Refractive surgery
Encyclopedia
Refractive eye surgery is any eye surgery
Eye surgery
Eye surgery, also known as orogolomistician surgery or ocular surgery, is surgery performed on the eye or its adnexa, typically by an ophthalmologist.-Preparation and precautions:...

 used to improve the refractive state of the eye
Human eye
The human eye is an organ which reacts to light for several purposes. As a conscious sense organ, the eye allows vision. Rod and cone cells in the retina allow conscious light perception and vision including color differentiation and the perception of depth...

 and decrease or eliminate dependency on glasses
Glasses
Glasses, also known as eyeglasses , spectacles or simply specs , are frames bearing lenses worn in front of the eyes. They are normally used for vision correction or eye protection. Safety glasses are a kind of eye protection against flying debris or against visible and near visible light or...

 or contact lenses. This can include various methods of surgical remodeling of the cornea
Cornea
The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. Together with the lens, the cornea refracts light, with the cornea accounting for approximately two-thirds of the eye's total optical power. In humans, the refractive power of the cornea is...

 or cataract surgery
Cataract surgery
Cataract surgery is the removal of the natural lens of the eye that has developed an opacification, which is referred to as a cataract. Metabolic changes of the crystalline lens fibers over time lead to the development of the cataract and loss of transparency, causing impairment or loss of vision...

. The most common methods today use excimer laser
Excimer laser
An excimer laser is a form of ultraviolet laser which is commonly used in the production of microelectronic devices , eye surgery, and micromachining....

s to reshape curvature of the cornea. Successful refractive eye surgery can reduce or cure common vision disorders such as myopia
Myopia
Myopia , "shortsightedness" ) is a refractive defect of the eye in which collimated light produces image focus in front of the retina under conditions of accommodation. In simpler terms, myopia is a condition of the eye where the light that comes in does not directly focus on the retina but in...

, hyperopia
Hyperopia
Hyperopia, also known as farsightedness, longsightedness or hypermetropia, is a defect of vision caused by an imperfection in the eye , causing difficulty focusing on near objects, and in extreme cases causing a sufferer to be unable to focus on objects at any distance...

 and astigmatism
Astigmatism (eye)
Astigmatism is an optical defect in which vision is blurred due to the inability of the optics of the eye to focus a point object into a sharp focused image on the retina. This may be due to an irregular or toric curvature of the cornea or lens. There are two types of astigmatism: regular and...

.

According to surveys of members of the American Society of Cataract and Refractive Surgery, approximately 948,266 refractive surgery procedures were performed in the United States during 2004 and 928,737 in 2005.

History

The first experimental studies about refractive surgery were published in 1896 by Lendeer Jans Lans, an ophthalmology
Ophthalmology
Ophthalmology is the branch of medicine that deals with the anatomy, physiology and diseases of the eye. An ophthalmologist is a specialist in medical and surgical eye problems...

 teacher in the Netherlands
Netherlands
The Netherlands is a constituent country of the Kingdom of the Netherlands, located mainly in North-West Europe and with several islands in the Caribbean. Mainland Netherlands borders the North Sea to the north and west, Belgium to the south, and Germany to the east, and shares maritime borders...

, where he developed a theoretical work proposing penetrating corneal cuts to correct astigmatism
Astigmatism (eye)
Astigmatism is an optical defect in which vision is blurred due to the inability of the optics of the eye to focus a point object into a sharp focused image on the retina. This may be due to an irregular or toric curvature of the cornea or lens. There are two types of astigmatism: regular and...

. In 1930 the Japanese
Japanese people
The are an ethnic group originating in the Japanese archipelago and are the predominant ethnic group of Japan. Worldwide, approximately 130 million people are of Japanese descent; of these, approximately 127 million are residents of Japan. People of Japanese ancestry who live in other countries...

 ophthalmologist Tsutomu Sato made the first practical attempt to perform such surgery in military pilots. He practiced radial cuts in the cornea to correct effects by up to 6 diopters, but this procedure was soon rejected by the medical community because of the high rate of corneal degeneration.

In 1963, in the Barraquer ophthalmologic clinic (Bogotá
Bogotá
Bogotá, Distrito Capital , from 1991 to 2000 called Santa Fé de Bogotá, is the capital, and largest city, of Colombia. It is also designated by the national constitution as the capital of the department of Cundinamarca, even though the city of Bogotá now comprises an independent Capital district...

, Colombia
Colombia
Colombia, officially the Republic of Colombia , is a unitary constitutional republic comprising thirty-two departments. The country is located in northwestern South America, bordered to the east by Venezuela and Brazil; to the south by Ecuador and Peru; to the north by the Caribbean Sea; to the...

) Ignacio Barraquer
Ignacio Barraquer
Ignacio Barraquer was a Spanish ophthalmologist known for his contributions to the advancement of cataract surgery. Barraquer was born in Barcelona, Catalonia, Spain...

 developed the first proficient refractive surgery technique called keratomileusis
Keratomileusis
Keratomileusis is the surgical improvement of the refractive state of the cornea performed by lifting up the front surface of the eye by forming a thin hinged flap under which the shape of the cornea is changed by using an excimer laser or other surgical device, and was developed by José Ignacio...

, meaning corneal reshaping (from Greek κέρας (kéras: horn) and σμίλευσις (smileusis: carving)). Keratomileusis allowed correction of not only myopia but also hyperopia. These early surgeries removed a corneal layer, froze it so it could be manually sculpted in the required shape, and finally reimplanted the layer (Keratomileusis with freezing). While this form of surgery was later improved by Dr. Swinger in 1986 (keratomileusis without freezing), it was still a relatively imprecise technique.

Meanwhile, experiments in 1970 using a xenon
Xenon
Xenon is a chemical element with the symbol Xe and atomic number 54. The element name is pronounced or . A colorless, heavy, odorless noble gas, xenon occurs in the Earth's atmosphere in trace amounts...

 dimer and in 1975 using noble gas
Noble gas
The noble gases are a group of chemical elements with very similar properties: under standard conditions, they are all odorless, colorless, monatomic gases, with very low chemical reactivity...

 halides
Halogen
The halogens or halogen elements are a series of nonmetal elements from Group 17 IUPAC Style of the periodic table, comprising fluorine , chlorine , bromine , iodine , and astatine...

 resulted in the invention of a type of laser
Laser
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of photons. The term "laser" originated as an acronym for Light Amplification by Stimulated Emission of Radiation...

 called an excimer laser
Excimer laser
An excimer laser is a form of ultraviolet laser which is commonly used in the production of microelectronic devices , eye surgery, and micromachining....

. While excimer lasers were initially used for industrial purposes, in 1980, R. Srinivasan
Rangaswamy Srinivasan
Rangaswamy Srinivasan is an inventor at IBM Research. One of the famous inventions he has contributed to is LASIK.-Ablative Photodecomposition :...

, a scientist of IBM
IBM
International Business Machines Corporation or IBM is an American multinational technology and consulting corporation headquartered in Armonk, New York, United States. IBM manufactures and sells computer hardware and software, and it offers infrastructure, hosting and consulting services in areas...

 who was using an excimer laser to make microscopic circuits in microchips
Integrated circuit
An integrated circuit or monolithic integrated circuit is an electronic circuit manufactured by the patterned diffusion of trace elements into the surface of a thin substrate of semiconductor material...

 for informatics equipment, discovered that the excimer could also be used to cut organic tissues with high accuracy without significant thermal damage. The discovery of an effective biological cutting laser, along with the development of computers to control it, allowed new refractive techniques which were previously unavailable.

In 1983, scientist Stephen Trokel of Columbia University
Columbia University
Columbia University in the City of New York is a private, Ivy League university in Manhattan, New York City. Columbia is the oldest institution of higher learning in the state of New York, the fifth oldest in the United States, and one of the country's nine Colonial Colleges founded before the...

 in collaboration with Srinivasan performed the first Photorefractive Keratectomy (PRK) or keratomileusis in situ (without separation of corneal layer) in Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...

. The first patent for LASIK was granted by the US Patent Office to Gholam Ali. Peyman, MD on June 20, 1989, US Patent #4,840,175, "METHOD FOR MODIFYING CORNEAL CURVATURE", describing the surgical procedure in which a flap is cut in the cornea and pulled back to expose the corneal bed. This exposed surface is then ablated to the desired shape with an excimer laser, following which the flap is replaced. In 1991 Creta University and the Vardinoyannion Eye coined the name "LASIK".

Flap procedures

Excimer laser ablation is done under a partial-thickness lamellar corneal flap.
  • Automated lamellar keratoplasty
    Automated lamellar keratoplasty
    Automated Lamellar Keratoplasty, commonly abbreviated to ALK uses a device called a microkeratome to separate a thin layer of the cornea and create a flap. The flap is then folded back, and the microkeratome removes a thin disc of corneal stroma below. The thickness and diameter of this disc...

     (ALK): The surgeon uses an instrument called a microkeratome
    Microkeratome
    A microkeratome is a precision surgical instrument with an oscillating blade designed for creating the corneal flap in LASIK or ALK surgery. The normal human cornea varies from around 500 to 600 micrometres in thickness; and in the LASIK procedure, the microkeratome creates a 83 to 200 micrometre...

     to cut a thin flap of the corneal tissue. The flap is lifted like a hinged door, targeted tissue is removed from the corneal stroma, again with the microkeratome, and then the flap is replaced.
  • Laser Assisted In-Situ Keratomileusis
    LASIK
    LASIK or Lasik , commonly referred to simply as laser eye surgery, is a type of refractive surgery for correcting myopia, hyperopia, and astigmatism...

     (LASIK): The surgeon uses a microkeratome
    Microkeratome
    A microkeratome is a precision surgical instrument with an oscillating blade designed for creating the corneal flap in LASIK or ALK surgery. The normal human cornea varies from around 500 to 600 micrometres in thickness; and in the LASIK procedure, the microkeratome creates a 83 to 200 micrometre...

     or femtosecond laser to cut a flap of the corneal tissue (usually with a thickness of 100-180 micrometres). The flap is lifted like a hinged door, but in contrast to ALK, the targeted tissue is removed from the corneal stroma with an excimer laser. The flap is subsequently replaced. When the flap is created using a femtosecond laser, the method is called IntraLASIK
    IntraLASIK
    IntraLASIK, also known as Femto-LASIK or All-Laser LASIK, is a form of refractive eye surgery similar to LASIK that creates a corneal flap with a femtosecond laser microkeratome rather than with a mechanical microkeratome, which uses a steel blade. The only difference between LASIK and IntraLASIK...

    . Proponents of this method assert its superiority over "traditional" LASIK, but there have been no conclusive independent studies to prove that this is a true statement. One supposed criticism of the use of the microkeratome is the deposition of microscopic metal fragments from the blade into the surgical site. In addition, much is made of the ability of laser flap creation to model novel edges to the corneal flap to aid in correct flap seating. It is clear that the use of laser flap creation has become a major marketing tool used by the large volume commercial laser eye surgery businesses to provide technological differentiation in the market place. This is part of a troubling commercialization of this serious invasive surgery.

Surface procedures

The excimer laser is used to ablate the most anterior portion of the corneal stroma. These procedures do not require a partial thickness cut into the stroma. Surface ablation methods differ only in the way the epithelial layer is handled.
  • Photorefractive keratectomy
    Photorefractive keratectomy
    Photorefractive keratectomy and Laser-Assisted Sub-Epithelial Keratectomy are laser eye surgery procedures intended to correct a person's vision, reducing dependency on glasses or contact lenses. The first PRK procedure was performed in 1987 by Dr. Theo Seiler, then at the Free University...

     (PRK) is an outpatient procedure generally performed with local anesthetic eye drops (as with LASIK/LASEK) . It is a type of refractive surgery which reshapes the cornea by removing microscopic amounts of tissue from the corneal stroma, using a computer-controlled beam of light (excimer laser
    Excimer laser
    An excimer laser is a form of ultraviolet laser which is commonly used in the production of microelectronic devices , eye surgery, and micromachining....

    ). The difference from LASIK is that the top layer of the epithelium is removed (and a bandage contact lens is used), so no flap is created. Recovery time is longer with PRK than with LASIK, though the final outcome (after 3 months) is about the same (very good). More recently, customized ablation has been performed with LASIK, LASEK, and PRK.
  • Laser Assisted Sub-Epithelium Keratomileusis
    Lasek
    Lasek may refer to:*LASEK or photorefractive keratectomy, a laser eye surgery technique*Lasek, Lower Silesian Voivodeship *Lasek, Kuyavian-Pomeranian Voivodeship *Lasek, Łódź Voivodeship...

     (LASEK) is a procedure that also changes the shape of the cornea using an excimer laser
    Excimer laser
    An excimer laser is a form of ultraviolet laser which is commonly used in the production of microelectronic devices , eye surgery, and micromachining....

     to ablate the tissue from the corneal stroma, under the corneal epithelium, which is kept mostly intact to act as a natural bandage
    Bandage
    A bandage is a piece of material used either to support a medical device such as a dressing or splint, or on its own to provide support to the body; they can also be used to restrict a part of the body. During heavy bleeding or following a poisonous bite it is important to slow the flow of blood,...

    . The surgeon uses an alcohol solution to loosen then lift a thin layer of the epithelium with a trephine blade (usually with a thickness of 50 micrometres). During the weeks following LASEK, the epithelium heals, leaving no permanent flap in the cornea. This healing process can involve discomfort comparable to that with PRK.
  • EPI-LASIK
    EPI-LASIK
    Epi-LASIK is a refractive surgery technique designed to reduce a person's dependency on eyeglasses and contact lenses. Invented by Dr. Ioannis Pallikaris , the technique is basically an automatic LASEK without alcohol:It can be better considered as superficial LASIK. The stromal bed is smoother...

     is a new technique similar to LASEK that uses an epi-keratome (rather than a trephine blade and alcohol), to remove the top layer of the epithelium (usually with thickness of 50 micrometres), which is subsequently replaced. For some people it can provide better results than regular LASEK in that it avoids the possibility of negative effects from the alcohol, and recovery may involve less discomfort.

Corneal incision procedures

  • Radial keratotomy
    Radial keratotomy
    Radial keratotomy is a refractive surgical procedure to correct myopia.- Discovery :The procedure was discovered by Svyatoslav Fyodorov who removed glass from the eye of one of his patients who had been in an accident. A boy, who wore eyeglasses, fell off his bicycle and his glasses shattered on...

     (RK) uses spoke-shaped incisions (usually made with a diamond knife) to alter the shape of the cornea and reduce myopia
    Myopia
    Myopia , "shortsightedness" ) is a refractive defect of the eye in which collimated light produces image focus in front of the retina under conditions of accommodation. In simpler terms, myopia is a condition of the eye where the light that comes in does not directly focus on the retina but in...

     or astigmatism
    Astigmatism
    An optical system with astigmatism is one where rays that propagate in two perpendicular planes have different foci. If an optical system with astigmatism is used to form an image of a cross, the vertical and horizontal lines will be in sharp focus at two different distances...

    ; this technique has now been largely replaced by the other methods (that use excimer laser).

  • Arcuate keratotomy (AK) is similar to radial keratotomy, but the incisions on the cornea are done at the periphery of the cornea. Arcuate keratotomy is used to correct astigmatism. Although most incisional procedures are replaced nowadays by Lasik, AK is still used in some special cases (correction of residual astigmatism after a keratoplasty procedure or during cataract surgery).

  • Limbal relaxing incisions
    Limbal relaxing incisions
    Limbal Relaxing Incisions are a refractive surgical procedure to correct minor astigmatism in the eye. Incisions are made at the opposite edges of the cornea, following the curve of the iris, causing a slight flattening in that direction...

     (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.

Other procedures

  • Thermal keratoplasty is used to correct hyperopia
    Hyperopia
    Hyperopia, also known as farsightedness, longsightedness or hypermetropia, is a defect of vision caused by an imperfection in the eye , causing difficulty focusing on near objects, and in extreme cases causing a sufferer to be unable to focus on objects at any distance...

     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.
  • Laser thermal keratoplasty
    Laser thermal keratoplasty
    -Procedure:The procedure employs a holmium laser to place a ring of concentric laser burns on the cornea between 6mm and 7mm in diameter. These burns cause a ring of constriction on the peripheral cornea causing the cornea to steepen making the eye focus better at near. This procedure may regress...

     (LTK) is a non-touch thermal keratoplasty performed with a Holmium
    Holmium
    Holmium is a chemical element with the symbol Ho and atomic number 67. Part of the lanthanide series, holmium is a rare earth element. Its oxide was first isolated from rare earth ores in 1878 and the element was named after the city of Stockholm....

     laser, while conductive keratoplasty
    Conductive keratoplasty
    Conductive keratoplasty is a type of refractive surgery that uses radio waves to adjust the contour of the cornea by shrinking the corneal collagen around it. It is used to treat mild to moderate hyperopia. It is a non-invasive alternative to other types of eye surgery....

     (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
    Intrastromal corneal ring segments
    Intrastromal corneal rings are small devices implanted in the eye to correct vision. A typical vision correction using corneal rings would involve an ophthalmologist making a small incision in the cornea of the eye, and inserting two crescent or semi-circular shaped ring segments between the...

     (Intacs) are approved by FDA for treatment of low degrees of myopia.
  • Lens implantation inside the eye can also be used to change refractive errors.
  • 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 pesbyopia)
  • For presbyopia correction, a corneal inlay consisting of a porous black ring surrounding a small clear aperture was originally developed by D. Miller and a group at Acufocus. The inlay is placed under a lasik flap or in a stromal pocket.


Christie,B, et al: Optical performance of a corneal inlay for presbyopia. Invest Ophth Vis Sci. Abstract 695, 2005

Silvestrini, TA, et al: Analysis of glucose diffusion across Acufocus inlay. Invest Ophth Vis Sci, abstract 2195, 2005

Expectations

Research conducted by the Magill Research Center for Vision Correction, Medical University of South Carolina, showed that the overall patient satisfaction rate after primary LASIK surgery was 95.4%. They further differentiated between myopic LASIK (95.3%) and hyperopic LASIK (96.3%). They concluded that the vast majority (95.4%) of patients were satisfied with their outcome after LASIK surgery.

Risks

While refractive surgery is becoming more affordable and safe, it may not be recommended for everybody. People with certain eye diseases involving the cornea
Cornea
The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. Together with the lens, the cornea refracts light, with the cornea accounting for approximately two-thirds of the eye's total optical power. In humans, the refractive power of the cornea is...

 or retina
Retina
The vertebrate retina is a light-sensitive tissue lining the inner surface of the eye. The optics of the eye create an image of the visual world on the retina, which serves much the same function as the film in a camera. Light striking the retina initiates a cascade of chemical and electrical...

, pregnant women, and patients who have medical conditions such as glaucoma
Glaucoma
Glaucoma is an eye disorder in which the optic nerve suffers damage, permanently damaging vision in the affected eye and progressing to complete blindness if untreated. It is often, but not always, associated with increased pressure of the fluid in the eye...

, diabetes, uncontrolled vascular disease, or autoimmune disease are not good candidates for refractive surgery. Keratoconus
Keratoconus
Keratoconus , is a degenerative disorder of the eye in which structural changes within the cornea cause it to thin and change to a more conical shape than its normal gradual curve....

, a progressive thinning of the cornea, is a common corneal disorder. Keratoconus occurring after refractive surgery is called Corneal Ectasia. It is believed that additional thinning of the cornea via refractive surgery may contribute to advancement of the disease that may lead to the need for a corneal transplant. Therefore, keratoconus is a contraindication
Contraindication
In medicine, a contraindication is a condition or factor that serves as a reason to withhold a certain medical treatment.Some contraindications are absolute, meaning that there are no reasonable circumstances for undertaking a course of action...

 to refractive surgery. Corneal topography and pachymetry are used to screen for abnormal corneas. Furthermore, some people's eye shape may not permit effective refractive surgery without removing excessive amounts of corneal tissue. Those considering laser eye surgery should have a full eye examination
Eye examination
An eye examination is a battery of tests performed by an ophthalmologist, optometrist, or orthoptist assessing vision and ability to focus on and discern objects, as well as other tests and examinations pertaining to the eyes....

.

Although the risk of complications is decreasing compared to the early days of refractive surgery, there is still a small chance for serious problems. These include vision problems such as ghosting, halos, starbursts, double-vision, and dry-eye syndrome. With procedures that create a permanent flap in the cornea (such as LASIK), there is also the possibility of accidental traumatic flap displacement years after the surgery, with potentially disastrous results if not given prompt medical attention.

See also

  • Orthokeratology
    Orthokeratology
    Orthokeratology , marketed under brand names like "", "MiracLens", "DreamLens", "i-GO OVC", "GOV", "Wake and See", "CRT" and "Emerald", is the use of rigid gas-permeable contact lenses, normally worn only at night, to improve vision through the reshaping of the cornea...

     - contact lenses worn only at night to reshape the eye.
  • Bates method
    Bates Method
    The Bates method is an alternative therapy aimed at improving eyesight. Eye-care physician William Horatio Bates attributed nearly all sight problems to habitual strain of the eyes, and felt that glasses were harmful and never necessary...


External links

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