Treatment of lenses
Anti-reflex coatings: it is a surface treatment to eliminate the reflexes that occur on each face of the lens. It improves contrast and visual acuity and reduces glare. Several layers of different materials are placed so that between the incident light and the reflection on each surface there is a phase contrast, so that they are canceled between them.
There are different types of antireflex coatings:
a- Blue Light: the light that reaches the eyes is formed by ultraviolet rays (UV) (200-400 nm) and visible light (400-700 nm). Violet light (400-440 nm) and blue (440-500 nm) correspond to short length. The cornea absorbs up to 300 nm and the crystalline up to 300-400 nm
In the retina, there are photopigments, which are responsible for capturing light. There are three different types: those that react to daylight (they give us the vision of colors), rhodopsin for when there is little light and melanopsin, which is used to modulate the pupillary function and the circadian rhythm.
In sunlight, UV, violet and blue light are responsible for phototoxicity of UV-blue light by 67%, 18% and 14%. At present, we spend a lot of time in front of the electronic devices (computers, tablets, smartphones), with LED light emitting blue light. This is a risk factor in the development of macular degeneration associated with age.
Blue light filter lenses have an absorbance peak at 440 nm. From this value, the lenses let all the light pass, since at 460 nm there is the maximum absorption of melanopsin, which regulates the circadian rhythm.
They are the most advanced treatment in the present. Very suitable for people who spend time in front of the screen of the computer, tablets, mobiles, ... They can be distinguished because the color of the reflection is purple. Also, there is a manufacturer that offers an additional infrared filter to improve eye health and decrease the appearance of skin wrinkles.
b) UV filter: the rays that pass through the glass are filtered by the material. Those that are reflected on the inside of the lens enter everywhere. This type of anti-reflex coating eliminates the reflected rays, achieving total protection to the UV.
c) For night driving: the anti-reflex coating is optimized for the led or xenon lights of cars, making it much easier to drive at night.
d) Easy cleaning: on the anti-reflex coating, a hydrophobic layer with anti-static, non-stick and sliding properties is placed to prevent dirty lenses.
e) Anti-fogging: with the help of a special cleansing cloth, it prevents the lenses from fogging.
Hardened: a layer based on polysiloxanes, deposited on the surface of organic lenses, causes it to have a much higher hardness than without treatment. Even so, the irradiated lens does not return.
Color: the lenses with different degrees of absorption of light have been used for reasons of sun protection or aesthetics. Depending on the degree of transmission of the light they are classified:
There are three main categories:
a) Solar: uniforms, gradients, mirrors, flash mirrors in any color and intensity
b) Photocromatic: they become very dark in the outside (they react to the ultraviolet light) and they are clarified little by little. Their response can be influenced by ambient temperature.
In organic glass, it is a layer that is placed between the lens and a protective layer on the outside. In mineral lenses, it is massive. In mineral lenses, they are halides of bromine, chlorine or fluoride the molecules responsible for color change. In organic, oxazines and naphthopyranes.
c) Polarized: light is an electromagnetic wave that vibrates in all directions. When the sunlight falls on a surface (sea, snow, highway, ...) is reflected, the part that vibrates horizontally increases and produces glare. Polarized lenses are opaque to the horizontal waves, allowing the rest of the light to pass. The produced effect is a clearer and more contrasting vision, without glare.