swelling of the optic nerve head: staging schemedisc anomalies reminiscent of acquired disc...

Journai of Neurology, Neurosurgery, and Psychiatry 1982 ;45 :13-18

Swelling of the optic nerve head: a staging schemeLARS FRISIEN

From the Department of Ophthalmology, University of Gdteborg, Sweden

SUMMARY A staging scheme based on ophthalmoscopic signs of disturbed axoplasmic transportis described. A study employing fundus photographs showed good reproducibility among differentobservers. Specificity ranged between 880% and 960%, and sensitivity between 930% and 100%.

The sinister implications of swelling of the opticnerve head are well known. Equally well known is anot infrequent uncertainty about the diagnosis.1-3Congenital variants of normal anatomy and burieddrusen of the optic nerve head are often difficultto differentiate from early acquired abnormality.More pronounced degrees of disc swelling areeasier to recognise but correct identification of theunderlying condition often presents problems. Thediagnostic difficulties may in part be attributedto the lack of a detailed terminology for the variouscomponents of the ophthalmoscopic picture. Adetailed scheme of description, for example in theform of a staging scheme, conceivably could facilitateevaluation. Such a scheme should also facilitateidentification of a change in swelling in the individualcase.

Recent experimental,4-7 and clinical and clinico-pathological studiesl 2 8 9 have in different waysilluminated the major role of swelling of axons inthe production of swelling of the optic nerve head.Swelling of axons appears to be a consequence of alocal arrest of axoplasmic transport (see Hayreh'0for a review). It is not specific for raised intracranialpressure but may occur in a large variety of condi-tions. The observations of axonal swelling furnish arational ground for the development of a discswelling staging scheme. Such a scheme will bepresented in the following, together with the resultsof a reproducibility analysis.

A PROPOSED DISC SWELLING SCHEMEThe scheme is built on ophthalmoscopic signsrelated to an increased mass of swelling axons. Itshould be applicable in most conditions causingdisc swelling, except those causing swelling by theoccupation of the nerve head by elements normallyAddress for reprint requests: Dr L Frisen, Ogonkliniken,Sahlgrenska sjukhuset, S-413 45 Goteborg, Sweden.Received 30 May 1981, and in revised form 23 September1981. Accepted 25 September 1981

foreign to the area (for example neoplastic cells).Any vascular components (including venous stasis,hyperaemia, haemorrhages and circumscribed in-farcts) are disregarded during staging as variousaetiologies and individual peculiarities allow for alarge variability in expression.3 4

Experience attests to the great difficulty ofrecognising early swelling of axons within the discitself. It is much easier to recognise a spill-over ofaxonal swelling at the disc border and in the adjacentperipapillary area. Therefore, the first stages dependfor their definition on changes at the disc border.These include decreased translucency of nervefibre bundles, and disruption of their normal,strictly radial arrangement. These changes lead tothe formation of a subtle, grayish, faintly reticulatedhalo that broadens the nerve head and obscuresunderlying retinochoroidal detail. These changesare often best appreciated by ophthalmoscopy inred-free light.' 9 The more advanced stages dependfor their definition on effects of anterior expansionof the swelling tissue. The intervals between suc-cessive stages have been made large enough toprevent influence by any short-term fluctuations inappearance. Stages I and 2 can be held to representearly disc swelling, while Stage 3 signifies moderateabnormality. Stages 4 and 5 represent severe discswelling, and identifies a transitional stage towardsprogressive atrophy. Photographic examples of thevarious stages are given in figs 1-6. The table gives ahighly condensed version of the staging scheme.

Stage 0 A normal optic disc, with blurring of thenasal and temporal disc borders by overlying nervefibre bundles in inverse proportion to the discdiameter (that is little blurring with large discs, andvice versa). The pattern of the peripapillary nervefibre bundles is strictly radial, without axon bundletortuosity. Blurring of the upper and lower poleareas is disregarded because of the large normalvariability. Rarely, a major vessel may be obscured

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Swelling of the optic nerve head: a staging scheme

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Figs 1-6 Flndus photographs exemplifying disc swelling stages 0-5. Magnification 20 x . See text for details.

Table Stages of disc swelling

Stage no Signs

niasal blur temtiporal blur peripheral TO VS* central TO VS* or filled cup smooth dome

234 +

5

*TOVS = total obscuration of major vessel segment(s) by axons.

by overlying nerve fibres at the disc border, usuallyin the upper pole.

Stage I Excessive (in relation to the disc diameter)blurring of the nasal border of the optic disc, withdisruption of the normal radial arrangement ofnerve fibre bundles. The temporal margin remainsnormal at least in the midst of the papillomacularsector. These changes lead to the formation of asubtle grayish halo (usually best appreciated in lowmagnification, indirect ophthalmoscopy) along thecircumference of the optic disc, with a temporal gap.

Stage 2 More pronounced changes than in Stage 1,with elevation of the nasal circumference of the

nerve head, and blurring of all of the temporalmargin. The halo now surrounds the disc completely.Concentric or radiating retinochoroidal folds mayappear in this stage.

Stage 3 More pronounced changes than in Stage 2,with elevation also of the temporal circumference,and a clearly increased diameter of the nerve head.The elevated borders now totally obscure one ormore segments of the major retinal vessels. Thecircumpapillary halo has an irregular outer fringe,with finger-!ike extensions.

Stage 4 More pronounced changes than inStage 3, with elevation of the whole nerve head in

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combination with obliteration of the optic cup, or

compression of the cup to a slit, or total obscurationof a segment of the central retinal artery or vein.

Stage 5 Anterior expansion of the nerve head nowdominates over sideways expansion. The nervehead assumes a relatively smooth, dome-shapedprotrusion, with a narrow and smoothly demarcatedhalo. The major retinal vessels climb steeply overthe dome surface. Segments of these vessels mayor may not be totally obscured by overlying swollentissue.The absence of notes in the staging scheme con-

cerning hyperaemia (or pallor), haemorrhages andso-called cotton wool spots is intentional, and relatesto the considerable variability of these signs betweendifferent pathogenetic conditions, and betweenpatients with one and the same condition. In theindividual case, however, it is highly appropriateto include with the stage number a note about thepresence or absence of each of these signs. Clearly,the more complete the information, the easier is therecognition of both the underlying cause and anychange in the appearance with time.A given disc should be examined in turn for

evidence of abnormality corresponding to Stage 1,Stage 2, Stage 3 and so on. If the signs associatedwith Stage 1 are absent any apparent swelling(even if pronounced) should raise the suspicionthat it is due to other factors than swelling of axons

(for example buried drusen). The use ofmore than onestage number for a given disc is discouraged. Thedefinitions of the various stages should be stringentenough to allow confident classification with theuse of one single numeral.

Reproducibility test methods and results

Three observers (one medical student, one resident inophthalmology, and the author) staged the appearance ofthe optic nerve head in a series of fundus photographs,on two separate occasions. The photographs wereobtained from 12 normal subjects, 12 subjects with opticdisc anomalies reminiscent of acquired disc swelling,and 56 subjects with different degrees of acquired discswelling of known aetiology. All cases had been subjectedto a full neuro-ophthalmological examination by theauthor. Each subject contributed one fundus photograph.These were obtained on colour diapositive film, usuallyat 2 5 x or 3-4 x nominal magnification. All slides werecopied in a Bowens Illumitran camera to obtain slidesfor projection with a uniform degree of magnification(5 x ). The coded slides were mixed and projected one at atime in an ordinary slide projector, and assigned a stagenumber without access to clinical information. Thestaging procedure was repeated for each of the threeexaminers with an interval of at least four weeks.

All the observers commented upon the difficulty ofunequivocally recognising elevation of the disc borders in

Frisen

some slides. This is inherent in the procedure used here:it could have been avoided only by using stereophoto-graphy. The poor depth of focus in fundus photographsalso created some difficulties. It can be expected that theseproblems will be much reduced in clinical ophthalmo-scopy, where parallactic cues and adjustment of focuscan be utilised.Two slides from patients with acquired disc swelling

were deleted from the analysis because of pronouncedvariability in scoring between and within the observers.The variability was thought to be due to the limitationsof fundus photography. For the remaining 78 slides,the reproducibility was fairly good (fig 7). In the re-test

5 h * * ~5 * * 5 * p

4 4 ~~~~~~~~~~~43 3 ~~~~~~~~~~~~3

2 .2.. - 2 .1

X2 L ~~~~1dg 1 i

1 2 3 4 5 1 2 3 4 5 1 2 3 4 5Test medical student Test resident Test specialist

Fig 7 Reproducibility for three different observers, whostaged the same fundus photographs for disc swellingon two separate occasions. Each dot represents onephotograph. The diagonals represent identity of stagenumbers on test and re-test.

the two senior observers gave exactly identical scoresfor four-fifths of the slides, and changed the score morethan one unit only once. The junior observer had greaterdifficulties, particularly with congenitally anomalousoptic discs. Nevertheless, exactly the same scores weregiven in three-fourths of the cases in the re-test, and adifference of one score emerged in one-fifth.The degree ofagreement between the different examiners

was analysed only for the re-test data. There was exactagreement in 49% of the slides, and a difference ofmaximally one unit in 86 %. In two instances the causeof larger differences was difficulty for the junior examinerin recognising anomalous optic nerve heads; the remain-ing differences were fully explained by failure by one ormore of the observers to adhere to the details of thestaging scheme.The most important aspect of erroneous classification

pertains to falsely positive or falsely negative diagnosesof acquired optic disc swelling. There was full agreementbetween the observers in 22 cases about a score = 0.An additional five slides were scored 0 by at least oneobserver: two of these cases had other clinical findingscompatible with acquired disease. Conversely, threecases thought to be completely normal in a full neuro-ophthalmological examination were given score I by atleast one observer. One of these cases had an optic discanomaly misinterpreted by the junior observer. The othertwo cases were erroneously diagnosed as acquired discswelling by failure to adhere to the details of the classifi-cation scheme. For the three observers, the specificity(defined as the fraction of normals correctly classified)ranged between 88 and 96 %, and the sensitivity (fractionof abnormals correctly identified) between 93 and 100%.



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Swnelling of the optic nwerve head: a staging scheme

Discussion

There are many obstacles to the construction of ameaningful scheme for the staging of disc swelling.Major difficulties concern the lack of an establishedterminology for the various components of theophthalmoscopic picture, and the very considerablevariability between individuals with respect tonormal morphology. There are many normalvariants which create problems, particularly in therecognition of early acquired abnormality. Suchvariants include the "crowded disc" (the smalldiameter optic nerve head where nerve fibre bundlesare tightly crowded at the disc border), discs withvery small cup/disc ratios, discs with unusualbranching patterns of major vessels, and discs withprepapillary membranes or ectopic patches ofmyelin. 3 The most important normal variableinfluencing upon the evaluation of disc swelling in agiven case appears to be the diameter of the scleralopening: eyes with small scleral openings tend tohave considerably more blurring of the disc marginsby overlying nerve fibres than do eyes with largescleral openings.1' Similar degrees of axonal swellingmay therefore result in different degrees of nervehead swelling (cf figs 8-1 1). The evaluation andaccurate staging of swelling of the optic disc

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obviously requires considerable attention to detail,and knowledge of normal variants which maymodify the picture in the given case. High magnifi-cation ophthalmoscopy'2 and refined fundus photo-graphy13 are often helpful in the evaluation of finedetails. The value of fluorescein angiography may bemore debatable.4 The presence or absence of burieddrusen can be proved by computed tomography.14

Optic nerve heads which have lost axons throughascending or descending degeneration obviouslycannot show equally pronounced swelling as normalnerve heads when axoplasmic transport isdisturbed.4 9 15 This limitation applies not only forpatients with ordinary acquired optic atrophy butalso for patients with congenital optic nerve hypo-plasia or drusen of the optic nerve head.9 Recogni-tion of early disc swelling in such cases is oftenexceedingly difficult also for experienced examiners.

Traditional ways of assessing disc swelling bybroad categorisation, ophthalmoscopic measure-ment of the degree of protrusion, counting thenumber of small vessels crossing the disc margin,and ascertaining the presence or absence of spon-taneous venous pulsations, appear to have poor re-liability.16 Clearly, it must be better to concentrateon direct signs of the most important element ofpathology, that is axonal swelling, as done in the

Fig.8 Fig. 9

Figs 8 and 9 Examples of Stage 1 disc swelling in eyes with large diameter nerve heads. 20 x .



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Fig. 10 Fg-11Figs 10 and 11 Examples of Stage 2 disc swelling in eyes with small diameter nerve heads. 20x.

proposed staging scheme. By focusing attention on

fine ophthalmoscopic details the scheme shouldalso be of aid in the differentiation of innocuousnormal variants from optic nerve heads withacquired disease. On the other hand, the schemecannot by itself improve differential diagnosisamong the multitude of conditions which may cause

swelling of axons. Aetiological diagnosis requiresadditional information.3

References

Hoyt WF, Knight CL. Comparison of congenital discblurring and incipient papilledema in red-free light-a photographic study. Invest Ophthalmol 1973;12:241-7.

2Cogan DG, Kuwabara T. Papilledema. Exp Eye ResSuppl 1977;25:419-33.

3Wirtschafter JD. Apparent enlargement of the opticdisc: a pathogenetic approach to diagnosis. PerspectOphthalmol 1977;1:274-303.

4Hayreh SS. Optic disc edema in raised intracranialpressure. V. Pathogenesis. Arch Ophthalmol 1977;95:1553-65.

5 Wirtschafter JD, Slagel DE, Foxx WJ, Rizzo FJ.Intraocular axonal swelling produced by partial,immediately retrobulbar ligature of optic nerve.

Invest Ophthalmol 1977;16:537-41.6 McLeod D, Marshall J, Kohner EM. Role of axo-

plasmic transport in the pathophysiology of ischae-

mic disc swelling. Br J Ophthalmol 1980;64 :247-61.7 Quigley HA, Addicks EM. Chronic experimental

glaucoma in primates. Invest Ophthalmol Vis Sci1980;19:137-52.

8 Tso MOM, Fine BS. Electron microscopic study ofhuman papilledema. Am J Ophthalmol 1976;82:424-34.

9 Frisen L. Ophthalmoscopic evaluation of the retinalnerve fibre layer in neuro-ophthalmologic disease.In: Neuro-ophthalmology, Focus 1980. Smith JL, ed.New York: Masson, 1979:53-67.

10 Hayreh SS. Fluids in the anterior part of the opticnerve in health and disease. Surv Ophthalmol 1978;23:1-25.

Frisen L, Holmegaard L. Spectrum of optic nervehypoplasia. Br J Ophthalmol 1978 ;62 :7-15.

12 Frisen L. High magnification direct ophthalmoscopy.Am J Ophthalmol 1978;86:272-3.

13 Frisen L. Photography of the retinal nerve fibre layer:an optimised procedure. Br J Ophthalmol 1980;64:641-50.

14Frisen L, Scholdstrom G, Svendsen P. Drusen in theoptic nerve head. Verification by computerizedtomography. Arch Ophthalmol 1978;96:1611-4.

15 Paul TO, Hoyt WF. Funduscopic appearance ofpapilledema with optic tract atrophy. Arch Ophthal-mol 1976;94:467-8.

16 Hedges TR. Papilledema: its recognition and relationto increased intracranial pressure. Surv Ophthalmol1975 ;19 :201-23.

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