Resumo: FUNDAMENTOS -O vitiligo atinge de 0,5 a 4% da população mundial, e 25% dos casos se iniciam antes dos 10 anos. Embora prevalente, estudos epidemiológicos de vitiligo na infância são raros na literatura brasileira. OBJETIVO

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Objetivos: Descrever e analisar a prevalência de baixa acuidade visual e suas causas em estudantes do ensino público de Belo Horizonte/MG. Métodos: Estudo transversal de 1452 escolares de 5 a 19 anos, do ensino público de Belo Horizonte/MG, triados e atendidos entre 2011 e 2014. Resultados: Da amostra total, 150 pacientes (10,33%) apresentaram baixa acuidade visual à triagem, recebendo encaminhamento para atendimento oftalmológico. Quarenta (26,66%) dos encaminhados compareceram à consulta, onde 29 (72,5%) desses apresentaram indicação de correção visual. O astigmatismo miópico simples e composto foram os diagnósticos mais relacionados à prescrição de óculos. Conclusão: O estudo mostrou que a prevalência de baixa acuidade visual na população estudada foi compatível com demais programas semelhantes. Em contra partida, a taxa de abstenção foi maior do que o esperado, evidenciando a importância da criação de medidas preventivas e informativas quanto à importância do cuidado com a saúde ocular.

Purpose: Crotoxin is the major toxin of the venom of the South American rattlesnake Crotalus durissus terrificus, capable of causing a blockade of the neurotransmitters at the neuromuscular junction. The objective of this study was to appraise the action and effectiveness of the crotoxin induced paralysis of the extraocular muscle and to compare its effects with the botulinum toxin type A (BT-A). Methods: The crotoxin, with LD50 of 1.5 μg, was injected into the superior rectus muscle in ten New Zealand rabbits. The concentration variance was 0.015 up to 150 μg. Two rabbits received 2 units of botulinum toxin type A for comparative analysis. The evaluation of the paralysis was performed using serial electromyography. After the functional recovery of the muscles, which occurred after two months, six rabbits were sacrificed for anatomopathology study. Results:The animals did not show any evidence of systemic toxicity. Transitory ptosis was observed in almost every animal and remained up to fourteen days. These toxins caused immediate blockade of the electrical potentials. The recovery was gradual in the average of one month with regeneration signs evident on the electromyography. The paralysis effect of the crotoxin on the muscle was proportional to its concentration. The changes with 1.5 μg crotoxin were similar to those produced by the botulinum toxin type A. The histopathology findings were localized to the site of the injection. No signs of muscle fiber's necrosis were seen in any sample. The alterations induced by crotoxin were also proportional to the concentration and similar to botulinum toxin type A in concentration of 1.5 μg. Conclusion: Crotoxin was able to induce transitory paralysis of the superior rectus muscle. This effect was characterized by reduction of action potentials and non-specific signs of fibrillation. Crotoxin, in concentration of 1.5 μg was able to induce similar effects as botulinum toxin type A. Keywords

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Purpose: Crotoxin is the main neurotoxin of South American rattlesnake Crotalus durissus terrificus. The neurotoxic action is characterized by a presynaptic blockade. The purpose of this research is to assess the ability of crotoxin to induce temporary paralysis of extraocular and facial muscles in humans. Methods: Doses of crotoxin used ranged from 2 to 5 units (U), each unit corres ponding to one LD50. We first applied 2U of crotoxin in one of the extraocular muscles of 3 amaurotic individuals to be submitted to ocular evisceration. In the second stage, we applied crotoxin in 12 extraocular muscles of 9 patients with strabismic amblyopia. In the last stage, crotoxin was used in the treatment of blepharospasm in another 3 patients. Results: No patient showed any systemic side effect or change in vision or any eye structure problem after the procedure. The only local side effects observed we re slight conjunctival hyperemia, which recovered spontaneously. In 2 patients there was no change in ocular deviation after 2U crotoxin application. Limitation of the muscle action was observed in 8 of the 12 applications. The change in ocular deviation after application of 2U of crotoxin (9 injections) was in average 15.7 prism diopters (PD). When the dose was 4U (2 applications) the change was in average 37.5 PD and a single application of 5U produced a change of 16 PD in ocular deviation. This effect lasted from 1 to 3 months. Two of the 3 patients with blepharospasm had the hemifacial spasm improved with crotoxin, which returned after 2 months. Conclusions: This study provides data suggesting that crotoxin may be a useful new therapeutic option for the treatment of strabismus and blepharospasm. We expect that with further studies crotoxin could be an option for many other medical areas.