Intraocular Lenses with Filters

What is the light spectrum?

Light spectrum

Light spectrum (https://www.educ.ar)

Natural light can split into different colours, in other words, it is polychromatic.  This happens when it passes from one medium to another, when it comes from the air and meets with water.

The colours of the light spectrum are those which are visible to the naked eye and are commonly known as the colours of the rainbow.  Each of them has their own wavelength and when a colour is referred to separately, it is known as monochromatic light.

 

How does sunlight affect the ocular system?

Ultraviolet rays are not visible to the human eye but they are present. Hence the importance of protecting yourself from them as they can be harmful to the eyes’ structures, especially as we are constantly exposed to sunlight.

The eyes’ lens naturally blocks a certain amount of ultraviolet rays.   It also has the capacity to protect the retina against blue monochromatic light, which is harmful to this structure.  When cataract or refractive lens surgery is performed, this natural lens is removed, so the eye is unprotected from this type of light rays.  This increases the risk of age-related macular degeneration developing or progressing as the eye is exposed to ultraviolet and blue light.

What are intraocular lenses with filters?

The lenses which have been used up to now are artificial clear lenses with an ultraviolet filter.  However, due to the wavelength of blue light, they are incapable of filtering it.  Over time it has been observed that the retinal tissues can be affected by this type of monochromatic light, which can have a negative impact on certain conditions such as Age-related Macular Degeneration (AMD).  The solution to this problem is to add a yellow filter to intraocular lenses, equipped to block the wavelength corresponding to blue light.  This ensures that only the rest of the light spectrum reaches the retina.

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Today, it is recommended to choose an intraocular lens with a yellow filter due to the known contraindications relating to blue light and also because they improve patients’ quality of vision.  This is a preventative and also therapeutic measure.

If the patient has been operated on before for cataracts and at the time a lens with a yellow filter was not implanted, it is not recommended to do so in the surgery on the second eye.  This is because the patient may note a difference in colour perception between one eye and the other.