LASER EYE
CORRECTION
ISLAM FARIS 119I1B-AMU
DR.AYSEL QELBINUR OPHTHALMOLOGY
INTRODUCTION
Refractive errors are one of the most
common eye conditions throughout the
population, laser corrective surgeries are
a way to treat such conditions while
providing the most comfort to the
patient in the long run.
Ametropia or refractive error
When light entering the eye does not focus on
the retinaThe focusing power of the cornea and lens
(corneal curvature, refractive power of lens) does
not match eye size (axial length of globe).
The condition requires a refractive device.
Types:
Myopia: nearsightedness
Hyperopia: farsightedness
Astigmatism: uneven focus
[1]
Focal
Myopia
Hyperopia
Astigmatism
In front of retina
Behind retina
Multiple sites
Eye too long, cornea with too
Eye too short, cornea with too
Uneven curvature of
much curvature
little curvature
the cornea
Cannot focus distant objects
Cannot focus near objects
Blurry vision
point
Causes
Result
Types of correction
Glasses
Contacts
Being the most available
and affordable correction
for most refractive errors
Alternative to glasses that
provide a more cosmetic
benefit
Laser
Other…
A more long lasting
solution that can
sometimes be more
comfortable for patients
ICL’s and more
Types of laser corrections
PRK
Standard LASIK*
(Excimer laser)
Traditional lasik using
microkeratome
involves removing the
outer layer of the
cornea while LASIK
does not
1
3
4
2
Femto LASIK
Similar to traditional lasik
substituting the microkeratome
with femtosecond laser
SMILE
Flapless
alternative to lasik
procedures
*laser assisted in situ keratomileusis
Success rates & Stats
99%
Success rate according to the latest LASIK
report by the American Refractive Surgery
Council
30,000,000
People treated with laser eye surgery
every year
90%
of people who undergo LASIK surgery
end up with vision that is 20/20 or better
[2]
Indications +
Contraindications
LASIK is indicated for the correction of low,
moderate, and high myopia with and without
astigmatism. The specific dioptric limits depends
on the specific laser system and the regulatory
agency of each country. Usually up to -8.0D
Contraindications
● Dry eyes
● Immune conditions
● Fuchs corneal endothelial dystrophy
● Keratoconus
● Pregnancy
[3]
Preoperative tests
Past Medical History/Past Ocular History
medical and ocular history is important to look for diseases that
potentially can affect the outcome of LASIK surgery.
Medications
Migraine drugs can alter wound healing in the cornea, and my need to
be stopped around the time of surgery. Acne meds, may result in ocular
surface drying. OTC medications such as antihistamines may exacerbate
dry eye problems after LASIK surgery
Visual Acuity
Refraction
Complete Eye Examination including tonometry and a posterior dilated
exam
Pupil Testing
Topography, Tomography and Corneal Biomechanics
Characterization of the front and back surfaces of the cornea, along with
thickness mapping. Several technologies for tomography, including
horizontal slit scanning, rotational Scheimpflug imaging, arc scanning
with high-frequency ultrasound, and anterior segment optical coherence
tomography, are available in various commercial instruments.
Tomography combines anterior and posterior corneal elevation with
complete pachymetry data to reconstruct corneal architecture in three
dimensions[4]
Excimer LASIK
The excimer laser vaporizes the corneal
tissue to be removed via photoablation.
Myopia even up to -10 dpt can be
treated by vaporizing a round piece of
tissue in the center of the cornea. To
correct hyperopia up to approximately
+3 dpt, the curvature of the central
cornea is intensified and the refractive
power of the cornea increased by
ablating the edge of the cornea [5]
Due to the flap style operation some
complications may arise including
● Uneven tissue growth
● Risk of displacement
● Healing times may very
● Increase risk for dry eyes
Even with this as the case it is still
considered very safe and rarely needs
touch up correction
Femto LASIK
Two different laser technologies are
applied consecutively in this method of
treatment. A femtosecond laser cuts
the outer layer of the cornea, which is
opened up as a flap for subsequent
treatment.
The excimer laser is then used to
correct defective vision in one of the
deeper layers of the cornea. The open
flap is then closed to allow the wound
to self-seal in a final step and reattach
in a matter of a few hours
[5]
Complications may be similar to
standard lasik but with decreased
healing time due to a thinner more
precise flap
PRK (photorefractive keratectomy)
PRK may be preferable to LASIK in certain patients
with thinner corneas or with corneal surface
irregularity since PRK disrupts less corneal tissue
than a comparable LASIK surgery.
PRK is technically simpler than LASIK and utilizes
the same modern laser treatment systems. For this
reason, some refractive surgeons prefer PRK to
LASIK.
Disadvantages
●
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[6]
Scars on your cornea.
Corneal haze, which is a cloudiness on your cornea
(using Mitomycin c can prevent this during operation)
An infection.
A glare and halo when you’re around lights, especially
at night.
Eye pain, irritation and/or watering.
Sensitivity to light.
Hazy vision. A medicine called mitomycin C is
sometimes used during surgery to minimize the risk of
haze after a PRK.
Regression, which means that the treatment becomes
less effective.
Delayed healing.
SMILE (Small incision lenticule extraction)
With SMILE®, the entire correction is performed as a single-step
without the creation of a flap: on one laser, with one treatment plan
and one laser process. It is the first only minimally invasive way of
correcting vision.
Using a high-performance femtosecond laser, SMILE® creates a
lenticule (tissue disc) inside the cornea which is removed through a
small 2 mm incision. The surface of the cornea is almost untouched
and there is less disturbance of the corneal nerves, meaning less
changes of prolonged dryness of the eyes.
● Saves significant time with entire treatment completed in a
single step
● Spares maximum cornea nerves due to the small incision
● Smaller healing phase because of small incision
● No risk of flap displacement even while engaging in extreme
activities
● Better preservation of the corneal architecture
[7]
Disadvantages
The primary disadvantages of SMILE include:
●
●
●
New procedure. Because SMILE is newer than other laser eye
surgeries, less research supports its uses.
Only for myopia and astigmatism. SMILE surgery is currently
approved to treat nearsightedness and astigmatism. People
with hyperopia (farsightedness) will need a different procedure,
such as LASIK or PRK.
High cost [8]
Postoperative Care
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[9]
Do not rub your eyes for two months or until your doctor says it’s safe.Wear the
sunglasses provided in the postoperative kit when you leave the Laser Refractive
Center.
If a bandage contact lens was placed in either eye, leave it alone until your doctor
removes it. If it falls or blinks out, simply leave it out.
If your pain level increases substantially as a result, inform your doctor.
Instill the antibiotic and anti-inflammatory eye drops prescribed by your doctor four
times a day for one week. Shake the anti-inflammatory medication. An easy routine
to follow is to instill the drops at breakfast, lunch, dinner, and bedtime. Instill the two
medications five minutes apart. The order is not important. Only one drop needs to
land in your eye.
Expect your vision to fluctuate for the first month or more following the procedure.
Often there will be halos around lights at night and your vision may fluctuate over
the course of the day. Your eyes may also feel dry for up to three or four months. All
of this is normal. If the dryness is bothersome, instill over-the-counter artificial tears
in between the medication eye drops. Once you finish the medication eye drops, you
can instill artificial tears anytime you have dryness symptoms.
REFERENCES
1.
2.
3.
4.
5.
6.
7.
8.
9.
Refractive errors: Concise medical knowledge (2023) Lecturio. Available at:
https://www.lecturio.com/concepts/refractive-errors/ (Accessed: April 26, 2023).
24 Laser Eye Surgery Statistics: Focus Clinics (2023) www.focusclinics.com. Available at:
https://www.focusclinics.com/blog/laser-eye-surgery-statistics/ (Accessed: April 26, 2023).
LASIK for myopia and astigmatism: Safety and efficacy (2023) American Academy of Ophthalmology .
Available at:
https://eyewiki.aao.org/LASIK_for_Myopia_and_Astigmatism:_Safety_and_Efficacy#:~:text=LASIK%20is%20i
ndicated%20for%20the,Drug%20Administration%20(FDA)%20labeling. (Accessed: April 26, 2023).
Preoperative evaluation for LASIK surgery (no date) American Academy of Ophthalmology. Available at:
https://eyewiki.aao.org/Preoperative_Evaluation_for_LASIK_Surgery (Accessed: April 26, 2023 ).
Photonics News , Eye Surgery Using Excimer and Femtosecond Lasers. Available at:
https://www.lasercomponents.com/us/news/eye-surgery-using-excimer-and-femtosecond-lasers-1/ (Accessed:
April 26, 2023).
PRK (photorefractive keratectomy): Treatment, side effects & recovery (2021) Cleveland Clinic. Available at:
https://my.clevelandclinic.org/health/treatments/8596-photorefractive-keratectomy-prk-eye-surgery (Accessed:
April 26, 2023).
Smile eye surgery (procedure, side effects, benefits & costs) (2023) Vision Center. Available at:
https://www.visioncenter.org/surgery/smile/ (Accessed: April 26, 2023).
Smile® Flapless Laser Eye surgery: LASERSIGHT Australia (no date) SMILE® Flapless Laser Eye Surgery |
LASERSIGHT Australia. Available at: https://www.lasik.com.au/eyetreatment/smile/#:~:text=SMILE%C2%AE%20is%20an%20advanced,the%20face%20of%20vision%20correcti
on. (Accessed: April 26, 2023).
Postoperative instructions - laser refractive surgery | UCLA health (no date) LASER REFRACTIVE SURGERY
Postoperative Instructions. Available at: https://www.uclahealth.org/medical-services/ophthalmology/laserrefractive-surgery/your-visit/postoperative-instructions (Accessed: April 26, 2023).
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