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THE EFFECT OF THE CURVATURE OF THE EYE SHELL ON THE ECHOGRAM
Author(s) -
OKSALA ARVO,
FRÄNKL GEORG
Publication year - 1974
Publication title -
acta ophthalmologica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.534
H-Index - 87
eISSN - 1755-3768
pISSN - 1755-375X
DOI - 10.1111/j.1755-3768.1974.tb00385.x
Subject(s) - optics , curvature , perpendicular , transducer , acoustics , ultrasonic sensor , lens (geology) , shell (structure) , sound (geography) , beam (structure) , materials science , physics , mathematics , geometry , composite material
When sensitive ultrasonic equipment is used, both clinical and experimental examinations reveal one or more low echoes in front of the high rear wall echoes if the sound beam is directed perpendicularly to the rear wall past the lens. In the experimental part of the study 7.5 MHz/2 mm, 6 MHz/5 mm and 6 MHz/8 mm transducers were used for the purpose of finding out the origin of these low echoes in pig eyes. The results showed that these low echoes were due to the difference in distances between the central and marginal parts of the sound beam caused by the curvature of the eye shell. Similar low echoes could be produced at clinical examinations at the frequencies of both 6 MHz and 10 MHz. The low echoes disappeared when the amplification of our equipment was lowered from 80 db to 72 db. Acoustic answers of low reflecting agents, as slight dense and flat preretinal exsudates or haemorrhages therefore can not be distinguished from these findings described above.