How Lasers Correct Vision by Reshaping the Eye's Front Surface

This patent describes a method for precisely reshaping the front surface of the eye using an ultraviolet laser to correct vision problems like nearsightedness, farsightedness, and astigmatism.

What it covers

The patent details a method for changing the optical properties of an eye by operating solely on the cornea's anterior surface. It uses selective ultraviolet (UV) laser radiation to remove corneal tissue through a process called ablative photodecomposition (Claim 1). This process sculpts the cornea to a predetermined curvature profile, correcting vision defects. For example, to fix astigmatism, the laser beam is focused to a tiny spot and scanned over the cornea in a specific pattern, removing tissue to a precise depth (Claim 3). This scanning action changes the cornea's shape, allowing it to focus light correctly.

What it doesn't cover

• —Does not cover vision correction methods that operate on parts of the eye other than the anterior surface of the cornea.
• —Does not cover laser eye surgery using non-ultraviolet light, as it specifically claims "ultraviolet irradiation" (Claim 1).
• —Does not cover methods that reshape the cornea without removing tissue through "ablative photodecomposition" (Claim 1).
• —Does not cover techniques that do not aim for a "predetermined curvature profile" to correct specific vision errors (Claim 1).
• —Does not cover procedures where the laser ablation does not penetrate into the stroma layer of the cornea (Claim 1).

The clever bit

The truly clever part was realizing that ultraviolet lasers could precisely remove corneal tissue layer by layer without causing heat damage to surrounding cells, a process called ablative photodecomposition. This allowed for the exact sculpturing of the cornea's surface to a predetermined shape, something previous surgical methods could not achieve with such control.

Why it matters

This patent is foundational for modern laser eye surgery, specifically procedures like Photorefractive Keratectomy (PRK). It introduced the precise use of UV lasers to sculpt the cornea, moving beyond less accurate surgical methods. This technology made it possible to correct common vision problems like nearsightedness, farsightedness, and astigmatism with high precision, significantly reducing reliance on glasses and contact lenses for millions of people.

Real-world examples

• 1.Photorefractive Keratectomy (PRK)
• 2.Laser-Assisted Subepithelial Keratomileusis (LASEK)
• 3.Epi-LASIK
• 4.Early forms of LASIK procedures