Eyeworld

FALL 2024 | EYEWORLD | 53 R References 1. Rocha KM, et al. Effects of Zernike wavefront aberrations on visual acuity measured using electromagnetic adaptive optics technology. J Refract Surg. 2007;23:953–959. 2. Rocha KM, et al. Enhanced visual acuity and image per- ception following correction of highly aberrated eyes using an adaptive optics visual simulator. J Refract Surg. 2010;26:52–56. Relevant disclosures Armstrong: None Gatinel: Alcon, BVI, Heidelberg Engineering, Moria, Nidek, Rayner Rocha: Alcon, Allergan, Bausch + Lomb, Johnson & Johnson Vision Contact Armstrong: brarmstrong@unmc.edu Gatinel: gatinel@gmail.com Rocha: karolinnemaia@gmail.com from the lens will be removed in cataract surgery. "In this situation, you need to direct the corneal wavefront," he said, adding that research should be conducted to understand the interactions between the IOL options and different corneal aberrations to "cherry pick the one that is most relevant for the patient." HOAs and refractive surgery If a patient is seeking refractive surgery, not yet needing cataract surgery, and has HOAs, Dr. Gatinel said he'll first tell patients to stop rubbing their eyes. Once it seems like they've understood the importance of this and they don't progress, he finds wavefront-guided PRK to be the best option to improve the corneal shape. If you're confident they won't rub their eyes in the future, and the corneal topography shows moderate abnormalities, LASIK could be an option. He added that he would avoid premi- um lens implantation after lenticular extraction for patients with elevated and/or symptomatic HOAs. Dr. Rocha, in a presentation, offered several pearls for managing HOAs in the setting of corneal refractive surgery. 1. Make sure maps are reproducible and verify long-term refractive stability. 2. Compare the wavefront refraction with the manifest and cycloplegic refractions and the topographic maps with wavefront aberra- tions. 3. For enhancements, use SD-OCT to deter- mine whether LASIK or PRK is better (PRK with mitomycin-C for cases with thin pa- chymetry and thick flaps; don't relift flaps if you can't identify the thickness profile). 4. Recognize that the ablation depth for a specific refraction increases with the magnitude of aberrations, leading to overcorrection. 5. Discuss with the patient that this might be a two-step treatment due to the potential shift in lower order aberrations when cor- recting HOAs. Dr. Rocha's presentation also emphasized that management of HOAs is technology dependent. Not all platforms perform the same, and HOA treatment is subject to technology limitations. A word about Zernike Dr. Gatinel spoke at length about Zernike polynomials and how they may not always accurately represent the visual quality be- cause they sometimes misrepresent defocus and other aberrations. Dr. Gatinel published an "alternative wavefront reconstruction method" in 2020, proposing that "some of the inherent limitations of Zernike polynomials in clinical ophthalmic application can be solved by a novel set of polynomials forming an al- ternative higher order basis. The new basis provides a clear separation between modes containing lower order terms versus higher order terms and offers clinicians a more clin- ically realistic wavefront analysis." 1 In his interview with EyeWorld, Dr. Gatinel said that the real defocus people select to correct with spectacles is not the Zernike de- focus. "Zernike defocus is in displays where you would say that's the defocus, but this is particular in eyes with a lot of spherical aberrations, which are eyes with a lot of problems. This Zernike defocus is not the refractive defocus," he said. In addition, the retinal image simulations and related met- rics for HOAs using Zernike decomposition are not always clinically relevant as some low order aberrations such as defocus or astigmatism are embedded in the expres- sion of some higher order Zernike modes. Reference 1. Gatinel D, et al. An alternative wavefront recon- struction method for human eyes. J Refract Surg. 2020;36:74–81.

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