Choosing a Cataract Lens

5 September 2019

Doctor explaining a cataract lens to a patient.

In modern cataract surgery, the clouded crystalline lens is removed and replaced by an artificial intraocular lens (IOL). Intraocular lenses represent a highly innovative technology – both in terms of corrective power and the quality of vision provided. Different types of intraocular lenses are available today, enabling good vision at near or far distance.

Size of intraocular lenses (IOLs) in comparison to an almond. — Actual IOL size compared to an almond

Intraocular lenses explained

IOLs can simulate the refractive properties of the natural lens, however they do not have the ability to accommodate. Advanced intraocular lenses are designed to meet additional, individual patient's vision requirements. Depending on the design, the advanced IOLs can offer further benefits, such as improved contrast perception.

Intraocular lenses are usually made of a soft, synthetic, and biocompatible material. A typical IOL measures approximately 13 mm in diameter. The thickness of the lens can vary, depending on its refractive power. The corrective power of the lens is individually calculated and may differ for each eye. An IOL is transparent and neither visible nor perceptible in the eye.

Different Types of Intraocular Lenses

There are different types of intraocular lenses available today.

Standard intraocular lenses are the most commonly used implants in cataract treatment. They have one focal point and can improve sight at one distance: far or near. These lenses are called monofocal lenses. For the remaining distances, the patient may still need to use glasses.
Advanced versions offer additional advantages on top of treating the cataract. For instance, aspheric IOLs can improve contrast sensitivity and general image quality.

Characteristics of Monofocal IOLs

Demonstration of the visual perception with a monofocal IOL in everyday life. — Vision Simulation with a monofocal IOL

Clear vision at one distance

This is the most common type of intraocular lens used in cataract surgery. When light enters the eye through a monofocal lens, it is bent to a single focus point on the retina.

Light cannot be focused from both distant and near objects at the same time, so it means that a monofocal lens can correct vision at one distance, providing good visual perception for either near, or far distance.

Most patients choosing this option want to be able to see at a distance, allowing them to perform activities such as driving and watching TV. They usually need to use glasses to help with near vision tasks, such as reading, cooking and working on the computer.

A couple enjoying good vision after cataract surgery. — Monofocal IOLs can correct far or near vision.

Choosing the Right Distance

While most surgeons implant the monofocal option with distant focus to correct far vision, it is also possible to choose a monofocal lens with near correction to enable good vision up close. For all other distances, the patient needs to wear glasses.

The decision about whether distant or near sight should be corrected depends on the patient's lifestyle and visual needs. The decision should be made in agreement with the surgeon after a close consultation with the patient.

Monofocal IOLs

What You Should Know

Standard types of monofocal IOLs have a spherical optic, which is equally rounded on both sides. It is normally paid for by your health insurance.

However, the natural crystalline lens of the eye has a slightly aspherical (not completely round) shape at the front, and is not equally curved on both sides. This shape enables it to precisely focus light rays entering the eye onto one point on the retina. The result is a clear, crisp image.

Advanced monofocal IOLs are available with an aspherical optic very similar to the original shape of the crystalline lens. The special design of the aspheric versions enable an enhanced image quality.

Aspheric IOL Functions

Additional advantages of advanced cataract treatment options

Advanced IOL solutions such as aspheric lenses correct certain light phenomena and improve contrast, providing an optimized image quality.

These additional functions are not always covered by the national health care system. Please check with your doctor if an aspheric and/or toric IOL is recommended in your case and discuss the potential extra costs of the lens.

How Aspheric Lenses Correct Vision

The special, not uniformly curved, design of the aspheric IOLs enables the correction of spherical aberrations.

Demonstration of the vision affected by astigmatism and corrected with a toric IOL. — Vision simulation with a spheric (left) and an aspheric IOL (right).

What is a spherical aberration?

A spherical aberration is a visual defect that occurs when light rays passing into the eye are not precisely focused at one single focal point. When we are young, the cornea and lens of the eye work together to focus the entering light rays at exactly one point on the retina, optimizing image contrast.

As we grow older, that interaction deteriorates, causing reduced vision quality. This means:

Vision gets blurry.
Contrast perception is decreased, leading to difficulty seeing in low-light conditions.

With aspheric IOLs, light rays entering the eye are once again sharply focused at a single point on the retina. The result is improved contrast sensitivity and an enhanced image quality, especially during activities such as driving at night or reading in dim lighting conditions.

If you are already suffering from spherical aberration or you want to prevent this visual change, an aspherical IOL may be a suitable option for you. Discuss this option with your ophthalmologist.