Getting your eye exams done at an optometrist in Central Oakville is now just a phone call away. Vision problems can affect anyone, anywhere, and any time of the day. Some eyesight problems are genetic and some are not. Genetic eyesight problems start at an early age, while common ocular problems just come because of cellular degradation as we age. They can aid in detecting these problems before they become worse.
An extensive eye examination should at least last an hour if conducted by a licensed optician. Eye examinations differ depending on the optician that you are consulting, although the tests also have a common ground.
Refractive errors often are the main reason a person seeks the services of an optometrist or ophthalmologist. But what does it really mean when we’re told that our vision is blurry because we have a refractive error?
We see the world around us because of the way our eyes bend (refract) light. Refractive errors are optical imperfections that prevent the eye from properly focusing light, causing blurred vision. The primary refractive errors are nearsightedness, farsightedness, and astigmatism.
Refractive errors usually can be “corrected” with eyeglasses or contact lenses, or they can be permanently treated with LASIK and other vision correction surgery (also called refractive surgery).
In order to see, we must have light. While we don’t fully understand all the different properties of light, we do have an idea of how light travels. A light ray can be deflected, reflected, bent or absorbed, depending on the different substances it encounters. When light travels through water or a lens, for example, its path is bent or refracted. Certain eye structures have refractive properties similar to water or lenses and can bend light rays into a precise point of focus essential for sharp vision.
Most refraction in the eye occurs when light rays travel through the curved, clear front surface of the eye (cornea). The eye’s natural (crystalline) lens also bends light rays. Even the eye’s tear film and internal fluids (aqueous humor and vitreous) have refractive abilities.
The process of vision begins when light rays that reflect off objects and travel through the eye’s optical system are refracted and focused into a point of sharp focus. For good vision, this focus point must be on the retina. The retina is the tissue that lines the inside of the back of the eye, where light-sensitive cells (photoreceptors) capture images in much the same way that film in a camera does when exposed to light. These images then are transmitted through the eye’s optic nerve to the brain for interpretation.
Just as a camera’s aperture (called the diaphragm) is used to adjust the amount of light needed to expose film in just the right way, the eye’s pupil widens or constricts to control the amount of light that reaches the retina. In dark conditions, the pupil widens. In bright conditions, the pupil constricts.
The eye’s ability to refract or focus light sharply on the retina primarily is based on three eye anatomy features: 1) the overall length of the eye, 2) the curvature of the cornea and 3) the curvature of the lens inside the eye.
More obscure vision errors, known as higher-order aberrations, also are related to flaws in the way light rays are refracted as they travel through the eye’s optical system. These types of vision errors, which can create problems such as poor contrast sensitivity, are detected through a new technology known as wavefront analysis.
Your eye doctor determines the type and degree of refractive error you have by performing a test called a refraction. The human eye focuses (refracts) light to produce clear images, similar to the way a camera does. This can be done with a computerized instrument (automated refraction) or with a mechanical instrument called a phoropter that allows your eye doctor to show you one lens at a time (manual refraction).
Often, an automated refraction will be performed by a member of the doctor’s staff, and then the eye care practitioner will refine and verify the results with a manual refraction. Your refraction may reveal that you have more than one type of refractive error. For example, your blurred vision may be due to both nearsighted and astigmatism.
Your optometrist will use the results of your refraction to determine your eyeglasses prescription. A refraction, however, does not provide sufficient information to write a contact lens prescription, which requires a contact lens fitting. Eyeglass lenses and contact lenses are fabricated with precise curves to refract light to the degree necessary to compensate for refractive errors and bring light to a sharp focus on the retina.
Vision correction surgeries such as LASIK aim to correct refractive errors by changing the shape of the cornea, o that light rays are bent into a more accurate point of focus.