Astigmatism Management in Cataract Surgery | Eyes On Eyecare

Astigmatism Management in Cataract Surgery

by Mark H. Blecher, MD, Marjan Farid, MD, Wendell Scott, MD, and Kevin Cornwell, OD

In this course, we’ll be discussing the importance of choosing the right IOL implant for our astigmatic patients undergoing cataract surgery and dive into three patient cases using toric lenses.

5.0 (6 ratings)
Updated Aug 5, 2021
30m
1 quiz
What You'll Learn
  • Why to consider toric IOLs for astigmatism management
  • How to account for different factors determining IOL choice for astigmatic cataract patients
  • How to present toric IOLs as an option to patients

Introduction

Today’s eyecare providers have an ever expanding plethora of options to address their patients’ uncorrected astigmatism. Between high index spectacle lenses, expanded parameters for toric soft contact lenses, and custom GP/scleral lenses, patients are no longer being left with uncorrected refractive error from astigmatism. This has also never been more true than in the context of cataract surgery, with increasing options for IOLs tailored for astigmats and presbyopes (soon to be pseudophakes). With cataract surgery being the most common ocular surgical procedure performed worldwide,1 IOL implantation has become a mainstay in addressing refractive error in addition to the cataract itself.

In this course, we’ll be discussing the importance of choosing the right IOL implant for our astigmatic patients undergoing cataract surgery and dive into three patient cases using toric lenses.

*Drs. Blecher, Farid, and Scott are paid consultants for Johnson & Johnson Surgical Vision Inc.

Background

Astigmatic refractive error results from irregular anatomy within various parts of the eye. Corneal astigmatism results from unequal curvature along the two principal meridians of the anterior (or posterior) cornea, commonly referred to as either with-the-rule (WTR) or against-the-rule (ATR) astigmatism. Lenticular astigmatism results from unequal curvatures of the front and back surfaces of the crystalline lens. Lastly, varying indices of refraction within the crystalline lens itself is known as internal or residual astigmatism.

The prevalence of astigmatism can be as high as 60% in the adult population and is generally WTR in nature.2 Based on ethnicity, some patient populations may have even greater amounts of astigmatism as compared to Caucasian subjects, namely Native American and Asian populations.2 Corneal curvature tends to shift in older adulthood, causing increasing amounts of ATR astigmatism, while internal astigmatism remains relatively stable.2

Chief Complaint

Patients with uncorrected astigmatism present with a wide range of visual symptoms. These can range from being completely asymptomatic to having debilitating blur, distortions, double vision, and photophobia (eg. increased glare at night).3 Astigmatic patients who develop significant cataracts can begin to re-experience all of these symptoms and more. Symptoms that were once alleviated through contact lens wear or spectacle correction may progressively return and persist.

Some patients’ cataracts are monitored over many years prior to needing surgery, while others tend to progress rapidly. When it comes to age-related cataracts, diabetes remains the greatest risk factor for developing them prematurely and/or progressing at a faster rate.2 It is not uncommon to see patients with uncontrolled type 2 diabetes needing cataract surgery earlier on in life, while their healthy counterparts may not need surgery until later in life.4


Treating Astigmatism in Cataract Surgery

Treating astigmatism in cataract surgery & choosing the right toric IOL

It is important for both the patient’s referring optometrist and the cataract surgeon to set clear expectations for patients undergoing cataract surgery. Many patients not only want to improve their visual function, but are also seeking to be less dependent on spectacle lens wear after cataract surgery. Patients desire the cosmetic and economic benefits to having satisfactory uncorrected vision postoperatively.

Numerous techniques have been developed and used to correct astigmatism during cataract surgery.7 These include selective positioning of the phacoemulsification incision, limbal/corneal relaxing incisions (typically along the steepest meridian of the cornea), and toric IOL implantation. Altering the shape of the cornea intraoperatively requires the surgeon to predict the healing pattern of the cornea, which can be a challenging task in some cases.

The use of toric IOLs has become an increasingly popular strategy to correct for astigmatism during cataract surgery. They provide optimal correction of the patient’s astigmatism while having a minimal impact on corneal curvature. While misalignment of a toric IOL can leave residual astigmatism, the enhanced rotational stability of newer toric IOL options is less likely to have this side effect.

After patients undergo cataract surgery, there is a brief window of time before the capsular bag condenses to enclose and secure the new IOL implant. It is during this time that rotation may occur. This is why it is important to wait at least a month before conducting a final post-op refraction, as this is the typical time frame for a full recovery after cataract surgery.8 In some cases, corneal healing can also leave the patient with varying degrees of residual corneal astigmatism as well.

Knowing the lens types available and those your preferred surgeon uses will be helpful to have these discussions with your patients. Johnson & Johnson Vision has a variety of toric IOLs to meet most of your astigmatic patient’s needs.

Typically, if a patient has > 1.00D of corneal astigmatism, they could be considered a candidate for a toric IOL. This is best determined by comparing topography to biometry values.

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What are some of the primary reasons toric IOLs aren’t as commonly utilized?

With today’s plethora of new toric IOL options, patients with astigmatism are no longer left with large amounts of refractive error after cataract surgery. Prior to new advances in toric IOLs, surgeons may have been reluctant to use toric IOLs due to concerns of rotational stability. However, the TECNIS lenses showed that in >94% of patients at 6 months had <5' rotation.6 Between 35% and 40% of patients undergoing cataract surgery have astigmatism > 1.00D9 and up to 22% will have astigmatism > 1.5D.7

The proper implantation of a toric IOL requires significantly more precision than a conventional spherical IOL implant. Alignment of the toric IOL in relation to the patient’s astigmatic refractive error is of utmost importance.

What are the main reasons to consider toric IOL options/good candidates for toric IOL?

After considering their refractive error, ocular anatomy, personality type and visual priorities, choosing the right IOL is an integral part in providing a satisfactory surgical outcome for these patients. It is no surprise that patients are more satisfied with their cataract surgery when they can recognize improvements to their visual function and performance.10

There are several reasons to choose a toric IOL for patients undergoing cataract surgery. For starters, patients with an astigmatic refractive error of > 1.00D will typically benefit from a toric IOL implant. Good candidates for toric IOLs generally desire little or no dependence on spectacle lens correction after surgery. Patients with less particular, more open (Type B) personalities can also make better candidates for toric IOLs.

Some patients may be good candidates for cataract surgery, but would do better with a conventional spherical IOL implant. Other patients may still benefit from a toric IOL implant but should understand that they may still need to wear glasses for optimal vision postoperatively. Patients with preexisting ocular disease (eg. macular degeneration, glaucoma) may be poor candidates for toric IOLs.13 Patients with high amounts of irregular astigmatism, especially if they have keratoconus or pellucid marginal degeneration, are poor candidates for toric IOLs..13

Patients with Type A personalities should also understand that they may still be dependent on spectacle lens wear, regardless of which type of IOL they receive.

How do you present toric IOL as an option?

Discussing the patient’s anticipated functional visual goals post-operatively will be crucial for determining who is a good candidate for a toric IOL. This discussion should begin with the referring optometrist. As the patient is starting to have functional vision problems while performing their daily activities, discussing that cataract surgery is imminent and starting the conversation about what their postoperative visual goals are is a crucial first step. If the patient wants sharp distance vision and limited glare, they would be a good candidate for a toric IOL.

For example, long-haul truck drivers or previous emmetropes may be very bothered by poor distance contrast if left with residual astigmatism or fit with a multifocal IOL and will likely appreciate the toric correction. If a patient is a 2-3D myope and is happy with their uncorrected near vision before surgery, they may need a stronger reading add power for satisfactory vision postoperatively. This is true regardless of whether they’re left wearing spectacle/contact lenses, or receiving a multifocal/extended range IOL.

Patients need to understand that they have an option to correct astigmatism with a toric IOL during surgery, or will need to correct the astigmatism with contacts or spectacles after surgery.

What are the most important considerations and processes to take in order to ensure a good surgical and visual outcome?

Candidate selection is of utmost importance in positive post-surgical outcomes. Candidates with compounding ocular disease such as age-related macular degeneration, ocular surface disease, or diabetic retinopathy are contraindicated for toric IOLs. Those with milder or asymptomatic conditions such as epithelial basement membrane corneal dystrophy, mild epiretinal membrane or keratoconus may also lead to post-surgical problems.

After candidate selection, setting patient expectations would be the most important next step to post-surgical success. Explain to patients before their surgery that even if the goal of surgery is to be minimally dependent on glasses, there may still be activities where glasses are required. Helping patients understand that there will be a neuronal adaptation period (especially if they do a multifocal or toric multifocal lens) will ensure they do not think the surgery had a “bad” outcome. Letting the patient know that symptoms of glare or halos are possible post-op symptoms that could occur. Patients need to understand what expected side effects to anticipate ahead of time instead of trying to address them as they happen.

Lastly, ocular surface disease (OSD) and meibomian gland dysfunction (MGD) should be evaluated and treated in every surgical patient in order to receive optimal surgical outcomes. The ASCRS OSD Pre-Operative Algorithm has shown that OSD and MGD can alter the ocular surface, causing surgical measurements to be inaccurate.11 Treating OSD before surgical referral allows the eyecare team to optimize the ocular surface and increase the likelihood of accurate measurements. In one study, treating MGD in surgical patients before surgery correlated with a 40% change in surgical plan.12 Optometrists have a great opportunity to identify and provide patients with both treatment and education before their first appointment with the surgeon.

Are there any special considerations when it comes to multifocal torics? How do you go about the IOL selection process?

When helping a patient determine which intraocular lens choice would best suit their visual needs, it all depends on their post-surgical expectations and goals. Does the patient spend a lot of time outdoors? If so, all Johnson & Johnson Vision’s lens implants are UV blocking. Has this patient returned to your office dissatisfied in the past with progressive lenses or multiple glasses redos? This personality type may not be ideally suited for multifocal lenses where some degree of halos is expected at least in the short term. Ideally, you want to recommend multifocals and multifocal toric IOL options to those patients whose main priority is to limit the amount of time they need to wear glasses, even if that means sacrificing a little bit of vision in certain instances (eg. dim lit settings or when focusing on fine detail).

For the patient with > 1.00D corneal astigmatism who wants uncompromised distance vision and doesn’t mind wearing reading glasses (think people who drive long distances or do other primarily distance viewing tasks like certain sports or watching TV) the TECNIS® Toric II 1-Piece IOL may be the ideal recommendation. This could be used as a monovision design as well, especially for those who have opted for and previously done well with monovision contacts.

For those with <1.00D corneal astigmatism who want to see well at all distances and don’t mind reading glasses occasionally for fine detail, they may prefer the extended depth of focus IOL found in the TECNIS Symfony™. The extended depth of focus virtually eliminates poor contrast and difficulty transitioning between zones of previous multifocal IOL designs. For those without significant corneal astigmatism but requiring detailed near vision range, the TECNIS® Multifocal IOL is available in near power ranges from +2.75 to +4.00.

For those patients with >1.00D corneal astigmatism and visual demands primarily at intermediate and distance locations, they would typically do very well with a TECNIS Symfony™ Toric lens to correct for their corneal astigmatism as well as their distance, intermediate, and near demands. Lastly, for those with significant corneal astigmatism but higher near demands, they may be better suited to a TECNIS® Multifocal Toric II lens with astigmatism correction and all-range viewing with a particular focus on demanding near work. This lens type is available in two different near ADD powers (+2.75 and +3.25)

Keep in mind that all of these lenses can be used in combination as well. So for example, a patient implanted with a TECNIS Symfony™ or TECNIS Symfony™ Toric in the first eye but still struggling with near tasks such as reading the standard J5 font on a smartphone, may be recommended a TECNIS® Multifocal Toric for the other eye. This may provide excellent vision at all distances after adaptation.

Due to the chromatic aberration compensation inherent in the TECNIS Symfony™ lens, auto-refractors (including aberrometers) may yield erroneous refractive results. Instead, Johnson & Johnson Vision recommends a post-op refraction to be done in a specific series of steps to determine the best refraction for those with TECNIS Symfony™ IOL.


Patient Cases

Case #1 - TECNIS Symfony™ Toric

Mark H. Blecher, MD - Co-Director of the Cataract and Primary Eye Care Service at Wills Eye Hospital. Dr. Blecher is a paid consultant of Johnson & Johnson Surgical Vision Inc.

Pre Operative Exam

A 63 y/o Female presents with chief complaint of constant blur at all distances, progressive dry eye symptoms OU and decreased tolerance to Gas Permeable contact lenses. Her exam findings were significant for 3+ nuclear cataracts OU, all other testing unremarkable - OCT, corneal topography, IOLMaster.

Her visual goals were to gain independence from her GP contact lenses and have satisfactory uncorrected vision at all distances after cataract surgery. She was also an avid motorcyclist—a hobby I took into consideration when deciding on the best lens to use.

Surgical Planning

The patient understood that she would need to be out of her GP contact lenses for at least a month to stabilize her corneal topography measurements and that prior to cataract surgery, her surgeon would like to see two serial K readings that are stable over time.

  • MRx
    • OD: +4.50 + 1.50 x 83 20/50
    • OS: +5.25 + 1.00 x 90 20/50
  • K’s
    • OD: 41.41/43.77 x 83, OS: 41.82/44.12 x 94

The Holladay® II formula and Optiwave Refractive Analysis (ORA) System™ Technology were both used to assist with optimal IOL selection and to ensure satisfactory post-operative refractive status. The Holladay II calculation advised a +29.00D IOL power.

The ORA System™ Technology device attaches to the surgical microscope and utilizes wavefront aberrometry to measure the patient’s refractive power once the cataract is removed. The ORA System™ Technology assists the surgeon in the real-time assessment of the patient’s refractive status intraoperatively.

jjv astigmatism figure 1.jpeg

Image courtesy of Mark H. Blecher, MD

For this patient, we opted for the TECNIS Symfony™ Toric Lens implant in both eyes (model ZXT150 +28.50 OD, +29.00 OS).

Post Operative Exam

  • Refraction, OD: Plano 20/20+
  • Refraction OS: Plano 20/20+
  • Near J1 OU @ 14” 20/20 vision

This patient was thrilled with their vision and surgical outcome. As with most patients undergoing cataract surgery, they are looking to improve their vision and gain more independence from spectacle lens wear, both of which we were able to achieve with this patient.

Takeaways

The TECNIS Symfony™ Toric IOL has all the performance of TECNIS Symfony™ with the addition of astigmatism correction. Pre-op planning is the same for both the TECNIS Symfony™ and Toric lenses. Similarly, implantation is the same as for the Toric lens; in my opinion, however, the Barrett Toric Calculator is more ideal for determining proper toric IOL lens alignment.

Case #2 - TECNIS Symfony™ Toric and TECNIS® Multifocal Toric II IOLs

Marjan Farid, MD - Professor of Ophthalmology, Director of Cornea, Cataract, and Refractive Surgery, Vice-Chair of Ophthalmic Faculty - Gavin Herbert Eye Institute at UC Irvine Health. Dr. Farid is a paid consultant of Johnson & Johnson Surgical Vision Inc.

Pre Operative Exam

A 72 y/o Female presents with significant decreased vision OU and was found to have bilateral 2+ nuclear cataracts. She is a therapist and much of her work is at the computer (On Zoom) meeting her patients. She also charts on paper and typically takes off her glasses when charting.

  • Preoperative MRx: OD: -2.75 + 1.50 x 90 OS: -3.25 + 1.50 x 100 OS
  • Preoperative biometry with: OD: 1.25 D cyl at 95 deg, OS 1.35 D cyl at 100 deg

The patient’s topography astigmatism assessment was fairly consistent with biometry measurements.

jjv astigmatism figure 2.png

Image courtesy of Marjan Farid, MD

Surgical Planning

The patient was scheduled for cataract extraction with the TECNIS Symfony™ Toric IOL OD first followed by the OS 1 week later. We chose this lens to maximize her distance and intermediate vision.

Post Operative Exam

Right eye

Following cataract surgery in her right eye with TECNIS Symfony™ Toric, the patient was satisfied with her distance and computer vision but dissatisfied with her uncorrected near vision. She stated that she was unable to do her charting, but does not want to wear reading glasses and prefers more near focus after cataract surgery in the left eye.

Based on this update from the patient, a decision was made to use the TECNIS® Multifocal Toric II with 3.25 add for her left eye cataract surgery. After both eyes underwent cataract surgery, the patient was much happier with her uncorrected vision at distance and near with both eyes open. On post-op refraction, no manifest residual astigmatism was present, and uncorrected visual acuity was 20/20 in each eye, with near vision J3 and J1 in the right eye and left eye respectively.

Takeaways

It is important to personalize vision related goals to maximize range of vision based on patient’s expectations and lifestyle. If a patient is a -2 to -3 myope preoperatively (and before they developed a cataract), they will typically require a greater reading add power as they are accustomed to good near focus prior to cataract formation.

The TECNIS® Multifocal Toric II now available for eyes that need a toric IOL and greater near add in their presbyopic correcting IOL.

Case #3 - CATALYS® Precision Laser System cOS 6.0

Wendell Scott, MD - Ophthalmologist at Mercy Hospital, Springfield Missouri. Dr. Scott is a paid consultant of Johnson & Johnson Surgical Vision Inc.

Pre Operative Exam

A 75 year-old farmer referred for progressive decreased vision that is interfering with driving, especially with night-time glare.

BCVA:

  • OD: +0.50 +2.00 x 013, 20/40
  • OS: +1.50 +1.25 x 169, 20/40
  • Glare vision testing OD: 20/70, OS: 20/60.

The patient has 2+ nuclear sclerosis and 2+ cortical cataracts in each eye. His examination is otherwise unremarkable.

A review of the pre-operative tests include the Zeiss IOLMaster® 700, Nidek® OPD, and the Cassini® topographer. I look at all three comparing the anterior/SIM-K®, and at the IOLMaster® and Cassini® for the TK and TCA, respectively. On the IOLMaster® I note the CCT and the CW Chord (angle kappa), the OPD wavefront analysis and RMS, and the Cassini® HOA, SRI, SAI, and IR QF. Based on the exam and the pre-operative tests, I decide what the IOL choices are for this patient.

scott case 3 figure 1 jjv astigmatism.jpeg

Image courtesy of Wendell Scott, MD

I let the patient know that he has cataracts and that the cataracts are the cause of his decreased vision and glare. I explain that we use the laser for cataract surgery because we can make precise incisions in the cataract capsule and that the laser also softens the lens so that we can remove it in a way that is more gentle on the eye. Also, once the cataract is removed, we place a lens implant in and that there are different choices. The single focus implant is covered by insurance and will help restore the vision, but he will still need glasses all the time. He also has astigmatism, which I explain as the cornea being more oval and not round, thus preventing the light from being sharply focused. This is true at all distances and one of the reasons he needs glasses all the time. Almost everyone has some measurable amount of astigmatism and that if it is low enough, it doesn’t have much effect. Unfortunately, his is higher and is likely to have an effect. I also explain that there are implants that have a range of vision, meaning less dependence on glasses. His choice is a single vision implant and glasses, or an implant called a toric lens for astigmatism, or an implant that has astigmatism correction in it plus a range of vision.

What are the patient’s goals after surgery? Do they mind wearing glasses or is their goal to reduce or eliminate the need for glasses? If I have determined that their eyes are otherwise healthy and that we have reliable measurements, I tell them that they are good candidates for all three choices and find out more about what their near and intermediate vision needs are. This patient works on his farm equipment. He reads normal print approximately one hour per day. He has a smartphone and checks his email on a desktop computer. He occasionally goes fly-fishing.

In this case, the patient does not mind wearing glasses, but he is interested in making his vision as sharp and clear as possible. I explain that reducing astigmatism is the best way to sharpen his vision. Although he will still need glasses, he will reduce how much prescription he needs in his glasses, especially at distance. He says that many of his friends only need reading glasses after surgery. In my opinion, this is true for 80% of patients who don’t have significant astigmatism, but I tell this patient that in his case, he would probably need the glasses for distance if the sharpness of focus is important to him. I truly believe that the toric IOL offers “value” and is worth it and I think patients can see that I mean it. With this assurance, he elects to proceed with a toric IOL.

Have I promised too much? In our practice, we will include laser PRK for patients that have a significant residual refractive error at no additional charge. We do this for all premium IOL patients. In my experience, I’ve found that the need for this is especially rare with the toric IOL where over 90% of patients have minimal refractive error. As I discussed, our goal is to reduce the astigmatism to a level low enough that it is not significant, not eliminate it. It is an important point for the referring doctor and the patient so that we comfortably meet expectations.

scott case 3 figure 2 jjv astigmatism.jpeg

scott case 3 figure 3 jjv astigmatism.jpeg

Images courtesy of Wendell Scott, MD

I usually do the non-dominant eye first, so let’s look at the toric planning for the left eye.

  • Current glasses RX: +1.25 @ 169
  • Nidek® OPD: +1.25 @ 179
  • IOLMaster® 700 anterior K: +1.10 @ 180
  • IOLMaster® 700 TK (total cornea): +1.41 @ 2
  • Cassini® SIM-K®: +1.09 @ 175
  • Cassini® TCA (total corneal astigmatism): +1.22 @ 176 degrees

I think the glasses RX is the least helpful, but it is reassuring if the axis is in the same general direction (ATR, WTR, or oblique). Next, I look at the anterior Ks of the OPD, IOLMaster®, and Cassini® and see that they are relatively close. At this point, you would expect the IOLMaster® TK and the Cassini® TCA, both of which measure the posterior astigmatism, to have a higher magnitude of astigmatism due to the posterior contribution. The finding confirms this. In the end, you have to pick a number to plug into the TECNIS® Toric calculator. Now that we have the CATALYS® Precision Laser System cOS 6.0 in combination with the Cassini® Ambient, I prefer to import the Cassini® iris registration and Ks. In this case, either the SIM-K® or the TCA will give similar results. However, remember that the PCA “No or Yes” must be selected. If you use the SIM-K®, you would select “Yes” so that the PCA adjustment would be included in the calculation. If you use the TCA Ks, select “No” because the TCA Ks already include posterior astigmatism as measured directly. An example of the calculation using the TCA Ks with “No” selected under PCA is provided. A ZCU150 @ 176 degrees is selected, which is the closest value to no residual refraction without flipping the axis. Some surgeons prefer to select an IOL that will leave a slight residual WTR result. This may be preferable in a younger patient due to the natural drift to more ATR with time.