Premium intraocular lenses (IOLs)

What are the main types of premium IOLs?

• Multifocal IOLs: They offer clear vision at multiple distances (near, intermediate, and far), reducing the need for glasses.
• Extended Depth of Focus (EDOF) IOLs: They provide seamless vision from far to intermediate distances, with fewer side effects than multifocal IOLs.
• Toric IOLs: Designed to correct astigmatism in addition to cataracts, offering more precise vision. Monofocal, multifocal, and EDOF IOLs are available in toric and non-toric formats. The choice depends on the specific corneal astigmatism of each eye.
• Accommodative IOLs: Aim to restore true accommodation, but to date, none have demonstrated conclusive efficacy. However, they represent a promising avenue for the future of premium IOLs, contrasting with the pseudo-accommodation currently in use.
  

Each type of lens is chosen based on the specific characteristics of each eye, as well as the patient's visual needs and lifestyle.

How do they work? Multifocal IOLs

Most multifocal IOLs work by using a special optical design based on light diffraction to provide clear vision at multiple distances (near, intermediate, and far). They have a series of concentric rings etched onto their surface, which divide and redirect incoming light to different focal points.

Here's how they work:

1. Light Diffraction: The diffractive rings distribute light to different focal distances, allowing the eye to simultaneously see near, intermediate, and distant objects.
2. Light Distribution: Part of the light is directed towards distance vision, another part towards intermediate vision, and yet another towards near vision, which allows the brain to automatically choose the sharpest image based on the object's distance.
3. Visual Side Effects: Light halos, glare, and reduced contrast, more pronounced at night, which result from the optical design of these IOLs.
   

Diffractive multifocal IOLs offer an effective alternative to glasses after cataract surgery, although they may require an adaptation period for the brain to get used to sharing light between different distances.

How it works? EDOF IOLs

Extended Depth of Focus (EDOF) IOLs work by expanding the eye's range of focus, providing clear vision from distance to intermediate while minimizing the side effects associated with multifocal IOLs.

Here's how they work:

1. Extended Focus: Unlike multifocal IOLs, which create several distinct focal points, EDOF IOLs use advanced optical technology to extend a single focal point, allowing for a smooth transition between different viewing distances.
2. Enhanced Intermediate Vision: Ideal for activities such as computer use and driving, they provide quality intermediate vision with good visual comfort.
3. Mini-monovision for Reading: To reduce the need for reading glasses, a technique called mini-monovision is often used. This involves slightly adjusting the correction of one eye for distance to intermediate vision and the other for intermediate to near vision, while maintaining comfortable binocular function and thus increasing visual independence.
4. Fewer Side Effects: Thanks to their advanced optical design, EDOF IOLs generate fewer halos and less nighttime glare, and provide better contrast than multifocal IOLs, offering more natural vision in various lighting conditions.
   

Thanks to these characteristics, EDOF IOLs offer an effective solution for patients seeking good vision at various distances with reduced dependence on glasses, generally without the optical aberrations observed with multifocal IOLs. Reading, meanwhile, is generally satisfactory without glasses thanks to the "mini-monovision" technique.