Intraocular lenses: monofocal, multifocal, EDOF

During cataract surgery something happens that few people think about in advance: besides removing the cloudy lens, the surgeon inserts a new one. This is the artificial lens, which ophthalmologists call an intraocular lens, and its type largely decides how you will see after the operation, up close, at intermediate distance and in the distance.

The choice, however, is made beforehand, and without being able to try it out. And it is a choice made of trade-offs: gaining freedom from glasses at a certain distance can mean accepting some extra halos around lights at night⁵.

In this article

1. What an artificial lens is
2. Monofocal: sharp at one distance
3. Multifocal: several distances, some extra halos
4. EDOF: extended depth of focus
5. Toric: when there is astigmatism too
6. And the blue light filter?
7. How the artificial lens is chosen
8. Frequently asked questions
9. Sources

What an artificial lens is

The artificial lens is a synthetic lens that the surgeon inserts into the eye after removing the clouded natural lens¹. Today it is usually made of hydrophobic acrylic, a material that repels water³, and it is designed to stay in the eye permanently². All modern lenses attenuate the passage of ultraviolet rays¹. Its power is calculated before the operation, on the basis of measurements of the eye⁴; we describe how the operation is carried out in our article on cataract surgery.

To find your way among the different types it helps to think of three distances: far, for driving or watching television; intermediate, that of the computer screen or the dashboard; near, for reading a book or the phone.

Monofocal: sharp at one distance

Monofocal lenses are the reference. They focus sharply at a single distance, chosen before the operation: usually the distance. Good distance vision without correction is now a realistic result, while for near vision some extra help is generally needed, usually reading glasses⁵.

There is also a variant, monovision: one eye is set for distance and the other for near⁶. NICE, the British National Institute for Health and Care Excellence, indicates it for people who already use it before the operation and want to keep it⁴. In comparison with multifocal lenses, the 2016 Cochrane review found that monovision leaves a greater need for glasses but gives less glare⁵.

Multifocal: several distances, some extra halos

Multifocal lenses have several focusing zones, to offer useful vision at several distances, including near⁵. The three-focus versions are called trifocal.

The recommendations published in 2024 by the European Society of Cataract and Refractive Surgeons (ESCRS) consider them an option for people who want a high likelihood of independence from glasses, but ask for considered use, because halos, glare and other light disturbances are more frequent than with monofocal lenses and contrast sensitivity may be reduced⁶. NICE goes further and recommends not offering them in cataract surgery⁴.

Not all studies agree: a 2022 network meta-analysis, on 27 studies and 2,605 patients, found no statistically significant differences between multifocal and monofocal lenses for contrast, glare and halos⁷.

EDOF: extended depth of focus

EDOF lenses, from the English extended depth of focus, try to lengthen the range of distances in focus, above all towards the intermediate distance. In the 2022 network meta-analysis they gave sharper unaided intermediate vision than monofocal lenses⁷; a similar analysis from 2024, on 28 randomised trials and 2,465 people, confirmed the intermediate advantage and found that trifocal lenses offer, compared with monofocal ones, sharper near vision⁸.

A 2024 Cochrane review compared trifocal and EDOF lenses directly, but found only five studies, with 233 people followed for three to six months. In the distance the results were similar; in a study of 60 people, unaided near vision below the threshold considered normal affected 3% of those with a trifocal lens and 30% of those with an EDOF lens. Halos and glare were reported with both, with no detectable differences, and the certainty of the evidence was low³.

The ESCRS recommendations summarise the comparison as follows, shown here in simplified form⁶:

What changes	Multifocal	EDOF	Monovision
Distances in focus	near, intermediate, far	intermediate and far	intermediate and far
Reading glasses	can often be done without	needed in most cases	needed in most cases
Halos and glare	more likely, reduced contrast	less likely	unlikely

Toric: when there is astigmatism too

Astigmatism often arises from a cornea that is more curved in one direction than in the other, and blurs images at all distances. According to a 2021 review, more than 40% of people having cataract surgery have astigmatism of at least one dioptre, an amount that, if uncorrected, affects vision⁹. Toric lenses also contain a correction for astigmatism.

A 2019 Cochrane review compared them with limbal relaxing incisions, small cuts at the edge of the cornea that change its curvature. In 10 studies on 517 people, about 700 eyes in 1,000 with a toric lens had residual astigmatism below half a dioptre, against about 500 in 1,000 with the incisions (evidence of moderate certainty); the difference in final vision, on the other hand, was small¹⁰. The ESCRS recommends considering toric lenses from corneal astigmatism of one dioptre, with stronger evidence above two dioptres⁶.

And the blue light filter?

Some lenses also filter part of the visible blue light, with the idea of protecting the macula. A 2018 Cochrane review of 51 randomised trials, covering more than 5,000 eyes, found no clinically relevant differences in vision compared with lenses without the filter, and concluded that it is not clear whether the filter affects the health of the macula or the risk of macular degeneration¹. We also discuss this in connection with glasses with a blue light filter.

How the artificial lens is chosen

NICE asks that the consequences of the different lenses for vision be discussed with the person and that the choice be based on the result they themselves prefer, recorded in their notes⁴. The ESCRS recommendations speak of shared decision-making and indicate three criteria for lenses that also correct presbyopia: other eye diseases, the wish for independence from glasses and realistic expectations⁶.

The useful questions concern everyday life: at which distances do you most want to do without glasses, how much do you drive at night, how much would halos around lights bother you. The alternatives for people who want fewer glasses for near vision are also collected in our article on solutions for presbyopia.

Frequently asked questions

Does the artificial lens last for ever?

It is designed to stay in the eye permanently². Among the possible complications, the ESCRS recommendations also list problems with the lens itself, such as displacement or clouding⁶. Another possibility is the veiling of the capsule that holds the lens, secondary cataract.

Are glasses still needed after cataract surgery?

It depends on the lens and on the result chosen. With monofocal lenses, glasses are generally needed for reading⁵; multifocal and EDOF lenses reduce the need, but do not eliminate it for everyone^3,5,6. NICE asks that people be told before the operation that glasses might be needed for some activities⁴.

Do multifocal lenses cause halos at night?

Halos are more frequent with multifocal lenses than with monofocal ones⁵; with EDOF lenses they are less likely than with multifocal lenses⁶, although not all studies agree on the extent of the problem⁷.

Is there an artificial lens that suits everyone?

No. The balance between benefits and undesirable effects changes from person to person⁵, and the guidelines ask that the decision be made together, taking into account other eye diseases, habits and expectations^4,6.

The artificial lens is not a technical detail: it is the lens through which you will look at the world after the operation. The studies describe what each family of lenses offers and what it asks in return, often with evidence of still low certainty; the rest depends on how you live, and is decided with your ophthalmologist.