CRST: How do you choose among LASIK, PRK, and lenticule extraction in routine practice?
Arthur B. Cummings, MBChB, FCS(SA), MMed(Ophth), FRCSEd, FWCRS: The decision between PRK and LASIK or keratorefractive lenticule extraction (KLEx) is based mainly on corneal pachymetry. LASIK and KLEx have the same preoperative requirements, whereas PRK can be performed on eyes with thinner corneas. PRK is also often an ideal enhancement strategy for eyes with a history of LASIK or KLEx. If the keratoconus indices or epithelial maps raise concern, an Implantable Collamer Lens (ICL, STAAR Surgical) is a safer option than PRK. LASIK and KLEx are contraindicated in eyes with suspicious corneas.
CRST: For a patient with high myopia, how do you choose among corneal laser surgery, phakic IOLs, and refractive lens exchange?
Dr. Cummings: This depends on several factors, including the patient’s age; whether they are presbyopic; the presence or absence of a grade D posterior vitreous detachment; the health of the peripheral retina, specifically the presence of lattice degeneration; and corneal pachymetry. Refractive lens exchange (lens replacement) increases the risk of retinal detachment with higher levels of myopia, younger age, no posterior vitreous detachment, increased axial length, and the presence of lattice degeneration.
The FYEO-Medical Retinal Detachment Risk Calculator (medisch.fyeo.nl/retinal-detachment/retinal-detachment-calculator) is a valuable tool for assessing the risk of retinal detachment in eyes undergoing lens replacement.
Phakic IOLs are not an option if the anterior chamber is not deep enough and the iridocorneal angles are not wide enough. Tools such as ICL Guru (Revai), which uses ultrasound biomicroscopy to determine lens sizing, have broadened the eligibility criteria and increased predictability.
Even if corneal pachymetry is sufficient for a large laser vision correction (LVC), consideration should be given to future IOL options. With recent developments in ray tracing–guided LASIK (WaveLight Plus, Alcon), the situation has changed, with no increase in spherical aberration irrespective of the level of myopia treated.
With three excellent options, additional factors come into play, such as cost, recovery, perceived risk, and the patient’s desire for full range of focus IOLs for future cataract surgery. In our clinic, the most common solution is an ICL, followed by LVC, and finally lens replacement for those patients with a low risk of retinal detachment (grade D posterior vitreous detachment, no lattice degeneration, shorter axial lengths due to corneal myopia/steepness) or, more simply stated, a low risk according to the risk calculator.
CRST: What are the key metrics you use to assess ectasia risk?
Dr. Cummings: Epithelial maps, corneal pachymetry, the Belin/Ambrósio Enhanced Ectasia Display (BAD) on the Pentacam (Oculus Optikgeräte), the predicted residual corneal bed, and percentage tissue altered are the key metrics. Percentage tissue altered is the softest of the metrics used in our clinic, but it has value on occasion in directing us one way versus another.
My colleagues and I use an age-adjusted BAD after a personal conversation with Michael Belin, MD, during which he informed us that the BAD is calibrated for a 30-year-old patient. For each year younger than 30, 0.05 is added to the BAD score, and for each year older than 30, 0.05 is subtracted from the BAD score.
CRST: Enhancements after LVC or presbyopia-correcting IOL implantation: What does your decision tree look like, and what is your threshold for treatment?
Francesco Carones, MD: At my practice, we offer all-inclusive services to our patients so that, when residual refractive error leads to suboptimal visual outcomes, patients are not charged for the enhancement. The threshold to treat a residual refractive error after presbyopia-correcting IOL implantation is determined by patient satisfaction. In other words, if the patient is not satisfied because of a residual refractive error and there are no contraindications to correcting the problem, I proactively suggest an enhancement.
The decision tree then involves choosing the type of procedure used to correct residual refractive error. After toric IOL implantation, we assess whether IOL rotation alone could fix the problem. When toric IOL axis realignment does not adequately address the refractive outcome, I consider LASIK as my primary option. When contraindications to LASIK exist—most commonly dry eye disease—I consider supplemental IOLs as the second choice. Both LASIK and supplemental IOLs allow fast visual recovery and a rapid return to normal life, which is critical when a patient is already unsatisfied. My third option is surface ablation. I consider an IOL exchange only for eyes that truly cannot be treated with one of the previous options.
Dr. Cummings: We enhance prior LASIK with flap-lift LASIK enhancements if the enhancement is performed within 3 years of the initial procedure. If LASIK was performed more than 3 years earlier, a sidecut-only flap is created using the original flap but gaining access to the interface via a new sidecut by cutting 10 µm deeper than the original flap thickness as measured with OCT. If the flap was created with a microkeratome and is therefore nonplanar, PRK is performed over the flap. This works well in my experience, and adjunctive mitomycin C is used routinely, even for minor corrections.
After IOL surgery, LASIK enhancements are performed for missed refractive targets at 6 months or later postoperatively. If a patient prefers earlier treatment and all parameters are stable, we offer PRK between 6 weeks and 3 months postoperatively.
CRST: What role do topical presbyopia drops play in your practice, and what do you tell patients about duration, side effects, and realistic expectations?
Jorge L. Alió, MD, PhD, FEBOphth: This is a good option for patients who require up to a +1.00 D near add in their spectacle correction. This is especially true for emmetropic patients, and they are the only group for whom I use this alternative. I prescribe pilocarpine 0.75% in a galenic formulation (off-label indication) and initiate a 7-day trial to evaluate the patient’s response and satisfaction.
I exclude from this approach patients with a history of retinal disease and those with a history of refractive surgery who had greater than -4.00 to -5.00 D of preoperative myopia. I think topical treatment is an excellent option for individuals with early presbyopia, but when they require more than a +1.50 D near add, I prefer a surgical solution.
Stefanie Schmickler, MD: Presbyopia-correcting eye drops are not yet available in Germany, where I practice. I am skeptical about their use because they can cause side effects such as headache and reduced distance visual acuity. I suspect that German patients will not readily accept this treatment modality.
