American Board of Ophthalmology (ABO) Practice Exam

What is the most common way to describe the location of a trifocal lens correction?

1. Centered on the bridge of the nose

2. Aligned with the pupil

3. At the upper edge of the pupil

4. Lower edge of the pupil

The correct answer is: Lower edge of the pupil

The most common way to describe the location of a trifocal lens correction is at the lower edge of the pupil. This positioning allows for the optimal alignment of the lens segments for different visual zones—distance, intermediate, and near. The lower segment of the trifocal lens, which usually accommodates near vision, is tailored to sit at the lower edge of the pupil, facilitating a smooth transition and clear vision across the various focal points. This arrangement is crucial for patients who require multifocal vision correction, as it maximizes the effectiveness of the lens design in conjunction with normal eye movements and gaze positions. Proper alignment ensures that patients can utilize the near vision segment comfortably without needing to tilt their heads excessively or adjust their gaze downward, which can lead to complications such as ghosting or blurry vision. Therefore, positioning at the lower edge of the pupil is recognized as the standard practice in fitting trifocal lenses.