Refractive Surgery and Optics
Core concepts
Understand basic optics: refraction, myopia, hyperopia, astigmatism, and presbyopia. Know the principles of LASIK, PRK, and refractive lens exchange. Learn the preoperative evaluation for refractive surgery: corneal thickness, topography, dry eye, and stability of refraction. Understand the complications: dry eye, ectasia, flap complications, and under/overcorrection. Know the optics of contact lenses and spectacles, including vertex distance and magnification.
Traps
Do not perform refractive surgery on a patient with unstable refraction or keratoconus. Recognize that PRK removes the epithelium and has a longer recovery but avoids flap complications. In patients with high myopia, consider the risk of ectasia. Understand that presbyopia is not a refractive error that laser surgery corrects.
Rule of thumb
Any topographic abnormality suggesting keratoconus is a contraindication to corneal refractive surgery. For a patient with dry eye, optimize the ocular surface before surgery.
Worked example
A 25-year-old with stable refraction and normal topography requests LASIK. Preoperative evaluation should include corneal thickness and topography; if normal, proceed with counseling on dry eye and flap risks.