What is the designed clear image distance for the intermediate portion of a trifocal?

The intermediate portion of a trifocal lens is specifically designed to provide a clear image at a distance that is optimal for activities that occur at arm's length. The standard clear image distance for the intermediate zone of trifocal lenses is typically around 30 inches, which is approximately the distance most individuals use when engaging in tasks like computer work, reading, or crafting.

This distance is chosen to allow for comfortable viewing without needing to strain the neck or adjust the frame excessively, as it aligns with the natural ergonomic position while working or using technology. Therefore, the correct answer of 30 inches reflects the practical application of trifocal lenses in daily life, ensuring that wearers can easily transition from distance viewing to near tasks without discomfort or blurriness.