Artificial crystals can be divided into foldable crystals and unfolded crystals, colorless crystals and yellow crystals, and can be divided into single and three pieces according to the same and different material combinations. The materials that make up crystals can be divided into: polymethyl methacrylate (PMMA), hydrogel, silica gel and other crystals.

Second, the function is different:

Functionally divided into single focus and multi-focus; UV-resistant and non-UV-resistant crystals (rarely used at present); Crystals with and without heparin sodium treatment on the surface.

Third, the price is different:

As far as crystal price is concerned: imported and folded crystals; Crystals treated with heparin sodium (Famacia crystals) are more expensive; Other prices are in the middle, and domestic ones are cheaper.

Fourth, users are different.

Normal people can see distant objects clearly because light passes through the refractive system including the lens and forms a clear image on the retina. When they look near, they pull the ligament of the lens through the contraction of the ciliary muscle to change the convexity of the lens, so that they can form a clear image on the retina when they look near and far.

Intraocular lens is a kind of lens with constant diopter synthesized from artificial materials. When you look far away, you can get a clear image. If you look closely, you can see clearly with +300-degree reading glasses. In recent years, with the continuous development of science and technology, the lens has been developed into a bifocal or multifocal intraocular lens, which is closer to the physiological lens, but more expensive.

Extended data:

First, yellow intraocular lens

1. All intraocular lenses are added with ultraviolet absorbers to block ultraviolet rays, but ordinary intraocular lenses cannot block blue light. Yellow intraocular lens is designed to block blue light and reduce light damage to macula.

Second, the introduction of yellow intraocular lens and white intraocular lens is suitable for the crowd:

1. The previous intraocular lens had only one focus, and it had no accommodation, so it could be seen clearly from far to near (presbyopia). Instead, they need short-sighted glasses to make up for it. In order to overcome this defect, people have developed and applied multifocal intraocular lenses in the past 30 years.

2. There are two main types: A. Multi-area and multi-focus type, including two areas, three areas, four areas and five areas. That is, the intraocular lens is divided into central zone and peripheral annular zone, and the diopters of each part are different, generally 2.5D apart, forming two focal points, one near and the other far. The disadvantage of this crystal is that far and near vision is affected by pupil size and ambient light intensity.

3, B, diffractive multifocal type, this crystal is based on Huygens' wave theory, and 30 small grooves with a depth of 2 microns are carved on the back of intraocular lens, which overcomes the influence of pupil size change on segmented multifocal crystal.

The same disadvantage is that the energy of light entering the eyes must be divided into two parts. Half is near and the other half is far away. The distance is not very clear, which affects the vision to some extent. It has not become the mainstream of a few doctors and patients.

Three, aspherical intraocular lens:

1, reducing aberration, effectively improving imaging quality, obviously improving night vision, approaching normal eyes, especially suitable for the elderly or drivers with mobility difficulties at night.

Baidu encyclopedia-artificial crystal