Who is not suitable for multifocal intraocular lenses?

Multifocal intraocular lenses are a popular choice during cataract surgery and lens replacement surgery because they can reduce dependence on reading glasses. They work by splitting light into different focal points, giving useful vision at distance, intermediate and near. However, they are not suitable for everyone. Choosing the wrong lens can lead to disappointment, glare, halos and reduced visual quality. A thorough assessment is essential to decide whether a multifocal lens is right for your eyes.

How multifocal lenses work

Unlike a standard monofocal lens, which focuses light at one distance, a multifocal lens creates multiple focal points. Your brain learns to select the image that is in focus for the task at hand. This design allows many people to see reasonably well without glasses for most activities, but it comes with trade-offs. The quality of vision in each individual focal point may be slightly softer than with a monofocal lens, and some people notice rings or halos around lights at night.

Corneal problems

The cornea must be healthy and regular for a multifocal lens to work well. If the cornea is irregular, scarred, or has subtle distortions such as keratoconus, the multifocal lens will not perform properly. Any irregularity on the front of the eye is amplified by a lens that splits light. People with significant dry eye, corneal dystrophy, or a history of corneal surgery may be better suited to a monofocal or extended-depth-of-focus lens instead.

Macular disease

Multifocal lenses split light, which means the retina receives less light at each focal point. This is usually fine in a healthy eye, but if the macula is affected by age-related macular degeneration, diabetic macular oedema, or another macular condition, the reduction in contrast can make vision worse. For these patients, a monofocal lens is usually preferred because it gives the brightest and sharpest image possible for the damaged retina.

Glaucoma and optic nerve disease

People with glaucoma or other optic nerve conditions may also be poor candidates for multifocal lenses. These conditions can reduce contrast sensitivity and peripheral vision, both of which can be made worse by the optical compromises of a multifocal lens. In general, patients with advanced or unstable glaucoma are advised to choose a monofocal lens to maximise the quality of the remaining vision.

Large pupils

Pupil size matters with multifocal lenses. People with larger pupils, especially in dim light, are more likely to notice halos, glare and starbursts around lights at night. This can be a problem for people who drive a lot at night or work in low-light environments. Pupil size is measured during the pre-operative assessment, and it is one of the factors that helps decide whether a multifocal lens is appropriate.

Dry eye and ocular surface disease

Dry eye is very common, particularly in older patients and contact lens wearers. An unstable tear film can make vision fluctuate and can worsen the performance of any premium lens, including multifocal lenses. If the ocular surface is significantly unhealthy, the vision with a multifocal lens can be particularly disappointing. In these cases, dry eye should be treated first, and a monofocal or extended-depth-of-focus lens may be a safer choice.

Occupations and lifestyle

Some people need the very best quality of vision for their work or hobbies. Professional drivers, pilots, people who work at night, and those who rely on fine contrast such as photographers or artists may find that multifocal lenses compromise their vision too much. For these patients, a monofocal lens with a well-chosen target focus or a low-add extended-depth-of-focus lens may give more reliable and comfortable vision.

Unrealistic expectations

Multifocal lenses can reduce the need for glasses, but they do not eliminate it in every situation. Some people still need reading glasses for very small print, prolonged computer work, or low light. There may also be a period of adaptation while the brain learns to use the lens. If a patient expects to be completely free of glasses with no visual side effects, they may be disappointed. Careful counselling before surgery is crucial to set realistic expectations.

Alternatives to multifocal lenses

If a multifocal lens is not suitable, there are several excellent alternatives. Monofocal lenses give the sharpest and most contrast-rich vision for a single distance, usually set for distance or for monovision. Extended-depth-of-focus lenses provide a wider range of vision than monofocal lenses with fewer night vision symptoms than multifocal lenses. Toric lenses correct astigmatism. Some patients are also suitable for blended vision or mini-monovision, where one eye is focused slightly closer than the other to improve reading without a full multifocal lens.

The importance of individual assessment

The decision about which lens to choose depends on the health of your eye, your visual needs, your lifestyle, and your willingness to accept some compromise in exchange for less dependence on glasses. There is no single best lens for everyone. Measurements of the cornea, macula, optic nerve and pupil size, combined with a detailed discussion of your goals, guide the recommendation.

Next steps

If you are considering cataract or lens replacement surgery and are interested in a multifocal lens, book a consultant-led assessment. We will examine your cornea, macula, optic nerve and tear film, measure your pupil size, and discuss your daily activities and expectations. If a multifocal lens is not the best choice for your eyes, we will explain why and recommend the lens that gives you the clearest, safest and most comfortable vision.