The Science of Natural Vision Meets the Science of NaturalVue® Multifocal
Depth of focus (DOF) is the range of focus along the visual axis, over which an image is clear, or simply, the range of clear vision. (Figure 1)
Depth of focus (DOF) is relative to aperture. (Figure 2)
• Large aperture, the DOF is narrow;
• Small aperture, the DOF is wider
Extended depth of focus (EDOF) allows continuous visual correction, from near to distance, across a wider range.
- A pinhole is an example of an extremely small aperture that creates a large DOF.
- The pinhole effect creates a virtual aperture that blocks peripheral rays to direct light to the foveal area, decreasing blur.
- This virtual aperture creates an extended depth of focus and provides clear vision at all distances.
The NaturalVue® (etafilcon A) Multifocal 1 Day Contact Lens uses the Principle of Pinhole Optics in its Design
- The Neurofocus Optics® technology of the NaturalVue® Multifocal relies on the rapid, continuous, and uninterrupted progression in plus power that creates peripheral blur which generates a virtual aperture effect.1
- This effect results in an extended depth of focus and a clear and continuous range of vision.
- Most importantly, this center-distance design provides spectacle-level visual acuity for clear vision at every distance for your patients.2
Neurofocus Optics® technology allows the visual cortex to optimize visual clarity enabling spectacle level stereoacuity for excellent depth perception.2
The high levels of uninterrupted plus power progression in the lens are integral to its performance. We now have a way of describing the lens power profile using customized wavefront software.
The NaturalVue® Multifocal Power Profile
There are two definitions of focal powers used to define lens optics:
- Sagittal (axial or radial)
- Instantaneous (tangential)
Both methods of description are useful in creating and describing lens designs, but provide different information and are used for different purposes.
- Also called axial or radial power
- Common output from wavefront sensors
- Describes a wavefront as it intersects the optical axis
- Defined by a normal surface line and its intersection with the optical axis
- A mathematical construct, easily measured
- Represents average power of the surface
- Also called tangential power
- Describes a wavefront that does not fall exactly on the optical axis, such as aspheric surfaces
- Allows us to assess the “true focus”
- Not measured directly, but calculated from the measured Sagittal power
The Plot of Instantaneous (Tangential) vs. Sagittal (Axial) Power Profile of the NaturalVue® Multifocal
This graph is a direct output from the NIMO (Lambda-X) wavefront sensor of a -3.00D NaturalVue® Multifocal lens over the central 5mm optic zone.
The Instantaneous profile is shown in red (“Instant”) and the Sagittal profile is show in blue (“Radial”).
So what does this mean for you and your patients?
The information here should help you better understand the optics of the NaturalVue® Multifocal design. Most importantly, the NaturalVue® Multifocal power profile showcases the large progression in plus power in the lens. That large amount of plus power is key to the clinical performance of the lens and is what differentiates the design.
1. Patents Awarded – MULTIFOCAL OPHTHALMIC LENS WITH INDUCED APERTURE, Canada #2121740, Europe (10 countries) #1381908, Japan #5379945, US #s 7178918, 6474814.
2. VTI data on file, 2015. N=59. Data assessed after 1 week of wear. Preference based on those who expressed a preference among brands tested.