Final Answer:
When we know the decentration and ED, the formula for MBS is:
- MBS = ED + 2 * Decentration + 2.
Step-by-step explanation:
The Monocular PD (Pupillary Distance) is calculated by adding the Eye Distance (ED) to twice the Decentration and then adding 2. This formula accounts for the off-center positioning of the lenses relative to the pupils. The Eye Distance represents the distance between the centers of the two lenses. When lenses aren't positioned directly in front of the eyes, the Decentration indicates how far each lens center is from the midpoint of the frame.
To find the Monocular PD, double the Decentration (as it affects one eye) and add it to the Eye Distance, compensating for the displacement. The additional 2 accounts for the initial offset inherent in the frame. This calculation is vital in ensuring the correct alignment of lenses with the wearer's eyes, optimizing vision quality and reducing potential discomfort or visual distortion.
Correct answer: MBS = ED + 2 * Decentration + 2.