With the enhancement of consumers’ consumption awareness, more and more customers are not only paying attention to the service of the consumption store, but also paying more attention to the curiosity of their purchased products (lenses). Selecting eyeglasses and frames is easy, because the trend is there and one’s preferences are clear, but when it comes to selecting lenses, one’s brain starts to hurt. They are all transparent two lenses, and the prices are simply different, refractive index, Abbe number, anti-blue light, anti-fatigue… there is a feeling of imminent collapse!
Today, let’s simply talk about how to break the password of these parameters of lenses!
I. Refractive Index
Refractive index is the most frequently mentioned parameter in lenses, which is defined as the ratio of the speed of light propagation in the atmosphere to that in the lens. It sounds cumbersome, but it’s actually very simple. Light propagation in the atmosphere is very fast, and this parameter describes how much they differ from each other. Through this parameter, we can also know the thickness of the lens.
Generally, it is reflected that the higher the refractive index, the thinner the lens and the more aesthetically pleasing the lens is made.
The refractive index of resin is generally: 1.499, 1.553, 1.601, 1.664, 1.701, 1.738, 1.76, etc. Generally, it is recommended that people with nearsightedness of -3.00D or less can choose lenses between 1.499 and 1.601; people with nearsightedness of -3.00D to -6.00D can choose lenses between 1.601 and 1.701; and people with nearsightedness above -6.00D can consider lenses with higher refractive index.
II. The Abbe Number
The Abbe number is named after Dr. Ernst Abbe and mainly describes the dispersion of the lens.
Lens Dispersion (Abbe Number): Due to differences in refractive index for different wavelengths of light in the same transparent medium, and white light being composed of different wavelengths of colored light, transparent materials will experience a special phenomenon of dispersion when refracting white light, similar to the process that produces a rainbow. The Abbe number is an inverse proportionality index that represents the dispersive ability of transparent materials, with a smaller value indicating stronger dispersion. The relationship on the lens is: the higher the Abbe number, the smaller the dispersion and the higher the visual quality. The Abbe number is generally between 32 to 59.
III. Refractive Power
Refractive power typically encompasses 1 to 3 pieces of information, including spherical power (i.e. myopia or hyperopia) and cylindrical power (astigmatism) and axis of astigmatism. Spherical power represents the degree of myopia or hyperopia and cylindrical power represents the degree of astigmatism, while axis of astigmatism can be regarded as the position of astigmatism and is generally divided into with the rule (horizontally), against the rule (vertically), and oblique axis. With equal cylindrical power, against the rule and oblique axis may be slightly more difficult to adapt to.
For example, a prescription of -6.00-1.00X180 represents a myopia of 600 degrees, astigmatism of 100 degrees, and an axis of astigmatism in direction 180.
IV. Blue Light Protection
Blue light protection is a popular term in recent years, as blue light is emitted from LED screens or lights and its harm is becoming increasingly apparent with the widespread use of electronic products.
Post time: Feb-21-2023