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Cataract lens options: monofocal, toric and multifocal intraocular lenses (IOL)

During cataract surgery, the cloudy natural lens is removed and a clear artificial lens takes its place. This artificial lens is called an intraocular lens, or IOL. It stays inside the eye for life and cannot be felt. Choosing the type of IOL is one of the main decisions before the operation, and the names can be confusing: monofocal, toric, multifocal, trifocal, EDOF, and the umbrella term "premium lens". This guide explains each in plain words, so that you can talk it through with our eye surgeon. For the operation itself, see cataract surgery in Vasco, Goa.

What is an intraocular lens (IOL), and what does it do?

Your natural lens focuses light on the retina. Once it is taken out, the IOL does that job instead. Most modern IOLs are foldable, so they pass through a small opening and unfold inside the eye; in manual small incision surgery (SICS) a rigid lens is sometimes used instead. Two separate choices are made for every IOL:

• The power: how strongly the lens bends light. It is worked out for your eye from the length of the eyeball and the curve of the cornea. Read the lens power test.
• The design: whether the lens has one focus, corrects astigmatism, or spreads focus over several distances. The design decides at which distances you can see clearly without glasses.

The power is a matter of measurement. The design is where your own needs, your eye health and the fee come in.

What is a monofocal lens?

A monofocal lens has a single point of focus. It is usually set for distance, so that faces, the TV and the road look clear. For close work such as reading, the phone or sewing, you then use reading glasses. Some people also need a light spectacle power for distance to make vision fully crisp.

Most cataract operations use a monofocal lens. It gives good-quality vision with few side effects at night and suits most eyes, including eyes with diabetes, glaucoma or retina changes. A variation is monovision: one eye is set for distance and the other a little for near. Some people enjoy it; others find the difference between the eyes tiring. If you have never tried monovision, your surgeon may suggest testing it beforehand with contact lenses or glasses.

What is a toric lens, and do I need one for astigmatism?

Astigmatism means the front window of the eye, the cornea, is curved more like the back of a spoon than a perfect dome. Light then focuses unevenly, and things look stretched or blurred at every distance. In spectacle prescriptions it appears as a "cylinder" power with an angle (axis).

Removing a cataract does not change the shape of the cornea, so astigmatism from the cornea stays after surgery. A standard monofocal lens does not correct it. A toric lens has the cylinder correction built into the lens itself, so that distance vision without a cylinder power in your glasses can be sharper.

How a toric lens is planned:

• The amount and direction of the corneal astigmatism are measured before surgery, along with the usual lens power test.
• The axis is marked or recorded on the eye, because the lens has to sit at that exact angle to work.
• During surgery, the lens is turned to the planned angle and left in place.

Rarely, a toric lens rotates away from its angle in the early days or weeks. If it turns enough to blur vision, a small second procedure can set it back. A toric lens may not suit an eye with an irregular cornea, such as keratoconus or an old corneal scar, or an eye where the natural lens has weak support. Small amounts of astigmatism often do not need a toric lens at all. Our eye surgeon tells you whether your astigmatism is large enough for a toric lens to make a real difference.

Toric correction can be built into a monofocal lens, which is the common form, and also into some multifocal designs. With a toric monofocal set for distance, reading glasses are usually still needed.

What are multifocal, trifocal and EDOF lenses?

These lenses are often called "premium" or presbyopia-correcting lenses. They aim to give a range of clear distances, not just one, so that you depend less on glasses after surgery. They work in different ways:

• Multifocal (bifocal design): rings on the lens split light into two focus points, usually distance and near (reading distance).
• Trifocal: a multifocal with three focus points: distance, intermediate (computer screen, dashboard, cooking counter) and near.
• EDOF (extended depth of focus): instead of separate focus points, the lens stretches one focus over a longer range, typically from distance to intermediate. Many people with an EDOF lens still use light reading glasses for small print. Night haloes are usually milder than with multifocal designs, though not always absent.

Lens makers keep bringing out new designs, and not every design is used at every hospital. Our eye surgeon explains which designs suit your eye and which can be arranged for your surgery, so the choice is made on your eye findings rather than on a lens name.

What are the trade-offs with multifocal and EDOF lenses?

Spreading light across several distances has a cost. Before choosing one of these lenses, know that:

• Some people see haloes or glare around headlights and street lights at night, which matters if you drive after dark.
• Contrast can be a little lower, especially in dim light or rain.
• The brain takes time to adapt, often weeks and sometimes months.
• Glasses may still be needed for fine print, long reading or night driving.
• These lenses are normally planned for both eyes, so the second eye matters too. Read surgery on the second eye.

They are often not advised if you have macular degeneration (see macular degeneration), diabetic changes in the retina, glaucoma with nerve damage, an irregular cornea, a lazy eye, or if you want the sharpest possible night vision. If you have diabetes, also read diabetes and cataract. Your surgeon will tell you if your eye is not suited.

Which lens suits my eye and my daily life?

No single lens is right for everyone. The right lens is the one that matches your eye health and how you spend your day. Before the consultation, think about:

• Which distances matter most: the road and TV, a computer or tablet at arm's length, or reading, sewing and the phone up close?
• How much do glasses bother you, and for which tasks would you happily keep them?
• Do you drive at night, for example on the highway home or for work shifts?
• Does your current spectacle prescription have a cylinder power? Bring your current glasses or prescription.
• Do you have diabetes, glaucoma, a retina condition or past eye surgery?
• Are you comfortable with a period of adjusting to new vision, or would you rather have predictable, simple vision?

Our eye surgeon examines your eye, measures it, tells you which lens types are suitable and explains the fee for each. You then decide with your family, without pressure.

Does the lens type change the cost of cataract surgery?

Yes. The lens is one of the largest parts of the fee, and toric, multifocal and EDOF lenses cost more than a standard monofocal lens because of the lens itself and the extra measurements and planning. There is no fixed price for all eyes. Read what decides the cost of cataract surgery, and ask for the fee for each suitable option at the consultation.

Will I need glasses after cataract surgery?

Most people still use glasses for some tasks. With a monofocal lens set for distance, reading glasses are usually needed. Toric, multifocal and EDOF lenses can reduce how often you reach for glasses, but no lens can promise that you will never need them. Your new spectacle power is checked a few weeks after surgery, once the eye has settled, and the spectacles can be made at our Vision Correction Centre in the same hospital.

Does the artificial lens wear out?

No. An IOL is designed to last a lifetime and does not need replacing. Months or years later, some people develop clouding of the thin capsule behind the lens, which blurs vision again. That is not the lens wearing out; it is treated with a quick YAG laser. Read YAG laser after cataract surgery.

To discuss which intraocular lens suits your eye, book a cataract check-up at ReNew Vision Eye Hospital, Vaddem, Vasco. Call or WhatsApp 072489 88039; the eye OPD is open Monday to Saturday, 4 pm to 7 pm.

Questions patients ask

What is a toric lens in cataract surgery?

A toric lens is an intraocular lens with astigmatism correction built in. It is placed at a measured angle inside the eye, so that distance vision without a cylinder power in your glasses can be sharper. It suits eyes with enough regular corneal astigmatism.

What is the difference between a multifocal and an EDOF lens?

A multifocal lens splits light into two or three focus points, such as distance and near. An EDOF lens stretches one focus over a longer range, usually distance to intermediate, so light reading glasses may still be needed. Your eye surgeon advises which design suits your eye.

What is a premium lens for cataract surgery?

"Premium lens" is a general term for lenses beyond the standard monofocal, such as toric, multifocal, trifocal and EDOF lenses. They cost more and suit some eyes, not all. Whether one suits you depends on your eye health, astigmatism and daily needs.

Can a multifocal lens remove the need for glasses?

It can reduce the need for glasses for many tasks, but it cannot promise you will not use them. Some people still need glasses for fine print or in dim light, and some notice haloes around lights at night.

Can the lens be changed later?

The lens is meant to stay for life. In rare cases a lens has to be repositioned or exchanged, which needs another operation. That is one reason the lens choice is planned carefully before surgery.

Can I feel the artificial lens in my eye?

No. The lens sits inside the eye, behind the iris, where there is no feeling. You will not feel it when you blink or move your eyes.

This page is general eye-health information, not personal medical advice. Your eye doctor advises you after examining your eyes.