A ecografia se constitui em método importante na avaliação de anormalidades do segmento posterior do globo ocular. OBJETIVO: Comparar as vantagens e desvantagens da sonda de 10 e 20 MHz da ultra-sonografia B-scan, na avaliação de imagens do segmento posterior do globo ocular. MÉTODOS: Pacientes acompanhados no ambulatório do Hospital das Clínicas da USP (HCFMUSP) entre fevereiro de 2006 e abril de 2007 foram submetidos a exame ultra-sonográfico usando o aparelho CINE-Scan® (Quantel Medical Inc.) com sondas de 10 e 20 MHz. Os pacientes foram examinados por três oftalmologistas experientes, em decúbito dorsal, após instilação de colírio de tetracaína a 1%, inicialmente com a sonda sobre as pálpebras e em seguida diretamente em contato com a esclera ou córnea. As imagens obtidas com sondas de 10 e 20 MHz foram comparadas entre si, durante e após a realização do exame. RESULTADOS: A sonda de 20 MHz mostrou-se superior na avaliação da detecção, forma e limites de estruturas do pólo posterior e a de 10 MHz avaliou com mais detalhes o humor vítreo. Não foram encontradas diferenças nas imagens obtidas com exame transpalpebral ou transescleral com a sonda de 10 MHz. Com a sonda de 20 MHz, as imagens obtidas em contato direto com o globo ocular apresentaram melhor qualidade. CONCLUSÕES: As sondas de 10 e 20 MHz têm diferentes intervalo de alcance ideal, assim como diferentes meios específicos de aquisição de melhores imagens.

The ultrasound is an important method in the evaluation of abnormalities of the posterior segment of the eye. PURPOSE: To compare the advantages and disadvantages of 10 and 20 MHz probe on B- scanning ultra-sonography in evaluation of vitreous and posterior pole diseases, providing recommendations for their use. METHODS: Patients from Hospital das Clinicas of the University of São Paulo (HC-FMUSP), attended between February 2006 and April 2007, were submitted to ultrasound exams using CINE-Scan® (Quantel Medical Inc) B-scan with 10 and 20MHz probe. The patients were examined by three experienced ophthalmologists, in horizontal dorsal position, after instillation of tetracaine 1% drops, first with the probe in direct contact with eyelids, and then with the probe placed directly in contact with the sclera or cornea. Theimages obtained were compared immediately during and after the examination. RESULTS: The 20 MHz probe reveled a superior resolution to study details, like shape and limits, on the posterior pole, and the 10 MHz probe provided better evaluation on vitreous humor. There were no differences if the exam was performed on eyelids or directly on sclera with the 10 MHz probe, but with the 20 MHz probe, the images had better resolution when the probe was used in direct contact with the eye. CONCLUSIONS: The 10 and 20 probes have different ideal range of reach, as different better specific means of image achieving.