Multifocal electroretinograms in cases of central areolar choroidal dystrophy. Invest Ophthalmol Vis Sci

PURPOSE. To study multifocal electroretinograms (mfERG) in patients with early-stage central alveolar choroidal dystrophy (CACD) with well-demarcated atrophic areas. METHODS. Eight eyes of eight patients with CACD (ages, 47-67 years) and 20 normal control subjects were examined. The first-and second-order kernels (K1 and K2) were extracted from the responses elicited by 61 standard hexagonal elements of a visual response imaging system. The amplitudes and peak times of the focal responses at various retinal eccentricities were studied. RESULTS. The amplitudes of K1 were reduced in the visibly atrophic areas, and they were also decreased in areas with no visible atrophy. The peak time was slightly delayed in many loci, but the delay was not as long as that in congenital stationary night blindness or diabetic retinopathy. The amplitude of K2 was very small in the central and peripheral areas, but the K2/K1 ratio in both areas was not significantly reduced, compared with that in normal subjects. CONCLUSIONS. Although the atrophic area was ophthalmoscopically well demarcated in patients with CACD, the abnormality of retinal function extended beyond the borders of the ophthalmoscopic and angiographic lesions. The retinal dysfunction outside the atrophic areas suggests a centrifugal progression of the disease, and abnormal K2 and K1 with preserved K2/K1 ratio are consistent with a presynaptic mechanism for the retinal dysfunction in this disease. (Invest Ophthalmol Vis Sci. 2003;44:1673-1679) DOI:10.1167/iovs.02-0885 C entral areolar choroidal dystrophy (CACD), originally reported by Nettleship in 1884, 1 is a rare macular dystrophy that is characterized by the development of fine, mottled, depigmented retinal pigment epithelium (RPE) in the macula. The round or oval macular lesion shows a distinct boundary and sometimes includes small areas with normal appearance inside the lesion. Although dominant and recessive inheritances have been reported, most cases are sporadic. 2 The associated findings include a central and/or paracentral scotoma and normal peripheral visual fields. Fluorescein and indocyanine angiograms reveal RPE atrophy and various degrees of loss of the choriocapillaris. Full-field electroretinograms (ERGs) are normal in the early stages, but may become abnormal in the advanced stages. 3,4 The technique for recording multifocal ERGs (mfERGs), based on an m-sequence stimulation, allows a rapid recording of focal ERGs from many retinal locations in the posterior pole of the eye. 9 -11 It has been reported that the amplitude and the peak time of the first-order kernel (K1) of the mfERGs can be used to monitor retinal function in different kinds of retinal dystrophies. 16 We extracted the first-and second-order kernels (K1 and K2) of the mfERG from eight eyes of eight patients with CACD (not in the advanced stage) to determine the correspondence between the areas of retinal dysfunction and the lesions that were visible ophthalmoscopically. Because the visible lesion in CACD has a distinct border, image processing allowed us to make an accurate comparison between the responses inside and outside the lesion. SUBJECTS AND METHODS Subjects Eight eyes of eight patients with CACD, ages 41 to 71 years (mean, 56.2), were recruited from the Department of Ophthalmology, School of Medicine, Nippon University. The diagnosis of CACD was made by the characteristic findings in color fundus photographs, fluorescein and indocyanine green angiograms, and other clinical findings (the onset of symptoms, slow progression, no history of chloroquine, normal dark adaptation, normal color vision, and normal peripheral field). Patients with secondary atrophy, such as age-related macular degeneration, were excluded. Stargardt disease was excluded by its earlier onset and typical angiographic findings (silent choroid). The inclusion criteria were good visual acuity (better than 0.7), normal electroFrom th