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Show Journal of Clinical Neuro- ophthalmology 11( 1): 53- 54, 1991 © 1991 Raven Press, Ltd" New York Pupillary Constriction to Darkness in a Patient with Blue- Cone Monochromatism Warren M. Sobol, M. D., Alan E. Kimura, M. D., Randy H. Kardon, M. D., Ph. D., and H. Stanley Thompson, M. D. A 17 year old male patient presented with bilateral photophobia, poor color vision, visual acuity 20/ 80- 20/ 200, nystagmus, and showed normal fundi. Electroretinography revealed evidence of blue- cone monochromatism. This patient showed constriction of the pupils to darkness or the paradoxic pupillary phenomenon. Key Words: Pupillary constriction- Blue- cone monochromatism- Photophobia- Paradoxical pupil- Achromatopsia. From the Department of Ophthalmology, University of Iowa Hospitals and Clinics, Iowa City, Iowa, U. S. A. Address correspondence and reprint requests to Dr. Sobol at Department of Ophthalmology, C. S. O'Brian Library, University Hospitals and Clinics, Iowa City, IA 52241, U. S. A. / 53 A male patient with bilateral photophobia, poor color vision, visual acuity in the 20/ 80- 20/ 200 range, nystagmus, a normal fundus appearance, and an abnormal cone response on electroretinography most likely has blue- cone monochromatism. It has been postulated that patients with blue cone monochromatism have only one type of functional retinal cones, with a peak sensitivity at 440 nm. Rod function remains intact in these patients, with peak rod sensitivity near 504 nm ( 1). Distinguishing patients with blue- cone monochromatism from those with rod monochromatism or severe cone dystrophies on purely clinical grounds can sometimes be difficult. Studying the inheritance pattern and using specific color plates ( 2) may help to identify the affected patients. In addition, pupillary constriction to " lights off" has been offered as a way of selecting out patients with rod monochromacy (" congenital achromatopsia"). We recently examined a young man with the diagnosis of blue cone monochromacy who showed a definite pupillary constriction to darkness ( Fig. 1). CASE REPORT A 17- year- old male complained of poor color vision and increasing photophobia since early childhood. Past ocular history was significant for mild hyperopic astigmatism, and a fine horizontal nystagmus, which had become gradually less noticeable in the last few years. Best corrected vision was 20/ 80 00 and 20/ 100 as, tested with and without fogging lenses over the contralateral eye for occlusion. The pupil constriction to darkness was visible clinically ( with the help of a handlight from below while the room lights were turned off). Slit lamp examination, eye move- 54 178 171 172 173 W. M. SOBOL ET AL. .; p. l u'" 5 - Light Time ( seconds) I'ghl all Dark 4, ,.../~,,- ~ = V' ."'. 1- OD ~'-+-"'-,\ ,., \ ZoOS - '\ \ FIG. 1. Tracing of paradoxical pupil contra? tion occurring when the light is turned off In patient with blue- cone monochromatism. The constriction to darkness was consistently observed using an infrared video system. ments, and confrontation visual fields were within normal limits. Dilated fundus examination was unremarkable. The patient failed color vision screening using Hardy- Rand- Rittler ( HRR) plates ( errors in 20 of 20 plates), and Farnsworth Munsell 100- hue testing showed errors in all meridians, with relative sparing along the tritan axis ( Error scores: 520, 00 and 660, OS). Color plate testing, as described by Berson et al. ( 2), found the patient able to identify all odd arrows with each eye tested separately. Electroretinography revealed a normal rod response with markedly attenuated cone response to a lightadapted single white flash as well as to 30 Hz stimulation ( Fig. 2). A review of the patient's family pedigree found similar symptoms in two maternal uncles and the maternal grandfather. No male- to- male transmission was evident, consistent with an x- linked mode of inheritance. A trial of photochromic filter lenses resulted in increased visual acuity of approximately one line in each eye tested separately, and two lines with both eyes tested together. DISCUSSION Pupillary constriction to darkness has been reported in numerous conditions, including congen- I Clin Neuro- ophthnlmol. Vol. 11. No. 1. 1991 FIG. 2. Electroretinography illustrating overall preserved scotopic nonattenuated respons~ ( left) and marked attenuation of cone response to flicker 30 Hz stimulation ( right). itaI stationary nightblindness, congenital achromatopsia, bilateral optic neuritis, and domin. ant optic atrophy ( 3). Speculation as to the mechamsm of this phenomenon has centered around abnormalities in the rod bleaching signal ( 4). The varied list of conditions associated with pupillary constriction to darkness has made it difficult to explain this pupillary response and an animal model has not yet been found. Some investigators have noted pupillary constriction to darkness to be a clinically valuable sign in the detection of congenital retinal disease, especially in children with poor vision ( 3,5). It is our hope that by drawing attention to this fascinating pupillary phenomenon in a patient with blue- cone monochromatism we will stimulate others to look for this combination of finding and so settle the question of whether blue- cone monochromacy should be added to the growing list of ocular conditions associated with pupillary constriction to darkness. REFERENCES 1. Alpern M, Lee CB, Spivey B. IT, Cone monochromatism. Arch Ophtha/ mol 1965; 74: 334. 2. Berson EL, Sandberg MA, Rosner B, Sullivan PL. Color plates to help identify patients with blue- cone monochromatism. Am I Ophthk/ mo/ 1983; 95: 741. 3. Frank JW, Kushner BJ, France TD. Paradoxic pupillary phenomenon. Arch Ophtha/ mo/ 1988; 106: 1564. 4. Flynn JT, Kazarian E, Barricks ME. Paradoxical pupil in congenital achromatopsia. Int Ophthalmol 1981; 3: 91. 5. Price MJ, Thompson HS, Judisch CF, Corbett JJ. Pupillary constriction to darkness. Br I Ophthalmol 1985; 69: 205. / |
