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Eliminate astigmatism for happier cataract patients
Its presence does not rule out presbyopia correction with IOLs.
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The majority of patients presenting for cataract surgery have at least 0.5 D of corneal astigmatism, and 36% have 1.00 D or more, according to Hoffman and colleagues. Yet, according to the 2017 American Society of Cataract and Refractive Surgery Clinical Survey, only about 10% of cataract patients get a toric IOL.
The major reason that so many patients with astigmatism are getting spherical lenses is the extra cost associated with these lenses. However, it is not necessarily the patient rejecting the higher cost. In many cases, optometrists and ophthalmologists are not even recommending toric IOLs because they think the extra cost won’t be “worth it” to the patient.
That is something we all need to re-think. We know from many contact lens studies that patients with astigmatism have better acuity (Richdale et al., Cho et al., Sulley et al.), improved visual quality of life and higher satisfaction (Cox et al.) when fitted with toric lenses compared to spherical lenses. Failing to correct astigmatism can lead to difficulty with everyday tasks such as reading, computer work and driving (Rosenfield et al., Read et al.).
Residual astigmatism
Some people believe that a small amount of residual astigmatism is actually desirable for improved depth of focus without affecting uncorrected visual acuity. “Small amount” is the operative concept here, and I do not like to induce astigmatism where it was not previously. So, if a patient had 0.50 D x 180° cylinder preoperatively, then I think plano -0.50 D x 180° would be an acceptable refractive outcome. Otherwise, I would likely recommend correction of the astigmatism.
Many of my colleagues rationalize that if the patient is going to be wearing glasses anyway (for near and intermediate vision), then they are best served by implanting a spherical IOL, leaving them with a postoperative refraction, for example, of -1.00 D -1.00 D x 180, with a 2.50 D add. It is true that some patients would be happy with that. But many others would be happier — and consider the extra cost well worth it — to have the astigmatism fully corrected, so they see 20/20 uncorrected at distance, have good quality of vision when driving at night and just need glasses for the computer and reading. The reality is that if we do not ask, we do not know. I recommend toric IOLs for any patient with corneal cylinder of 1.00 D or more. Another way to think about it is if I would recommend toric contact lenses to this patient in my chair, I should also recommend toric IOLs.
Case report
One recent example that comes to mind is my 67-year-old female patient who developed moderate cataracts that reduced her best-corrected distance vision to 20/30 OU. She had been up to this point a successful toric contact lens wearer with a refraction of -2.50 D -2.25 D x 170 OD and -3.00 D -1.25 D x 180 OS. After discussing the various IOL options available to her, we mutually decided that she would be happiest if she could continue to wear spectacles only for reading. Thus, the decision was made to implant Tecnis Toric IOLs (Johnson & Johnson Vision) in each eye.
She had successful surgeries and now, 14 months postoperatively, she is experiencing 20/20- vision without eyeglasses for driving. Had we not elected to implant toric IOLs, she would more than likely have been dependent on eyeglasses for the majority of her day.
It is important, of course, to be sure the refractive astigmatism is actually coming from the cornea. If the refraction is -2.25 D -1.75 D x 90 but the keratometry reading showed -0.50 D cylinder at 170°, that would be an indication that the majority of the astigmatism is coming from the crystalline lens and would be greatly reduced simply by removing the lens and implanting a spherical IOL.
Additionally, if the patient has a low level of astigmatism, one might consider correcting it by placing the corneal incision on the steep axis. However, this can be tricky to pull off, as it is difficult for the surgeon to know exactly how deep and wide to make the incisions. In my experience, expecting to correct more than 0.50 D of cylinder with an on-axis incision is a recipe for disappointment. A femtosecond laser-guided arcuate incision is far more predictable, as the depth is precisely controlled and it is easier to delineate the specific axis of orientation for the incision. Femto arcuate incisions work well for with-the-rule astigmatism; I prefer a toric IOL for more than 0.75 D of cylinder.
Consider correcting presbyopia, too
For our practice, extended depth-of-focus (EDOF) lenses have made a huge difference in our view of presbyopia correction at the time of cataract surgery – for patients with or without astigmatism.
There is a great deal of hesitation in the optometric community about presbyopia correction in general, but I think it is worth looking closely at the differences between the multifocal IOLs that have been around for several years (which are actually bifocal) and EDOF lenses.
The pattern of concentric rings on the Tecnis Multifocal, AcrySof IQ Multifocal (Alcon) and Tecnis Symfony EDOF IOLs looks very similar across all three lenses, leading many to think they work the same way. However, there is a very important difference. The multifocal IOLs produce two distinct foci, with a blurred area in between, in the intermediate range. The blur of the out-of-focus image (the near peak when looking in the distance, or the distance peak when looking up close), combined with the lack of an intermediate focal point, have contributed to dissatisfaction and visual symptoms in some patients implanted with these lenses.
EDOF lenses use a special echelette design to provide an elongated, uniform range of focus. Studies cited in the Tecnis Symfony Directions for Use indicate that night vision symptoms and contrast sensitivity with EDOF lenses are comparable to that of a monofocal. We have also found that patients’ vision continues to improve as they neuroadapt to EDOF lenses. While they are seeing objectively fine day 1 and week 1, there is a big jump in satisfaction by week 8, in my experience.
Personal results
I recently analyzed results for a series of 42 eyes of 39 patients implanted with toric IOLs in my practice who had been followed for at least 3 months. All 42 eyes were implanted with toric lenses from the same IOL platform (29 monofocal Tecnis Toric and 13 EDOF Symfony Toric). The patients included all comers with reasonably healthy eyes, including those with dry eye (9.5%), mild glaucoma (7.1%), mild age-related macular degeneration (7.1%), ocular allergies (2.4%), diabetes without retinopathy (2.4%) and ocular hypertension (2.4%).
Postoperative refractive astigmatism was low (0.42 ± 0.41 D) and statistically significantly reduced from the preoperative mean corneal astigmatism of 2.54 D (p < 0.001). More than 85% of eyes had no more than 0.75 D of residual cylinder after surgery.
The mean postoperative spherical equivalent was -0.13 ± 0.68 D, with nearly three-fourths of eyes within 0.5 D of plano. Mean uncorrected visual acuity (UCVA, LogMAR) was 0.12 ± 0.14, and more than 90% of eyes had distance UCVA of 20/32 or better. There were no significant lens rotations requiring repositioning or explantation.
Talking to patients about options
Although the proliferation of new IOL options can seem overwhelming, it actually simplifies the conversation for the referring primary care optometrist, because one no longer has to worry about the patient’s astigmatism ruling out presbyopia correction (or vice versa). We can simply talk to patients about their preferences for wearing glasses after surgery.
I like to give patients a few clear options and discuss the pros and cons of each. Sometimes it is best not to be too specific, especially if the practice does not perform corneal topography. Preoperative measurements can change the calculation of how much corneal astigmatism needs to be corrected and whether or not a toric IOL is indicated.
For example, many surgeons will overtreat against-the-rule astigmatism and undertreat with-the-rule astigmatism to account for the contribution of posterior corneal astigmatism. It is important that patients know, at minimum, that there are new options with additional costs, so that when they get to the surgery center, they are prepared to make a decision about what is right for them.
- References:
- ASCRS Clinical Survey 2017. EyeWorld. http://supplements.eyeworld.org/eyeworld-supplements/2017-ascrs-clinical-survey-supplement-dl-final. Posted October 23, 2017. Accessed March 12 2019.
- Cho P, et al. Clin Exp Optom. 2012;doi: 10.1111/j.1444-0938.2011.00649.x.
- Cox SM, et al. Eye Contact Lens. 2018;doi:10.1097/ICL.0000000000000418.
- Directions for Use, Tecnis Symfony IOL.
- Hoffmann PC et al. J Cataract Refract Surg. 2010;doi:10.1016/j.jcrs.2010.02.025.
- Read SA, et al. Ophthalmic Physiol Opt. 2014;doi:10.1111/opo.12128.
- Richdale K, et al. Optom Vis Sci. 2007;doi:10.1097/OPX.0b013e318157c6dc.
- Rosenfield M, et al. Ophthalmic Physiol Opt. 2012;doi:10.1111/j.1475-1313.2011.00887.x.
- Sulley A, et al. Ophthalmic Physiol Opt. 2013;doi: 10.1111/opo.12028.
- For more information:
- Eric E. Schmidt, OD, is founder and president of Omni Eye Specialists, a multispecialty secondary and tertiary care practice headquartered in Wilmington, N.C. He can be reached at: schmidtyvision@msn.com.
Disclosure: Schmidt reports he is a member of the speakers’ bureau and a paid consultant for Johnson & Johnson Vision.