The meaning of lens data
What is BC?
- Abbreviation for Base Curve, it indicates the degree of curvature of the lens. The unit is mm.
- Because the human eyeball is a sphere, black eyes are also curved, and its degree has individual differences.
- Since the color control is worn directly on the eyes, it is necessary to fit the curvature of the lens to the curvature of the eye (curve) to fit it.
- Difference in numerical value of BC
- The smaller the numerical value of BC is, the harder the curve is, and the larger the numerical value, the looser the curve.
- (Example / BC: 8.4 is more tight curved, BC: 9.0 has a more curved curve.)
- What happens if BC does not look good?
- If the curve of the lens is looser than your own eye, the lens may not fit in the correct position and it may shift vertically or horizontally.
- If the curvature of the lens is tighter than your own eye, you may feel pain or foreign body feeling by pressing the eyeball with the lens or hitting the edge of the lens.
- BC inconsistency is also considered when the worn lenses come off.
- How can I tell BC that suits me?
- You can know the numerical value of BC suitable for your own eyes by receiving an examination at the eye clinic.
What is DIA?
- It is an abbreviation of Diameter and indicates the lens diameter. The unit is mm.
- The size of DIA
- Currently (2014) Approved color models sold in Japan are mainly those with DIA 13.9 ~ 14.8 mm.
There are many products of 14.0 mm for transparent contact lenses used for correcting vision, but not only 14.0 mm for color control, but also many products with large lens diameters such as 14.2 mm to 14.8 mm for the purpose of making black eyes larger .
What is moisture content?
- Soft contact lenses, including color containers, contain moisture inside the lens.
- The percentage of moisture contained in the lens is called the moisture content (cancer concentration), and the unit is%.
- Lenses with a high moisture content of about 38% in color containers are classified as "low water content" and lenses with a moisture content of 50% or more are classified as "high water content".
- "Low water content" and "High moisture content"
- There are advantages and disadvantages for low water content lens and high water content lens, respectively.
- "High water content = good" "Low water content = Bad" is not right.
- Advantages and disadvantages of "low moisture lens"
- The advantage of a low moisture lens is that the eye thirst you feel during wearing is low.
The moisture taken in by the lens being worn is [tears]. Lower hydrated lenses are said to be less sensitive to eye thirst compared to high hydrated lenses because the amount of tears taken by the lens is small because the amount of moisture taken in is low.
The disadvantage of low moisture lens is that it is easy to feel foreign body feeling and low oxygen permeability.
Lower water-containing lenses with less water content in lenses may have a rough feeling and foreign body feeling when wearing, because lenses are harder than high-moisture lenses.
In addition, oxygen supplied to eyes uses water as a medium, but a low water content lens with a small amount of moisture reduces the amount of oxygen supplied to the eyes through the lens because the amount of oxygen passing through the lens is small.
- ※Since oxygen permeability is also influenced by DIA (lens diameter), comparing low water-containing lens and high water-containing lens, it is not necessarily that the low water content lens has lower transmittance.
- Advantages and disadvantages of "high water content lens"
- The merit of the high water content lens is that it has little foreign body feeling and high oxygen permeability.
Highly water-containing lenses containing much moisture in the lens are said to have soft lenses, so that there is little foreign body feeling during wearing.
Also, since the lens passes much oxygen, it is advantageous that there are a lot of oxygen reaching the eye.
The disadvantage of the high water content lens takes in tears to the lens so much, so those who have a small amount of tears after a long period of wearing may feel especially thirsty.