What frequency range is typically used for A-scan measurements?

The frequency range typically used for A-scan measurements in ophthalmic ultrasound is 10-15 MHz. This choice is optimal because it strikes a balance between adequate resolution and penetration depth required for accurately measuring the dimensions of the eye, such as the axial length and the distance to internal structures.

Higher frequencies, such as those in the 15-20 MHz or 20-25 MHz ranges, provide better resolution but can be limited in their ability to penetrate deeper structures, which may be necessary depending on the patient's anatomy or the specific condition being evaluated. Conversely, lower frequencies like those in the 5-10 MHz range may penetrate deeper but compromise resolution, making it difficult to obtain precise measurements.

Thus, 10-15 MHz represents the appropriate frequency range for A-scan measurements, ensuring both clarity of data and sufficient depth of visibility within the ocular structures.