Important optical factor - Abbe number

Important optical factors 

The Abbe number is a physical number used to measure the degree of chromatic aberration of a medium. The dispersion of light will directly affect the clarity. The higher the Abbe number, the smaller the degree of dispersion when the light passes through the lens, that is, the clearer. The Abbe number of rubber lenses is generally between 30 and 60. The Abbe number of glass lenses is about 10% higher than that of rubber lenses. (The higher the Abbe number, the better)

Abbe number comparison

If the degree of dispersion of the lens is high, the wearer’s eyes will “force to correct the effects of dispersion” (brain correction), and long-term use will make the eyes tired and dry.

When choosing lenses, you usually only look at budget and thickness, and Abbe number is rarely mentioned. Some customers whose eyes are more sensitive to chromatic dispersion feel uncomfortable when choosing low Abbe number lenses. They should switch to high Abbe number lenses (refractive index below 1.61) or choose glass lenses.

Refractive Index1.51.561.611.671.74
Abbe Number5838413233

The relationship between refractive index and Abbe number of mainstream brands

Considerations 

There are no strict rules on what power is matched with what refractive index lens. Most people will refer to their own refractive power, frame size and budget to choose. Generally, 1.5 & 1.56 refractive index lenses are used below 300 degrees, 1.6 refractive index lenses are used for 300-500 degrees, and the refractive index above 1.67 is used for more depth.


Tokai's highest refractive index lens 1.76

In addition to budget and diopter, there are the following considerations: The 1.5 and 1.56 refractive index lenses have low hardness and are not suitable for rimless spectacle frames or thin steel design frames, otherwise the edge of the lens may be cracked. The higher the refractive index of the lens, the lower the Abbe number. Unless the refractive power is very high (eg: ultra-deep myopia), for a comfortable wearing experience, you should choose a high Abbe number lens.

    We offer Hoya aspheric lens with a refractive index of 1.5. If the distance/near vision is not high (~200 degrees), don't miss it.

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