Many people have Laser Vision Correction done so that they are no longer dependent on glasses or contact lenses for distance vision. Individuals over 40 will still need glasses for reading after Laser Vision Correction to correct both eyes for distance.

For more information on Laser Vision Correction, click here: KP Laser Vision Correction

How Does the Eye Work?

Kaiser Permanente’s best patient is a well-informed patient. We hope you will use the information in this website and the advice of your Kaiser Permanente surgeon to determine if Laser Vision Correction is right for you. To understand how Laser Vision Correction or “refractive surgery” could eliminate or reduce your need for corrective eyewear, it is important to understand why you need to wear corrective eyewear now.

The Normal Eye (Emmetropia)

The term “refractive” refers to how light rays focus on the retina, the photosensitive membrane that lines the back of the eye. A variety of factors determine how sharply an image is focused. The cornea provides most of this focusing power. In a normal (emmetropic) eye, near and distant objects appear sharp and clear because they are focused directly on the retina.

The Nearsighted Eye (Myopia)

In the nearsighted eye, the cornea is too steeply curved in relation to the length of the eye, causing light rays to focus in front of the retina. Distant objects appear blurred or fuzzy. Near objects, viewed at the proper distance, can be seen clearly. Modern surgical techniques can change the shape of the cornea to correct or significantly reduce many cases of myopia. To date, two techniques have gained a wide following among refractive surgeons: LASIK (Laser Assisted InSitu Keratomileusis) and PRK (Photorefractive Keratectomy). These procedures reshape (or slightly flatten) the cornea to allow distant images to be focused appropriately on the retina for the myopic patient.

The Farsighted Eye (Hyperopia)

Hyperopia (farsightedness) occurs when the curvature of the cornea is too flat in relation to the length of the eye. Light rays entering your eye focus behind the retina, causing distant objects to appear blurred and near-by objects to appear fuzzier. The muscles controlling the focusing power of the lens can overcome some degree of hyperopia, but these muscles weaken with age. This is why many hyperopes begin to require distance glasses after the age of 30.

Laser Vision Correction increases the corneal curvature in hyperopes. This increases the power of the cornea and allows images to be clearly focused on the retina. The goal of LASIK or PRK for the hyperopic patient is improved near and distance vision.

Astigmatism (Distorted Vision)

Astigmatism is usually caused by an abnormal corneal curvature. In the normal eye, the surface of the cornea is round like a soccer ball (spherical). With astigmatism, the cornea is slightly oblong, like a football. This causes light rays to focus at different places on the retina. Objects at all distances appear blurred. Both nearsighted and farsighted individuals may have astigmatism that further contributes to their poor vision. For astigmatic patients, Laser Vision Correction can correct this oblong shape of the cornea, and thus eliminate the blurred vision caused by astigmatism.

Presbyopia (Aging Eyes)

Lens thinner for distance vision Lens thicker for near vision

Presbyopia is the name given to the focusing problem that develops in almost everyone between 40 and 50 years of age. As we age, the eye’s natural lens hardens and loses its flexibility. This prevents the lens from changing its shape, making it impossible for us to vary our focus from far to near objects. To compensate for this problem, most people need to use reading glasses or bifocals. As this is a problem due to the lens inside the eye and not the cornea, this cannot currently be corrected by refractive surgery.

Your Prescription

The power of lenses necessary to correct your vision is measured in units called diopters, and consists of up to three numbers. The first number designates the amount of myopia (minus numbers) or hyperopia (plus numbers) and the second and third numbers (if present) indicate the amount and direction of astigmatism. Please contact your eye care professional if you have questions regarding your prescription.