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Refractive Errors

Hyperopia (Farsightedness)

Hyperopia is generally characterized by an eyeball that is proportionally too short in relation to its focusing elements. In some cases, it is also characterized by a cornea that is flatter than normal. As a result of these irregularities, light rays do not have enough space in which to converge and focus before reaching the retina.

People who are farsighted are usually able to see distant objects clearly because the parallel rays coming from the distance can be brought to a focal point easier by the eye than the diverging light rays from near objects.

Lens Exchange for Hyperopia

For our near- and over-40 patients, we frequently treat hyperopia with a lens exchange procedure. This is an excellent solution and also prevents future cataracts. Read more about our lens exchange procedure.

Myopia (Nearsightedness)

Myopia affects about one in every four people in North America and is the most common refractive problem. It is generally characterized by an eyeball that is too long in the relation to the rest of its parts. In some cases, it may also be characterized by a cornea with more curvature than normal. As a result, light rays converge to a focal point before they reach the retina, and then they begin to diverge. Since the retina can only respond to the quality of the image that reaches it, the brain receives unclear messages of visible objects to interpret.

People who are myopic see near objects more clearly than distant objects. The reason for this is that the light rays from near objects are still diverging when they reach the eye, thus counteracting the eye’s tendency to cause them to converge too soon, allowing some degree of focused vision. Light rays from distant objects are more parallel, so they converge before they reach the retina of an elongated eye.

Excimer Laser Correction of Hyperopia & Myopia

When directed at nearsighted eyes, an excimer laser can vaporize microscopic layers of tissue to reduce the curvature of the cornea and improve focus.

When directed at farsighted eyes, an excimer laser can vaporize microscopic layers of tissue to flatten the curvature of the cornea and improve focus. While farsightedness is more difficult to correct than nearsightedness, the excimer laser is capable of delivering excellent vision correction for lower levels of hyperopia.

The outer protective layer of the cornea known as the epithelium is gently removed. The laser controlling device verifies the patient’s eye position, and at the appropriate time the control switch is activated. The unique flying spot laser light sculpts the cornea into the new shape. The total laser application time is only seconds.

The excimer laser beam can be controlled so precisely that it can remove tissue 0.25 microns at a time. This ability is amazing considering that one-micron equals one millionth of a meter. The cornea is about 550 microns thick at its thinnest point. Most excimer procedures remove less than 50 microns of tissue, which is less than 10% of the original corneal thickness.