How to measure Visual Performance with Multifocal Intraocular Lenses?

There are different tests for measuring visual performance after cataract surgery with IOL implantation, refractive lens exchange (RLE), or any other technique for presbyopia correction such as laser refractive surgery or even contact lens. For understanding the best test to use, it is important to know the compromise in testing vision between distance and spatial frequency. The choice of the test that fits our needs will depend on your aim and the time you have in the clinic to carry out the measurement. In the following article, we will introduce you to the standard testing and recommendations to help you choose the test that fits your needs.

logo test-eye
When these considerations are applicable?

Although some considerations specified in this article are also applicable for a monofocal IOL such as visual acuity or contrast sensitivity tested at distance, the article has been written considering a complete suite available for the cataract surgeon who wants to better understand the visual performance or visual outcome with a multifocal IOL. Some of these considerations are also applicable to multifocal contact lens testing.

What can affect visual performance?

Visual performance with multifocal intraocular lens has been reported in several studies with a multifocal IOL (Acrysof Restor, Tecnis multifocal IOL, and any other diffractive IOL or accommodative IOL) either in photopic or mesopic vision. Cataract surgeons should know which factors can affect the visual outcome, including biometric eye parameters, and the possibilities they have to optimize outcomes based on evidence: using an aspheric IOL to correct spherical aberration, a toric IOL for correcting corneal astigmatism, etc. Exploring how patients can be affected by several factors give the cataract surgeon confidence about when to implant a multifocal intraocular lens or a monofocal IOL in cataract patients.

What are the new findings?

The use of our Apps for testing vision with multifocal intraocular lenses is growing continuously. We will work in a section that summarizes the latest findings obtained with any of our Apps. Thanks for your patience.

 

Basic App (VisionC)

High and Low Contrast Visual Acuity with ETDRS chart

High Contrast Visual Acuity is considered the current standard for measuring either visual performance with multifocal intraocular lens or with a monofocal IOL. With the App VisionC you can integrate this measurement at three distances (far, intermediate, and near) and you can also set the exact distance in cm that each of these three classifications represents. Additionally, you can measure Low Contrast Visual Acuity at any of these distances.

Variables of Interest

which can be measured with VisionC

Efficacy plot
  • CDVA

    Corrected Distance Visual Acuity

    Distance Vision with Correction (monofocal or multifocal)
  • UDVA

    Uncorrected Distance Visual Acuity

    Distance Vision without Correction (monofocal or multifocal)
  • UIVA

    Uncorrected Intermediate Visual Acuity

    Intermediate Vision without Correction (Special interest in Trifocal IOL or EDOF)
  • DCIVA

    Distance Corrected Intermediate Visual Acuity

    Intermediate Vision with Distance Correction (Special interest in Trifocal IOL or EDOF)
  • CIVA

    Corrected Intermediate Visual Acuity

    Intermediate Vision with Best correction at testing distance
  • UNVA

    Uncorrected Near Visual Acuity

    Near Vision without Correction (multifocal)
  • DCNVA

    Distance Corrected Near Visual Acuity

    Near Vision with Distance Correction (multifocal)
  • CNVA

    Corrected Near Visual Acuity

    Near Vision with Best correction at testing distance
VisionC ETDRS chart
VisionC Recommendations
  • Set the brightness % to 40% or 70% depending on whether you want about 85cd/m2 (clinical studies) or 200 cd/m2 (clinical practice).

  • Follow the standard procedure to decide the threshold value for visual acuity.

  • Record the results in standard logMAR notation for the three distances.

  • (Optional) Incorporate Low Contrast Visual Acuity (10% contrast) if you want to take additional information.

Frequencies (ClinicCSF)

Contrast Sensitivity with Sinusoidal Gratings

The disadvantage of High Contrast Visual Acuity is that it is not very sensitive to small changes in optical quality so patients can have good visual acuity and still complain about poor quality of vision, Contrast Sensitivity for different spatial frequencies measured with ClinicCSF allows to have more information than Visual Acuity measured with VisionC.

Contrast Sensitivity Function

Variables of Interest

that can be measured with ClinicCSF

  • CSF

    Contrast Sensitivity Function

ClinicCSF can be used to measure Contrast Sensitivity in photopic vision (photopic cs) under photopic or mesopic environmental lighting conditions. ClinicCSF does not allow measuring CSF in mesopic vision because it is not possible to guarantee that contrast steps in 0.1 logCS can be reliably reproduced in mesopic vision even with prior calibration.

To measure CSF with glare, you will need an external glare source that produces a mean drop of 0.1 logCS in 6 cpd in healthy subjects.

ClinicCSF Recommendations
  • Set the % brightness to 70% to maintain an average background luminance of about 85cd/m2.

  • Select the presentation distance at which you want to measure the visual performance and don't forget to always keep the best patient distance correction (infinity).

  • Conduct the Version 1 procedure if your aim is to compare the results with those obtained with the CVS-1000 in previous studies. We recommend this version in patients with reduced visual performance "Floor Effect".

  • Conduct the Version 2 procedure if your goal is to compare the results with those obtained with FACT in previous studies. We recommend this Version for multifocals because it has less "Ceiling Effect".

Contrast Sensitivity Function

Distances (MultifocalLA)

Visual Acuity and Contrast Sensitivity Defocus Curves

ClinicCSF allows you to measure multiple frequencies for a particular distance, however, it is a procedure that requires a longer measurement time which is a disadvantage if we want to have information for a wide number of distances. To solve this problem we can conduct a Defocus Curve that allows us to have information for a dominant spatial frequency (high frequency).

Visual Acuity Defocus Curve

Variables of Interest

that can be measured with MultifocalLA

  • VADC

    Visual Acuity Defocus Curve

  • CSDC

    Contrast Sensitivity Defocus Curve

MultifocalLA integrates the calculation of the areas under the defocus curve in addition to the calculation of the effective addition or the detection of defocus shifts. In addition, it can calculate the average results according to the Protocol or Intraocular Lens implanted.

MultifocalLA Recommendations
  • Set the % brightness to 40% which corresponds to 85cd/m2 (clinical studies).

  • Select the Sloan letters, preferably at 4 m.

  • Select a range from +1.00 D to -4.00 D for Bi / Trifocal or +1.50 D to -2.50 D with extra step of +/- 0.25 D for EDOF or Monofocal

  • Opt for Contrast Sensitivity Defocus Curves instead of Visual Acuity when your goal is to detect small changes in optical quality.

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