PRK or advanced surface ablation 2017

Cataract Surgery
Dr B Farpour
Geneva 2017
www.visionlaser.ch
PRK : Advanced Surface Ablation
Geneva refractive public education lectures
Courtesy of AAO
presentation support

Advanced Surface Ablation
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.
2
Eye anatomy

How the eye works
3

Refractive errors
• 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
4

• 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.
• Light rays focus in front of the
retina instead of on it.
• Close objects will look clear,
but distant objects will appear
blurred.
5
Refractive errors: myopia
Myopia, or nearsightedness

• 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.
6
Refractive errors: hyperopia
Hyperopia, or farsightedness

• In astigmatism, the cornea is
curved unevenly — shaped
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.
7
Refractive errors: astigmatism
Astigmatism occurs when light passes
through an uneven cornea.

• Presbyopia is a normal
condition in which your eyes
gradually lose the ability to
focus on 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.
8
Refractive errors: presbyopia

• Refractive surgery is 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 and PRK.
9
What is refractive surgery?
Refractive
surgery
procedure on
the cornea

• 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 don’t reshape the
cornea; instead, the eye’s natural lens is either replaced or
enhanced by an implantable lens that helps correct vision.
10

Advanced Surface Ablation 11

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)
 laser epithelial keratomileusis (LASEK)
12

• 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 eye’s 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.
13
What is PRK?
With myopia, the laser
is used to flatten the
corneal surface.

• In addition to a complete preoperative 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 eye’s
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
14
How is PRK performed?
A phoropter is used to
measure refractive errors.

• Anesthetic eyedrops are applied
to your eye(s).
• The nontreated eye is patched.
15

• The epithelium is removed using
an Amoils brush or by using the
laser itself.
16
An Amoils brush is used to
remove the epithelium.

• 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 6 millimeters to 9 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.
17

• The laser removes tissue from
the cornea, either decreasing
the steepness of curvature for
nearsightedness or increasing
the steepness of curvature for
farsightedness.
18
With myopia, the laser is used
in a central, circular pattern.

and postoperative eyedrops are
applied.
• After the procedure:
a transparent bandage contact lens
is placed over the cornea to promote
healing . . .

Considerations for PRK surgery
• PRK 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.
• PRK may be recommended for people with thin corneas who would
not be good candidates for LASIK.
• PRK 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.
• There may be certain occupational restrictions against other forms
of refractive surgery (i.e., LASIK).
• PRK is a less invasive procedure than intraocular surgery, thus
reducing quality-of-vision complaints.
21

Considerations against PRK surgery
• PRK provides slower visual recovery than LASIK or phakic IOL surgery.
• PRK is not recommended for people with significant ocular disease of
any type, especially corneal disease.
• PRK is not recommended for people with significant skin or systemic
disease that could adversely affect healing.
• PRK is not recommended for people with a history of excessive
scarring when skin is broken.
• PRK is not recommended for people with unstable or changing
refractive error.
• There may be some discomfort immediately following surgery, lasting
for 2 to 3 days, occasionally requiring narcotics or topical anesthetics
for pain control.
22

Risks and possible side effects of PRK surgery
• Overcorrection or undercorrection (with a possible need for
retreatment)
• Blurry vision 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
23

What is laser epithelial keratomileusis (LASEK)?
• LASEK is an 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; and
 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.
24

How is LASEK performed?
which allows it to be peeled back
from the cornea.
• As with other procedures, preoperative measurements are taken of your eye.
A special alcohol solution is used to
loosen the epithelium, . . .

• Once the epithelium is displaced, an excimer laser controlled by
a computer is programmed to reshape your cornea.
26

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.

• The reshaped cornea focuses light more accurately on the
retina.
28

Considerations for LASEK surgery
• LASEK may be recommended for people with lower levels of myopia
or hyperopia.
• LASEK may be recommended for people with thin corneas who would
not be good candidates for LASIK.
• LASEK 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.
30

Considerations for LASEK surgery
• There may be certain occupational restrictions against other forms of
refractive surgery (i.e., LASIK).
• LASEK may be less painful during healing than PRK.
• LASEK may offer faster visual recovery than PRK (but not as fast as
LASIK).
• LASEK is a less invasive procedure than intraocular surgery, thus
reducing quality-of-vision complaints.
31

Considerations against LASEK surgery
• LASEK provides slower visual recovery than LASIK or phakic IOL
surgery.
• LASEK is not recommended for people with significant ocular disease
of any type, especially corneal disease.
• LASEK is not recommended for people with significant skin or
systemic disease that could adversely affect healing.
• LASEK is not recommended for people with a history of excessive
scarring when skin is broken.
32

Considerations against LASEK surgery
• LASEK is not recommended for people with unstable or changing
refractive error.
• LASEK is not recommended for people with myopia, hyperopia or
astigmatism beyond the range of PRK.
• There may be some discomfort immediately following surgery, lasting
for 2 to 3 days, sometimes requiring narcotics or topical anesthetics
for pain control.
33

Risks and possible side effects of LASEK surgery
• Overcorrection or undercorrection (with a possible need for
retreatment)
• Blurry vision 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
34

Is refractive surgery right for you?
• 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 or contacts may still be needed for activities such as fine or
detailed work, reading and perhaps night driving.
35

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.
36

• With the help of your ophthalmologist, it’s 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.
37
Discuss options and questions with your ophthalmologist

PRK or advanced surface ablation 2017

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