Refractive Errors

Nearsightedness
Nearsightedness or myopia implies that a patient can see better up close than at far distances. Myopia occurs because the eye's length is longer than average. Since the eye is longer than average, light is focused in front of the retina rather than on the retina. Nearsighted glasses, contact lenses, and laser refractive surgery are all used to move the image from in front of the retina onto the retina itself.

Farsightedness
Farsightedness or hyperopia implies that a patient can see better far away than at closer distances. With higher amounts of farsightedness, a patient cannot see well at near or far distances. Hyperopia occurs because the eye is shorter in length than average. Since hyperopia is caused by the eye being shorter than average, light is focused behind the retina rather than on the retina. Farsighted glasses, contact lenses, and refractive surgery are all used to move the image from behind the retina onto the retina itself.

Astigmatism
Patients with astigmatism may have distorted vision in addition to blurred vision at distance and at near. Normally, the cornea is shaped round, like a basketball. With astigmatism, the cornea is shaped more like a football which means it is curved more in one direction than the other. When light enters the eye, it focuses at two separate points instead of one which causes blurred or distorted vision. Large amounts of astigmatism can indicate other eye conditions such as keratoconus or pellucid marginal degeneration. Astigmatism can be corrected with glasses, contact lenses, or laser refractive surgery.

Presbyopia
Presbyopia usually occurs at around age 40, when patients start to experience blurred vision while reading at near. It is a gradual loss of accommodation, which is the ability of the eye to adjust its focus from far to near. Loss of accommodation occurs gradually throughout our lives. As the lens of the eye ages, it becomes less flexible, which results in less accommodative power. Correction of presbyopia involves making up for the lost accommodative power of the lens of the eye. Presbyopia can be corrected with multifocal contacts, glasses, and in some cases, refractive surgery.