Keratoconus, cataract surgery, residual hyperopia: What are the options?
Welcome to another edition of CEDARS/ASPENS Debates. CEDARS/ASPENS is a society of cornea, cataract and refractive surgery specialists, here to discuss some of the latest hot topics in ophthalmology.
This month we are going to discuss how to handle a specific case, a 71-year-old man who underwent cataract surgery with implantation of a toric IOL 8 months ago by another surgeon. He has a history of keratoconus with a maximum keratometry of 53.8 D and about 3 D of irregular astigmatism. Despite his corneal limitations, his postop uncorrected visual acuity is 20/30 at distance and J1 at near. His manifest refraction is +1.50 –0.25 × 41, yielding 20/20 best corrected visual acuity. He is unhappy with his UCVA and is presenting for a second opinion about other procedures to improve his vision and correct his residual hyperopia. He does not want to give up any of his near vision. What would you propose to this patient? Think about it, and then read how William B. Trattler, MD, and Vance Thompson, MD, would handle the case. Learn and enjoy!
Kenneth A. Beckman, MD, FACS
OSN CEDARS/ASPENS Debates Editor
IOL exchange or a piggyback monofocal
When we perform refractive cataract surgery, our ultimate goal is to provide patients with the best possible vision.
Source: William B. Trattler, MD
However, no matter how well we plan ahead of time to end up on target, the eye can heal in a way that is not entirely predictable, and some patients come back and report disappointment in their outcome due to residual refractive error. In the case we are discussing today, the patient ended up on the hyperopic side.
There are three main ways to manage residual refractive error after cataract surgery: laser refractive surgery, IOL exchange and piggyback IOL implantation (Figure 1). But when you have keratoconus in a pseudophakic patient, that reduces the options to two because laser surgery on the cornea is typically not an option.
Of course, in this case, we still have to watch out for keratoconus progression because even at the age of 60, 70 or 80 years, some patients with keratoconus can still have a cornea that is not stable. In these cases, corneal cross-linking, although not routinely required before cataract surgery, might be advisable. Cross-linking is effective at stabilizing the corneal shape even in older patients. The caveat is that it can cause a hyperopic shift, and if you are doing both cross-linking and some kind of additional lens surgery, I recommend targeting a slightly myopic outcome.
Going back to the patient we are examining, assuming that he has proven stable keratoconus, my first choice would be an IOL exchange. In my practice, I do this in 95% of the cases when I need to address residual refractive error because the procedure has become accurate, safe and easy to perform. The key, of course, is that the capsule is intact, with no prior YAG and an uneventful surgery. I typically use the Barrett IOL exchange formula that is available for free through the ASCRS app. You upload the patient’s IOL power, the current refraction and the target refraction (as well as other parameters), and the calculator will provide the new power of lens to place in the eye.
IOL exchange surgery is straightforward, but here are some pearls from my experience. First, what I find helpful is to use a small viscoelastic cannula to get under the capsule and viscodissect it from the IOL. Second, if you cannot get the haptics out, you can amputate them and leave them in place, taking out just the body of the lens. Sometimes the haptics are easier to remove once they have been amputated from the IOL optic, but there is no harm in leaving them there if needed. Third, when you have pulled the IOL out of the bag, consider implanting the new lens. It will serve as a scaffold and protect the capsule before you start working on the original lens. My technique is to use micrograspers and microscissors to cut the IOL in half and remove it from the eye through a 2.5-mm incision. The fourth thing to consider is that you have to be cautious of the main incision. Sometimes when you create your main incision for an IOL exchange, you are passing through or near the original wound, and this can lead to some leaking. You therefore might need to place a suture to secure the wound.
In patients with keratoconus, I like to use a lens with zero asphericity because it improves the quality of vision in these specific cases. Going from hyperopia (the current outcome) to mild myopia (–0.25 D), we will improve the patient’s distance vision, and near vision should also improve to a degree. Because this patient was implanted with a toric IOL, and assuming that the toric IOL corrected the astigmatism completely and efficiently, I would plan on replacing the current lens with another monofocal toric and placing it on the same axis.
The other option would be a piggyback lens. Because the toric lens is already taking care of the astigmatic correction, I would use a zero asphericity three-piece monofocal IOL such as the LI61AO by Bausch + Lomb. Fortunately, we often have a number of IOL options that can be used as a piggyback IOL. While the capsule was intact in this patient, piggyback IOLs are a great option in patients with residual refractive error who have an open capsule.
- For more information:
- William B. Trattler, MD, director of cornea at the Center for Excellence in Eye Care in Miami, can be reached at wtrattler@gmail.com.
Start with the keratoconus
The first thing I would do is explain to the patient that he had a quality surgery and why cataract surgery is not as accurate as we would like it to be but that he has good options if he does not want to wear glasses or contact lenses.
Secondly, I would want to make sure he has keratoconus. With a best corrected visual acuity of 20/20, I would map his epithelium, and if thick over the corneal elevation, I would change the diagnosis to anterior basement membrane dystrophy and include corneal refractive surgery as an enhancement option. If the epithelium is thin over the 53.8 D of elevation, which I predict it is in this case, I would confirm the diagnosis of keratoconus.
Next, I would also tell him that I handle keratoconus differently at his age of being more naturally cross-linked than a 16-year-old in whom I would be cross-linking first. I would want to make sure he does not rub his eyes or sleep with his eye into a pillow. Behavior modification is so important in keratoconus. If his keratoconus is stable, I would not cross-link, and if not stable (past records help), I would cross-link first and have him wait 6 months for any refractive enhancement decision because cross-linking promotes a regularization of the cornea, which includes a flattening and hyperopic shift. At a minimum, if this is true keratoconus, I would educate him to have follow-up and decide in 6 months and a year if his keratoconus is stable or not. I predict it is.
If this is stable keratoconus and he wants to treat his refractive result, I would want to also document that he is happy with his best corrected image quality (BCIQ). A BCVA of 20/20 on the chart does not mean he is happy with his BCIQ. If his BCIQ is reduced, I would do a gas permeable contact lens over refraction to see if this helps. If he is not happy with his BCIQ, the gas permeable lens over refraction helps his vision, and his tear film is optimized. Cross-linking is a quality option to improve his irregular astigmatism, which could improve his BCIQ, and lessen his hyperopia (again, due to corneal flattening). If he is happy with his BCIQ (I predict he is), then I would recommend an IOL exchange. I would be prepared in surgery for a potential change in plans to convert to a piggyback lens if the exchange is not possible because of capsular issues. I predict the IOL exchange would go well, and I would go to the ASCRS.org website and use the Barrett Rx formula to calculate the implant power for a hyperopic surprise. If I wanted to do a piggyback lens, I would use the Barrett Rx formula while keeping in mind the calculation of a piggyback IOL power can also be determined by multiplying the manifest refraction times 1.5, which in this case with roughly 1.4 D of hyperopia would be a +2 D three-piece IOL. If I did a piggyback lens, I would also consider the LAL+ (RxSight), which is now available in low powers of –2 D, –1 D, 0 D, +1 D, +2 D and +3 D and works great in the sulcus. We would need to document that his pupil dilates to 6.5 mm or larger to consider the LAL. If he did not dilate well and a piggyback is his best option, I would choose another three-piece IOL. Most likely, though, this patient would do best with an IOL exchange.
- For more information:
- Vance Thompson, MD, founder of Vance Thomson Vision in Sioux Falls, South Dakota, can be reached at vance.thompson@vancethompsonvision.com.
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