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The report describes two cases of four- and five-month-old Mangalarga Marchador fillies showing signs of night blindness. The animals appeared to have disorientation at night. Ophthalmic examination revealed all parameters as normal except for the absence of menace response in the penumbra. Fundoscopy examination did not demonstrate any morphological abnormalities in the retina. Electroretinography examination confirmed a failure in the electrical activity of rods, which are retinal photoreceptors responsible for night vision. However, we noted a small reduction in the electrical activity of the cones, suggesting that the animals may have visual difficulties in clear environments. Genomic analysis of the hair follicles from their mane (Veterinary Genetics Laboratory/UC – Davis, USA) did not reveal the presence of homozygosity for the Leopard Complex, a gene pool associated with congenital stationary nocturnal blindness (CSNB) in horses with depigmented hair. Outcomes of the studbook analysis suggested the presence of kinship among the described animals. Additional research is required for the genomic determination of nocturnal blindness in Mangalarga Marchador horses.&nbsp, Objetivou-se relatar dois casos clínicos de potras com 4 e 5 meses de idade da raça Mangalarga Marchador, demonstrando sinais de cegueira noturna. Os animais apresentavam histórico de desorientação no período noturno. No exame oftálmico, todos os parâmetros foram normais, exceto pela ausência de reflexo de ameaça na penumbra. A fundoscopia não demonstrou nenhuma anormalidade morfológica da retina. A eletrorretinografia confirmou falha na atividade elétrica dos bastonetes, fotorreceptores da retina responsáveis pela visão noturna. No entanto, percebeu-se também uma pequena redução da atividade elétrica dos cones, demonstrando que os animais podem ter uma dificuldade visual em ambientes claros. O exame genômico dos folículos pilosos (Veterinary Genetics Laboratory/UC – Davis, USA) não demonstrou homozigose para Complexo do Leopardo, conjunto de genes associado à cegueira noturna estacionária congênita (CSNB) em cavalos com pelagem despigmentada. A análise genealógica demonstrou um parentesco em comum entre os animais descritos. Assim, tornam-se necessárias pesquisas adicionais para determinação genômica da cegueira noturna em equinos da raça Mangalarga Marchador.

In congenital night blindness of the Schubert-Bornschein type both fast and slow EOG oscillations were found to be normal. In acquired night blindness due to vitamin A deficiency no EOG oscillations a

The night-blind subject examined in 1952 by Schubert and Bornschein was reexamined electrophysiologically. All findings were unchanged. Normal a, d and g-waves in the ERG indicated undisturbed receptor function. Fast and slow oscillations of the EOG were normal. The subjective darkness-adaptation curve revealed minimal scotopic function after the 14th min of adaptation. The significance of clinical and electrophysiological findings for the classification of stationary congenital night blindness is discussed. The hereditary factor appears to be the most preferable criterion for the classification of stationary congenital night blindness.

In clinical electroretinography the extreme expression of rod- or cone dysfunction is found in the complete form of congenital total color blindness and in Schubert-Bornschein’s form of congenital night blindness. The ERG traces of both anomalies represent models for the analysis of rod- and cone function or dysfunction. Comparative studies of these conditions, first performed by Goodman & Bornschein, can enable investigators to gain a deeper insight into electrophysiology and patho-physiology of the eye.

In the analysis of the human electroretinogram, the study of subjects with congenital night blindness and total color blindness is of great value. The absence of specific electroretinographic components in these anomalies simplifies the complex pattern of response, allows a more detailed investigation of the remaining components, and aids in the analysis of the photopicscotopic nature of the different waves. However, the few investigations which deal with the electroretinogram in congenital night blindness and total color blindness have studied each condition separately; therefore, no direct comparison has been made between their electroretinographic responses. The purpose of this study is to investigate quantitatively the influence of dark-adaptation and stimulus intensity on the electroretinogram of normal, congenitally night-blind, and totally color-blind subjects,* examined under identical experimental conditions. Subjects The night-blind subject is a 28-year-old married white woman. She has been aware of poor night vision in both eyes since childhood, nonprogressive in

Since 1952, when Schubert & Bornschein published the electroretinographic results of a subject with congenital night blindness, the specific anomalies of the ERG in these cases are well known: a-wave and x-wave are recordable, but the scotopic b-wave is completely absent. Up to now slow potentials of ERG were not studied in this form of night blindness.

The photopic flicker ERG in response to intense intermittent light of fixed brief duration has been investigated in normal subjects and those with some specific congenital deficiencies of the retina.

THE PRESENCE of distinct defects in the electroretinogram (ERG) in the varying forms of night blindness has been well documented in recent reports. The most conspicuous changes have been recorded from frank cases of primary pigmentary degeneration of the retina. In these cases the tracings are usually extinguished or greatly reduced in amplitude.* A recent article in the Japanese literature 4 describes similar but less marked changes in Oguchi's disease. Bornschein and Vukovich 5 have observed subnormal recordings with avitaminosis A, and definite changes have also been seen in cases of congenital night blindness without fundus change.† This latter form of nyctalopia appears to us to be of more interest than other forms. The existence of clear-cut alterations is of pertinent significance when clinically evaluating alleged night blindness—especially in the military service. In the past such patients have been frequently looked upon as psychiatric problems, if not actually designated as