What term describes the prismatic effect that occurs during reading for those with bifocal prescriptions?

The term that accurately describes the prismatic effect that occurs during reading for individuals with bifocal prescriptions is known as "Image Jump." When a person with bifocal lenses shifts their gaze from one prescription area (typically the distance prescription) to another (the near prescription), there can be a noticeable shift in the position of the image they are viewing. This shift creates a feeling of the image jumping, as they transition between the two different optical powers of the lenses.

The phenomenon is particularly evident when switching from the top part of the lens, which is meant for distance vision, to the bottom portion, intended for near tasks like reading. This shift can lead to disorientation or an uncomfortable experience for individuals adjusting to their bifocal lenses. Therefore, "Image Jump" is the term that specifically identifies this occurrence during reading and other near-vision tasks with bifocals.

The other terms do not accurately capture this specific effect: "Image Displacement" typically refers to a more general movement of an image rather than the specific abrupt transition experienced with bifocal usage. "Optical Distortion" refers to any unwanted alteration in an image due to lens imperfections or incorrect prescription and does not specifically relate to the bifocal transition. "Refraction" describes the