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The Optic Disc in Glaucoma I: Classification

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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). In contrast, individuals with In this paper the term glaucoma has been used glaucomatous disease usually show manifest asym- for all cases in which the intraocular pressure metry of the two optic discs (Fishman, I970; exceeded 22 mmHg and glaucomatous cupping Kolker and Hetherington, 1970). was visible on stereoscopic examination of the disc. http://bjo.bmj.com/ Many criteria have been used to describe the This has meant including cases in which the optic glaucomatous optic disc. Important among these is disc appeared normal by uniocular ophthalmoscopy, the ratio of the cup diameter to the diameter of the and even cases in which glaucomatous cupping was entire disc (Pickard, I923; Snydacker, I964; visible without detectable field loss. Hollows and McGuiness, I967; Armaly, i967, I968; Schwartz, I973; Tomlinson and Phillips, I974). was Material and methods This initially measured horizontally, but on September 29, 2021 by guest. Protected recently measurement of the vertical cup to disc This study was based on analysis of stereoscopic disc (C/D) ratio has been stressed, after recognition that photographs of 252 patients from the files of the changes in the optic cup tend initially to affect the Glaucoma Clinic at Wills Eye Hospital. The patients vertical diameter (Chandler and Grant, I965; were mostly cases of known or suspect glaucoma Kronfeld, I967; Kirsch and Anderson, 1973; attending the Glaucoma Service. In addition, 25 normal Weisman, Assif, Phelps, Podos, and Becker, 1973). patients on the files of the Glaucoma Service were Stereoscopic examination of the optic disc in early included. The diagnosis was unknown at the time of glaucoma reveals signs which help to distinguish analysis of the stereophotographs. the normal from the Most photographs were taken within an I8-month glaucomatous cup (Anderson, period using a Zeiss fundus flash II camera with a X 2-0 I975; Reed and Spaeth, I974). These signs are adaptor. Stereoscopic photographs were obtained after evidence for acquired tissue loss and account for maximal pupillary dilatation by photographing the clear the asymmetry previously noted. Tissue loss may optic disc images obtained at each end of a horizontal appear in a variety of forms: thinning of the neuro- traverse of the camera body. This traverse was usually retinal rim, either localized or generalized; depres- 3 to 4 mm. sion or steepening of the walls of the cup (the Slides were examined with a stereoscopic viewer. tinted hollow (Reed and Spaeth, 1974) or saucer); The stereo pairs of the two eyes were directly compared. Special note was made of identifying characteristics Address for reprints: R. A. Hitchings, FRCS, Moorfields Eye suggestive of tissue loss. Hospital, City Road, London ECIV 2PD The following criteria were analysed: Br J Ophthalmol: first published as 10.1136/bjo.60.11.778 on 1 November 1976. Downloaded from The optic disc in glaucoma 779 THE VERTICAL CUP/DISC (C/D) RATIO retinal vessel as it passed over the surface of the optic The 'cup' was defined in terms of configuration; its disc and a sharp 'kinking' or change in the vessel's extent was determined by drawing a hypothetical line direction either in the same plane as the disc surface or vertically on the anterior surface of the disc from the at an angle to it. The gradual curve was considered most superior to the most inferior aspect of the disc normal; the kink was thought to be an acquired change margin; the segment of the line not in contact with the that occurred secondary to enlargement of the optic cup. disc surface was considered to be 'the cup'. The ratio Kinking resulted in nasal displacement of the vessels, (expressed in tenths) of that segment to the length of and was of most significance when it occurred at the the entire line was the 'cup/disc ratio' (C/D). Pallor of outer margin of the disc. the optic disc played no part in the assessment of the C/D ratio (Schwartz, 1973). PIGMENT CLUMPING The presence or absence of pigment clumping around THE WALLS OF THE OPTIC CUP the margin of the optic disc was noted. The specific points checked were: degree of inclination in the walls, variation in the slope of the walls of any one cup, and difference between cups of the two eyes NERVE FIBRE LAYER in each patient. The presence of a more steeply-sided The nature of the nerve fibre layer was observed as far cup despite identical C/D ratios was considered sus- as possible within the limits of the examination tech- picious of enlargement of the cup. nique. Where refractile lines taking the known pattern of the nerve fibre layer (NFL) were visible the NFL was THE DEPTH OF THE OPTIC CUP thought to be present. If none of the gutters or grooves described by Hoyt and others (1973) was visible the The depth of the optic cup was described as 'normal', NFL was called 'intact'. If such a gutter was observed 'deep', or 'bean-pot'. 'Normal' depth referred to an it was listed as a nerve fibre bundle defect (NFBD). If optic cup which did not show evidence of actual posterior no NFL could be seen at all it was called 'invisible'. bowing of the lamina cribrosa itself; the cup, however, copyright. could extend as far posteriorly as the 'laminar dots' (taken to represent the lamina cribrosa) described by Results Reed and Spaeth (I974). In a 'deep' cup the lamina cribrosa appeared posteriorly bowed. A 'bean-pot' cup, Stereoscopic photographs from 504 eyes of 252 so called because of its likeness to a spherical clay pot, patients were analysed. The optic discs were was diagnosed when posterior displacement of the divided into two groups, normal and pathological, lamina cribrosa coexisted with undermining of the this second being subdivided into five types of neuroretinal rim; in transverse section the walls and glaucomatous cupping (overpass, cupping without base of the cup formed the major part of a circle. There pallor of the neuroretinal rim, cupping with pallor http://bjo.bmj.com/ was usually little difficulty distinguishing between a of the neuroretinal rim, focal notching of the flat or a posteriorly-bowed lamina cribrosa. Similarly, neuroretinal rim, and although there was clearly a spectrum of changes, bean-pot cupping), whose differentiation between the 'deep' and the 'bean-pot' characteristics will be described. The overall cup was usually fairly straightforward. In those few numbers and characterizing features are seen in cases where differentiation between two descriptive the Table. Stereophotographs illustrating each of types was not easy, the shallower type of cup depth was these examples may be seen in Figs 1-5. chosen. on September 29, 2021 by guest. Protected CHARACTERISTICS OF DISC SUBTYPES THE NEURORETINAL RIM Normal disc The pallor and the width of the neuroretinal rims were graded. The colour achieved with transparencies was A disc was considered 'normal' in appearance if not an exact match with the colours seen on stereoscopic the neuroretinal rim was pinkish and of equal examination, and pallor of the rim could not always be thickness throughout, or with its thinnest portion differentiated from the normal pinkish colour. As a at the temporal margin on the horizontal meridian result, comments on colour were to restricted recording of the disc. There were no sharp whether the neuroretinal rim was pale or pink. Thinning deviations of any of the neuroretinal rim was far more easily quantitated, retinal vessel where it traversed the disc surface. and ranged from being just noticeable to a complete This type of disc usually had a C/D ratio of less absence of rim tissue with extension of the cup to the than o 5, an optic cup of 'normal' depth (as defined outer disc margin. The size of the arc involved in above), and a visibly intact nerve fibre layer. When thinning ranged from a localized segment (producing a the two optic discs from any patient were highly 'notch') to circumferential thinning of the entire symmetrical, they were considered 'normal'; this neuroretinal rim. latter definition allowed optic discs with a C/D ratio greater than o 5, a sharply deviating retinal DISPLACEMENT OF THE RETINAL VESSELS vessel, or a poorly visualized nerve fibre layer to be Distinction was made between a gradual curve of a included in this normal group.
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