, almost The vascular or “blood flow” theory proposes end-on, within the eye. that the pressure of the eye has an effect on blood flow to the optic nerve. If the nerve Each nerve fibre receives visual signals from fibres are starved of blood, nutrients and a certain area of retina and thus represents oxygen, then they undergo atrophy. an area of your field of vision. The loss of nerve fibres means that there will The typical optic disc is a circular structure be a corresponding loss or defect in the visual where the nerve fibres exit the eye.
    [Show full text]
  • The Future of Imaging in Detecting Glaucoma Progression
    The Future of Imaging in Detecting Glaucoma Progression Fabio Lavinsky, MD, MBA, Gadi Wollstein, MD, Jenna Tauber, BS, Joel S. Schuman, MD Ocular imaging has been heavily incorporated into glaucoma management and provides important information that aids in the detection of disease progression. Longitudinal studies have shown that the circumpapillary retinal nerve fiber layer is an important parameter for glaucoma progression detection, whereas other studies have demonstrated that macular parameters, such as the ganglion cell inner plexiform layer and optic nerve head pa- rameters, also are useful for progression detection. The introduction of novel technologies with faster scan speeds, wider scanning fields, higher resolution, and improved tissue penetration has enabled the precise quantification of additional key ocular structures, such as the individual retinal layers, optic nerve head, choroid, and lamina cribrosa. Furthermore, extracting functional information from scans such as blood flow rate and oxygen consumption pro- vides new perspectives on the disease and its progression. These novel methods promise improved detection of glaucoma progression and better insight into the mechanisms of progression that will lead to better targeted treatment options to prevent visual damage and blindness. Ophthalmology 2017;124:S76-S82 ª 2017 by the American Academy of Ophthalmology Glaucoma is a multifactorial optic neuropathy characterized Despite the usefulness of OCT, there are also challenges in by structural damage of retinal ganglion cells (RGCs)
    [Show full text]