How exactly is the power of contact lenses calculated_

How exactly is the power of contact lenses calculated?

 

Everyone knows about the prescription of glasses,

 

In order to better understand the condition of our eyes, we will all go for regular vision tests.

 

Understand recent changes in prescription and adjust the prescription of glasses in time to help correct vision.

 

Recommended Reading:

 

What are the characteristics of the four popular contact lens brands of Haichang, Hailien, Johnson & Johnson, and Bausch & Lomb.

 

This is because the glasses are about 12mm away from the surface of the eyeball.

 

When wearing contact lenses, the distance from the eye to the cornea is almost negligible.

 

This difference in distance causes a change in refractive ability, the higher the power,

 

The greater the visual gap.

 

The prescription power obtained by refraction is based on the plane of the eyeglasses as the refraction reference surface.

 

After we get the prescription, we have to calculate the prescription of the contact lens through the power analysis.

 

1. Myopia/Hyperopia (no astigmatism) (1) The simplest is empirical:

 

When the diopter is less than ±4.00 (commonly known as ± 400 degrees):

 

Contact lenses are directly used with the original power,

 

No conversion is required.

 

Above 400 degrees is calculated as follows:

 

4.00D to 5.00D,

 

The power of the contact lens is:

 

myopia minus 0.25D, hyperopia plus 0.25D; 5.00D to 7.00D,

 

The power of the contact lens is:

 

myopia minus 0.50D, hyperopia plus 0.50D; 7.00D to 9.00D

 

The power of the contact lens is:

 

myopia minus 0.75D, farsightedness plus 0.75D; 9.00D to 11.00D

 

The power of the contact lens is:

 

Myopia minus 1.00D, hyperopia plus 1.00D.

 

(2) Calculated by formula:

 

Contact lens power = frame power÷ (1-0.012X frame power) 0.012m is the distance between the posterior apex of the frame lens and the cornea,

 

As a result, the closest prescription contact lens is 25 degrees to 50 degrees.

 

Illustrate:

 

The refraction power is -5.00D,

 

So this is how it is calculated:

 

-5.00÷(1-0.012x-5.00)=-4.71，

 

Take the nearest -4.50D as the power of the contact lens.

 

2. If there is astigmatism, the situation is more complicated, you must go to a professional optical store for consultation,

 

Choose the right astigmatism lens based on your luminosity, source of astigmatism and corneal curvature.

 

Choose the right contact lenses and see the world together.

 

Contact lenses.