Counseling patients on dysphotopsias necessary with presbyopia-correcting IOL use
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Part one of this series focused on balancing the three interrelated concepts of presbyopia-correcting or visual range IOLs: visual quality, visual range and visual symptoms, or dysphotopsias.
This article will address what dysphotopsias are, why they occur and how to address them in clinical practice.
Source: Daniel H. Chang, MD
First, it is important to understand that using refractive or diffractive optics as a means to increase visual range — the goal of presbyopia-correcting or visual range IOLs — necessarily results in off-axis light, which leads to the visual symptoms of dysphotopsias, including glare/flare, halos and starbursts (Figure 1).
To understand why, consider a monofocal lens at plano. Incoming light from a distant light source focuses to a single point on the retina (Figure 2a). The same monofocal lens set at near with a myopic focal point (eg, –2 D) focuses light rays in front of the retina, so the rays diverge to cover a larger area on the retina. This off-axis light leads to the symptoms of dysphotopsias (Figure 2a). Plotting plano and myopic (monofocal) eyes on a defocus curve demonstrates that any shift in focus to the right of the monofocal peak results in off-axis light and dysphotopsias (Figure 2b). A traditional (bifocal) multifocal IOL has two focal points, which can be represented by two peaks on a defocus curve (Figure 2c). The interaction of these two focal points is actually what creates the halo. A distant point source of light is focused by the far and near focal points like two monofocal IOLs, one at plano and one at near. There is a relative dim region in between, thus creating the appearance of a ring or halo of light from the defocused near focal point.
Based on this mechanism, halo size is directly related to multifocal add power, and halo brightness is related to near acuity. Therefore, with lower-add multifocal IOLs, patients noted smaller halos and improved dysphotopsia symptoms. This was a natural consequence of a longer near focal point.
We can expect every visual range IOL to have a unique dysphotopsia profile related to its defocus curve and mechanism of action. The Tecnis Symfony extended depth of focus (EDOF) IOL (Johnson & Johnson Vision), for example, is not a multifocal lens. Instead of a traditional multifocal halo (Figure 3), it produces starbursts with multiple fine halos, a phenomenon descriptively named “spiderwebbing” (Figure 3). The term spiderwebbing typically does a good job of communicating the symptoms to patients in both preoperative and postoperative discussions; most patients find these spiderwebs around lights not too bothersome.
Improvements in dysphotopsias
As described in part one, improvements in visual quality — and low-contrast visual acuity in particular — can make dysphotopsias more tolerable. High-energy, short-wavelength light scatters more, so filtering out the shortest violet and even blue light with a chromophore can potentially improve dysphotopsia profiles. Johnson & Johnson Vision and Alcon have taken advantage of this fact to improve the unwanted symptoms of their respective Tecnis and AcrySof visual range IOL platforms.
When the InteliLight features of violet light filtering as well as high-resolution lathing were added to Johnson & Johnson Vision’s visual range IOLs, symptoms of halos were reduced by almost one-third. Additionally, contrast vision under challenging light conditions improved by up to 13%, according to van der Mooren and colleagues. In a retrospective study conducted in my practice and presented at the American Society of Cataract and Refractive Surgery meeting in 2022, we found that these two improvements reduced dysphotopsias complaints by up to 45% and resulted in a reduction in counseling needed for dysphotopsias by up to 72%.
Educate your patients
Overall, because dysphotopsia symptoms are less severe with newer-generation EDOF and even full vision range IOLs, I spend less time counseling than I did with previous generation multifocal IOLs. Nevertheless, improper or insufficient counseling will still inevitably lead to many unhappy patients.
In my experience, the Tecnis Symfony OptiBlue IOL improves upon the dysphotopsia profile of the original colorless Tecnis Symfony by about one-third. Futhermore, the dysphotopsia profile of the Tecnis Odyssey full visual range IOL with a digitally optimized freeform diffractive profile has all but eliminated the spiderwebbing symptoms, even with its increased visual range. Given its full visual range, halos are present but surprisingly well-tolerated. As noted in part one of this series, a multicenter real-world retrospective study reported 93% with no or mild symptoms of glare, halos or starbursts at 1 month postop. Despite these improvements, dysphotopsias still occur, so it remains critical that we adequately counsel our patients.
I recommend counseling patients about dysphotopsias specifically, descriptively and preoperatively. Making sure patients are listening and understanding what is being explained, describing expected symptoms clearly and vividly (preferably with pictures such as Figure 3), and doing this before surgery are paramount. It is not enough simply to tell patients that they will have “glare and halos,” that “the newer technology is much better than it used to be” or that “the night vision problems aren’t as bad.” Patients have a poor understanding of dysphotopsias in general, and they have no yardstick for understanding changes relative to earlier technology.
Because patients only know what they have seen before, it is important to describe how IOL-related dysphotopsias will differ from the night vision symptoms they are currently experiencing with their cataracts. Depending on what a patient has, I typically tell them that the overall quality and crispness of their vision will be greatly improved, especially in dim light and low-contrast situations. However, they will notice unique halos and/or spiderweb-like dysphotopsias around bright lights in specific situations, such as with oncoming headlights. I then reassure them that most patients are not bothered by these and that they should be able to see the road, signs and cars despite the dysphotopsias.
Many surgeons would rather not deal with dysphotopsias at all and have chosen to give up on presbyopia-correcting IOLs rather than to counsel patients that the dysphotopsias are a by-product of the greater visual range. I believe that is a mistake. Leaving presbyopia correction to multifocal spectacles can result in increased rates of falls, injuries and even death. Patients are quite capable of understanding and accepting the tradeoffs when we take the time to educate them about what to expect.
- References:
- Chang DH. J Refract Surg. 2021;doi:10.3928/1081597X-20210408-02.
- Chang DH, et al. The effect of violet light filtration and manufacturing improvements on the clinical performance of an extended depth of focus IOL. Presented at: American Society of Cataract and Refractive Surgery meeting; April 22-26, 2022; Washington.
- van der Mooren M, et al. Clin Ophthalmol. 2023;doi:10.2147/OPTH.S396823.
- For more information:
- Daniel H. Chang, MD, of Empire Eye and Laser Center in Bakersfield, California, can be reached at dchang@empireeyeandlaser.com.
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