41 EyeWorld Asia-Pacific | December 2024 REFRACTIVE SURGERY ASIA-PACIFIC PERSPECTIVES Fam Han Bor, MD Senior Consultant, Tan Tock Seng Hospital 11 Jalan Tan Tock Seng, Singapore 308433 famhb@singnet.com.sg Higher-order aberrations (HOAs) are complex optical imperfections in the eye that may significantly impact visual quality. HOAs include spherical aberration (SA), coma, trefoil, and others, which can cause symptoms like glare, halos, starbursts, reduced contrast sensitivity, and induced defocus. In cataract surgery, HOAs are crucial in determining visual outcomes. Cataracts can induce or exacerbate HOAs. Cataract surgery replaces the cloudy, aberrated crystalline lens with an intraocular lens (IOL). The choice of IOL is critical as it can influence postoperative visual quality. Modern IOLs, such as SA compensating, SA neutral intraocular lenses, can minimize HOAs and improve visual outcomes. Matching aspheric IOLs can neutralize or reduce the prevailing cornea spherical aberration, thereby enhancing contrast sensitivity and overall visual quality. Laser refractive surgery, including procedures like LASIK, PRK, and SMILE, can induce HOAs, particularly if the optical zone is too small or the ablation is decentred. The induction of HOAs can lead to suboptimal visual outcomes, such as night vision problems and decreased visual acuity. Wavefront-guided and topography-guided LASIK are advanced techniques that map the eye’s aberrations and customize the laser treatment to correct or minimize the induction of HOAs. Preoperative assessment of HOAs is essential for both cataract (figure 1) and refractive surgeries. Technologies such as wavefront aberrometry, corneal topography, and optical coherence tomography (OCT) measure and quantify HOAs. These measurements help in planning the surgical procedure and selecting the appropriate IOL or laser treatment parameters. Determining the total eye HOAs is important in laser refractive surgery, but only the cornea HOAs are required for cataract surgery. In LASIK, patients with significant preoperative HOAs may benefit from wavefront-guided LASIK. Cataract patients with significant SA, particularly those who have had myopic LASIK with older excimer lasers, may benefit from the appropriate aspheric or SA-correcting IOLs. Different populations have different amounts of cornea SA. Knowing the amount of corneal SA helps me match the appropriate IOL for better visual outcomes (Table 1). Of note is dry eye which can induce considerable but inconsistent HOAs. This should be treated before surgery, and adequately controlled postoperatively to maintain good visual outcomes. In conclusion, HOAs are a significant consideration in both cataract and refractive surgery. Proper assessment and management of these aberrations are essential for achieving optimal visual outcomes and patient satisfaction.
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