Types of Intraocular Lenses for Cataracts

Types of Intraocular Lenses for Cataracts

When we operate on a cataract —or perform clear lens exchange surgery to correct presbyopia— we remove the natural lens, which has become cloudy or has lost its flexibility, and replace it with an intraocular lens. That lens is permanent and, above all, it is what determines how you will see afterwards. This is why choosing the model is, by far, the most important part of the planning.

Here is the key point I usually explain in the consultation: there is no single “best lens”, only the right lens for each eye and each way of life. In this guide I review the main types of intraocular lenses, what each one offers and who it suits, so you can arrive at the appointment with a clear picture.

What exactly does an intraocular lens do?

The natural lens is an internal lens of the eye. Over the years it becomes cloudy (cataract) or loses its ability to focus (presbyopia). Surgery replaces it with an artificial lens that restores transparency and provides the correction.

The difference between one model and another does not lie in the safety of the operation, which is practically the same, but in how many distances stay in focus and in the optical trade-offs each design accepts.

The three distances and the optical trade-off

To understand lenses it helps to think in terms of three distances:

• Far: driving, television, the street.
• Intermediate: the computer, the car dashboard, cooking.
• Near: reading, the phone, sewing.

No lens gives everything for free. There is a balance between three factors: independence from glasses, the appearance of night-time phenomena (halos around lights) and contrast quality. The more spectacle independence you seek, the more some small trade-off comes into play in the other two. Understanding this balance is the key to choosing well.

The types of lenses at a glance

Here I review them briefly. Each type of lens will have its own article, where I go into detail about its advantages, its limits and who it suits best.

• Monofocal: Focuses sharply at a single distance, usually far. It offers excellent image and contrast quality and produces virtually no halos. In exchange, glasses are needed for near vision. It is a very safe and predictable option.
• Monofocal plus (mild extended focus): An evolution of the monofocal that adds some intermediate vision without giving up sharpness. Of interest to those who spend time in front of screens but prefer not to take on night-time phenomena.
• EDOF (extended depth of focus): Stretches the focus continuously between far and intermediate. It provides plenty of autonomy for daily life with a very low incidence of night-time halos, in exchange for more limited near vision (glasses are sometimes needed for small print).
• Bifocal: allow good near and distance vision but not intermediate distances. Currently in disuse.
• Trifocal: Focuses far, intermediate and near, and offers the greatest independence from glasses. Its diffractive design can produce night halos which, in most cases, the brain learns to ignore over time (neuroadaptation).
• Toric: Not a separate range, but an add-on: it corrects astigmatism and combines with any of the above (toric monofocal, toric trifocal, etc.). It is what allows astigmatism to be corrected in the same surgery.

How do we choose the lens in the consultation?

There are no shortcuts: the right lens comes out of a personalised prior study. In the consultation in Girona we assess:

• Biometry and eye measurements, which determine the exact power.
• General ocular health: the ocular surface, the retina and eye pressure influence which designs are advisable.
• Lifestyle: a night driver is not the same as someone who spends the day reading or at the computer.
• Expectations: how far you want to depend or not on glasses, and which trade-offs you accept.

Compare it before deciding

Explaining halos or near vision in words has its limits. That is why you can try our lens simulator, where you can see the differences between a monofocal, an EDOF and a trifocal, both in reading and in night-time phenomena.

In summary

Choosing the intraocular lens means choosing how you want to see after surgery. With a thorough study and an honest conversation about what each design offers and what it asks in return, it is possible to find the option that best fits each case.