All about Sunglasses with Dioptre
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Every time the sun blazes high up in the sky, the first and most important thing you should do is to keep your eyes protected from its harsh brightness without compromising your level of visibility. This is the reason why sunglasses with dioptre get glowing recommendations from many ophthalmologists far and wide.
Even though it’s technically a measurement unit, dioptre refers to lenses with close-up filters that allow easier focus when closer. It means that these are prescription glasses.
Quick Definition of Dioptre
You are probably curious about the meaning behind the numbers on your prescription contact lenses or glasses. You might have even attempted to decipher the numbers on the dioptre chart while shopping for a pair of reading glasses at the local drugstore.
For your information, these numbers refer to the lenses’ focusing strength. A dioptre is the unit used to calculate the focusing strength of a pair of contact lenses or glasses. This is also the measurement unit for optical prescriptions. You can determine the focal length or distance where the light is focused when you know the lens’s power in dioptres and take the inverse.
Relationship between Meters and Dioptres
A lens with a focusing power of one dioptre focuses light from something extremely far away, such as the sun, at a distance of one meter behind the lens. The focal length of the lens is the distance where light is focused.
If you double the lens’s focusing power to two dioptres, the sun’s light will get focused twice as near behind the lens at half a meter, resulting in half a meter focal length.
Connection between Focal Length and Dioptres
Taking the inverse of a lens’ power in dioptres gives you the focal length. Being familiar with the concept of focal length and dioptre will help you understand why some people need to wear contact lenses or glasses while others don’t.
The human eye has two focusing lenses: the crystalline lens and the cornea. The cornea has approximately 45 dioptres while the crystalline has around 15 dioptres, resulting in a combined focusing power of 60 dioptres.
