Refractive errors and treatments
Some people may be diagnosed with visual refractive errors after an eye exam, which means the eyes can not refract or focus light properly. The eye’s ability to focus light is decisive for people’s vision sharpness. Refractive eyeglasses, contact lenses as well as refractive surgeries can be used to correct a refractive error.
The principle of light focus of the eye
It is commonly known that light rays can be deflected, reflected, bent or absorbed by different objects. Light is essential for vision. Like the way in which the water or curved lens refracts light rays, certain parts of the eye such as the cornea, crystalline lens, tear film and internal fluids can refract light rays into a precise point of focus, which is critical for sharp vision. The focus point should be centered on the retina, which lines at the inside of the eye back.
The responsibilities of light-sensitive cells and the pupil
The light-sensitive cells in the eye back are responsible for capturing images and then transmitting them through the eye’s optic nerve to the brain for interpretation. In this process, the eye’s pupil is responsible for controlling the amount of light that reaches the retina, by widening or constricting itself. For instance, the pupil becomes small when there is fierce sunshine and enlarges in cloudy days.
Organic reasons for myopia and hyperopia
Both eye length and cornea curvature can affect the eye’s refractive ability. While eye length is determined mainly by the natural crystalline lens, corneal curvature is closely linked with the corneal surface. In fact, all refractive errors are caused by abnormalities of these two points. In detail, myopia is always caused by too long eyes, which focus images in front of the retina. In opposite, farsightedness is caused by short eyeball, which can never focus light on retina timely.
Astigmatism and higher-order aberrations
Different from myopia and hyperopia, astigmatism is always linked with aspherical eyes, which bring irregular light refraction. Aspherical eyes have irregular curvature on the cornea, whilst healthy cornea surface is spherical. According to medical terms, all of these three vision defects are called visual refractive errors. In addition, there is another category of refractive error, named higher-order aberrations. They can be detected only by wavefront technology.
How to treat visual refractive errors?
Today, prescription eyeglasses and contact lenses with precise powers are widely used by people to help the impaired eyes intercept and refract light rays, and thus achieve light focus on the retina. It is worth mentioning that these medical devices only provide temporary vision aid. Refractive surgeries such as LASIK achieve the same effect by changing the corneal surface. Surgical solutions differ from eyewear devices significantly that they can create permanent effect.