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Review Glaucoma Pearls for Correct Assessment of Optic Disc at Glaucoma Diagnosis Burak Turgut Department of Ophthalmology, Faculty of Medicine, Yuksek Ihtisas University, Ankara, Turkey T he correct evaluation of the optic disc, and related structures in ophthalmoscopy, is critical for the diagnosis of open angle glaucoma because usually glaucomatous optic nerve damage firstly occurs in the optic disc before detectable visual field defects become apparent; however, some studies have demonstrated that visual field defects can also be found without any glaucomatous changes in the optic disc. The purpose of this review is to provide a guide to clinicians for the evaluation of the optic disc in glaucoma suspects and patients. This guide can facilitate the diagnosis and exclusion of glaucoma in these subjects. Keywords Glaucoma, diagnosis, optic nerve head, optic disc, correct evaluation Disclosure: Burak Turgut has nothing to declare in relation to this article. No funding was received in the publication of this article. Compliance with Ethics: This study involves a review of the literature and did not involve any studies with human or animal subjects performed by any of the authors. Authorship: All named authors meet the International Committee of Medical Journal Editors (ICMJE) criteria for authorship of this manuscript, take responsibility for the integrity of the work as a whole, and have given final approval to the version to be published. Open Access: This article is published under the Creative Commons Attribution Noncommercial License, which permits any non-commercial use, distribution, adaptation and reproduction provided the original author(s) and source are given appropriate credit. Received: 21 April 2017 Accepted: 21 August 2017 Citation: US Ophthalmic Review, 2017;10(2):104–10 Corresponding Author: Burak Turgut, Yuksek Ihtisas University, Faculty of Medicine, Department of Ophthalmology, Street 1377, No.21, 06520, Ankara, Turkey. E: drburakturgut@yahoo.com The optic nerve head (ONH) is the region where retinal ganglion cells (RGCs) leave the eyeball via the scleral canal. It also consists of blood vessels, glial, and connective tissue. Glaucoma is a progressive optic neuropathy characterized by the loss of retinal nerve fibres and the axons of RGCs at the level of the ONH. The primary site for glaucomatous damage is the ONH. 1–3 Although the ONH and the optic disc are often used to mean the same thing, in fact the optic disc is the part of the ONH which is observed in ophthalmoscopy. Although there are no clear lines demarcating the histologic layers of ONH, the ONH consists of the surface retinal nerve fibre layer (RNFL), and pre-laminar, laminar (lamina cribrosa [LC]), and retrolaminar layers. 1–6 Therefore, we actually observe the superficial RNFL and the optic cup in the ONH. Glaucomatous optic nerve damage usually occurs in the ONH before there are any detectable visual field (VF) defects; however, some studies have demonstrated that VF defects can also be found without any glaucomatous changes in the optic disc. 7–9 It is understood that glaucomatous VF defects can be detected on standard automated perimetry when 20–40% of RGCs are lost. 10,11 Thus, the correct and careful evaluation of the optic disc and tissues immediately surrounding the disc are very important for detecting early glaucomatous damage. However, firstly it is crucial to know what the features and appearance of a healthy optic disc should be. In the examination of the ONH, the size and shape of the optic disc should be correctly evaluated, as should: • • • • • • • the size, color, and integrity of the neuroretinal rim (NRR); the size and shape of the optic cup; the cup-to-disc ratio (CDR); the shape and configuration of the vessels in the ONH; the presence of the laminar dot sign in the cup; the changes in peripapillary region (ONH hemorrhages, peripapillary atrophy [PPA]); and the loss of lines belong to RNFL in red-free illumination (Figures 1A and B, and 2A–F). 1–6,12 The main techniques for clinical examination of the ONH include direct ophthalmoscopy, indirect ophthalmoscopy, and slit-lamp biomicroscopy with a contact lens or non-contact handheld lens (+66, +78, +90 diopter [D]) or a Hruby lens. The use of a slit lamp with a handheld lens is the preferred method because it provides good stereopsis and magnification for the physician and also convenience for the patient. 13–19 Although retinal tomography and optical coherence tomography (OCT) are useful methods to perform some measurements such as optic disc diameter, CDR, NRR thickness and optic disc area, direct evaluation of the optic disc by the physician is necessary. 104 TOUCH ME D ICA L ME D IA