Visual Errors Corrected by LASIK
When LASIK was first developed, the procedure was performed to correct lower order refractive errors: myopia (nearsightedness), hyperopia (farsightedness), and astigmatism. Since then, LASIK techniques have advanced, expanding the type of visual errors that can be corrected with the procedure. With custom wavefront LASIK, higher order aberrations can also be corrected. For patients suffering from presbyopia, monovision LASIK may be performed to treat the condition. Here, the professionals at our Rapid City laser eye surgery practice, Black Hills Regional Eye Institute, review the visual errors that can be correct with LASIK, along with the techniques that are employed to correct each condition.
Patients that are nearsighted have trouble seeing distant objects clearly. This can make it difficult to see:
- Road signs while driving
- The television
- Movie screens
- Blackboards, whiteboards, or projector screens
- People’s faces
Myopia is caused when the cornea (the clear protective covering of the eye) is too curved. For nearsighted patients, our Rapid City LASIK surgeons perform conventional LASIK to reduce the curvature of the cornea so patients can focus on distant objects.
Patients that are farsighted have trouble seeing near objects clearly. This can make it difficult to see words or images on:
- The computer screen
Hyperopia is caused with the cornea is too flat. In these cases, traditional LASIK surgery is performed to increase the curvature of the cornea so the patient can focus on near objects.
Patients with astigmatism may suffer from poor near vision, poor distant vision, or both. Like myopia and hyperopia, astigmatism results from an irregularly shaped cornea. In patients with astigmatism, the cornea has more of a football shape rather than a round shape. During conventional LASIK surgery, the cornea is reshaped to take on more of a spherical shape.
Higher Order Aberrations
Myopia, hyperopia, and astigmatism are lower order aberrations that affect the shape of the cornea. Higher order aberrations are more unique and minute; they refer to imperfections of the eye’s refractive components, which include the cornea, lens, tear film, aqueous humor, and vitreous humor. Higher order aberrations affect vision in a number of ways; they can cause poor night vision, starbursts, halos, double vision, and glare.
Eye doctors were unable to detect or treat higher order aberrations until wavefront LASIK technology was developed. Today, lower and higher order aberrations can be corrected with custom wavefront LASIK.
Presbyopia differs from all of the aforementioned visual conditions, which are refractive (affect the eye’s ability to focus light on the retina) in nature. Presbyopia is an age-related vision condition in which the eye loses it ability to focus on near objects. Since the vision problems caused by presbyopia aren’t related to the shape of the cornea, many patients wonder how LASIK could possibly treat the condition. To treat presbyopia, the traditional LASIK procedure is adjusted; one eye is reshaped to produce clear near vision and the other eye is reshaped to produce clear distant vision in a treatment known as monovision.