How does the PanOptix Pro reduce light scatter and improves light utilization?
- Subhabrata Bhattacharya
- May 2
- 7 min read
Updated: Jul 27
Alcon recently launched the Clareon Panoptix Pro with ENLIGHTEN® NXT Optical technology that utilizes more light (94%) which is significantly higher than that of the parent version (88%). This has been possible due to a reduction in light scatter. For those who follow quickguide.org closely will know that this website is created to understand the 'HOW' part, rather than just be content with the 'WHAT' part. So the objective of my communication here is to understand 'How' does Alcon achieve minimizing light scatter and increase diffractive efficiency with Clareon Panoptix Pro? At the outset, let me tell you that not many information is available about the IOL, and therefore, I try to decipher what little information is available on the Panoptix Pro.
The FDA premarket approval for Clareon PanOptix Pro refers to minor optical modification on the parent model (Panoptix). This 'minor optical modification' referred to by Alcon as ENLIGHTEN® NXT Optical technology, may be the reason behind reducing light scattering. The question is, what particular minor optical modification has been done with the PanOptix Pro?
To understand this, we need to have an idea of the different ways of light scattering.
What is light scattering?
Light scattering refers to a change in the light path to many directions compared to the intended path of light, once light encounters with optical inhomogeneities, like diffractive steps or rings. Light scattering should not be confused with aberrations in the optics or in eye. Higher order or lower order aberrations are related to light that travels at small angles and reach the fovea. Light scatter is related to light that travels at larger angles and spreads on the retina. There could be many different types of light scattering, like Rayleigh scattering and Mie scattering depending on the size of the optical inhomogeneities that light encounters. Rayleigh scattering happens when light interacts with particles in the optical medium that are many times smaller than the wavelength of light that crosses the optics.
But Mie scattering of light is more appropriate for discussion, as this kind of scattering happens when light encounters particles or optical inhomogeneities that are comparable to the wavelength of light. Or in other words, Mie scattering happens when the diffractive steps or rings are similar or larger in size compared to the wavelength of light.
Nature of Mie Scattering of Light
Thus when Alcon refers to reduction in optical light scattering, my understanding is that the reduction referred to is Mie scattering. In Mie scattering of light, light is scattered in all directions, but with stronger intensity towards the forward direction, that is in the context of the eye and diffractive IOLs, towards the retina. In Ophthalmology, we refer to both forward and back scattering of light. When the optical inhomogeneities are larger in size (that is diffractive steps or rings), then they produce Mie scattering, that is forward scattering of light on the retina that creates a 'veil of luminance' bringing down contrast of the patient. This in optics is often referred to as straylight and is debilitating to vision, particularly in presence of glare.
The concept of straylight
The useful light that is refracted or diffracted through an IOL travels through the vitreous medium and fall on the fovea at an angular range of less than 1 degree of the visual angle (the highest concentration of cone cells in this region). Any deviation of more than 1 to 2 degree of this refracted or diffracted light will be a source of scattering on the retina, called as straylight reducing contrast and causing glare phenomenon for the patient. The PSF( point spread function) or the MTF analysis of a diffractive IOL is done with respect to the refracted and diffracted light within very narrow angular range. The MTF or PSF scores of IOL does not provide us any understanding of the amount of light scattering. It rather gives us an understanding of the quality of image with respect to the aberrations in the optics of eye.
Point Spread Function and presbyopia correcting IOLs (trifocal IOLs):
With presbyopia correcting IOLs like trifocal IOLs measurement of visual acuity and contrast sensitivity is given utmost importance. As standardized by the International Standards Committee (Commission Internationale d Eclairage) the below image shows the different parts of the retinal image as interpreted with the PSF. At the absolute center of the visual angle (0 degree) is the visual acuity, forming the core of the PSF that takes the form of a tall raised building. This corresponds to 1 min of arc which is about 1/60th of a degree.
Contrast sensitivity is measured between 3 cpd to 18 cpd. Cycles per degree (cpd) and visual angle are inversely related, meaning a higher cpd value corresponds to a smaller visual angle and vice versa. To convert between them, you can use the following relationship: visual angle (in degrees) = 60 / cpd. For example, a visual acuity of 30 cycles per degree (cpd) corresponds to a visual angle of 2 minutes of arc (60/30 of a degree). If we take an average cpd of 6, this will correspond to a visual angle of 10 min of arc, which is .16 of a degree.
Most manufacturing companies provide MTF (modulation transfer function) test results according to 50 lines/mm or 15 cpd. 15 cpd would correspond to a visual angle of .06 degrees of visual angle. That is the contrast measurements would correspond to a visual angle of less than half of a degree, wherein we have the highest concentration of cone cells.
However, beyond the visual acuity and contrast sensitivity measurements, there is another aspect that is critical to a patient's vision- stray light. Straylight is a result of the light scattering as it pass the IOL optics, in this case the steps or rings of the diffractive optics.
( For more information in what is PSF and MTF follow the below articles in quickguide.org
In their study, Straylight With Types of Different Intra Ocular Lenses, Augusto Arias and co-authors (1) compared the straylight between a monofocal IOL (AcrySof IQ), and diffractive IOLs like Panoptix (parent version) and Symfony. They found a higher value of straylight with Symfony IOL, but also moderately high straylight with PanOptix compared to the monofocal IOL. Much of the scattering of light is due to the non homogeneous nature of the diffractive steps on the IOLs. The authors observed that nonhomogeneous micro rings within the diffractive etching of the Symfony IOL may have caused higher amounts of straylight.
Thus possible sources of light scattering are:
1) Surface irregularities in the steps or rings of the diffractive IOL
2) Irregularities in the spacing of the steps or rings may cause more of destructive interference of light leading to less light utilization. This could be in the form of discrepancy between the diffractive steps phase distribution on the optics of the lens to energy distribution to useful orders on the image plane.
(more in my article https://www.quickguide.org/post/the-science-behind-diffractive-presbyopia-correcting-iols )
3) Irregularities in the depth of the steps or rings grooved in the IOL base material.
Possible 'minor design modification with Panoptix Pro'
It is largely agreed that scattering of light occurs at the edges of the steps or rings of the diffractive IOLs. This is not surprising, as diffraction is a phenomenon that is attributed to light spreading when hitting an obstruction or slit at the edges. If the edges of this slit or step is not smooth enough, much of the diffraction will be scattered on the retina contributing to a 'veil of luminance' thus significantly contributing to glare and photic phenomenon. Therefore, many companies today are investing on efforts to smoothen the edges of the steps or rings of the diffractive IOL, to minimize light scatter.
Zeiss markets its diffractive IOL, AT LISA, that incorporates Smooth Microphase (SMP) technology that eliminates sharp edges on the steps.
Another case in point is the Vivinex Gemetric trifocal IOL that incorporates a Gaussian style optical smoothening of steps to reduce light scatter as per their patent (image 4). You can see the clear modification of the step from a top hat structure to a bell shape design to reduce light scatter and straylight on the retina.
Given these points, the Panoptix Pro may not have gone through any significant modification of the optics, like the diameter of the diffractive steps ( 4.5 mm ), the number of steps (15), and the size of the center of the diffractive element/bull's eye (1.164 mm) from the parent Panoptix IOL. The only difference here is the smoothening of the steps to reduce the Mie scatter of light that may otherwise create straylight and bring down the contrast of the patient.
The eIFU of the PanOptix Pro does state the following:
"Compared to Clareon™ PanOptix™ Toric Trifocal Hydrophobic IOL (Models CNWTT3 -CNWTT6), Clareon™ PanOptix™ Pro Trifocal Toric IOL improves the fidelity of the diffractive structure to enhance the overall light utilization and image quality between the distance and intermediate peaks." (7)
Diffractive efficiency is lower with shorter wavelengths of light as shorter wavelengths of light pass through the diffractive steps bending less. Patients are also exposed to an integrated wavelength of light, that is white light. Research also points out that higher wavelength of light like red light is predominant for far vision while blue light is more significant for near and intermediate (6). Therefore simulated photopic through focus PSF with white light PanOptix Pro with white light is a welcome move (image 4 below), as this is the light that patients are exposed to in their daily life. Due to reduced light scatter as claimed by Alcon, some improvements (16%) is visible in a region of 100 cms that is described in the below image as far intermediate. However, no significant difference in MTF is seen between the PanOptix Pro and its older version so far as the infinity or distance is concerned.
In the absence of information related to the 'How' part, that is 'how does the PanOptix Pro reduce light scatter and increase light utilization', the objective of this write up and the associated video was to help readers understand what could be the possible 'minor design modification' per the FDA pre market approval. As more information is available, I intend to update the article. So keep your eyes on this post for future updates.
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References:
Augusto Arias1, Harilaos Ginis2, and Pablo Artal3 Straylight in Different Types of Intraocular Lenses https://doi.org/10.1167/tvst.9.12.16 TVST | November 2020 | Vol. 9 | No. 12 | Article 16 | 2
AT LISA brochure https://www.zeiss.com/meditec/en/products/iols/trifocal-iols/at-lisa-tri-family.html#product-brochure
https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfpma/pma.cfm?ID=P190018S029
Tom Van Den Berg; Optics of light scattering in human eye Article in Acta Ophthalmologica · September 2014
Laura Clavé, Miguel Faria-Ribeiro, and Maria S. Millan; Chromatic changes in vision with diffractive ophthalmic optics Optics Express Vol. 32, Issue 6, pp. 10348-10361 (2024) •https://doi.org/10.1364/OE.512212
eIFU Clareon PanOptix Pro Trifocal Toric with AutonoMe - PXYAT3-T6
