# 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. - **Patent:** US 4665913 - **Original title:** Method for ophthalmological surgery - **Owner:** LRI LP - **Granted:** 1987 - **Status:** Public domain (expired) - **Times cited:** 381 - **Field:** medical_devices, biotech, healthcare, lasers, ophthalmology ## What it does 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 does NOT 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. ## Real-world examples 1. Photorefractive Keratectomy (PRK) 2. Laser-Assisted Subepithelial Keratomileusis (LASEK) 3. Epi-LASIK 4. Early forms of LASIK procedures ## 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. ## Frequently asked questions ### What does How Lasers Correct Vision by Reshaping the Eye's Front Surface cover? 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. ### Who owns patent US 4665913? LRI LP owns this patent, granted in 1987. ### When does this patent expire? This patent has expired and is now in the public domain — anyone can use the invention freely. ### What is patent US 4665913 cited by? This patent has been cited by 381 later patents that build on its ideas. ### What problem does this patent solve? 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. ### What does this patent NOT cover? Does not cover vision correction methods that operate on parts of the eye other than the anterior surface of the cornea. **Full plain-English explainer:** https://patentbrief.org/patent/us/4665913/laser-eye-surgery-lesperance **Original patent:** https://patents.google.com/patent/US4665913 --- _Source: PatentBrief — https://patentbrief.org. Patent facts are from public records; the plain-English explanation is PatentBrief's._ ## Related patents Semantically similar inventions in the PatentBrief corpus: - [How Early CT Scans Created Detailed Body Images](https://patentbrief.org/patent/us/3778614/ct-scanner-hounsfield) — This 1973 patent describes a method for using X-rays from many angles to build a detailed 2D image of the inside of a body, like a slice of a CT scan. - [How Soft Contact Lenses Were Invented Using Hydrogels](https://patentbrief.org/patent/us/3220960/soft-contact-lens-hydrogel) — This patent describes the chemical recipe for soft, water-absorbing plastic materials that form the basis of modern soft contact lenses. - [How 3D Printers Build Objects Layer by Layer from Liquid](https://patentbrief.org/patent/us/4575330/stereolithography-3d-printing) — This patent describes the foundational method for 3D printing, where a machine builds a three-dimensional object layer by layer by hardening a liquid material with light or other energy. - [How Laser Printers Use Rotating Mirrors to Write Information](https://patentbrief.org/patent/us/3867571/laser-printer-starkweather) — A 1972 Xerox patent describing how to use a spinning mirror to scan a laser beam across a page, adjusting the speed of the data to keep the image sharp. - [Using Nuclear Magnetic Resonance to Detect Cancer in Tissue](https://patentbrief.org/patent/us/3789832/mri-magnetic-resonance-imaging) — This 1974 patent describes a method and apparatus using nuclear magnetic resonance (NMR) to measure how quickly certain atomic nuclei in a tissue sample return to their normal energy state, helping to distinguish cancerous from healthy tissue.