Britishjournal ofOphthalmology 1993; 77: 709-712 709 Contrast sensitivity function in Graves' ophthalmopathy and dysthyroid optic neuropathy Br J Ophthalmol: first published as 10.1136/bjo.77.11.709 on 1 November 1993. Downloaded from Maria S A Suttorp-Schulten, Rob Tijssen, Maarten Ph Mourits, Patricia Apkarian Abstract defocus greatly facilitates the process of subjec- Contrast sensitivity function was measured by tive refraction correction, but reduced contrast a computer automated method on 38 eyes with sensitivity at low spatial frequencies may present dysthyroid optic neuropathy and 34 eyes with with normal Snellen acuity. As there are various Graves' ophthalmopathy only. The results degrees ofvisual loss within the group ofpatients were compared with 74 healthy control eyes. with dysthyroid neuropathy, assessment of Disturbances of contrast sensitivity functions spatial vision across the frequency and contrast were found in both groups when compared with spectrum may reveal visual impairment not controls. The eyes affected with dysthyroid readily detected by standard visual acuity optic neuropathy showed pronounced loss of measures. contrast sensitivity in the low frequency range, The contrast sensitivity function has proved a which facilitates differentiation between the useful tool for detecting visual disturbances two groups. when Snellen acuity fails to show comparable (BrJ Ophthalmol 1993; 77: 709-712) dysfunction - for example, in glaucoma,'4 retinal disease,'516 and pterygia." The clinical potential for contrast sensitivity functions has also been Graves' ophthalmopathy is related to thyroid demonstrated in patients with optic neuro- disease and is characterised by oedema and pathies, " 2"02' including dysthyroid optic neuro- infiltration ofthe extraocular muscles and orbital pathy."22 This study compares the contrast tissue. The resulting exophthalmus can cause sensitivity functions of patients with uncompli- damage to the anterior as well as to the posterior cated Graves' ophthalmopathy and patients with regions of the orbit. Exophthalmus per se rarely Graves' ophthalmopathy complicated by dysthy- results in visual loss and when such loss occurs it roid optic neuropathy, to determine the value of is caused by secondary lesions - for example, dry the measurements in distinguishing between the eye, keratopathy, eyelid retraction, and/or two groups. induced astigmatism.' However, if the posterior part of the orbit and optic nerve are affected dysthyroid optic neuropathy can occur with Subjects and methods visual loss. Mechanical compression can precipi- tate optic nerve neuropathy: increased muscle PATIENTS AND SELECTON CRITERIA http://bjo.bmj.com/ volume gives rise to intraorbital pressure at the Included in this study were consecutive patients apex and thereby compresses the optic nerve.` with Graves' ophthalmopathy accompanied by The exacerbated condition of dysthyroid optic dysthyroid optic neuropathy (group I) and with neuropathy is said to occur in less than 10% of Graves' ophthalmopathy only (group II). patients with Graves' ophthalmopathy. 67 All patients underwent a complete ophthalmic Symptoms and signs of dysthyroid optic examination including best corrected Snellen neuropathy include decreased visual acuity, rela- visual acuity, pupillary reflexes, funduscopy, on September 28, 2021 by guest. Protected copyright. tive afferent pupillary defect, oedema ofthe optic proptosis measurement by Hertl ophthal- nerve head, visual field defects, impairment of mometer, ocular motility, Nospecs classifica- colour vision, and abnormal visual evoked tion,23 and assessment of the total eye score.24 responses. The decrease in visual acuity may not Coronal computed tomography (CT) ofthe orbit be dramatic; about half of the patients with was also performed on each patient. Patients with Netherlands Ophthalmic Research Institute dysthyroid optic neuropathy maintain a visual Graves' ophthalmopathy did not undergo visual R Tijssen acuity of 20/40 (05) or more.34 field testing, as no defects were expected. P Apkarian As the symptoms described above are neither Patients suspected of dysthyroid optic neuro- Department of pathognomonic nor invariably present3 4 6'89 the pathy underwent additional visual field examina- Ophthalmology, disorder may remain undiagnosed. However, tion (Rodenstock perimeter). Visual field defects Academic Hospital, because of the potential for irreversible visual were defined as scotomas or enlarged blind spot. Utrecht M Ph Mourits loss, early treatment is important. The treatment Colourvision was not assessed. Each patient gave of first choice in the group of patients with informed consent for participation in the study. Department of neuropathy is surgical decompression or high The diagnosis ofGraves' ophthalmopathy was Ophthalmology, 10 1 Academic Hospital, doses of prednisone. 12 based on standard clinical features and enlarged Amsterdam We have evaluated risk factors and diagnostic extraocular muscles on coronal computed tomo- M S A Suttorp-Schulten methods, including various measures of spatial graphy scan. Several criteria were required for Correspondence to: vision.5"' The standard ophthalmic test of spatial inclusion in group I versus group II. M S A Suttorp-Schulten, Netherlands Ophthalmic vision is the Snellen acuity estimate. In general, Graves' ophthalmopathy complicated by dys- Research Institute, PO Box Snellen acuity yields an estimate ofhigh contrast thyroid optic neuropathy (group I) was diag- 12141, 1100 AC Amsterdam, The Netherlands. and high spatial frequency resolution, both of nosed when apical crowding on coronal Accepted for publication which are readily impaired by simple optical computed tomography scan was present and 31 May 1993 aberration alone. This sensitivity to optical accompanied by one or more of the following 710 Suttorp-Schulten, Tijssen, Mourits, Aplaarian Table I Clinical characteristics ofpatient groups In addition to no signs or positive history of dysthyroid optic neuropathy, for all patients of Group I (Graves' group II, a visual acuity ofat least 20/25 (0 8) also accompanied by Br J Ophthalmol: first published as 10.1136/bjo.77.11.709 on 1 November 1993. Downloaded from dysthyroid optic Group II (Graves' was required. neuropathy) only) Group I consisted of 25 consecutive patients Number ofeyes 39 34 with dysthyroid optic neuropathy (39 eyes); the Number ofpatients 25 17 Male/female ratio 4/21 1/16 mean age was 55 years (range 29-79 years). In 11 Mean patient age patients only one eye could be included; three (years) 55 44 (range) (29-79) (27-69) because of unilateral dysthyroid optic neuro- Visual acuity 20/25 (0-8) 11 eyes 20/20 (1-0) 22 eyes pathy, seven because ofvisual acuity of less than 20/30 (0-6) 17 eyes 20/25 (0 8) 12 eyes 20/40 (0 5) 4 eyes 20/70 (0-3), and one because of amblyopia. 20/50 (0 4) 4 eyes Group II consisted of 17 consecutive patients 20/60 (0 3) 3 eyes Optic nerve head 15 segmental pallor 0 eyes with bilateral Graves' ophthalmopathy and no oedema 8 mild swelling signs of dysthyroid optic neuropathy (34 eyes); 3 marked swelling Total eye score the mean age was 44 years (range 27-69 years). 0-20 20 eyes 33 eyes There was no statistical age difference (Student's 21-30 17 eyes I eye >30 2 eyes 0 eyes t test; p>0. 1) between the two groups. Clinical Visual field characteristics for the two patient groups are No defects 23 eyes not done Defects present 16 eyes summarised in Table 1. Hertl readings 10-15 0 eyes 1 eye 16-20 4 eyes 18 eyes 21-25 31 eyes 13 eyes METHODS >25 4 eyes 2 eyes Relative afferent 3 eyes 0 eyes pupillary defect Stimulus andprocedures Contrast sensitivity function was tested by a computer automated method as described in symptoms: decrease in optimally corrected detail elsewhere.25 Briefly, sine wave gratings Snellen visual acuity of one line or more, a were generated on a computer controlled cathode relative afferent pupillary defect, oedema of the ray tube display unit (Joyce Electronics, Cam- optic nerve head, or visual field defect. For bridge, England). The cathode ray tube was patients with a decrease in visual acuity of only masked with an equiluminant surround. The one line, inclusion in the test group proceeded stimulus field subtended 5 degrees at a viewing only ifthe patient showed one or more additional distance of 228 cm; space average luminance was signs. 300 cd/m2. Contrast thresholds were measured For either group any eye affected with a non- with a computer automated method ofascending related unilateral condition that might influence limits. Contrast was automatically increased at a contrast sensitivity testing was excluded - for rate of 1-75 dB/s. The patient, who was tested example, amblyopia, cataract, and glaucoma. under self paced conditions, triggered the Further, eyes with significant visual loss (less random delay (0 to 5 seconds) for the stimulus than 20/60) were also excluded, as the contrast onset and the subsequent threshold (five sensitivity test in this study was designed to thresholds were measured per spatial frequency). http://bjo.bmj.com/ detect low, medium, and high spatial frequency Stimulus range was 1 to 32 cycles per degree loss; an acuity of less than 20/60 (0-3) would (c/deg) (spatial frequencies 1, 2, 4, 8, 12, 16, and restrict the useful test range-to the lowest fre- 32 c/deg). The test session began with practice quency range only. Patients with a history of trials at a spatial frequency of 4 c/deg. Further, orbital decompression surgery were excluded to before each