What Are IOLs?
During cataract surgery, the natural lens of the eye that has become clouded over time is removed. An IOL serves as an artificial replacement for the eye’s natural lens, allowing patients to see clearly after treatment. Prior to the development of IOL implants, patients who underwent cataract surgery had to wear thick eyeglasses or contact lenses to be able to see well after the removal of the eye’s natural lens.
Approved by the FDA in 1981, IOL implants have actually been in use since the mid-1960s. The first generation of IOLs is known as monofocal IOLs. Premium IOLs represent an innovative improvement in IOL technology, allowing good distance and near vision, and reducing the chances of glasses.
Premium IOLs vs. Monofocal IOLs
There are two basic types of IOLs: monofocal and premium (sometimes referred to as multifocal). Traditional IOLs, also known as monofocal IOLs, restrict patients’ vision, allowing them to see well at one distance only (near, intermediate, or far). With monofocal IOLs, patients must rely on corrective lenses in order to be able to focus on objects at other distances. Premium or multifocal IOLs, on the other hand, offer patients the ability to see clearly at more than one distance without glasses. Although premium IOLs allow a greater range of vision than monofocal IOLs, the procedure required to implant each type of lens is similar.
Premium IOL Candidates
Ideal candidates for premium intraocular lens implants typically:
- have a clinically significant cataract, but are in otherwise excellent ocular health
- communicate a strong desire for a range of vision with reduced dependence on corrective lenses
Multifocal IOLs are another category of presbyopia-correcting IOLs that can decrease your need for reading glasses or computer glasses after cataract surgery.
Like multifocal contact lenses, these premium IOLs contain added magnification in different parts of the lens to expand your range of vision so you can see objects clearly at all distances without glasses or contact lenses.
Some studies have shown multifocal IOLs tend to provide better near vision than accommodating IOLs, but they also are more likely to cause glare or mildly blurred distance vision as a tradeoff.
Your cataract surgeon can help you decide if you are a good candidate for multifocal IOLs at your preoperative exam and consultation. Laser cataract surgeryoften is recommended if you are interested in multifocal IOLs, because precise alignment of these lenses is very important to give you the best visual outcome at all distances.
Age-related cataract (senile cataract)
Toric IOLs are premium intraocular lenses that correct astigmatism as well as nearsightedness or farsightedness.
Like toric soft contact lenses, toric IOLs can correct astigmatism because they have different powers in different meridians of the lens. They also have alignment markings on the peripheral part of the lens that enable the surgeon to adjust the orientation of the IOL inside the eye for optimal astigmatism correction.
Just prior to cataract surgery, the surgeon places temporary markings on the patient’s cornea that identify the location of the most curved meridian of the front of the eye. Then, when the toric IOL is implanted during the cataract procedure, the surgeon rotates the IOL so the markings on the IOL are aligned with the markings on the cornea to insure proper astigmatism correction.
Prior to the development of toric IOLs, cataract surgeons had to perform a procedure call limbal relaxing incisions (LRI) to correct astigmatism during or after cataract surgery. In LRI, small incisions are made at opposite ends of the cornea, very near the junction between the cornea and the surrounding white sclera. (This junction is called the limbus.) When these incisions heal, the cornea becomes more spherical in shape, reducing or eliminating astigmatism.
In some cases — even when a toric IOL is used — limbal relaxing incisions may be needed after cataract surgery to fully correct astigmatism. But typically in such cases, the amount of astigmatism remaining after implantation of a toric IOL is far less, making a better LRI outcome more likely.
Traditional intraocular lenses have a spherical optical design, meaning the front surface is uniformly curved from the center of the lens to its periphery. Though a spherical IOL is relatively easy to manufacture, this design does not mimic the shape of the natural lens inside the eye, which varies in curvature from center to periphery. In other words, the eye’s natural lens is aspheric (“not spherical”).
Why is this important?
A spherical intraocular lens can induce minor optical imperfections called higher-order aberrations(HOAs), which can affect quality of vision, particularly in low-light conditions such as driving at night.
Premium aspheric IOLs, on the other hand, match more closely the shape and optical quality of the eye’s natural lens, and thereby can provide sharper vision — especially in low light conditions and for people with large pupils.