British Journal of Ophthalmology, 1980, 64, 613-617

Loss of contrast sensitivity followingcontusional eye injuryY. CANAVAN AND D. B. ARCHERFrom the Department of Ophthalmology, the Queen's University of Belfast, and theEye and Ear Clinic, Royal Victoria Hospital, Falls Road, Belfast

SUMMARY Contrast sensitivity was evaluated in 95 patients who regained a visual acuity of 6/6following a contusional injury to one eye. The injuries occurred 2 to 12 years prior to examination.A book of printed sinusoidal grating patterns of varying contrasts and spatial frequencies wasused, and 15 patients were found to have a significant difference in contrast sensitivity betweeninjured and uninjured eye. Eight patients had abnormalities of the media or fundus, and in 2 patientsamblyopia was probably a factor. Five patients had a defect in contrast sensitivity in their injuredeye, although no structural abnormalities could be detected on full clinical examination. Alterationsin contrast sensitivity appeared to be a sensitive indicator of functional abnormality in eyes whichappeared normal on ophthalmoscopy and other clinical investigations.

Contrast sensitivity is an important and measurableparameter of visual function, although its anatomi-cal and physiological basis has yet to be fullyexplained. Loss of contrast sensitivity may occur incertain ocular disorders where there is no detectablealteration in visual acuity or field and where nostructural abnormalities of the eye can be identified.Bodis-Wollner1 described loss of contrast sensitivityin patients with intracranial lesions and normalvisual acuity, and Sjostrand and Frisen2 notedsignificant loss of contrast sensitivity in patientswith macular disease accompanied by only minimalloss of central visual functions. Patients withamblyopia3 or myopia and astigmatism4 may alsodemonstrate loss of contrast sensitivity.

Arden,. in 1978, described a simple technique forthe clinical measurement of contrast sensitivity. Hetransferred a selection of 6 sinusoidal grating pat-terns of varying contrast and spatial frequency onto paper and produced a book which could be usedrapidly and easily in the clinical evaluation ofpatients. The book was loose-leaf and each pagewas enclosed and protected by a plastic folder. Eachtext contained six sheets exhibiting sinusoidalgrating patterns (plates 2-7), each sheet illustratinga grating of specific spatial frequency and designedto be read at 57 cm. The contrast on each plateincreased progressively from subthreshold (uniform

Correspondence to Professor D. B. Archer, Department ofOphthalmology, Royal Victoria Hospital, Belfast BT12 6BA.

grey appearance) to higher and higher contrastareas. An arbitrary scale placed at the side of eachplate facilitated the numerical recording of thepatient's threshold position.Arden and Gocukoglu6 reported on 57 patients

with retrobulbar neuritis (with or without other signsof multiple sclerosis) and found that the gratingtest highlighted abnormalities in contrast sensitivityin affected as well as unaffected eyes. They foundthat the abnormalities in contrast sensitivity thres-holds compared favourably with electrophysio-logical testing as a technique to evaluate abnormali-ties of visual functions in such patients. Arden andJacobson7 determined that the grating test was alsoof value in screening patients for glaucoma. Patientswith glaucoma gave higher test scores than thenormal range of the population and their loss ofcontrast sensitivity corresponded to the severity ofthe disease. Patients with ocular hypertension alsodemonstrated abnormal contrast sensitivity, furtherenhancing the effectiveness of this test as a screeningprocedure for glaucoma.

This paper reports an investigation of contrastsensitivity in 95 patients who suffered a contusionalinjury to the eye but who regained a visual acuityof 6/6 or better in the injured eye.

Materials and methods

In a recent survey8 of 1063 patients with contusional(nonperforating) eye injuries of sufficient severity to

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necessitate hospital admission it was found that 431(40 5%) regained a visual acuity of 6/6 or betterand were asymptomatic. Ninety-five of these patientswere available for review, which was carried outbetween 2 and 12 years following injury. Thepatients' ages ranged from 10 to 75 years with anexpected predominance in young adulthood.

Twenty-eight of the 95 patients were found tohave no detectable structural abnormalities of theeyes on full ocular examination. Sixty-seven patientshad significant structural alterations, of which themost common was recession of the anterior chamberangle. Fourteen patients had additional signs ofanterior segment trauma including pupillary sphinc-ter tears, iridodialyses, and localised lens opacities.Twelve patients were found to have lesions of theposterior segment of the eyes, the most commonbeing retinal pigment epithelial alterations, smallchoroidal tears, or breaks in Bruch's membrane inthe posterior and equatorial fundus.

Contrast sensitivity studies were carried out inthis group of patients using the book of gratingpatterns and the technique advocated by Arden.5Each eye was tested in turn, the other eye beingcovered. The injured and noninjured eyes weretested in a random fashion and appropriate readingspectacles used in those patients who requiredthem. The patients were positioned at a table andthe plates were scrutinised at a reading distance of57 cm under indoor lighting conditions along witha near-by desk lamp (60W bulb). The procedurewas explained to the patient and one practice testwas allowed. Each plate (2-7) was then read inturn, the plate being covered by a card whichrevealed only the subthreshold contrast, so that thepatient appreciated only a uniform grey area. Thecard was then withdrawn slowly revealing higherand higher contrasts until the grating patternbecame visible to the patient. The scale reading atthis position was recorded, and the procedure wasthen repeated for each of the 6 plates and the scalereadings for each plate indicating the contrastthreshold summated to give a score.The procedure was then repeated for the second

eye. A difference of 10 or more between the scoresfor the 2 eyes was considered significant, indicatingan abnormality of contrast sensitivity in the higherscoring eye.

Results

Of 95 patients reviewed 15 had significant loss ofcontrast sensitivity in the injured eye (i.e., a differ-ence of more than 10 in the scores between theinjured and uninjured eye). The score value differ-ence between the 2 eyes ranged from 10 to 25 +

Table 1 Analysis of 15 patients with significant loss ofcontrast sensitivity in injured eye

Patientnunmber

2

3

4

5

6

7

8

9

10

Distance vision(with glasses ifhabitually worn)

6/6

6/6

6/6

6/6

6/6

6/6

6/6

6/6

6/6

6/6

11 6/6

12

13

6/6

6/6

14 6/6

15 6/6

Grating scoredifferencebetween injureduninjured eyes

100

10-5

10-5

11-5

16-0

14-5

16-0

10-0

10-0

10.5

11-0

11-5

240

245

25-0 +

(Table 1). Patients 1 to 5 showed

Clinicalexamination ofthe injured eye

Normal

Normal

Normal

Normal

Normal

? Amblyopia

? Amblyopia

Lens opacities

Choroidal tears

Lens opacities

Sector opticAtrophy

Choroidal tears

Repaired retinalDetachment

Optic discPallor

Choroidal tears

significant loss ofcontrast sensitivity in the injured eye, though theywere asymptomatic and had a corrected visualacuity of 6/6 or better. No physical abnormalitieswere detected on detailed ocular examination inthis group to account for the discrepancy. Similarfindings were noted in patients 6 and 7, but theinterpretation of results was complicated, as patient7 had a small intermittent divergent strabismus inhis injured eye. The latter patient was unaware ofthe strabismus, and it was not possible to ascertainwhether it predated the injury. Patient 6 also had asquint treated in childhood, but no significantdeviation was noted on clinical evaluation.

Patients 8 to 15 were also found to have significantdefects of contrast sensitivity in their injured eyes,but all patients in this group had structural abnor-malities in the injured eyes which could have hadan effect on contrast discrimination. Patients 8 and10 had anterior and posterior cortical lens opacitiesrespectively in the region of near-by iris tears orareas of iris atrophy. Three patients, 9, 12, and 15,had areas of retinal pigment epithelial atrophy orproliferation and areas of choroidal atrophy usuallyassociated with 'choroidal tears'. In patient 9 only

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Loss of contrast sensitivity following contusional eye inj

a small localised area of retinal pigment epithelialand choroidal atrophy was present (Figs. 1, 2), butin cases 12 and 15 complex retinal pigment epithelialand choroidal degenerative changes were present in

Wiry 615

the region of the posterior pole of the fundus (Figs.3, 4). Patients 11 and 14 had significant opticatrophy. Patient 14 had moderate pallor of theoptic disc, while in patient lIthe atrophic changes

Nom: .....r-t^-M ........... OD 1% D.t#.: !2................. 9.4 .3 .R.U .............. Diagn.: ...........................Visus: .................. ...............................

............................. r ............ 0 vio

Fig. 1 Right fundus photograph ofpatient 9 showing3 small areas of retinal pigment epithelial and choroidalatrophy involving the superior papillomacular region.

Fi.nf2ld: C t v u f (T o pt indecationsnsurnounding: \/\_...............................b.. ab..............................

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Fig. 2 Central visualfield (Tiubinger) ofpatientshown in Fig. I demonstrating inferotemporalconstriction of the visual field in the 5° and 10° isoptres.

Nom: OD OS.W.Z17...

V'sus: .............................

.............................

Fig. 3 Right fundus photograph ofpatient 12demonstrating extensive patchy atrophy of the retinalpigment epithelium and choroid involving a sectorinferior to the optic disc.

Dat- ... .7...D,agn .............................................

U feld: 4 C t vu fe (Tudcatiire.

shownsning:.F3e l g c a n e

Figt sueior field.The.fvt...ea.is.sp.......................................I.......I.... . ...No. 5563 Prlr+tee ,nGcrmar,y

Fig. 4 Central visualfield (Tuibinger) ofpatientshown in Fig. 3. Several large scotomata involve theright superior field. The fovea is spared.

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Y. Canavan anldc D. B. A ic/icr

I1 LG,5E.......................... 9 1 .6 .4 55 ....

V,sus: .............................-

Fig. 5 Right fundus photograph ofpatient 11demonstrating atrophy of the inferotemporal margin ofthe optic disc. Wrinkles in the internal linmiting menmbratneradiate from11 the telnporal part of the disc and nervefibre str-iatiolis are absent in the inferior retina.

were localised to an inferior sector of the right opticdisc and associated with a superior altitudinalvisual field defect (Figs. 5, 6).

Patient 13 developed a localised rhegmatogenousretinal detachment following injury and subse-quently had an encirclement procedure to reattachthe retina. This patient subsequently developed a

diffuse retinal pigment epithelial disturbance overthe superior half of the right fundus.

Discussion

Prolonged observation of a high-contrast gratingreduces the visibility of a low-contrast grating ofequal spatial frequency; however, sensitivity togratings of other spatial frequencies remainsunaffected.9 1) Campbell and Robson"1 suggestedthat within the nervous system there exist linearlyoperating, independent 'channels', selectively sensi-tive to limited ranges of spatial frequencies. Thus,one channel could be inactivated by adaptationwhile other functions remain unaffected. Highspatial frequencies must be received at the foveaand the retinal periphery is probably receptive tolower frequencies. It is therefore likely that contrastsensitivity is affected in the presence of eitherperipheral or central retinal pathology.5 The abilityto see low spatial frequency gratings is not limitedby the refractive properties of the eyes. Difficultiesin perceiving high frequency gratings, however, may

OD C DJ't 7.1D.agn* ......................-

f-dg

h,ati............N.6..oFFxainG.0,,,_,.......................... ....................................................... N.. 5563 ... ntc<J ,fGc,. mar,:

Fig. 6 Central visual field (Tiibinger) ofpatientshown in Fig. 5. There is a superior altitudinal fielddefect, but the fovea is spared.

be attributable to a refractive error; therefore,difficulty with low frequency gratings identifiedpatients suffering from a pathological condition.5Until recently evaluation of contrast sensitivity hasremained a laboratory investigation, most workersusing oscilloscopic or televised displays. Thesemethods were not suitable for clinical use, beingexpensive and difficult to transport. The develop-ment of a book of printed sinusoidal patterns hasbeen a useful advance in testing contrast sensitivityin the clinical situation. The test is easily transportedand rapidly performed. Patients in all age groupsfind the test relatively easy to understand, and apractice run using one plate is generally all that isrequired. Younger patients tend to see the gratingpattern more quickly than older patients and hencehave lower average scores. The test is thereforeparticularly useful in comparing right and left eyesof one patient and it is more difficult to compareresults from patient to patient. There are certainvariations in results depending on the observer'stechnique, and it is preferable that all tests in onestudy be carried out by one person, as was the casein this survey.The Arden grating test in this particular investiga-

tion was reliable and reproducible, and only 2 falsepositive results occurred in 95 patients investigated.In I patient there was a marked and unexplaineddiscrepancy in the scores between the 2 eyes, theuninjured eye having the higher score. A second

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Loss of contrast sensitivity following contusional eye injury

patient who also had a significantly higher score inthe uninjured eye gave a definite history of squintand amblyopia in this eye which could haveaccounted for the discrepancy.

This investigation has established that themajority of patients who regained a visual acuityof 6/6 after contusional eye injury have no significantdifferences in contrast sensitivity in the injured anduninjured eyes. Fifteen patients, nevertheless, inthis survey (14%) showed a significantly raisedscore (greater than 10) in the injured eye on testingwith the Arden gratings. Eight of these patients hadwell-defined structural abnormalities of either themediae or fundi which undoubtedly contributed tothe defect in contrast sensitivity. In general themore severe the structural abnormality of the eyethe more marked was the difference in contrastsensitivity score between the normal and injuredeyes. Injuries associated with impaired visual acuityshowed correspondingly severe diminution incontrast sensitivity in the affected eye.8

It is significant that 2 patients with early anteriorand posterior cortical lens opacities secondary totrauma also showed loss of contrast sensitivity inthe affected eye. This observation has been madepreviously by Arden5 and explains why patientswith early lens opacities of any aetiology maycomplain of visual disturbances which seem out ofproportion to a visual acuity of 6/6. In 2 furtherpatients there were definite defects in contrastsensitivity in the injured eye where amblyopia wasprobably the contributory factor. Patients 1 to 5are particulaly instructive as they showed gratingscore differences of 10 to 16 between the injured anduninjured eyes in the presence of a normal visualacuity and absence of symptoms. The only structuralabnormality detected in these patients was a milddegree of anterior chamber angle recession which

was not considered clinically significant. Contrastsensitivity testing therefore appears to be a sensitiveindicator of functional abnormality in an eyejudged to be normal using other clinical parameters.

We are grateful to the Eastern Area Health and SocialServices Board for providing a research grant from theendowment fund of the Royal Victoria Hospital to facilitatethis project.

References

1 Bodis-Wollner I. Visual acuity and contrast sensitivityin patients with cerebral lesions. Science 1972; 178:769-71.

2 Sjostrand J, Frisen L. Contrast sensitivity in maculardisease. Acta Ophthalmol (Kbh) 1977; 55: 507-14.

3 Hess RF, Howell ER. The threshold contrast sensitivityfunction in strabismic amblyopia: evidence for a twotype classification. Vision Res 1977; 17: 1049-55.

4 Fiorentini A, Maffei L. Spatial contrast sensitivity ofmyopic subjects. Vision Res 1976; 16: 437-8.

5 Arden GB. The importance of measuring contrastsensitivity in cases of visual disturbance. Br J Ophthalmol1978; 62: 198-209.

6 Arden GB, Gocukoglu AG. A simple clinical test ofcontrast sensitivity demonstrates unsuspected visuallosses in patients with minimal demyelinisation of theoptic nerve. Arch Ophthalmol 1978; 96: 1626-9.

7 Arden GB, Jacobson J. A simple grating test for contrastsensitivity: preliminary results indicate value in screeningfor glaucoma. Invest Ophthalmol 1978; 17: 23-32.

8 Canavan Y. A ten year retrospective survey of eyeinjuries in Northern Ireland (1967-1976) with particularreference to blunt injury of the globe. Thesis submittedfor the degree of Doctor of Medicine, Queen's Universityof Belfast, 1979.

9 Blakemore C, Campbell FW. Adaptation to spatialstimuli. J Physiol 1969; 200: l P- 13P.

10 Maffei L, Fiorentini A, Bisti S. Neural correlate ofperceptual adaptation to gratings. Science 1973; 182:1036-8.

11 Campbell FW, Robson JG. Application of Fourieranalysis to the visibility of gratings. J Plhysiol 1968;197: 551-66.

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