Eyeworld

SPRING 2026 | EYEWORLD | 73 R Contact Klyce: sklyce@klyce.com McDonald: margueritemcdmd@aol.com Trattler: wtrattler@gmail.com Relevant disclosures Klyce: Nidek McDonald: Oculus Trattler: ArcScan, Heidelberg, Oculus, Zeiss Dr. Trattler also brought up the Artemis (ArcScan), a high-frequency ultrasound arc scanner. This technology uses a water bath and can differentiate between the epithelium and the tear film. Even with these other technolo- gies, Dr. Trattler reiterated that topography is the most used and reliable for detecting irregu- lar astigmatism. Dr. Klyce and McDonald said, "Skiasco- py and ray tracing add the ability to measure aberrations from the whole eye to determine whether the corneal endothelium or (more likely) the lens contribute significantly to ocular aberrations in addition to those due to the corneal surface. Corneal tomography with slit scanning instruments adds the ability to measure corneal endothelial optics and corneal thickness profiles. While corneal tomography provides these additional measurements and is less prone to error in highly aberrated corneas than corneal topographers, the latter remain the most accurate method to characterize the irregular astigmatism that has an early impact on visual acuity." Many treatments for causes of irregular astigmatism are covered by insurance, Dr. Trattler said, even if the initial topography that identified the astigmatism was not covered. "If a patient with a history of cataracts comes in with complaints of reduced vision, unless you per- form topography/tomography and OCT of the macula, you may not identify other causes of the reduced vision, such as keratoconus (which can have a normal slit lamp exam when not too advanced), as well as vitreomacular traction syndrome. The advantage of performing topog- raphy and OCT prior to cataract surgery is that you identify these conditions prior to surgery." When it comes to cataract surgery planning for patients with irregular astigmatism, Dr. Trattler said patients with significant irregular astigmatism (even after ocular surface optimiza- tion, for example) are typically not candidates for a multifocal lens. He said a toric lens can be used if there is a "visible axis" and the degree of irregularity is mild. He said the Light Adjustable Lens (RxSight) or the IC-8 Apthera (Bausch + Lomb) are options as well. "You might be able to use the IC-8 Apthera lens as a technology to help reduce the impact of the irregular astigmatism on vision. There are a lot of choices and options," Dr. Trattler said. Dr. Klyce and Dr. McDonald said it bears repeating that irregular astigmatism is defined and determined by evaluation of the HOAs mea- sured from the reflections of Placido mires on the corneal surface. They added that some sim- pler HOAs have some optical properties that are useful for corneal diagnostics and IOL design. "For example, coma is often associated with the inferior steepening seen in the topog- raphy of keratoconus. Spherical aberration is sometimes enhanced in laser refractive sur- gery to increase depth of focus in presbyopes," they said. "However, the more complex HOAs generally combine to produce blur, halos, glare, starburst, or reduced contrast sensitivity that are uncorrectable with simple spherocylindrical optics. Topographic and wavefront-guided laser keratorefractive surgeries can reduce some of the HOAs but are generally most effective when treating the relatively simple HOAs (coma and spherical aberrations)." When it comes to IOL selection in the set- ting of HOAs, Dr. Klyce and Dr. McDonald said that a general "rule of thumb used by some phy- sicians for IOL selection is to prefer a monofocal IOL rather than a premium channel extended focus or toric IOL, if the HOAs are greater than 0.5 µm RMS for a patient's photopic pupil size." They said that quality of vision for an eye at different pupil sizes with an aberrated cornea can be obtained with Zernike terms and using optic calculations, assuming the rest of the eye is normal (Figure 2). "This approach can also be extended to address the impact of various IOL designs on vision obtainable for the individual patient if the optical design principles of an IOL are known," they said. Dr. Trattler's final message was that he hopes topographic screening becomes more routine. He said it's not uncommon that he discovers keratoconus, treatable with crosslink- ing, when patients have a screening topogra- phy, whether prior to cataract surgery, LASIK, pterygium surgery, or other procedures. "The key issue is that we currently do not perform screening topographies on every single patient who comes to our office. Early kerato- conus is often not detectable on slit lamp exam alone. If keratoconus is identified at an early stage, prior to vision loss, patients can be protect- ed from progressive visual decline that may oth- erwise develop years later," Dr. Trattler said.

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