Certified Paraoptometric (CPO) Practice Exam 2024

What is the primary function of Progressive Addition Lenses (PAL)?

1. Provide multiple fixed viewing distances

2. Gradually change power from top to bottom

3. Offer a uniform power throughout the lens

4. Eliminate the need for bifocals

The correct answer is: Gradually change power from top to bottom

Progressive Addition Lenses (PAL) are designed to provide a seamless transition between different viewing distances, which is accomplished by gradually changing power from the top to the bottom of the lens. This design allows for clear vision at various distances—far, intermediate, and near—without the visible lines that traditional bifocals or trifocals have. The gradual power change is essential because it accommodates the natural visual needs of individuals as they age, often reducing the abrupt transition and discomfort associated with lens types that have fixed viewing distances. This gradual progression enhances usability and comfort for the wearer as they move their gaze vertically across the lens. While PALs do indeed eliminate the need for bifocals, this is more of an additional benefit rather than their primary function. The other options, like providing multiple fixed viewing distances or offering uniform power throughout the lens, do not accurately describe the key characteristic that sets PALs apart from other lens types.