Advanced Surface Ablation

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Advanced Surface Ablation

• KHADER FARWAN

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How the eye works

• Light rays enter the eye through the clear
  cornea, pupil and lens.
• These light rays are focused directly onto the
  retina, the light-sensitive tissue lining the
  back of the eye.
• The retina converts light rays into impulses,
  sent through the optic nerve to your brain, where
  they are recognized as images.
• 70 of the eye's focusing power comes from the
  cornea and 30 from the lens.

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Refractive errors myopia

• The distance between the cornea and the retina
  may be too long or the power of the cornea and
  the lens may be too strong.
• Four types of refractive error
• Myopia (nearsightedness)
• Hyperopia (farsightedness)
• Astigmatism
• Presbyopia

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Refractive errors myopia

• In myopia (nearsightedness), there is too much
  optical power in the eye.
• The distance between the cornea and the retina
  may be too long or the power of the cornea and
  the lens may be too strong.

Myopia, or nearsightedness
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Refractive errors hyperopia

• In hyperopia (farsightedness), there is too
  little optical power.
• The distance between the cornea and the retina
  may be too short.
• Light rays are focused behind the retina instead
  of on it.
• In adults (but not children), distant objects
  will look clear, but close objects will appear
  blurred.

Hyperopia, or farsightedness
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Refractive errors astigmatism

• In astigmatism, the cornea is curved
  unevenlyshaped more like a football than a
  basketball.
• Light passing through the uneven cornea is
  focused in two or more locations.
• Distant and close objects may appear blurry.

Astigmatism occurs when light passes through
uneven cornea
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Refractive errors presbyopia

• Presbyopia is a normal condition in which your
  eyes gradually lose the ability to focus things
  up close.
• When we are young, the lens in our eyes is
  flexible and is able to change focus easily
  between near and far objects, like an autofocus
  on a camera.
• At around age 40, this flexibility naturally
  begins to gradually decrease, making it more
  difficult to see objects up close.

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What is refractive surgery?

• A group of outpatient surgical procedures used to
  alter how your eye focuses light rays on the
  retina, thereby improving vision and reducing
  dependence on glasses and contact lenses.
• In most cases, refractive surgery affects the
  shape of your cornea to redirect how light is
  focused onto the retina. Popular procedures
  include LASIK, LASEK, PRK and CK.

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What is refractive surgery?

• Most refractive surgery is performed on the
  cornea and affects only the front of your eye,
  while the rest of your eye will change naturally
  as you age.
• In some cases, refractive surgery procedures
  dont reshape the cornea instead, the eyes
  natural lens is either replaced or enhanced by an
  implantable lens that helps correct vision.

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What is Advanced Surface Ablation (ASA)?

• A refractive surgery procedure where the
  outermost layer of the cornea, the epithelium, is
  removed or displaced to expose the stroma (the
  middle, thickest layer of tissue in the cornea).
• A computer-controlled excimer laser then reshapes
  the front surface of the corneal stroma.

The outermost layer of the cornea, the
epithelium, lies on top of the stroma
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What is Advanced Surface Ablation (ASA)?

• The epithelium is either replaced or assisted in
  healing back over the surface of the cornea
  underneath a bandage contact lens.
• Types of ASA Photorefractive Keratectomy (PRK)
  and Laser Epithelial Keratomileusis (LASEK).

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What is Photorefractive Keratectomy (PRK)?

• Outpatient refractive surgery used to treat
  nearsightedness (myopia), farsightedness
  (hyperopia) and astigmatism.
• PRK involves
• Manually removing the corneal epithelium.
• Using an excimer laser to precisely sculpt the
  stroma according to the specific refractive error
  to be treated.
• Covering the cornea with a bandage contact lens
  to facilitate healing of the epithelium.
• The goal of PRK is to focus light rays more
  precisely on the retina to improve uncorrected
  vision.

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What is PRK?

• To treat myopia, the surgeon uses the laser to
  flatten the corneal surface in a lenticular
  (lens-like) pattern.
• By reducing the curvature of the cornea, the
  eyes focusing power is decreased.
• Images that are focused in front of the retina
  are pushed closer to or directly onto the retina,
  producing clearer uncorrected vision.

With myopia, the laser is used to flatten the
corneal surface
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What is PRK?

• To treat hyperopia, the surgeon uses the laser to
  steepen the cornea by removing tissue from the
  periphery of the cornea.
• By steepening the cornea, the focusing ability of
  the cornea is changed, thereby adding refractive
  power to focus the incoming images more directly
  on the retina instead of behind it.

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What is PRK?

• To treat astigmatism, the laser is programmed to
  selectively reshape specific portions of the
  cornea more than others.
• The laser flattens areas that are steeper than
  normal and steepens areas that are flatter than
  normal, usually in an elliptical pattern.
• Allows the surgeon to deliver the correct amount
  of laser energy to the appropriate areas of the
  cornea, thereby improving uncorrected vision.

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How is PRK performed?

• In addition to a complete pre-operative eye exam,
  measurements are taken to give the surgeon the
  necessary information to perform the procedure
• Refractive error measurement.
• Pupil evaluation and measurement.
• Tonometry measurement of your eyes intraocular
  pressure (fluid pressure inside your eye).
• Corneal topography mapping the surface details
  of the cornea.
• Keratometry measurement of the form and
  curvature of the cornea.
• Pachymetry measurement of corneal thickness.

A phoropter is used to measure refractive
errors
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How is PRK performed?

• Anesthetic eyedrops are applied to your eye(s).
• The non-treated eye is patched.

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How is PRK performed?

• A lid speculum is placed to keep the eyelids open
  during the procedure.

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How is PRK performed?

• The epithelium is removed using an Amoils brush
  or by using the laser itself.

An Amoils brush is used to remove the epithelium
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How is PRK performed?

• An excimer laser controlled by a computer is
  programmed to reshape the cornea, depending on
  the amount and type of correction desired.
• The laser sculpts an area six to nine millimeters
  in diameter on the surface of the eye, depending
  on whether the laser is correcting for myopia or
  hyperopia.
• The depth of the sculpting depends on the degree
  of correction needed.

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How is PRK performed?

• The laser removes tissue from the cornea, either
  decreasing the steepness of curvature for
  nearsightedness or increasing the steepness of
  curvature for farsightedness.

With myopia, the laser is used in a central,
circular pattern
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How is PRK performed?

• After the procedure, a transparent bandage
  contact lens is placed over the cornea to promote
  healing

and postoperative eyedrops are applied.
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Considerations for PRK surgery

• May be recommended for people with lower levels
  of myopia or hyperopia, although it is FDA
  approved to treat between -12 to 6 diopters of
  refractive error.
• May be recommended for people with thin corneas
  who would not be good candidates for LASIK.
• May be recommended for people with dry eyes.
• Because a stromal flap is not created in the
  cornea (as with LASIK), less corneal tissue is
  disturbed, therefore some surgeons consider PRK
  to be a safer procedure than LASIK.
• Certain occupational restrictions against other
  forms of refractive surgery (i.e., LASIK).
• Less invasive procedure than intraocular surgery,
  thus reducing quality-of-vision complaints.

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Considerations against PRK surgery

• Slower visual recovery than LASIK or phakic IOL
  surgery.
• Not recommended for people with significant
  ocular disease of any type, especially corneal
  disease.
• Not recommended for people with significant skin
  or systemic disease that could adversely affect
  healing.
• Not recommended for people with a history of
  excessive scarring when skin is broken.
• Not recommended for people with unstable or
  changing refractive error.
• Some discomfort immediately following surgery,
  lasting for 2 to 3 days, occasionally requiring
  narcotics or topical anesthetics for pain control.

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Risks and possible side effects of PRK surgery

• Over-correction or under-correction (with a
  possible need for a re-treatment).
• Vision may be blurry for a few days up to several
  weeks, with the achievement of best vision taking
  up to a month or longer.
• Glare and halos around lights, particularly at
  night.
• Corneal scarring and corneal haze.
• Corneal infection.

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What is Laser Epithelial Keratomileusis (LASEK)?

• Outpatient refractive surgery useful in
  correcting nearsightedness (myopia),
  farsightedness (hyperopia) and astigmatism.
• LASEK involves
• Temporarily displacing the corneal epithelium
  using dilute alcohol.
• Using an excimer laser to precisely sculpt the
  stroma according to the specific refractive error
  to be treated.
• Replacing the epithelium and using a bandage
  contact lens to speed healing and reduce
  discomfort.
• The goal of LASEK is to focus light rays more
  precisely on the retina to improve uncorrected
  vision.

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How is LASEK performed?

• As with other procedures, pre-operative
  measurements are taken of your eye.
• A special alcohol solution is used to loosen the
  epithelium

which allows it to be peeled back from the
cornea.
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How is LASEK performed?

• Once the epithelium is displaced, an excimer
  laser controlled by a computer is programmed to
  reshape your cornea.

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How is LASEK performed?
The laser removes tissue, either decreasing
the curve of your cornea to correct
nearsightedness or increasing the curve of your
cornea to correct farsightedness.
After the laser treatment, the epithelium is
smoothed back into position over the cornea, and
a bandage contact lens is placed to promote
healing.
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How is LASEK performed?

• The reshaped cornea focuses light more accurately
  on the retina.

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Considerations for LASEK surgery

• May be recommended for people with lower levels
  of myopia or hyperopia.
• May be recommended for people with thin corneas
  who would not be good candidates for LASIK.
• May be recommended for people with dry eyes.
• Because a stromal flap is not created in the
  cornea (as with LASIK), less corneal tissue is
  disturbed, therefore some surgeons consider LASEK
  to be a safer procedure than LASIK.
• Certain occupational restrictions against other
  forms of refractive surgery (i.e., LASIK).
• May be less painful during healing than PRK.
• May offer faster visual recovery than PRK (but
  not as fast as LASIK).
• Less invasive procedure than intraocular surgery,
  thus reducing quality-of-vision complaints.

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Considerations against LASEK surgery

• Slower visual recovery than LASIK or phakic IOL
  surgery.
• Not recommended for people with significant
  ocular disease of any type, especially corneal
  disease.
• Not recommended for people with significant skin
  or systemic disease that could adversely affect
  healing.
• Not recommended for people with a history of
  excessive scarring when skin is broken.
• Not recommended for people with unstable or
  changing refractive error.
• Not recommended for people with myopia, hyperopia
  or astigmatism beyond the range of PRK.
• Some discomfort immediately following surgery,
  lasting for 2 to 3 days, sometimes requiring
  narcotics or topical anesthetics for pain control.

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Risks and possible side effects of LASEK surgery

• Over-correction or under-correction (with a
  possible need for a re-treatment).
• Vision may be blurry for a few days up to several
  weeks, with the achievement of best vision taking
  up to a month or longer.
• Glare and halos around lights, particularly at
  night.
• Corneal scarring and corneal haze.
• Corneal infection.

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Is refractive surgery right for you?

• New surgical procedures, including PRK and LASEK,
  are creating more opportunities for people who
  want to be less dependent on glasses or contacts.
• Surgery may not entirely eliminate your need for
  corrective lenses. Glasses/contacts may still be
  needed for activities such as fine or detailed
  work, reading and perhaps night driving.

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Is refractive surgery right for you?

• A large part of the success of any refractive
  surgery depends on your understanding of the
  procedure and your expectations.
• Since refractive surgery is an elective
  procedure, you have the opportunity and
  responsibility to become fully informed about its
  risks and benefits.
• Your ophthalmologist will explain the specific
  technique, its benefits, as well as possible
  risks and side effects associated with your case.

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Discuss options and questions with your
ophthalmologist

• With the help of your ophthalmologist, its
  ultimately your responsibility to weigh the risks
  and side effects of a procedure with the benefits
  it has to offer.
• If you decide refractive surgery is right for
  you, you may join millions of people who have
  reduced their dependence on glasses or contacts.