Talking about lenses

The diameter of myopia spot lenses is 65-80, the most common is 70 or 75 diameter, and 80 diameter is relatively rare. The central thickness, refractive index, curvature and thickness of myopia lenses are the same.

The spot diameter of hyperopia/presbyopia lenses ranges from 60-70, and the spot diameter of hyperopia/presbyopia lenses is 50 (usually white coated lenses). The most common is the 65 diameter. Theoretically, the smaller the diameter is, the thinner the hyperopia/presbyopia lens is. Therefore, the smaller the lens diameter is, the better.

However, lenses do not exist independently. They need to be matched with the lens frame to make appropriate glasses for customers to wear. This involves whether the diameter can achieve the actual pupil distance of customers.

How to determine whether the lens frame can achieve the actual pupillary distance?

We have a formula:

For example, if the geometric pupil distance of the lens frame is 70, the pupil distance of the customer is 62, and the maximum diagonal line of the lens is 54, then the minimum diameter is:

70-62+54+2=64, then 65 diameter lens can achieve the actual pupillary distance.

How to choose a larger lens frame in this case? If the minimum diameter is greater than 65, the 65 lens cannot achieve the pupil distance of customers.

This method often needs to be considered during hyperopia/presbyopia matching, and the eyes that people see near need to rotate inward, and the distance between near pupils is smaller than that between far pupils. Especially for high hyperopia/presbyopia glasses, the smaller the diameter, the thinner it will be. Experienced optometrists will recommend customers to choose a more appropriate lens frame, so they can choose a smaller diameter, and then the lenses will be thinner. Even if the lens with low refractive index is chosen, it is relatively thin as long as the diameter is small enough.