Refractive Laser Surgery to correct myopia, hyperopia, and astigmatism is subdivided into three major types:
- LASIK: this involves the creation of a thin flap of cornea that is folded back on itself. The flap is created by either cutting with a blade or by laser (intralase). Excimer laser is applied to the area of exposed cornea to reshape it. The folded corneal flap is then used to cover the treated area. LASIK with a flap heals quickly with minimal discomfort
- Surface treatment: In this procedure, a very thin corneal flap is peeled away from the surface.
- Photorefractive Keratatectomy (PRK). The outer layer of the cornea is removed and excimer laser is applied directly to the cornea.
Each procedure has the end result of allowing light rays to focus on the retina resulting in good uncorrected vision.
Determining if a patient is a good candidate for Refractive Surgery (LASIK surgery)
- Multiple factors are considered in the process of determining whether a patient is a good candidate for refractive surgery:
- Refraction, which measures the presence of myopia, hyperopia and astigmatism.
- Corneal exam with the slit lamp microscope.
- Retinal examination to determine the presence or absence of pathologic conditions that may influence the outcome of surgery.
- Corneal thickness measurement (pachymetry)
- Corneal topography, which maps the contour of the corneal surface
Complications of Refractive Surgery
Refractive surgery is generally safe and effective. However, complications from laser refractive surgery can be difficult to remedy or alleviate.
- Ectasia: The cornea is thinned to the point where it buckles inward or outward. It is more commonly associated with refractive procedures involving a corneal flap and in treatment of high myopia or hyperopia Conventionally, no less than 250 microns depth of corneal tissue should remain after the flap creation and removal of corneal tissue by laser. However, this guideline is subject to the influence of other corneal parameters. Ectasia may lead to a pronounced irregular corneal shape that distorts vision. A tendency towards ectasia can be detected prior to surgery using topography.
- Buttonhole flaps: This can occur during flap creation, when the blade or laser cuts central flap too thin. An opening (buttonhole) is created in the corneal flap. At this point, the procedure is aborted and the cornea is allowed to heal for several months before attempting another procedure.
- Epithelial ingrowth: cells can grow underneath the flap, compromising visual clarity. The corneal flap may need to be relifted and the cells scraped and irrigated
- Flap striae: if the flap doesn’t rest evenly on the treated surface, folds known as striae develop and may distort vision. The corneal flap may need to be relifted and repositioned before the striae become permanent.
- Dry eye syndrome: corneal nerves that regulate tear production can be affected after refractive surgery. Tear production can be measured preoperatively by clinical observation and tear testing. Many LASIK patients may experience dry eyes for a few months after LASIK.
- Over- and –under corrections, requiring correction.
Dr. Lefkowitz can provide expert witness services, as a refractive surgery expert witness, for a defendant or plaintiff.
LASIK and REFRACTIVE SURGERY..CAVEAT EMPTOR!
In 2005, LASIK became a popular modality for correcting refractive errors in patients with nearsightedness (myopia), farsightedness (hyperopia) and astigmatism (corneal irregularity). Successful refractive surgery can do away with the need for glasses or contact lenses.
Although the surgical procedure is simple, it must be understood that not every patient is a good candidate for LASIK. A careful pre-operative examination must be performed by the surgeon in which the following are evaluated:
- Corneal thickness.
- Corneal topography
- Examination of the peripheral retina (dilated exam)
- Presence of corneal disease
- Presence of glaucoma
The cornea must be thick enough to perform the required corneal ablation, while leaving a minimum corneal thickness of 250 microns. The topography can reveal presence of corneal disease such as keratoconus. The retinal exam must verify that there are no peripheral weaknesses that can lead to retinal detachment during or after the surgery. Any pre-existing corneal disease must be considered, to determine whether LASIK is contraindicated. Glaucoma must be ruled out, since the high intraocular pressure induced during LASIK flap creation can damage already existing optic nerve probems.
Patients over 40 must be made aware of the problems of age-related near vision problems (presbyopia), which could be exacerbated by LASIK
Patients must be educated about the possibility of dry eye, halos and distortions which take time to resolve. Patients must also be aware of the possibility of under and overcorrections, requiring later surgical correction.
Ask questions and find a surgeon who answers questions and gives you personal attention. Avoid “LASIK” mills.
WHAT IS MYOPIA?
Myopia is a refractive state of the eye, in which the eye is very long from front to back. This results in images being focused in front of the retina, instead of on the retina. This leads to blurred distance vision, which requires correction with glasses, contact lenses or refractive surgery, such as LASIK. It is NOT a disease.
WHAT IS HYPEROPIA?
Hyperopia is a refractive state of the eye, in which the eye is very short from front to back. This results in images being focused behind the retina, instead of on the retina. This leads to blurred near vision, which requires correction with glasses , contact lenses or refractive surgery. It is NOT a disease.
WHAT IS ASTIGMATISM?
Astigmatism is a refractive state in which the irregularities of the cornea lead to distorted focus on the retina. It requires correction with glasses, contact lenses or refractive surgery. It is NOT a disease
WHAT IS PRESBYOPIA?
Presbyopia is a refractive state in which aging of the eyes leads to inability to focus up close. It comes with middle age and requires correction with glasses. It is NOT a disease
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