Refractive eye surgery is non-essential eye surgery used to improve the refractive state of the eye and decrease or eliminate dependency on glasses or contact lenses. This can include various methods of surgical remodeling of the cornea (keratomileusis), lens implantation or lens replacement. The most common methods today use excimer lasers to reshape the curvature of the cornea. Successful refractive eye surgery can reduce or cure common vision disorders such as myopia, hyperopia, presbyopia and astigmatism.
Corneal incision procedures
- Radial keratotomy (RK), developed by Russian ophthalmologist Svyatoslav Fyodorov in 1974, uses spoke-shaped incisions, always made with a diamond knife, to alter the shape of the cornea and reduce myopia or astigmatism; this technique is, in medium to high diopters, usually replaced by other refrective methods.
- Arcuate keratotomy (AK), also known as Astigmatic keratotomy, uses curvilinear incisions at the periphery of the cornea to correct high levels of non-pathological astigmatism, up to 13 diopters. AK is often used for the correction of high post-keratoplasty astigmatism or post-cataract surgery astigmatism.
- Limbal relaxing incisions (LRI) are incisions near the outer edge of the iris, used to correct minor astigmatism (typically less than 2 diopters). This is often performed in conjunction with an Intraocular Lens implantation.
- Radial Keratocoagulation, also known as Radial Thermokeratoplasty, was invented in 1985 by Svyatoslav Fyodorov and is used to correct hyperopia by putting a ring of 8 or 16 small burns surrounding the pupil, and steepen the cornea with a ring of collagen constriction. It can also be used to treat selected types of astigmatism. It is now generally replaced by laser thermal keratoplasty/laser thermokeratoplasty.
- Laser thermal keratoplasty (LTK) is a non-touch thermal keratoplasty performed with a Holmium laser, while conductive keratoplasty (CK) is thermal keratoplasty performed with a high-frequency electric probe. Thermal keratoplasty can also be used to improve presbyopia or reading vision after age 40.
- Intrastromal corneal ring segments (Intacs) are approved by FDA for treatment of low degrees of myopia.
- Phakic intraocular lens (PIOL) implantation inside the eye can also be used to change refractive errors. The newest type of intervention is a type of PIOL called the implantable collamer lens (ICL) which uses a biocompatible flexible lens which can be inserted in the eye via a 3 mm incision. The ICL is used to correct myopia ranging from −0.5 to −18 diopters, and +0.5 cylinder power to +6.0 for the Toric ICL models.
- Generally refractive surgery can be broadly divided into: corneal surgery, scleral surgery, lens related surgery (including phakic IOL implantation, clear lens extraction, photophacoreduction and photophacomodulation for correction of presbyopia)
- For presbyopia correction, a corneal inlay consisting of a porous black ring surrounding a small clear aperture was originally developed by D. Miller, H. Grey PhD and a group at Acufocus. The inlay is placed under a LASIK flap or in a stromal pocket.
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Journal of optometry : open access