Mr. Zhang, a businessman in Changshu, had a significant vision loss in the last year and had difficulty driving at night. Cataract surgery is the fastest growing and most technically mature of modern ophthalmic microsurgery. As long as it is not accompanied by other eye diseases that affect vision, such as fundus hemorrhage and macular degeneration, the visual function will be significantly improved after surgery. In clinical practice, the success of cataract surgery is not only closely related to the technical level of the surgeon and the surgical and examination equipment, but also the correct choice of IOL is a very important aspect. Mr. Zhang precisely chose the right IOL to meet his requirement of driving at night.
The current IOLs are divided into two types according to the production materials, namely hard and soft IOLs. Hard IOLs are made of polymethyl methacrylate (PMMA), while soft IOLs, also known as foldable IOLs, are made of acrylate and silicone.
Hard IOLs have been used in clinical practice for a long time and their clinical results have been well proven. They are inexpensive, but the surgical incision for implantation is large, usually around 6 mm. Soft IOLs are characterized by being foldable, so the incision at implantation is small, generally at 2~3 mm, without sutures, and the recovery of vision after surgery is fast, but the price is relatively high.
Currently, soft IOLs are mostly used in clinical practice. This is because only this kind of lens can be made into adjustable IOLs and aspheric IOLs.
Adjustable IOLs improve post-operative vision Most of the IOLs in clinical use are monofocal IOLs, which have only one focal point and the implanted eye can only see objects at one distance. Therefore, after the surgery, it is still necessary to wear nearsighted glasses or fancy glasses to meet the needs of seeing far and near. Adjustable IOLs, developed in recent years, are based on two main principles: displacement adjustment and multifocal imaging, and the corresponding IOLs are also called adjustable IOLs and multifocal IOLs. These IOLs are useful to improve the vision throughout the post-cataract surgery period and are less dependent on glasses.
Aspheric IOLs are visually effective In recent years, the concept of wavefront aberration in the human eye has been introduced in the field of refractive ophthalmology. Studies have shown that the normal human eye has a negative spherical aberration in the lens and a positive spherical aberration in the cornea, and this complementary positive and negative spherical aberration reduces the total spherical aberration in the human eye, which results in good visual quality. As age increases, the negative spherical aberration of the lens gradually decreases, while the positive spherical aberration of the cornea remains the same, and the lens compensates for the positive spherical aberration of the cornea gradually decreases, resulting in a decrease in visual quality. Aspheric IOLs are designed to compensate for the positive spherical aberration of the cornea based on the above theory.
This IOL increases the negative spherical aberration by modifying the curvature of the anterior or anterior-posterior surface of the IOL to balance the positive spherical aberration of the cornea and reduce the whole-eye aberration of the IOL eye, thus improving the visual quality of post-cataract patients.
Individualized selection can meet the needs of patients Compared to the measurement of the prescription of glasses, the calculation of the prescription of IOLs is much more complicated. Prior to cataract surgery, the refraction, corneal curvature and axial length of the operated eye must be measured. The surgeon then selects the appropriate IOL formula based on these data, and the calculated prescription needs to be adjusted with the constants of different IOLs before determining the IOL to be implanted.
Individualized IOL selection based on the patient’s preoperative examination results and subjective desires is the choice of a highly qualified cataract surgeon. There are many types of IOLs available, including ordinary rigid IOLs, foldable IOLs, aspheric IOLs, and multifocal IOLs, which can meet the needs of different patients’ conditions and economic conditions.