Journal of Neuro-Ophthalmology, September 1993, Volume 13, Issue 3

Amaurotic mydriasis.

Amaurotic mydriasis is characterized by larger than normal pupils in patients with visual loss. In sought to establish whether amaurotic mydriasis can reliably identify different kinds of visual loss and whether this static measurement might prove useful in discerning "balanced" bilateral optic neuropathies where no relative afferent pupillary defect (RAPD) is detected. Patients with binocular pregeniculate visual loss, patients with balanced binocular pregeniculate loss without RAPD, and patients with monocular pregeniculate visual loss had significantly larger pupils than age-matched controls. Although pupils of patients with binocular pregeniculate visual loss (20/50 or better in one or both eyes) were significantly smaller than pupils of age-matched patients with binocular pregeniculate deficits of worse than 20/50 in one or both eyes, no such correlation between Snellen visual acuity and amaurotic mydriasis was found in patients with monocular pregeniculate visual loss. Amaurotic mydriasis is a clinically useful phenomenon that may identify pregeniculate disease in the absence of a RAPD or distinguish pregeniculate from postgeniculate visual loss.

Journal of Clinical Neuro·ophtlzalmology ]3(3): 200-203, 1993. Amaurotic Mydriasis Frederick E. Lepore, M.D. © 1993 Raven Press. Ltd. w York Amaurotic mydriasis is characterized by larger than nor­mal pupils in patients with visual loss. I sought to es­tablish whether amaurotic mydriasis can reliably iden­tify different kinds of visual loss and whether this static measurement might prove useful in discerning "bal­anced" bilateral optic neuropathies where no relative af­ferent pupillary defect (RAPD) is detected. Patients with binocular pregeniculate visual loss, patients with bal­anced binocular pregeniculate loss without RAPD, and patients with monocular pregeniculate visual loss had significantly larger pupils than age-matched controls. Although pupils of patients with binocular pregenicu­late visual loss (20/50 or better in one or both eyes) were significantly smaller than pupils of age-matched patients with binocular pregeniculate deficits of worse than 20/50 in one or both eyes, no such correlation between Snellen visual acuity and amaurotic mydriasis was found in pa­tients with monocular pregeniculate visual loss. Amau­rotic mydriasis is a clinically useful phenomenon that may identify pregeniculate disease in the absence of a RAPD or distinguish pregeniculate from postgeniculate visual loss. Key Words: Monocular pregeniculate visual loss­Monocular postgeniculate visual loss---RAPD-Binocu­lar field loss. From the Department of Neurology. University of Medicine and Dentistry of New JerseylRobert Wood Johnson Medical SchooL New Brunswick, New Jersey, U.S.A. This paper was presented at the 9th meeting of the Interna­tional Society of Neuro-ophthalmology. Williamsburg, VA. June, 1992. Address correspondence and reprint requests to Dr. Frederick E. Lepore. Department of Neurology. UMDNJ/Robert Wood Johnson Medical SchooL One Robert Wood Johnson Place, New Brunswick, NJ 08903. U.S.A. 200 In the mid-eighteenth century, Robert Whytt's observation that "whatever intercepts the rays of light so as to prevent their affecting the retina, or whatever renders this membrane insensible to their action, occasions a preternatural dilation of the pupil" (1), was among the earliest descriptions of amaurotic mydriasis. Amaurotic mydriasis is characterized by larger than normal pupils in pa­tients with visual loss in one or both eyes (2,3). Although confusion has arisen as to whether amaurotic mydriasis is unilateral or bilateral, pu­pillary dilation should be equal in both eyes even when visual loss is unilateral in the vast majority of cases. Anisocoria with relatively greater dilation of the blind eye rarely occurs and implies the combi­nation of an afferent visual pathway defect and a consensual defect (4). I sought to establish whether amaurotic mydri­asis can reliably distinguish visual loss arising from unilateral and bilateral lesions of different portions of the afferent visual pathways. In lesions where amaurotic mydriasis was present I sought to deter­mine whether the pupil behaves as a photometer in which mydriasis increases with greater severity of visual loss. Patients with "balanced" bilateral optic neuropathies were studied to ascertain whether amaurotic mydriasis could identify this subgroup of pregeniculate visual loss in which no afferent pupillary defect could be elicited. Finally, simplicity of technique and the basic equipment of a flashlight and pupil gauge were stressed to make testing for amaurotic mydriasis readily accessible to the clinician. PATIENTS AND METHODS The diameter of maximal pupillary constriction was measured to the nearest 0.5 mm within sev­eral seconds of exposure to a flashlight with a vac­uum bi-pin bulb held apprOximately 15 em from the subject's eye. With the subject fixing on a dis- AMAUROTIC MYDRIASIS 201 TABLE 1. Etiologies of visual loss in 130 consecutive patients tant target, the light beam was directed at the pupil and provided illumination of 5,500 lux in a room with 700 lux ambient illumination. Pupils were measured by this technique in 130 consecutive pa­tients with visual loss demonstrated by Snellen vi­sual acuity of worse than 20/20 or abnormal visual fields by Goldmann perimetry. All patients were referred to a university neuro-ophthalmology practice and were evaluated by the same examiner (F.E.L.) in the same room. Patients were grouped according to the site of visual pathway dysfunction (40 with monocular pregeniculate lesions, 15 am­blyopes with monocular postgeniculate lesions, 53 with binocular pregeniculate lesions, 22 with bin­ocular postgeniculate lesions) (Table 1) and com­pared with 51 age-matched control patients. Etiology Monocular pregeniculate visual loss Unspecified optic neuropathy Multiple sclerosis Traumatic optic neuropathy Ischemic optic neuropathy Neoplasm Papillitis Miscellaneous (aneurysm, central retinal vein occlusion, sarcoid) Monocular postgeniculate visual loss Amblyopia ex anopsia due to Esotropia Exotropia Anisemetropia Congenital ptosis Binocular pregeniculate visual loss Multiple sclerosis Unspecified optic neuropathy Neoplasm Senile macular degeneration Pseudotumor cerebri Ischemic optic neuropathy Trauma Diabetic retinopathy Miscellaneous (nutritional optic neuropathy, macular hypoplasia, papillitis, Leber's congenital amaurosis, retinal detachment, retinitis pigmentosa, ION and SCNVM, syphilitic optic neuropathy, aneurysm, degenerative myopia) Binocular postgeniculate visual loss Cerebrovascular accident Trauma Tumor Arteriovenous malformation Miscellaneous (temporal lobectomy, unknown) No. of patients 16 84 33 3 3 40 6 5 31 15 12 9 6 43333 10 53 10 5 32 RESULTS Monocular Pregeniculate Visual Loss Twenty-five patients with monocular pregenic­ulate visual loss had significantly (p = .004, Stu­dent's t-test unless otherwise stated) larger pupils (3.11 ± 0.47 mm) than controls (2.88 ± 0.46 mm) with an age difference of ~1O years. Eleven pa­tients with visual loss no worse than 20/50 in one eye had no significant difference of pupillary size when compared to age-matched ~8 years' differ­ence) patients with monocular visual acuity worse than 20/50. Similarly no significant difference of pupillary size was present when comparing 10 pa­tients with minor monocular pregeniculate visual field loss (central scotoma equal or less than 10 degrees with I 2 E or brighter target, or peripheral field constriction not within 10 degrees of fixation to I 4 E or larger target, and visual acuity no worse than 20/50) and 10 patients with major monocular field loss (central scotoma greater than 10 degrees, or peripheral field constriction within 10 degrees of fixation, and visual acuity no worse than 20/50). These patients were age-matched with ~11 years difference. Monocular Postgeniculate Visual Loss There was no significant difference in the pupil­lary size of 15 patients with amblyopia ex anopsia and age-matched (~8 years difference) controls. One amblyope had an afferent pupillary defect. Pupil­lary size did not differ significantly in 10 am­blyopes and 10 age-matched (~9 years difference) patients with binocular postgeniculate visual loss. Binocular Pregeniculate Visual Loss Twenty-five patients with binocular pregenicu­late visual loss had significantly (p = .004) larger pupils (3.37 ± 0.80 mm) than age-matched controls with ~11 years' difference (2.96 ± 0.55 mm). Se­verity of visual acuity loss determined the pres­ence of amaurotic mydriasis in patients with bin­ocular pregeniculate visual loss. Fifteen patients with mild visual loss, which was not worse than 20/50 OU, did not have significantly larger pupils than age-matched (~8 years) controls, whereas 15 patients with more severe binocular acuity loss, which was worse than 20/50 in at least one eye, had significantly (p = .0004) larger pupils (3.56 ± 0.95 mm) than age-matched (~1O years) controls (2.80 ± 0.58 mm). Twenty-five patients with no apparent afferent pupillary defect due to symmetrical binocular pre- I Clin Neuro-ophthalmol, Vol. 13, No.3, 1993 202 F. E. LEPORE geniculate visual loss had significantly (p .033) larger pupils (3.06 ± 0.62 mm) than age-matched (:0;;;14 years) controls (2.81 ± 0.53 mm). There was no significant difference in pupillary size of 11 patients with binocular pregeniculate major field loss (defined as central scotoma greater than 10 degrees to the I 2 E or brighter target or peripheral constriction within 10 degrees of fixa­tion to the I 4 E or larger target) and age-matched (:0;;;9 years) patients with minor field loss (defined as central scotoma of :0;;;10 degrees or peripheral constriction not within 10 degrees of fixation). There was no significant difference in pupillary size of 25 patients with binocular pregeniculate vi­sualloss of varying severity and age-matched (:0;;;9 years) patients with monocular pregeniculate vi­sual loss of varying severity. However, pupils were significantly (p = .032) larger (3.68 ± 0.95 mm) in 10 patients with binocular pregeniculate visual loss worse than 20/50 in at least one eye than in 10 age-matched (:0;;;10 years) patients (3.15 ± 0.46 mm) with monocular pregeniculate loss worse than 20/50. Binocular Postgeniculate Visual Loss There was no significant difference in the pupil­lary size of 22 patients with binocular postgenicu­late visual loss and age-matched (:0;;;11 years) con­trols. CONCLUSIONS With this technique, patients with monocular or binocular pregeniculate lesions have demonstrated larger pupils than people with intact afferent vi­sual systems or patients with postgeniculate le­sions. This finding may speak more for the sensi­tivity of the pupillary light reflex to insult than for the sensitivity of this methodology which arbi­trarily employs a non-Maxwellian stimulus, i.e. the light beam is larger than the pupillary aperture, of a single intensity. Measurement of pupillary diam­eter was rounded off to relatively large 0.5-mm increments, and with monocular pregeniculate vi­sual loss the methodology of measuring only di­rectly illuminated pupils created "chimeric" pa­tients with relative miosis of the normal eye and amaurotic mydriasis of the visually impaired fel­low eye. Although data generated by this tech­nique were useful in distinguishing monocular pregeniculate lesions, they sidestep the question as to whether patients with such lesions have larger than normal pupils under conditions of dif­fuse illumination. JGill Neuro-ophthallllof. Vol. 13. No.3. 1993 Can this static measurement of the pupillary light reaction augment the information provided by the widely used swinging flashlight test (5) for relative afferent pupillary defect (RAPD)? The an­swer is affirmative in the special circumstance of balanced binocular pregeniculate visual loss, which precludes a RAPD (6). Amaurotic mydriasis significantly delineates this group when compared to age-matched controls. Even though amaurotic mydriasis may be present in cases undetectable by RAPD, amaurotic mydriasis alone cannot distin­guish unilateral from bilateral pregeniculate dis­ease, except in patients with more severe visual acuity loss. Despite success as a qualitative indicator of pre­geniculate disease, amaurotic mydriasis fared less well as a quantitative indicator. Although amau­rotic mydriasis did correlate with severity of im­paired visual acuity in patients with binocular pre­geniculate visual loss, amaurotic mydriasis did not correlate with severity of acuity loss in patients with monocular pregeniculate lesions or with se­verity of binocular or monocular pregeniculate field loss. In contrast to the RAPD, which is closely related to visual field loss (7), the static measure­ment of amaurotic mydriasis lacks sensitivity to the amount of field loss or monocular acuity loss. In this regard the pupil does not behave as a pure photometer, and additional factors such as level of alertness or retinal/cerebral adaptation to light may obscure a straightforward relationship in which pupils enlarge as pregeniculate visual loss in­creases. Further research is warranted to show whether this poor performance of the pupil as a light meter is akin to the perceptual function of maintaining subjective brightness constancy at the cost of lessened ability to determine absolute amounts of illumination (8). The lack of pupillary photomotor changes in­duced by postgeniculate disease is supported by the absence of amaurotic mydriasis in patients with binocular postgeniculate visual loss and am­blyopia ex anopsia. Amblyopia of sufficient severity to produce a RAPD (9) was present in 1 of 15 pa­tients studied. Whether amaurotic mydriasis is as­sociated with severe amblyopia cannot be deter­mined with this patient population. When age-related variation of pupillary size (10) is accounted for, amaurotic mydriasis is a signifi­cant marker for both monocular and binocular pre­geniculate visual loss. The necessity of establishing an age-matched population of pupillary controls for a given level of illumination is time-consuming, and it is unlikely that amaurotic mydriasis will supplant the RAPD where the patient's sound fel- AMAUROTIC MYDRIASIS 203 low eye is readily available as a control. Neverthe­less, simplicity of method combined with "low­tech" apparatus makes testing for amaurotic my­driasis readily accessible to the clinician, and in the special situation of symmetrical binocular prege­niculate visual loss amaurotic mydriasis may prove particularly useful. REFERENCES 1. Whytt R. An Essay on the Vital and Other Involuntary Motions of Animals. John Balfour, Edinburgh, 1763:128. 2. Walsh FB, Hoyt WF. Clinical Neuro-ophthalmology. Vol. 2. 3rd Ed. Williams & Wilkins, Baltimore, 1969:476. 3. Duke-Elder S. Text-book of Ophthalmology. Vol. 4. CV Mosby, St. Louis, 1949:3746. 4. Thompson HS. Pupillary signs in the diagnosis of optic nerve disease. Trans Ophthalmol Soc UK 1976;96:377-81. 5. Levatin P. Pupillary escape in disease of the retina or optic nerve. Arch OphthalmoI1959;62:768-79. 6. Sadun A. Swinging flashlight test. [Letter}. Neurology 1989; 38:154. 7. Thompson HS, Montague P, Cox TA, Corbett JJ. The rela­tionship between visual acuity, pupillary defect, and visual field loss. Am' Ophthalmol 1982;93:681-8. 8. Hubel DH. Eye. Brain and Vision. Scientific American Li­brary, New York, 1987:56-7. 9. Portnoy J2, Thompson HS, Lennarson L, Corbett JJ. Pupil­lary defects in amblyopia. Am JOphthalmoI1983;96:609-14. 10. Loewenfeld I. "Simple, central" anisocoria: a common con­dition, seldom recognized. Trans Am Acad Ophthalmol Otol 1977;83:832-9. JCli" Neuro-ophlhalmol, Vol. 13. No.3, 1993