Which combination results in better echo resolution?

The combination of a narrow, focused sound beam results in better echo resolution because it allows for enhanced detail and clarity in the images produced during an ultrasound examination. When the sound beam is narrowed and focused, it can better distinguish between adjacent structures because the echoes returning from those structures will originate from a more defined area. This increased spatial resolution is crucial in ophthalmic sonography, where precise imaging is often necessary to evaluate fine details of the eye and any potential pathologies.

A narrow, focused beam typically has a smaller area of divergence compared to a wider beam, which means that it can reduce the amount of spectral and axial resolution loss that can occur when surrounding tissues interfere with the echoes. This helps to clarify the images of the various ocular structures, enabling better differentiation of conditions such as tumors, retinal detachments, or other abnormalities.

In contrast, while other options may have their uses in ultrasound techniques, they do not provide the same level of detail and clarity as a narrow, focused sound beam. Consequently, this approach is essential in optimizing image quality in diagnostic settings.