The main components of human lens are protein and water. It will be atomized or turbid due to aging, and the atomized lens will prevent light and image from projecting onto the retina. Eye damage, some diseases, and even some drug treatments may cause the phenomenon of crystal atomization; According to statistics, more than 90% of cataract cases also originate from the aging process that humans must go through. It is the lens of the eye that becomes turbid, and then the vision is affected. The mechanism is still unclear, and no breakthrough has been made in drug treatment so far. The only effective treatment for cataract is surgery, that is, remove the opaque lens and replace it with an artificial lens, which is called intraocular lens. Intraocular lens implantation is the most effective method to treat cataract. Thousands of cataract patients have obtained good vision through this safe and effective surgical method.
The intraocular lens, also known as intraocular lens, is a precision optical component that is implanted into the eye after surgery to replace the extracted self turbid lens, which is equivalent to replacing a lens.
It is usually composed of a circular optical part and a supporting loop around it. The diameter of the optical part is generally about 5.5~6 mm. The supporting loop is used to fix the intraocular lens. It can be two C-shaped or J-shaped wire mounted supporting loops.
According to the placement position, it can be divided into anterior chamber fixed intraocular lens, iris fixed intraocular lens and posterior chamber fixed intraocular lens. Usually, the best placement of intraocular lens is in the capsule of natural lens, that is, the location of posterior chamber fixed intraocular lens.
According to hardness, it can be divided into hard intraocular lens and foldable intraocular lens. The hard intraocular lens cannot be folded, and an incision (about 6 mm) the same size as the optical part of the lens is required to implant the lens into the eye. In order to adapt to the progress of surgery, the materials of intraocular lenses have been gradually improved, and foldable intraocular lenses have emerged, which can be folded or even curled up. They can be implanted through implantation forceps or implants. After entering the eye, the foldable intraocular lens will automatically expand and support at the designated position.
IOLs can be divided into hard IOLs, foldable IOLs, specially treated IOLs, multifocal/adjustable IOLs, and aspheric IOLs with different characteristics.
(1) Hard intraocular lens
The incision is about 5.6~6 mm. Such a wound sometimes requires suture, which will cause a certain amount of astigmatism. In the short term after surgery, the reaction is greater and the recovery time is longer.
(2) Foldable intraocular lens
First fold the intraocular lens, put it in a special implant, and then push it inside to expand. The incision is generally 2.8~3.2 mm. The incision does not need to be sutured. The astigmatism is relatively small, and the recovery time is faster. The disadvantage is that the price is more expensive than ordinary crystals. It is especially suitable for diabetics to prevent the formation of hindrance. The foldable crystals are mainly made of silicone, hydrogel and acrylic acid.
(3) Specially treated intraocular lens
For some patients with specific eye diseases, this type of intraocular lens may be required, such as heparin surface treated intraocular lens, and the postoperative inflammatory reaction may be much smaller; The intraocular lens containing collagen can improve the compatibility between the intraocular lens and the tissue.
(4) Multifocal/adjustable intraocular lens
The front several intraocular lenses have only one focus, and have no adjustment power. They can see far and see near clearly (presbyopia phenomenon). On the contrary, they need myopic lenses to fill the gap. In order to overcome this defect, people have developed and applied multifocal intraocular lenses over the past 30 years, which are mainly divided into two types:
A， The multi zone and multi focus type has two zones, three zones, four zones and five zones. That is to say, the intraocular lens is divided into the central zone and the surrounding annular zone. The diopter of each part is different, generally 2.5 D, forming two focuses, one looking near and the other looking far. The disadvantage of such crystals is that near and far vision is affected by pupil size and ambient light intensity.
B， Diffractive multifocal crystal, which is based on Huygens' wave theory of light, is carved with 30 small grooves with a depth of 2 μ m on the back surface of the intraocular lens, which overcomes the influence of the pupil size change on the segmented multifocal crystal.
The common disadvantage is that the energy of the light entering the eye must be divided into two parts. Half of the energy is used to see near and half of the energy is used to see far. The distance is not very clear. The visual acuity is affected to some extent. A few doctors and patients have not become mainstream.
(5) Aspheric intraocular lens
It can reduce aberrations, effectively improve imaging quality, and significantly improve night vision, close to normal eyes, especially suitable for the elderly or driver patients with night mobility problems.
(6) Yellow intraocular lens
All IOLs are added with UV absorbers to block UV light, but ordinary IOLs cannot block blue light. Yellow IOLs are designed to block blue light and reduce light damage to the macula.
(7) Implantable micro telescope intraocular lens
It is applicable to cataract patients with macular degeneration. It can magnify the object image by 3 times to provide patients with a single eye magnified central vision
To improve the quality of life, this kind of crystal is still under clinical observation.
Type of intraocular lens Normal people can see distant objects clearly because the light passes through the refractive system, including the lens, to form a clear image on the retina. When looking near, it is done by the ciliary muscle contracting and pulling the crystalline ligament to change the lens convexity, so that when looking near and looking far, clear images can be formed on the retina.
The intraocular lens is a kind of lens with fixed diopter synthesized from artificial materials, which can get a clear image when looking far, and can be seen clearly when looking near with the aid of a+300 degree flower lens. In recent years, with the continuous development of science and technology, the crystal has been developed into a bifocal or multifocal intraocular lens, which is closer to the physiological lens, but the price is relatively expensive.
