Which ocular tissue produces A-scan spikes?

The lens is responsible for producing A-scan spikes in ultrasonic biometry due to its unique acoustic properties. When A-scan ultrasound is performed, sound waves are transmitted into the eye, and when these waves encounter different ocular tissues, they generate echoes that correspond to the boundaries of those tissues. The lens, being a denser and more elastic structure than some of the surrounding tissues, reflects a significant portion of the ultrasound waves, resulting in a clear spike on the A-scan graph.

The other tissues, while they do interact with ultrasound waves, do not create spikes with the same prominence as the lens. The iris is more soft and less dense compared to the lens, therefore it does not reflect sound waves as efficiently. The cornea is the outermost layer of the eye and while it does reflect sound, it is the lens that produces the most distinct spikes due to its structure. The sclera, being the white part of the eye, also has different acoustic characteristics that do not produce the same pronounced spikes. Thus, the lens is the primary ocular tissue responsible for the noticeable A-scan spikes observed in ultrasound measurements.