Ah Ma's cataract lens: monofocal, multifocal, toric

Key takeaways

After cataract surgery the cloudy lens is replaced by a clear artificial lens (an IOL), and its power and design decide where Ah Ma sees sharply and what she may still need glasses for.
A monofocal lens has one focusing distance, usually set for distance, so reading glasses are common afterwards. It is the most common type and has been used for decades.
Multifocal and extended depth-of-focus lenses are designed to give clear sight at more than one distance, but glare, halos and lower contrast are more common, and they are generally not recommended with glaucoma, macular degeneration or other eye disease.
A toric lens has extra built-in correction for astigmatism. Ask whether her astigmatism is enough to matter.
If sight turns cloudy again months or years later, it is usually posterior capsule opacification, not a new cataract, and a laser of about five minutes can clear it.

The family has been told that Ah Ma needs cataract surgery, and then comes the question at the counter: a basic lens, or a "premium" one? This page is for the son or daughter who has to answer it. It does not choose a lens for her. It explains what each type is designed to do, what it can cost her in other ways, and what to ask, so that the talk with her surgeon is a real one.

The money side of the decision has its own page. Our article on cataract surgery in Malaysia, government or private tells you to ask "which lens". This page explains what the answer means.

What does the artificial lens in Ah Ma's eye actually do?

It does the job her own lens did: it bends the light coming into the eye so that it focuses at the back. A cataract is a cloudy natural lens. Surgery takes it out and puts in a clear artificial lens, called an intraocular lens, or IOL. The American Academy of Ophthalmology (AAO) says an IOL comes in different focusing powers, just like glasses or contact lenses, and most are made of silicone, acrylic or another plastic.

That is why there is a choice at all. The lens is not only a clear window. Its power and design decide where Ah Ma will see sharply, and whether she will still need glasses for some things afterwards. The NHS says people may still need glasses for reading or for seeing at a distance after surgery, and that the prescription may be different from before.

What is a monofocal lens, and why will she probably still need reading glasses?

A monofocal lens has one focusing distance. It is the most common type used in cataract surgery. The AAO says it can be set for near, middle or far, and most people have it set for clear distance vision, then wear glasses for reading and close work.

Some families prefer the reverse: a lens set for near, with glasses for the television and the road. Others try "monovision", where one eye is set for distance and the other for near. The AAO says this is not for everyone, though for many people the brain adapts and blends the two. Whether Ah Ma would like it depends on how she lives: does she sew, read the newspaper every morning, play mahjong, or mostly watch television? Tell the surgeon what her days are like.

A monofocal lens is the plain option, and its trade-off is simple: sharp at the chosen distance, glasses for the rest.

What do multifocal and extended-depth lenses add, and what can they cost her?

They are designed to give clear sight at more than one distance, so she may depend less on glasses. They also bring side effects that a monofocal lens usually does not. The AAO calls these lenses "presbyopia-correcting".

A multifocal lens has several zones set at different powers, so near and far focus work at the same time and the brain learns to pick the right one. An extended depth-of-focus (EDOF) lens has one stretched zone that covers distance and the middle range, such as a computer screen or a cooking pot on the stove. The AAO says this may mean less effort when changing focus.

The cost is in the quality of vision. The AAO lists glare, rings (halos) around lights, lower contrast, and sight that is less sharp in dim light or fog. It says most people adapt, but night drivers may be happier with a monofocal lens, and it can take six to eight weeks for the eye to learn to focus fully at all ranges.

A Cochrane review of 20 trials found that people with multifocal lenses may have had better near vision and may have needed glasses less, and also reported more glare and haloes. The reviewers said whether the gain is worth it varies from person to person, and that the wish to be free of glasses is likely to be the deciding factor.

These lenses are also not for every eye. The AAO says they are generally not recommended for people with vision loss from glaucoma, macular degeneration or other eye disease, because they let less light into the eye and can make things worse. If Ah Ma has one of these, read our pages on macular degeneration in a grandparent and glaucoma in the family first, and tell her surgeon about it before any lens is quoted.

When is a toric lens worth asking about?

When Ah Ma has astigmatism: the front of her eye is curved more like an egg than a football, and that blurs both near and far. A toric lens has extra built-in correction for it. The AAO says people with moderate to high astigmatism are usually happier with toric lenses, and that they come in monofocal form and in some of the presbyopia-correcting types.

So a toric lens is not a different kind of focus. It is a monofocal or other lens with the astigmatism corrected as well. Ask whether her astigmatism is enough to matter, because the answer decides whether this is worth discussing at all.

Why does the "premium" lens cost more, and what should we ask?

The sources say the special types cost more. The AAO says multifocal, EDOF, toric and similar lenses are called premium lenses, that they are more expensive than monofocals, and that in the United States they are usually paid for out of pocket. It does not itemise why, and no figure from this page would fit Malaysia, so we give none.

What a family can do is ask clear questions, in writing if possible:

Which lens is being quoted, and why does it suit her eyes?
What will she still need glasses for, even with this lens?
What are the side effects of this type, and what happens if she cannot tolerate them? The AAO notes that some people need further surgery to fine-tune a lens.
Does the fee include the follow-up visits, and a laser later if one is needed (the last section)?

The AAO says monofocal lenses have been used for decades and are the most popular type, so "basic" is not a poor choice. A higher fee buys a different design with different trade-offs, and for some people the plain lens is the better fit.

How is the lens chosen, and what about the second eye?

The surgeon measures Ah Ma's eye before surgery and chooses the lens with her. The AAO says the length of the eye and the curve of the cornea are measured to set the lens power. For presbyopia-correcting lenses it also lists the refractive error, the pupil size and function, and the shape of the cornea. This is why the choice cannot be made from a brochure.

Bring her own eye history, including other eye disease, past eye operations and any laser. If she has cataracts in both eyes, the NHS says they are treated on separate days. Ask the surgeon how that applies to her, and whether the same lens type is planned for both.

What if her sight turns cloudy again months later?

That is not the cataract coming back. The AAO says a cataract does not return once the natural lens is out, but weeks, months or years later the thin membrane behind the lens can turn cloudy, and the sight blurs again. This is called posterior capsule opacification, and it is sometimes described as a "secondary cataract". The NHS says it can happen months or years after surgery.

The treatment is short. A YAG laser makes a small opening in the cloudy membrane. The AAO says it takes about five minutes, is done in the clinic or an outpatient centre, usually needs doing once per eye, and that sight should improve in about 48 hours when there is no other eye problem.

It has its own risks, including a raised eye pressure and, rarely, a retinal detachment, so a curtain or shadow across the sight, many new floaters or flashes of light mean calling the eye doctor straight away.

If Ah Ma says the fog has returned, take her for an eye check and do not wait for it to pass. For the first weeks after the operation itself, and when to phone the unit, see after Ah Ma's cataract operation. And if you were hoping drops or supplements might do the job instead, this page on what helps and when surgery is due sets out why they do not.

Do not wait for the next appointment if Ah Ma…

Sees a dark curtain or shadow across her sight, many new floaters (dots and lines), or flashes of light, after surgery or after a laser. These can be signs of a retinal detachment.
Has an eye that becomes more painful or more red, or sight that gets worse instead of better, in the days after surgery. Phone the operating unit the same day.
Has sight that turns misty again some months after the operation. This can be treated, so book an eye check and do not wait for it to pass.

Common questions

What is the difference between a monofocal and a multifocal lens for cataract surgery?

A monofocal lens has one focusing distance, usually set for distance, so most people wear glasses for reading. A multifocal lens has several zones set at different powers to give clear sight at more than one distance. The trade-off is that glare and halos are more common with multifocal lenses.

Will my mother be able to see without glasses after cataract surgery?

It depends on the lens and on her eyes, and no lens can promise it. The American Academy of Ophthalmology says multifocal and similar lenses can reduce the need for glasses but that the ability to read without them varies from person to person. The NHS says people may still need glasses for reading or distance.

What is a toric lens, and who needs one?

A toric lens is a lens with extra built-in correction for astigmatism, where the front of the eye is curved more like an egg than a football. The American Academy of Ophthalmology says people with moderate to high astigmatism are usually happier with a toric lens. Ask the surgeon whether her astigmatism is enough to matter.

Can a multifocal lens be used if she has macular degeneration or glaucoma?

Usually not. The American Academy of Ophthalmology says multifocal and extended depth-of-focus lenses are generally not recommended for people with vision loss from glaucoma, macular degeneration or other eye disease, because they let less light into the eye. Tell the surgeon about any eye disease before a lens is quoted.

What should we ask when the hospital quotes a higher fee for a special lens?

Ask which lens is quoted and why it suits her eyes, what she will still need glasses for, what the side effects are, and whether the fee includes the follow-up visits and any laser needed later. Ask for the answer in writing. The sources used here give no figures for Malaysia, so none are given.

Why has Ah Ma's sight gone cloudy again after cataract surgery?

It is usually posterior capsule opacification, where the thin membrane behind the lens turns cloudy weeks, months or years after surgery. A cataract does not return once the natural lens is removed. The American Academy of Ophthalmology says a short laser treatment can clear it, and it typically needs doing once per eye.

What happens during the laser for clouding after cataract surgery?

It is called a YAG laser capsulotomy. The eye is numbed with drops and the pupil is widened. A laser makes a small opening in the cloudy membrane behind the lens. The American Academy of Ophthalmology says it takes about five minutes and that sight should improve in about 48 hours if there is no other eye problem.

References

American Academy of Ophthalmology · Intraocular lenses (IOL) for cataract surgery · www.aao.org
American Academy of Ophthalmology · Factors to consider in choosing an IOL for cataract surgery · www.aao.org
American Academy of Ophthalmology · Presbyopia-correcting IOLs · www.aao.org
American Academy of Ophthalmology · What is posterior capsulotomy? · www.aao.org
American Academy of Ophthalmology · Cataract surgery: risks, recovery, costs · www.aao.org
NHS · Cataract surgery · www.nhs.uk
Cochrane Database of Systematic Reviews 2016 · Multifocal versus monofocal intraocular lenses after cataract extraction · pubmed.ncbi.nlm.nih.gov

By Dr Chan Li Yen. General information only. It does not replace a consultation. If you are worried about your child's eyes or vision, please see an eye doctor.

Choosing the lens for Ah Ma's cataract operation: monofocal, multifocal or toric