How to measure Visual Performance with Multifocal Intraocular Lenses?
There are different tests for measuring visual performance after with , refractive exchange (RLE), or any other technique for correction such as laser or even . For understanding the best test to use, it is important to know the compromise in testing between distance and . 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.
Although some considerations specified in this article are also applicable for a such as or tested at distance, the article has been written considering a complete suite available for the who wants to better understand the visual performance or with a . Some of these considerations are also applicable to multifocal testing.
has been reported in several studies with a (, , and any other or ) either in or mesopic . surgeons should know which factors can affect the , including biometric parameters, and the possibilities they have to optimize outcomes based on evidence: using an to correct , a for correcting , etc. Exploring how patients can be affected by several factors give the confidence about when to implant a or a in .
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 is considered the current standard for measuring either or with a . 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 at any of these distances.
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Set the brightness % to 40% or 70% depending on whether you want about 85cd/m2 (clinical studies) or 200 cd/m2 (clinical practice).
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Follow the standard procedure to decide the threshold value for visual acuity.
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Record the results in standard logMAR notation for the three distances.
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(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.
Variables of Interest
that can be measured with ClinicCSF
ClinicCSF can be used to measure Contrast Sensitivity in photopic vision () 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.
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Set the % brightness to 70% to maintain an average background luminance of about 85cd/m2.
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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).
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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".
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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".
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).
Variables of Interest
that can be measured with MultifocalLA
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.
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Set the % brightness to 40% which corresponds to 85cd/m2 (clinical studies).
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Select the Sloan letters, preferably at 4 m.
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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
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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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