Which IOL is preferred for cataract surgery after previous RK?
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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, Lisa K. Feulner, MD, PhD, shares a case about cataract surgery in a patient with previous RK, while Quentin B. Allen, MD, and Mitchell A. Jackson, MD, discuss the benefits of choosing either a toric lens or a Light Adjustable Lens for these patients. We hope you enjoy the discussion.
Kenneth A. Beckman, MD, FACS
OSN CEDARS/ASPENS Debates Editor
The case
The patient is a 65-year-old man referred to me by a local optometrist for evaluation of a cataract. He had a 2-year history of gradually worsening vision in both eyes with glare and hazy vision at distance and near. He also wanted to be glasses-free after cataract surgery. His ocular history was significant for RK in 1995 in both eyes.
His corrected vision was 20/20 in the right eye and 20/20 with 1 D of astigmatism in the left eye with significant glare to 20/50 in both eyes. Due to the mild cataracts, I recommended a rigid gas permeable or scleral lens trial to determine if it was corneal or lenticular glare causing his symptoms before scheduling surgery. He was not interested in this option.
Due to his higher-order aberrations and irregular cornea, he was not a good candidate for presbyopic lenses. After taking measurements, I selected the enVista MX60ET lens (Bausch + Lomb).
Source: Lisa K. Feulner, MD, PhD
Postoperatively, the patient has uncorrected vision of plano 20/20 in each eye. He reported that his vision was clear and bright without blur or glare.
- For more information:
- Lisa K. Feulner, MD, PhD, can be reached at Advanced Eye Care & Aesthetics, 104 Plumtree Road, Suite 107, Bel Air, MD 21015; email: lkf@advancedeyecaremd.com.
Toric lens
One of the important things about RK patients is that they typically have fluctuation in vision over the course of the day. That makes it difficult to target an exact refractive outcome. The good news is that a large number of these patients have done monovision in the past and are accustomed to potentially having one eye more suited for reading and one eye more suited for distance.
It may not be necessary to use a Light Adjustable Lens (LAL, RxSight) in these patients because we are already going to target a low amount of myopia in the nondominant eye for most cases. This helps to prevent a hyperopic overcorrection which can occur more frequently in these patients where we typically overestimate the central keratometric measurements. So, targeting low myopia provides a hedge against overcorrection, or a very functional intermediate or near range if we land at the predicted target. We also know that even if we end up at –1 D, they may fluctuate from plano to –2 D throughout the day, so having the ability to titrate the refraction with the LAL may be somewhat futile for this sort of patient. Do we lock in the morning or the evening refraction for these patients? How many serial refractions and extra visits are reasonable to require, especially if our patients come from far away and want less trips to our office, not more?
As long as there is reproducible astigmatism with a well-defined axis on multiple modalities of testing, we can treat the astigmatism while targeting low myopia on the first eye, using intraoperative guidance or aberommetry to help achieve a consistent astigmatic correction. With this strategy, I have found we can reliably debulk their astigmatism, in most cases leaving them with 0.75 D or less.
Additionally, with a low myopic outcome in the nondominant eye, we have the ability to look back and calculate which formula was most accurate. From there, we can aim a little more for distance (first minus) in the dominant eye with a toric lens and one procedure without necessarily having to bring patients back for the lock-ins that would be required for a LAL. That is an excellent thing to offer patients. We can streamline their whole surgical process and typically at a lower cost.
Generally, this process works better for patients with no more than eight RK cuts. There is more variability and irregularity for both sphere and cylinder in patients with more than eight cuts. In those cases, a LAL is probably a sounder strategy, and could help refine a large miss in sphere or cylinder. However, for the group of patients with just four or eight cuts, a toric lens is a great option and can have a high degree of success.
- For more information:
- Quentin B. Allen, MD, can be reached at Florida Vision Institute, 1050 SE Monterey Road, Suite 104, Stuart, FL 34994; email: qallen2000@gmail.com.
Light Adjustable Lens
This case is typical of a post-RK patient. I always say that these patients’ corneas act like trampolines, causing fluctuation in vision with a tendency for more flattening early in the day. Over time, the corneas continue to have progressive hyperopia.
It can be hard to nail the planned end target in patients after RK, and the more RK incisions they have, the more unstable and less reliable the readings are going to be, even with modern-day IOL calculation formulas.
You always want to shoot for myopia in these patients because they are going to tend to be more hyperopic with time. With a Light Adjustable Lens (LAL, RxSight), you can plan for a little myopia, and once patients are all healed and stable in both eyes, then you can do your adjustment and leave them exactly where you want their end target.
You get one shot at this case if using a toric IOL. The patient in Dr. Feulner’s case ended up plano in both eyes, but not every surgeon is going to nail that target perfectly each time. If a patient pays for a toric lens and you are not on target, they are not going to be happy. From there, it can be difficult to make an adjustment in that further corneal refractive surgery is not always warranted in these cases. With the LAL, you can make that adjustment right on the lens when you feel they are stable enough postoperatively, and you do not have to worry about doing a piggyback lens or IOL exchange if off target with a toric IOL. With the recent upgrade in the LAL technology with ActivShield, further UV protection can allow the surgeon to wait longer for refractive stability before performing the adjustments and lock-in treatments if desired.
If there is any kind of irregular astigmatism, then it is a whole different ballgame, but for regular astigmatism, then the LAL is the way to go.
- For more information:
- Mitchell A. Jackson, MD, can be reached at JacksonEye, 300 N. Milwaukee Ave., Suite L, Lake Villa, IL 60046; email: mjlaserdoc@msn.com.
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