If you are able to see perfectly at both near and far distances, then you are lucky enough to enjoy normal vision. This will change as you get older and the lens of the eye become less flexible – but not until you’re about 45 years old.
However, many people in their twenties, thirties and early forties have trouble seeing either close up or far away, and it’s usually the result of a refractive error due to the shape of the cornea at the front of the eye.
The shape of the cornea dictates the eye’s ability to bend or ‘refract’ light, impacting the way it gets projected onto the retina at the back wall of the eye to form an image. People who have a ‘refractive error’ or an issue with the curvature of the cornea need to rely on corrective eyewear, like glasses or contact lenses, to see properly.
However without corrective eyewear, people are vulnerable and have blurred vision. In cases of myopia or short sightedness, people are relatively helpless without their glasses, and its effect on vision means they find it virtually impossible to carry out simple daily tasks without wearing glasses.
Hyperopia or long sightedness affects near vision so it normally becomes a problem when it comes to reading or deciphering small text at close range. With hyperopia, glasses need only be worn in certain instances.
Understanding your prescription is important to evaluate how advanced your refractive error is and whether it has stabilized. Your Optilase Optometrist will be able to explain it to you in detail when you meet for your consultation, but basically the scale of your eye problem is measured in diopters.
The refractive power of each eye is measured in diopters (D) and if you are short sighted, your prescription will begin with a minus, e.g. -1.50D, while long sightedness prescriptions begin with a plus, e.g. +1.50D.
In cases of astigmatism, the error is measured in ‘cylinders’ because the amount of distance is not the same in all directions since astigmatism is caused by an irregular shaped cornea.
A person who is short sighted and needs a -1.00D lens has low or mild myopia and may not need to wear glasses constantly, while a prescription above -1.50 is considered moderate myopia and a person would rely heavily on glasses.
A diopter represents the inverse of a person’s focal length in metres, so that if a short sightedness person with a -2.00D prescription was to experience their “normal vision”, he/she would only be able to see objects up to ½ metre in front of them.
Oppositely, a long sighted person who needs +1.00D reading glasses can see objects at 1metre in focus, but anything closer is blurred.
Laser Eye Surgery can correct a person’s refractive error, reducing or eliminating their dependence on glasses and contact lenses. Laser surgery on the eye is swift and painless; the patient is awake throughout with numbing anaesthetic drops applied directly to the surface of the eye.
A laser is used to quickly reshape the cornea, making it better at its job of bending light evenly to form a clear image. The treatment is tailored to your particular vision issue, with a very precise amount of tissue being removed to make the cornea a better shape to allow clear vision from any distance.