"How Does Femtosecond Laser Work for Correcting Nearsightedness?"

The Envy of Wearing Glasses and the Journey to Myopia

Previously, I envied those classmates who wore glasses, feeling that they exuded an air of erudition and versatility. Eventually, in pursuit of that perceived erudition, I too became myopic, and then I suffered greatly, especially during basketball and other physical activities – the pain was indescribable! At that time, many classmates would undergo a corrective surgery before the college entrance examination, eliminating certain restrictions in their college application choices. When I first heard of "laser surgery," I genuinely felt it was something sophisticated and high-end.

Today, I'll briefly explain the basic principle of one of the laser surgery techniques: the Femtosecond Laser-Assisted In Situ Keratomileusis (SMILE) for myopia correction. SMILE for myopia correction can be categorized into two types: full-SMILE and half-SMILE surgeries.

The full-SMILE surgery utilizes the femtosecond laser throughout the entire procedure. It creates a lens-shaped piece within the corneal stroma and removes it through a small incision in the cornea, achieving the goal of myopia correction. On the other hand, the half-SMILE surgery involves using the femtosecond laser to create a corneal flap, followed by laser ablation to reshape the cornea, making it softer and more conducive to myopia correction. The full-SMILE surgery boasts faster recovery, minimal trauma, and no risk of corneal flap complications, but it may take longer for visual quality to fully recover, approximately six months to a year. The half-SMILE surgery also offers relatively fast recovery and minimal trauma, but there is a risk of corneal flap complications. However, visual quality tends to be better post-surgery, allowing individuals to choose the surgery based on their needs.

Laser-Assisted In Situ Keratomileusis (LASIK) is a relatively mature and stable technology in China for myopia correction. There are two main types of LASIK:

1. Photorefractive Keratectomy (PRK): This surgery uses a 193nm ultraviolet laser to precisely reshape the optical zone of the cornea, altering its surface curvature. It is effective for correcting myopia up to 600 degrees. However, it has drawbacks such as damaging the corneal epithelium, potentially leading to haze, regression of vision, and steroid-induced high intraocular pressure. A few patients may experience a regression of vision over time.
2. LASIK: This surgery shares the same basic principle as PRK but without damaging the corneal epithelium. It uses laser ablation to precisely reshape the corneal stroma, combining high-precision ablation with in situ keratomileusis, enhancing the predictability, reliability, and safety of the surgery. It can correct a wide range of myopia, up to 3000 degrees (under specific pre-operative conditions). After treatment, there is minimal discomfort, no need for eye patching, and patients can resume work, study, and routine physical examinations the next day.