Analysis of Echoes From the Rear Eye Wall With the Aid of Experimental Research

Abstract

Diagnosis of the eye by ultrasound has been successfully applied since 1956 in various eye diseases. The circumstance that ultrasonic diagnosis was easy to apply to the examination of eye diseases is due to the fairly clear-cut macroscopic structure of the eye. From the point of view of ultrasonic diagnosis the eye can be interpreted as a ball filled with fluid, inside of which there are some parts separated from each other by marked border surfaces. If we place the crystal in the middle of the cornea and guide the sonic waves axially in the direction of the rear wall of the eye, we shall get an echogram on which there is at first an initial echo, followed by the zero-line representing the anterior chamber. The anterior and posterior surfaces of the lens reflect clear echoes, in between of which there is a zero-line. The longest zero-line represents the vitreous and one or several echoes are obtained from the rear wall of the eye. If the sonic waves are guided past the lens, only the initial echo and the echo or echoes from the rear wall are obtained, there being only a zero-line between them.A closer analysis of the echoes from the rear wall of the eye was not easy, because the resolving power of the present-day ultrasonic equipment is only about 0,3-0,5 mm, because the continuous direction of the sound beam perpendicularly against the rear wall of the eye produces considerable difficulties in practice, and because it is difficult to clarify the exact direction of the sound beam in regard to the rear wall. E. g. we have had up to the present no exact knowledge from what point of the rear eye wall the first echo is reflected and *) This study was supported by Sigrid JusClius Stiftelse. **) Received Nov. 14th 1963.

Repeatability, reproducibility and intersession variability of the Allergan Humphrey ultrasonic biometer

“…Using the 40% gain there is a greater chance of error when the biometer automatically assesses the retinal echospike, which with the lower gain setting tends to be confused with echospikes from surrounding tissue interfaces at the posterior pole. A similar observation was made by Oksala 8c Varonen (1964). With the 60% gain the retinal echospike is more clearly defmed and more easily distinguished.…”

Analysis of Echoes From the Rear Eye Wall With the Aid of Experimental and Clinical Research*) Ii Effect of the Absorption of the Lens and of Amplification

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In a previous paper of ours (2) we made an experimental study of the both theoretically and clinically important question whether the first echo from the rear wall is reflected by the retina, the choroid or the anterior surface of the sclera. This study was made by guiding the ultrasound to the rear wall past the lens.

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