Provide a valuable resource to your clients or customers by linking to this resource page. Just place the following link on your website.
Optical density (also called absorbance) is a measure of how much light is absorbed when it passes through a transparent material, such as a contact lens, sunglass lens, or camera filter. A higher optical density means the material absorbs more light.
read more about optical density ...In prescription eyewear, optical density determines the tint or darkness of a lens. A lens with high optical density blocks a large percentage of light, which is desirable for outdoor sunglasses or safety lenses that need to filter bright light or specific harmful wavelengths.
No, optical density is a quantifiable physical factor of a material, not a medical condition. In safety terms, using a lens with too low an optical density for high-exposure activities (like welding) is dangerous, but the property itself is simply a measurement.
You do not need a prescription for the optical density measurement itself. However, when selecting sunglass lenses or specialty filters, your eye doctor may recommend a specific level of visible light transmission (VLT), which is the inverse of optical density, to guarantee proper glare protection for your sensitivity level.
The purpose is protection and comfort. Sunglasses use optical density to:
Is a dark lens always UV protective?
No. The darkness (visible optical density) only reduces glare. UV protection requires a separate chemical coating in the lens material.
How is optical density measured?
It is measured using a spectrophotometer, which calculates the ratio of light transmitted through the material versus the total light entering it.
Is it the same as refractive index?
No. Refractive index measures how much light bends, while optical density measures how much light is absorbed.