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Show Journal of Clinical Neuro- ophthalmology 10( 4); 266- 270, 1990. Color Vision Defect as First Symptom of Progressive Cone- Rod Dystrophy Maija I. Mantyjarvi, M. D. © 1990 Raven Press, Ltd., New York A IS- year- old girl complained of color vision difficulties and was found to have an acquired color vision defect with no other abnormalities in the eyes. After 9 years, in addition to the color vision defect, there was gradual loss of visual acuity in both eyes, small central scotomas in the visual fields, elevation of the cone and rod thresholds in the dark adaptation, and decreased response in the photopic and scotopic electroretinogram. The diagnosis of a progressive cone- rod dystrophy was made. It is unusual for cone- rod dystrophy to begin with a distinct color vision defect only; the case report is presented. Key Words: Cone- rod dystrophy- Color vision- Dark adaptation- Visual fields- Electroretinogram. From the Department of Ophthalmology, University of Kuopio, Kuopio, Finland. Address correspondence and reprint requests to Dr. Maija I. Mantyjarvi at Department of Ophthalmology, University of Kuopio, Kuopio, Finland. This study was supported by the Finnish Eye Foundation. 266 Progressive cone- rod dystrophy is a hereditary eye disorder that usually begins in the first or second decade of life. The first symptom is most often gradual loss of visual acuity followed by photophobia and defects in color vision. At the beginning of the disease, no abnormal changes in the retina can be seen. Later in the course of the disease, the eye grounds can show macular bull's eye formation, diffuse pigmentary clumping in the macular area, attenuation of retinal vessels, and temporal pallor in the optic disc. The visual fields often show a central scotoma. In the color vision, a red- green defect and/ or a blue- yellow defect and later in the disease complete achromatopsia has been described. In the dark adaptation, abnormal or no cone threshold can be found. The rod threshold can be normal or slightly elevated ( 1,2). In the electroretinogram ( ERG), the photopic response is greatly reduced or abolished. If only the macular cones are affected, the ERG can still be normal. The scotopic response in the ERG can be normal or slightly affected ( 2,3). The heredity of the disease has been described as autosomal recessive ( 2,4), autosomal dominant ( 5- 7), or x- chromosomal recessive ( 8- 10). In the Outpatient Department of the Eye Clinic at the University Central Hospital in Kuopio, an acquired color vision defect was detected in a ISyear- old girl with no other abnormal findings in the eyes. Nine years later, her visual acuity began to decrease and progressive cone- rod dystrophy was diagnosed. This case of progressive cone- rod dystrophy with color vision defect as the first symptom is presented. CASE REPORT The patient was a IS- year- old girl who was sent to the eye examination because of difficu1! s in color vision. At the first eye examination in - 9, PROGRESSIVE CONE- ROD DYSTROPHY 267 her visual acuity was normal ( 20/ 15) in both eyes with and without correction of the refraction: cyl + 0.25 x 90° in the right eye, + 0.25 cyl + 0.25 x 90° in the left eye. No phorias or tropias could be found, the media in both eyes was clear, and the fundi were normal. She had no photophobia. The visual fields were normal with the Goldmann perimeter ( Haag- Streit, Bern, Switzerland). The dark adaptation was examined with the Della Casa equipment ( Haag- Streit) and was reported slightly subnormal. The color vision was examined with the Hardy- Rand- Rittler ( HRR) pseudoisochromatic plates ( 11) and with the Panel D 15 test ( 12). In the red- green part of the HRR test, she only made mistakes in two of the four screening plates, and all of the diagnostic plates were correctly seen. In the blue- yellow part, she made mistakes in two screening plates and in one of the four diagnostic plates. In the Panel D 15 test, a distinct blue- yellow ( tritan) defect was observed ( Fig. 1). At that time, the ERG examination was not available, so no definite diagnosis could be presented. The evident acquired color vision defect ( both red- green and blue- yellow color vision affected) and the doubt of a subnormal dark adaptation brought to mind a possible early cone- rod dystrophy, and an observation was recommended. It was not until nine years later, in 1988, however, when she came to the next eye examination. In addition to the color vision difficulties, she had noticed for a couple of months a gradual loss of visual acuity in both eyes. The eye examination revealed a visual acuity of 20/ 30 in the right eye and 20/ 40 in the left eye. The refraction was the same as before, and the correction of the refraction did not improve the visual acuity. The media was clear and the fundi normal. She did not have photophobia. In the visual fields, a small central scotoma of 5° in both eyes was detected with the Humphrey automatic perimeter ( Humphrey Instruments, San Leandro, CA, U. s. A.). The dark adaptation with the GoldmannWeekers adaptometer ( Haag- Streit) showed in both eyes an elevated cone threshold of 1.0 log units and an elevated rod threshold of 1.2 log units from the upper normal limits. The patient had not noticed any trouble in her night vision, however The Neurophysiology Laboratory of the University Central Hospital in Kuopio performed the ERG examination according to the guidelines of American Electroencephalographic Society ( 13) and reported that cone and rod responses in both eyes were significantly decreased ( Fig. 2). In the color vision, she did not see any of the red- green or blue- yellow figures of the Standard Pseudoisochromatic Plates part 2 test ( 14). The result in the Panel D 15 test was almost exactly the same as 9 years before ( Fig. 1). The Nagel anomaloscope ( Schmidt & Haensch, Berlin, FRG) examination showed an enlarged matching range in both eyes ( 9 scale units in the right eye, 24 scale units in the left eye), and shifting to red in the right eye ( pseudoprotanomalia, anomalous quotient 0.6). In the FarnsworthMunsell 100- hue ( FM lOO- hue) test ( 15), the error score was above the normal age- corresponding upper limit ( 16), 397 in the right eye and 437 in the left eye. In addition, a blue- yellow axis ( 17) could be found in both eyes ( Fig. 3). According to all of these findings, a progressive cone- rod dystrophy was diagnosed. The nearest family of the patient consisted of her parents and her older brother. They and the other relatives were reported healthy and had no eye trouble. No consanguinity was known in the parents or in the grandparents of the patient. A family study will follow. DISCUSSION The progressive cone dystrophies can be divided in different stages. The defect can only involve the 8 7 6 , 3 ' 4 s 2 I , I , I z.' I Z .( 1 1 « 1- 1 ,..- 0, ,':' « , ~ 0..,. 10 ' .' "" 8 " 6 s 12 11 12 II FIG. 1. The result of the Farnsworth Panel 0 15 test in the right eye: in 1979 ( left) and in 1988 ( right). 14 JClin Neuro- ophthalmol, Vol. 10, No. 4, 1990 M. I. MANTYjARVI A 500jJV A 44ms 33ms - 20jJV - 1 OjJ V B B 76ms 73ms 11 OjJ V 420jJV - 300 300jJV 67jJV - 200 - 100 200JlV - 200 200jJV 268 50 100 150ms 50 100 150ms FIG. 2. In 1988, the ERG of the right eye of the patient ( top and bottom, left), and a normal ERG ( top and bottom, right). The upper curves represent the ERG response of the dark adapted eye to a dim blue flash, 0.5/ s ( rod response; the normal value of B- wave amplitude in the Neurophysiology Laboratory of the University Central Hospital in Kuopio: 418 uV ::':: 84, SD). The lower curves represent the ERG produced by a high intensity white flash, 30/ s ( cone response; normal amplitude: 147 uV ::':: 24). central cones ( central cone disease), peripheral cones ( peripheral cone disease), or both ( diffuse cone disease). In many cases, the rods are also deficient but the symptoms related to cone impairment are always predominant. It is also possible that in the progression of the disease, all the stages starting from central cone dysfunction until the generalized cone- rod dysfunction can be passed ( 1,2,9,18). In this case, the patient most probably has a diffuse cone disease and an additional involvement of the rods confirmed by the photopic and scotopic ERG responses. In 1979, the cones were already affected because of the distinct defect in the color vision. The rods may also have been affected; the Della Casa dark adaptation was reported slightly subnormal. The type of the color vision defect in progressive cone- rod dystrophy has been described as Verriest ". --- ~~~~~ ! , "'-----~~ .~ , ---- I' FIG. 3. The result of the Farnsworth- MunseI1100- hue test in 1988. Left, right eye test; right, left eye test. ~ 1' 190 PROGRESSIVE CONE- ROD DYSTROPHY 269 type I red- green defect ( 3,19), or a blue- yellow defect or both together. In addition, a total achromatopsia has been observed ( 1,2). The present patient showed both red- green and blue- yellow defect. Her red- green defect was of Verriest type I according to the Nagel anomaloscope finding in the right eye with a pseudoprotanomalous quotient. The left eye had probably already passed the pseudoprotanomaly stage; the matching range extended to both red and green areas. The main defect was, however, in the blue- yellow color vision as seen in the Panel 0 15 and FM 100- hue tests. The color vision defect of the present patient was not a congenital defect but evidently an acquired defect because it consisted of difficulties in both red- green and blue- yellow color vision. Congenital red- green defects are common in boys and rare in girls; the prevalence is 8% and 0.4%, respectively. These defects are clearly defined without errors in blue- yellow tests. Congenital blue- yellow defects are much more uncommon, their prevalence is only 0.002- 0.007%, both sexes equally affected ( 20). In acquired defects, it is typical to have different results in color vision tests in the right and left eye, as it happened in the present case study in the Nagel anomaloscope and FM 100- hue test. It is also usual for the patient to notice the loss of color vision, as the patient in this study did. The congenital defects are the same in both eyes, and most people do not know about their defect; it is revealed only when a screening test is performed. The visual field defects in progressive cone- rod dystrophy have been described to be central or paracentral scotomas, generalized constriction, and also ring scotomas ( 1- 3,18,21,22). The small central scotomas of the present patient agree well with the earlier studies. In the dark adaptation, both cone and rod thresholds were elevated. The elevation of the rod threshold was only about 1 log unit, and the patient did not complain about nightblindness. An elevation of the cone threshold and a small elevation of the final rod threshold have also been reported in previous studies ( 2,7). In earlier studies, the cone response in the ERG has been greatly diminished or abolished. The rod response has been reported normal, slightly decreased, or even greatly affected ( 1- 3,23). There does not always seem to be a correlation between the scotopic ERG and the dark adaptation curve, however ( 2,3). It was also observed in this study that both the photopic and scotopic responses in the ERG were decreased. Although the rod response in the ERG was distinctly affected, the el-evation of the final rod threshold in the dark adaptation curve was small. It is not usual to find poor color vision as the first symptom in progressive cone- rod dystrophy. None of the 45 patients examined by Krill et al. ( 2) complained of difficulties in color vision before the loss of visual acuity. In other case studies, the loss of vision is mentioned first and color vision defects later ( 2,4). Another unusual beginning in cone dystrophy has been observed in the study of Zervas and Smith ( 22); five of six patients had symptoms of visual field defects as the first sign of cone dystrophy; only one of the patients had complaints of visual loss. The possibility of a cone dystrophy must be remembered when a patient complains of poor color vision, an acquired color vision defect is found, and the eye examination does not reveal any explanation. In a diffuse cone disease, the ERG examination can show decreased photopic response and the diagnosis is confirmed. A central cone disease might not show ERG changes, and the diagnosis is more difficult to reach. It is important to confirm the diagnosis, especially when the patient is young as in the present study. In the career guidance, the possible deterioration of the visual acuity must be taken into consideration. REFERENCES I. Goodman G, Ripps H, Siegel 1M. Cone dysfunction syndromes. Arch Ophthalmo/ 1963; 70: 21~ 23I. 2. Krill AE, Deutman AF, Fishman M. The cone degenerations. Doc Ophthalmol 1973; 35: 1- 80. 3. Francois J, De Rouck A, Verriest G, De Laey JJ, Cambie E. Progressive generalized cone dysfunction. Ophtha/ mologica 1974; 169: 255-- 284. 4. 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