Journal of Neuro-Ophthalmology, March 2002, Volume 22, Issue 1

Photophobia in Anterior Visual Pathway Disease

EDITORIAL Photophobia in Anterior Visual Pathway Disease Jonathan D. Trobe, MD In this issue of the Journal ofNeuro- Ophthalmology, Kawasaki and Purvin describe five patients with tumors in the optic chiasm region ( three pituitary adenomas, a craniophar­yngioma, and a clivus chordoma) whose primary symptoms were not headaches or blurred vision, but photophobia ( pp 3- 8). Even ordinary light was too bright for them; it blurred their vision and caused enough discomfort that they took to wearing sunglasses. One patient reported that the Ishihara color plates appeared " too bright." Any physician hearing this complaint would be reasonably tempted to attribute it to an anterior ocular segment inflammation if it sounded like light- induced periocular pain, and to a cone receptor disorder if it sounded like light- induced blurring of vision. Actually, light-induced periocular pain is a nonspecific symptom of ocular or intracranial trigeminal irri­tation. Light- induced blurring of vision (" hemeralopia," or " day blindness"), although typi­cal of outer retinal disturbances, may also occur with affections of the optic nerve and chiasm ( 1). The combination of these two symptoms makes a good fit with perisellar masses because these lesions activate trigeminal afferents in the dura and impair transmission in the anterior visual pathway. Light- induced periocular pain comes principally from irritation- by inflammation, local chemical stimulation, or sudden deformation- of trigeminal endings in the basal middle fossa meninges, particularly those in the diaphragma sellae ( 2,3). The irritated tri­geminal endings become " upregulated" or hypersensitive, so that light in the eye causes pain in the eye. The neural pathways that mediate this phenomenon may not be worked out, but the phenomenon itself is well known in infectious and chemical meningitis, subarachnoid hemorrhage, and migraine ( 2,4). In migraine, sound is as powerful a cause of head pain (" sonophobia") as light, proving that trigeminal hypersensitivity is not limited to a single sensory input. Light- induced pain is not described by patients who have optic neuritis or orbital inflammations, so that irritating the extracranial meningeal coverings of the optic nerves will not do. Similarly, lesions of the portions of the visual pathway outside the reach of trigeminal innervation ( lateral geniculate body, optic radiations) never bring on pain. ( Lesions of the occipital cortex that irritate the adjacent trigeminally innervated meninges often cause pain referred to the ipsilateral eye, but the pain is not light induced.) In the cases reported by Kawasaki and Purvin, the tumors were large enough to distort the basal meninges, especially the richly innervated diaphragma sellae. In two patients, acute light- induced pain probably resulted from deformation of the diaphragma sellae by sudden hemorrhage into a pituitary adenoma (" pituitary apoplexy"). One patient with chronic light- induced pain suffered from acromegaly, a condition in which photophobia and headache are commonly described, even when the tumor is too small to distend the sella. These symptoms often persist in acromegaly after surgical decompression, prompting the theory that the symptoms originate from bone afferents ( 5). What is remarkable about the patients of Kawasaki and Purvin is that light- induced periocular pain preceded or was more prominent than headache. Often reported in meningitis, encephalitis, and migraine, this feature has not been emphasized in perisellar tumors ( 6,7). Departments of Ophthalmology and Neurology, Kellogg Eye Center, University of Michigan, Ann Arbor, Michigan, USA. Address correspondence to Jonathan D. Trobe, MD, Departments of Ophthalmology and Neurology, University of Michigan, Kellogg Eye Center, Ann Arbor, MI 48105, USA; E- mail: jdtrobe@ umich. edu J Neuro- Ophthalmol, Vol. 22, No. 1, 2002 1 Copyright © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited. JNeuro- Ophthalmol, Vol. 22, No. 1, 2002 EDITORIAL Light- induced obscuration of vision, or hemeralopia, the other symptom described by the patients of Kawasaki and Purvin, is a common symptom in albinotics, whose eyes lack the pigment needed to attenuate normal- intensity light, and in cone photoreceptor disorders ( 8), in which cones cannot regenerate enough cyclic guanosine mono­phosphate ( cGMP) to change their resting potentials when exposed to normal- intensity light stimuli ( a failure of " light adaptation") ( 9,10). Many albinotics and cone- dystrophy patients find this dazzling sensation more unpleasant than visually disabling, proving that hemeralopia overlaps with photophobia. A similar complaint, with less noisome prop­erties, is described by patients with any type of optic neu­ropathy ( 1). They are " blinded" in bright light, perhaps be­cause it further degrades their already poor contrast sensi­tivity. Curiously, the patients of Kawasaki and Purvin had relatively subtle optic nerve and chiasmal dysfunction, at least as measured by conventional tests. No wonder, then, that their symptoms were initially considered psychogenic. Psychogenic photophobia may be a specific phobia- an emotionally aversive reaction to vi­sual stimuli. Unlike those with organic illnesses, such pa­tients go to incredible lengths to avoid light exposure- withdrawing from outdoor activities, dimming all the lights in the house, drawing the window blinds, and wearing sev­eral layers of sunglasses. In some cases, bright light is the provocative stimulus; in others, it is intricate or brightly col­ored patterns, or bright objects moving in the peripheral fields. In my experience, many such individuals also have symptoms of anxiety or panic disorder. If there are no or­ganic findings, they should be managed with the desensiti-zation techniques and pharmacotherapy that have been very successful in other phobic disorders. But the paper of Ka­wasaki and Purvin serves as a reminder that a diagnosis of psychogenic photophobia should not be made without seri­ously considering a perisellar mass as the cause of photo­phobia, even if signs of anterior visual pathway dysfunction are subtle or absent. References 1. Safran AB, Kline LB, Glaser JS. Positive visual phenomena in optic nerve and chiasm disease: photopsias and photophobia. In: Glaser JS, ed. Neuro- ophthalmology. Symposium of the Bascom Palmer Eye Institute, Vol X. St Louis: CV Mosby, 1977: 225- 31. 2. Raskin NH. Headache, 2nd ed. New York: Churchill- Livingstone, 1988. 3. Ray BS, Wolff HG. Studies on pain: " spread of pain;" evidence on site of spread within the neuraxis of effects painful stimulation. Arch Neurol Psychiatry 1945; 53: 257- 61. 4. Lance JW, Goadsby PJ. Mechanism and Management ofHeadache, 6th ed. London: Butterworth- Heinemann, 1998. 5. Jenkins JS. Pituitary Tumours. London: Butterworth, 1972. 6. Vance ML. Diagnosis, management and prognosis of pituitary tu­mors. In: Thapar K, Kovacs K, Scheithauer BW, Lloyd RV, eds. Diagnosis and Management of Pituitary Tumors. Totowa: Humana Press, 2001: 165. 7. Hankinson J, Banna M. Pituitary andParapituitary Tumours. Lon­don: WB Saunders, 1976. 8. Krill AE, Deutman AF, Fishman M. The cone degenerations. Doc Ophthalmol 1973; 35: 1- 80. 9. Rando RR. Molecular mechanisms of visual pigment regeneration. Photochem Photobiol 1992; 56: 1145- 56 10. Hart WM Jr. Adler's Physiology of the Eye: Clinical Application, 9th ed. St. Louis: Mosby Yearbook, 1992: 525- 7. 2 © 2002 Lippincott Williams & Wilkins Copyright © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.