Monofocal vs multifocal lens for cataract surgery

During cataract surgery the natural lens is removed and an intraocular lens is placed in the eye permanently. The choice of lens determines how well you see at different distances afterwards and how much you rely on glasses.

No lens restores the focusing flexibility of a young eye. Each option trades something: monofocal lenses give crisp vision at one distance, multifocal lenses widen the range but dilute image quality, and extended depth of focus lenses sit in between.

Most people choose or are given a monofocal lens set for distance. Distance vision, including night driving, is typically sharp, and the cost is a need for reading glasses and possibly intermediate glasses for computer work. Some people choose to set one eye for near and one for distance (monovision), which NICE mentions as an option for those who already use it.

Monofocal lenses are the NHS standard, have a very long track record, and carry the lowest risk of visual side effects from the lens design.

Multifocal lenses have rings or zones that focus light at more than one distance. Many people with them rely less on glasses, which is attractive to those who dislike spectacles. But some people notice haloes around lights, glare at night, reduced contrast in dim light and, in a minority, a persistent dissatisfaction that leads to lens exchange.

They suit people with otherwise healthy eyes, regular astigmatism that can be corrected and realistic expectations. They are generally not advised in the presence of macular disease, advanced glaucoma, corneal irregularity or other conditions that already reduce contrast. They are usually offered privately with extra cost, which a provider should itemise.

NICE NG77 on cataracts in adults advises not offering multifocal intraocular lenses to people having cataract surgery, reflecting the balance of visual side effects and cost against benefit.

In private practice, surgeons discuss lens choice according to lifestyle, eye health, occupation and tolerance of visual side effects. Professional bodies such as the Royal College of Ophthalmologists provide guidance and patient information on cataract surgery.

• You drive a lot at night or have any other eye disease: a monofocal lens is usually the safer choice.

• You strongly dislike glasses, have healthy eyes and understand the trade-offs: ask a private surgeon whether a multifocal or extended depth lens could suit.

• You have significant astigmatism: ask whether a toric lens or other correction is appropriate.

• You currently use monovision contact lenses successfully: tell the surgeon, as this can be replicated.

• You want certainty about the outcome: discuss what happens if you are unhappy and what an exchange would involve.

A multifocal lens does not guarantee freedom from glasses; many people still need them for some tasks. And a monofocal lens does not mean poor vision; with the right glasses, vision is excellent.

It is also not true that private lenses are simply better. They offer different trade-offs that suit some people and not others.

• What would my vision be like with each lens and which glasses would I still need?

• Do I have any eye condition that makes a multifocal lens unsuitable?

• What is the itemised cost of the lens and surgery?

• What happens if I am unhappy with the lens?