Obtaining the correct knowledge of eyeglasses and lenses, which you do not know unexpectedly, will help you to care for your own eyes and eyesight. Please use it as a reference for living a healthy and comfortable visual life.
INDEX
Vol.4 Story of bifocals
1. Advantages and disadvantages of bifocals 2. How to use bifocals 3. How to choose a frame
Vol.4 Story of bifocals
Many people find it difficult to see small letters when they are in their 40s.
Therefore, it is necessary to take off the glasses or put them on in order to see nearby.
There is "bifocal glasses" as a method to eliminate the troublesomeness of putting on and taking off and the difficulty of seeing at hand.
On this page, we will talk about the advantages and disadvantages of bifocals, as well as points to note when choosing eyeglasses.
1. Advantages and disadvantages of bifocal lenses
A bifocal lens refers to a lens whose power gradually changes from the "power" placed at the top of the lens for looking far away to the "power" placed at the bottom of the lens for looking near, and moving the line of sight. It is possible to focus on the part you want to see with.
In addition to being able to see from a distance with a single pair of glasses, it looks the same as a general single-focus lens and does not make you feel age.
However, since there is a gentle change in power up and down, distortion will appear in the peripheral part, and it will be blurred when looking at an object in an oblique direction.
For those who are sensitive to changes in the field of view, the field of view seen at the bottom of the lens may appear to be shaken or distorted depending on the power added, which has the disadvantage of taking time to get used to.
Precautions for use
Some people use bifocals without difficulty from the beginning, but until they can use it without any discomfort, such as how to use their line of sight.
It takes time, especially the steps such as stairs.
We also recommend that you fully familiarize yourself with the lens before using it when driving a car.
Proper fitting is essential for comfortable use of bifocals.
If it becomes uncomfortable to wear or if it shifts, it will affect the appearance, so frequent maintenance is required.
2. How to use bifocals
When looking far
When looking into the distance, pull your chin and look up at the object.
When looking at your feet
When looking at your feet, if you look down only, your eyes will be blurred in the near area, so lower your head and look at the top of the lens.
When looking near
When looking near, you can see the object at the bottom of the lens, so you can easily see it by raising your chin and lowering your eyes.
Also, if you move only the line of sight sideways, the distorted part will come in, so make sure that the object you want to see comes to the front.
3. How to choose a frame
There is basically no limit, but since different powers are applied to the upper part of the lens and the lower part of the lens, the vertical width of the lens is required to some extent.
Especially for those who are using bifocals for the first time, if you choose a frame with a certain width (32 mm to 35 mm or more), you can use it without difficulty even if the power changes from far to near. You can.
* It is only recommended, and it is possible to make a type with a narrow vertical width.
The upper and lower parts of the lens have different powers, and the interval is called the progressive band length.
By changing this progressive band length, it is possible to put a bifocal lens in most glasses unless the frame is very narrow in height.
For frames with a narrow progressive zone length
The narrower the progressive band length, the greater the distortion of the lens.
However, it is easy to switch the viewpoint between far and near, and it is recommended for those who frequently compare far and near.
For frames with a wide progressive band length
If the progressive band length is wide, the distortion will be small if the addition power is the same, so it is recommended for those who are using bifocals for the first time.
For those who often keep looking far or near with few viewpoint changes, a lens with a wide progressive band length is recommended.
At our shop, our staff with specialized knowledge will carefully counsel each customer and propose the most suitable lens.