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Understanding Eye Refraction

Our eyes need light in order to see. While we do not understand every aspect of light, we do know how it travels. A ray of light can be reflected, deflected, absorbed, or bent. When light travels through a lens or water, its path is refracted or bent. When the light that enters the eye does not focus directly on the retina, it causes a refractive error.

What Are Refractive Errors?

Refractive errors are a type of vision problem that makes it difficult for a person to see clearly. Checking for refractive errors is the primary part of the standard eye exam. They can be treated with the help of prescription eyeglasses, contact lenses, or surgery. There are four main types of refractive errors:

  • Myopia (nearsightedness)
  • Hyperopia (farsightedness)
  • Presbyopia (inability of the lens to focus)
  • Astigmatism (a refractive issue based on the shape of the eyes’ cornea)

How Do The Eyes See?

The eye contains certain structures that contain refractive properties similar to lenses or water, and can bend light rays into a specific point of focus. This is essential for sharp vision.

Most eye refraction occurs when rays of light travel through the curved, clear front surface of the eye (cornea). The eye’s lens then further bends light rays..

The process of vision begins when rays of light reflect off objects and pass through the eye’s optical system. The rays of light are then refracted and focused into a point of sharp focus. For clear vision, the focus point should be on the retina, the back part of the eye. The retina has nerves to capture the light rays The retinal nerves transmit signals through the optic nerve from the eye to the brain, where they are interpreted.

What Is Eye Refraction?

Eye refraction is how the power for a person’s eyeglasses or contact lenses is calculated. This measurement is based on the curve of the cornea, the lens, and the length of the eye. The optical prescription is determined by the refraction test, also known as a vision test, which is part of your standard eye examination. This refraction allows your eye doctor to provide the eyeglass or contact lens prescription to achieve clear vision.

Eyes change as we age and regular testing helps your eye doctor learn if you need a new prescription. Schedule a refraction test at EYEcenter Optometric in , Gold River, Rocklin, Folsom, Sacramento.

At EYEcenter Optometric, we put your family’s needs first. Talk to us about how we can help you maintain healthy vision. Call us today: 916-727-6518 or book an appointment online to see one of our Citrus Heights eye doctors.

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How to Choose the Right Lenses for Your Glasses

Buying glasses is no easy task because there are so many elements to consider. Not everyone has the time to research eyeglass lens materials, designs and coatings.

To make it easier, we’ve compiled a list of different lenses and coatings that offer the best features for your needs.

Types of Lenses and Coatings

Glass lenses

All eyeglass lenses used to be made from glass. Although they offer excellent optics, they’re heavy and can easily crack and break, which can cause harm to the eye. This is why it is very rare to come across such lenses nowadays.

Plastic lenses

Lenses for eyeglasses moved from glass to plastic in the early 1980s as lightweight plastic eyeglass lenses (CR-39) weigh half of what glass lenses weighs, cost less, and possess exceptional optics.

Polycarbonate lenses

Originally these types of lenses were used for safety glasses. Later on, they were used for regular glasses. Polycarbonate is lighter and significantly more impact-resistant than CR-39 plastic, making it a preferred material for children’s eyewear, safety glasses and sports eyewear.

Trivex lenses

Trivex is a urethane-based pre-polymer. It is a newer lightweight eyeglass lens material that is a stronger, more resistant, clearer alternative to standard polycarbonate.

High-index plastic lenses

In response to the demand for thinner, lighter eyeglasses, a number of lens manufacturers have introduced high-index plastic lenses. These lenses are thinner and lighter than other plastic lenses (CR-39) because they have a higher index of refraction and may also have a lower specific gravity.

Anti-scratch coating

Most of today’s modern anti-scratch coatings (also called permagard or hard coats) can make your eyeglass lenses nearly as scratch-resistant as glass.

Anti-reflective coating

Anti-reflective (AR) coating eliminates reflections in lenses that reduce contrast and clarity, especially at night. AR-coated lenses are also much less likely to have glare spots in photographs.

UV-blocking treatment

Cumulative exposure to the sun’s harmful ultraviolet (UV) radiation over a person’s lifetime has been associated with age-related eye problems including cataracts and macular degeneration.

Thankfully, polycarbonate and nearly all high-index plastic lenses have 100 percent UV protection built-in, due to the absorptive characteristics of the lens material.

But if you choose CR-39 plastic lenses, be aware that these lenses need an added coating applied to provide equal UV protection afforded by other lens materials.

Photochromic treatment

This lens treatment enables eyeglass lenses to darken automatically in response to the sun’s UV and high-energy visible (HEV) light rays, and then quickly return to clear (or nearly clear) when indoors. Photochromic lenses are available in virtually all lens materials and designs.

At EYEcenter Optometric, we put your family’s needs first. Talk to us about how we can help you maintain healthy vision. Call us today: 916-727-6518 or book an appointment online to see one of our Citrus Heights eye doctors.

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