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Show Peripheral Cone Dystrophy: A Diagnostic Improbability? Michael S. Vaphiades, DO, Jennifer I. Doyle, MD Abstract: A 19-year-old man reported bilateral peripheral visual field loss, hemeralopia, and photophobia. Examina-tion and testing was in keeping with peripheral cone dystrophy. This rare entity is discussed. Journal of Neuro-Ophthalmology 2014;34:366-368 doi: 10.1097/WNO.0000000000000119 © 2014 by North American Neuro-Ophthalmology Society A19-year-old man presented with worsening peripheral visual field loss in his right eye greater than his left eye over 8 months. He also complained of hemeralopia and photophobia. His medical history was otherwise negative, and his medications included cetirizine and montelukast sodium for seasonal allergies. The family history was nega-tive for ocular disease, and social history was negative for drug and alcohol use. He had undergone a thorough eval-uation including contrasted, fat-suppressed magnetic reso-nance imaging of the brain and orbits, computed tomographic angiography, cerebrospinal fluid analysis, and multiple hematological studies. The visual acuity was 20/20 in each eye with normal color vision. Automated visual fields showed generalized constric-tion in the right eye and a temporal defect in the left eye (Fig. 1). Pupils were isocoric at 5 mm with normal reactivity and no relative afferent pupillary defect. Ocular motility and trigeminal and facial nerve functions were normal. Anterior segment and funduscopic examinations showed no abnor-mality (Fig. 1). Visual evoked potentials were normal. Mul-tifocal electroretinography (mfERG) showed well-preserved local responses in the central retina and severely reduced responses in the perifoveal retina (Fig. 1) corresponding to the visual field defects. Full-field ERG disclosed normal sco-topic responses in both eyes but diminished photopic ampli-tudes (Fig. 2). Macular optical coherence tomography with autofluorescence revealed loss of the intensity of the ellipsoid zone in the macula corresponding to the regions of signal loss on the mfERG (Fig. 3). The ABCA4, BEST1, ELOVL4, PROM1, RDS-sequencing panel using polymerase chain reaction amplification for Stargardt disease was negative. The patient was diagnosed with peripheral cone dystrophy. Cone dystrophy refers to a group of genetically heteroge-neous disorders with fundus appearance ranging from normal to mild pigmentary mottling to bull's eye maculopathy (1). Patients typically experience a progressive decline in visual acuity and color vision and aversion to bright light. On ERG, the cone system initially is affected; and in advanced disease, the rod system becomes involved (1). Cone dystrophy can be further subdivided into central and peripheral forms. In both, the cone system is predominately impaired with preser-vation of the rod system and lack of fundus changes on oph-thalmoscopy (2). Central cone dystrophy, also named occult macular dystrophy, may be sporadic or dominantly inherited and affects only the macular cones, sparing the macular rods (2,3). Peripheral cone dystrophy, the rarer of the 2 types, involves only the perifoveal cones, sparing the central cones (1). Peripheral cone dystrophy, like central cone dystrophy, presents with photophobia, hemeralopia, and visual field loss. Because the peripheral cones are affected, visual acuity and color vision are preserved. Because of its rarity, peripheral cone dystrophy may be misdiagnosed as acute idiopathic blind-spot enlargement or functional visual loss. Recent technological advances, particularly mfERG, have facilitated the diagnosis of peripheral cone dystrophy (1-3). Our case illustrates a strik-ing correlation between visual field depression and mfERG attenuation in the peripheral retina whereas central record-ings are preserved in the setting of a normal fundus (Fig. 1). Peripheral cone dystrophy should be kept in the differential diagnosis of patients with peripheral field loss who complain of hemeralopia and photophobia. With clinical suspicion and wider access to mfERG, this entity may no longer be a diagnostic improbability. Departments of Ophthalmology (MSV, JD), Neurology (MSV), and Neurosurgery (MSV), University of Alabama at Birmingham, Bir-mingham, Alabama. Supported in part by an unrestricted grant from the Research to Prevent Blindness Inc, New York, NY. The authors report no conflicts of interest. Address correspondence to Michael S. Vaphiades, DO, Department of Ophthalmology, University of Alabama at Birmingham, Suite 601, 700 South, 18th Street, Birmingham, AL 35233; E-mail: vaph@uab.edu 366 Vaphiades and Doyle: J Neuro-Ophthalmol 2014; 34: 366-368 Photo Essay Section Editor: Timothy J. McCulley, MD Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. FIG. 1. A. The fundi are normal in appearance. B. Automated visual fields show peripheral depression and relative central sparing in both eyes. C. Results of multifocal electroretinography shown on 2-dimensional and 3-dimensional graphs correlate with the visual field changes. Vaphiades and Doyle: J Neuro-Ophthalmol 2014; 34: 366-368 367 Photo Essay Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. REFERENCES 1. Lam BL. Electrophysiology of Vision: Clinical Testing and Applications. Boca Raton, FL: Taylor and Francis Group, 2005. 2. Kondo M, Miyake Y, Kondo N, Ueno S, Takakuwa H, Terasaki H. Peripheral cone dystrophy: a variant of cone dystrophy with predominant dysfunction in the peripheral cone system. Ophthalmology. 2004;111:732-739. 3. Mochizuki Y, Shinoda K, Matsumoto CS, Klose G, Watanabe E, Seki K, Kimura I, Mizota A. Case of unilateral peripheral cone dysfunction. Case Rep Ophthalmol. 2012;3:162-168. FIG. 2. Full-field ERG reveals diminished photopic responses in both eyes. ERG, electroretinography. FIG. 3. Fundus autofluorescence shows abnormal subretinal pigmentation abnormality in both eyes, which is more marked in the left eye (OS) than in the right eye (OD). 368 Vaphiades and Doyle: J Neuro-Ophthalmol 2014; 34: 366-368 Photo Essay Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. |
