Certified Diagnostic Ophthalmic Sonographer (CDOS) Practice exam

In ophthalmic ultrasound, particularly for A-scan measurements, the frequency range of 10-15 MHz is preferred because it provides a balance between resolution and penetration. Higher frequencies generally offer better resolution and enable more detailed visualization of structures within the eye, such as the vitreous, lens, and retina. However, they also have a limited depth of penetration. Frequencies in the 10-15 MHz range effectively achieve sufficient resolution for detailed imaging while still being able to penetrate the ocular structures adequately, making them suitable for accurate axial length measurements, which are critical for cataract surgery and other ocular procedures.

Using lower frequencies, while they can penetrate deeper, would result in poorer resolution, making them less optimal for the detailed anatomic information needed in ophthalmic care. Conversely, frequencies higher than 15 MHz, while providing excellent resolution, might not penetrate deep enough to be effective for all ocular examinations. Therefore, the 10-15 MHz range is considered the standard in performing A-scan ultrasound in an ophthalmic setting.