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Multifocal IOL

For those experiencing cataracts that increasingly interfere with their daily activities, lens replacement surgery is a recommended option. The clouding of the original lens cannot be undone. In the very common procedure of cataract surgery, a synthetic lens, called an intraocular lens (IOL), is put in place of the old lens. There are many different options in the nature of the replacement lens, some of which will be dictated by one’s exact medical condition and other considerations for which there may be a choice.

The first option is in whether to get traditional monofocal lenses versus multifocal IOLs. As the names imply, one type of lens comes with an optimal focusing distance that is fixed, the other allows some variation. With monofocal IOLs, one essentially chooses between being near or far sighted, and gets corrective lenses accordingly. There is also an option of being near sighted for one eye and far sighted for the other, called monovision, and the brain learns to choose the specific eye for the need. Of the many people who sample this effect with similarly differing contact lenses, it is clearly for some but not for others. Fortunately, much as bifocal eyeglasses were developed for those needing both near and far correction, there are also now multifocal IOLs.

Multifocal lenses come in two varieties, depending on whether they refract or diffract light. Refraction is bending of light at a certain angle, while diffraction is the diffusion of light, its spreading out. Refraction causes one to see a straight stick as crooked in the water. Diffraction is light’s spreading out again after going through a small opening – not staying in a column of light, but making a cone of light. In any case, this subtle difference has practical effects for exactly how light falls on our retinas, at the back of each eye, as follows.

Refractive multifocal IOLs will give optimum vision at intermediate to far distances, but one may still want a corrective lens for very close work or reading small type with relative ease. Diffractive multifocal IOLs, by contrast, are good at both close and distant ranges, yet can be hazy at midrange, so that during certain activities such as using a computer or watching home entertainment, one feels the need to get closer.

With either form of multifocal IOL, about one quarter of all patients will experience halos or glare around lights at night, in contrast with about eight percent of those with monofocal IOLs. The inherent bending or spreading of light in multifocals essentially raises the risk of experiencing halos and glare, with another part contributed by individual variations in eye structure and function. Depending on the extent, the brain can learn to ignore or compensate for such side effects. However driving at night can be problematic and quite possibly unsafe, though night-driving glasses exist and are said to help.

In general, those receiving multifocal IOLs have not needed additional corrective lenses – up to eighty percent so in the USFDA-required studies. Odds of being glasse-s or contacts-free are a bit lower for those with astigmatism, but in any case one will still improve their overall vision with a new, clear lens. Multifocal IOLs are not recommended to people with existing eye conditions, such as macular degeneration, diabetic retinopathy, and a variety of other conditions that will be known to eye doctors and eye care professionals.

As always, each person’s case and situation is unique. Different surgeons will have certain preferences based on experience - or at the very least, different ways of explaining the options. Patients are always entitled and generally encouraged to seek multiple opinions regarding medical procedures. Become educated! Having multiple options to choose between can be initially confusing, but with a bit of time and learning one realizes that, even under the circumstances, this part is one of those ‘good problems’ to have!

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