Refractive eye surgeries have become enormously popular worldwide. Although numerous types of surgical and laser refractive procedures are available today, a procedure known as laser in situ keratomileusis (LASIK) to correct nearsightedness is currently the most common type.

1. REFRACTIVE SURGERIES
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Getachew Kassahun
University of Gondar Hospital
Gondar, Ethiopia

2. Requirements prior to surgery
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 Counseling
 Motivation
 Age b/n 20 and 45 will have best result
 Stabilization of refractive errors
 Removal of contact lens 1 week before surgery for
daily disposable and 3 week before if SCL
 R/o no ocular surface infection exists

3. Contarindications
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 Unwilling patient
 Infectious conditions on anterior adnexa
 Systemic or local immune suppression

4. Testes should be done
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 VA
 Slit lamp exam
 Corneal sensation
 Shirmur test if dry eye existed
 Keratometery
 Videokeratography
 Pachymetry

5. CLASSIFICATION
REFRACTIVE SURGERIES
CORNEA BASED LENTICULAR BASED COMBINED(BIOPTICS)
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-R.K.
-PRK
-LASIK
-EPILASIK
-LASEK
-Conductive
Keratoplasty
-Corneal
Inlays and
rings
-Clear Lens
extraction for
myopia
-Phakic IOL
- Prelex Clear
Lens
Extraction
with use of
Multifocal
Combination
of the two

6. Based on refractive error
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 For myopia
LASIK
PRK Laser
LASEK
Inter corneal ring
non laser
Radial keratotomy
 For hyperopia
LTK
CK
LASIK, PRK

7. CORNEAL
REFRACTIVE
SURGERY
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8. Corneal Physiology
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 Transparent, dome shaped, outermost layer that covers the
front of theeye.
 Provides greatest amount refractive power to the eye.
 Avascular, relies on atmosphere for oxygen and
aqueous humor for its nutritional needs.
 Corneal surface is kept smooth by
constant moistening action of tears.

9. Layers of Cornea
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Epithelium (55µm).
 It evenly distributes the nutrients to other
layers.
 It maintains stromal dehydration.
Stroma (470µm)
 Collagen fibers arrangement are
responsible for corneal strength, optical
characters.
Endothelium (5µm).
 It stretches to cover the dead cells,
which reduces the cell density and
impact on fluid regulation.
 It pumps the excess fluid from stroma.

10. Shape of Cornea
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10 Slightly oval
 Horizontal & vertical dimensions are 11mm & 12 mm
app.
 Pupil diameter ranges from 2mm to 6mm, which
reduces optical zone of
cornea to its central 6mm.
 Peripheral cornea is thicker than central cornea.

11. Pachymetry
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11 It is the process of measuring the thickness of the cornea.
 Corneal Pachymetry is essential prior to a LASIK
procedure for ensuring sufficient corneal thickness to
prevent abnormal bulging of the cornea, a side effect
known as ectasia.
 Ultrasonic & Optical pachymetry.
 It also helps in finding the development of glaucoma when
combined with
standard measurement of IOP.
 Corneal thickness is 560 microns.

12. Corneal Topography
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12 It is a process of mapping the surface curvature of the
cornea.
 It is to produce a detailed description of the shape and
power of the cornea because shape determines the visual
ability.

13. Photorefractive keratectomy (PRK)
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 An outpatient refractive surgery procedure used to
treat all types of refractive error.
 In PRK the wavefront guided excimer laser is used to
reshape the stroma portion of the cornea.
 In order to access the stroma, however, the epithelial
layer must be removed.
 There are a handful of methods to remove this layer.
 Once the top layer of epithelial cells are removed the
wavefront guided excimer laser is used to reshape the
cornea.
 .

14. Cont…
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 A bandage soft contact lens is placed on the newly corrected
cornea to promote epithelial healing and to protect the
exposed lower layers of the cornea
 The epithelium usually takes around 4 days to regrow.
 It may take a few days for vision to stabilize with PRK and
varying levels of discomfort and pain result during the first
days after surgery.
 The bandage lens is removed approximately 5 to 6 days after
surgery.
 Best for -2.00 D - -6.00 D myopia

15. PRK
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Used to correct mild to moderate
 Myopia.
 Hyperopia.
 Astigmatism.
Advantages:
 Highly accurate for myopia.
 80% patients have 20/20 vision
Disadvantages:
 Mild discomfort including
minor eye irritation.
 Dry eyes.

16. Complications
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 If there is decenteration to ablation, causes diplopia,
glare, haloes and astigmatism
 Corneal haze ( high myopia)

17. LASIK
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 LASIK stands for Laser-Assisted In Situ Keratomileusis
and is a procedure that permanently changes the shape of
the cornea, the clear covering of the front of the eye.
 Uses high energy UV (193 nm ) excimer light
 LASIK is the most advance form of laser vision correction
that is currently available.
 corrects up to -1.50D myopia, +4.00D hyperopia and
+6.00D astigmatism
 Uses Automated microkeratome to remove partial thickness
of cornea
 no suture is used
 In LASIK, a 100-200 µm corneal flap is created using a
microkeratome (blade) or femtosecond laser .

18. LASIK
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Advantages:
 Pain free recovery.
 Quick restoration of eyesight.
 Better result for
severe short sight.
Disadvantages:
 Dry eyes.
 Halos, starburst.
 Loss of contrastsensitivity.
 Thick corneal flap (100-180
microns).

19. Femto LASIK
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20. CONTRAINDICATIONS
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 Systemic factors-
 Poorly controlled IDDM
 Pregnancy/lactation
 Autoimmune / connective tissue disorders(RA,SLE,PAN etc)
 Clinically significant Atopy,Immunosuppressed patients
 Keloid tendency(esp PPK)
 Slow wound healing-Marfans,Ehler-Danlos
 Systemic Infection-(HIV,TB)
 Drugs-Azathioprene,Steroids(Slow wound healing)

21. CONTRAINDICATIONS
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 Ocular Factors-
 Glaucoma,RP(Suction Pressure-ON damage,Blebs)
 Previous h/o RD or f/h of RD.
 One eyed individual
 Pre-existing dry eye,Keratoconus.pellucid marginal
degeneration,Superficial corneal
dystrophy,RCE,Uveitis,early Lenticular changes
 h/o Herpetic Keratitis(one year prior to surgery)

22. COMPLICATIONS OF LASIK
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 Intra operative hydration or dehydration
flap dislocation
 Post operative faulty adhesion of lost flap
 Late post operative regression
under/over correction
unwanted astigmatism

23. COMPLICATIONS OF LASIK
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 Under/over correction and regression (over time).
 Post –op Keratectasia
 Presents 1-12 months
 Progressive regression
 Treatment-RGP,Corneal transplant.
 Prevention-Leave residual stromal bed
-Do surface ablation
-Don’t violate corneal topography diagnosis of
forme-fruste keratoconus

24. COMPLICATIONS OF LASIK
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 Night vision disturbances-Haloes/Glare
 Decenteration and central islands.
 Post Lasik Dry eye-
 Fluctuating vision,SPK
 Temporary neuropathic cornea
 Confocal microscopy-90% reduction in corneal nerve
fibres-regeneration by 1 year.
 Rx-Preservative Free lubricants

25. COMPLICATIONS OF LASIK
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 Post op Glaucoma(Pseudo DLK)-Steroid induced.
 Vitreoretinal Complications-
 Increased risk of RD due to alteration of anterior vitreous
by suction ring-Risk 0.08%.
 PVD(0.1% Risk)
 Macular Hemorrage(0.1% Risk)

26. COMPLICATIONS OF LASIK
 Flap Complications-
 Button Hole-If
K>50D,due to central
corneal buckling.
 .
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27. Laser Assisted Sub Epithelial Keratomileusis
(LASEK)
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 Uses alcohol (18-20%) instead of microkeratome for
ablation
 Cuts and peel the epithelial layer of cornea
 Reshape upper stroma just below epithelium with laser
 Rather than removing the corneal epithelium as in PRK,
LASEK involves loosening the epithelium with alcohol,
carefully rolling it back, treating the underlying surface
with the laser, then replacing the sheet of epithelium back
over the cornea.
 A bandage contact lens again is used for a short time.

28. LASEK
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Advantages:
 No flap complications.
 Causes less dry eyes than LASIK.
 Less chance of post operative corneal
ectasia .
 Good for patient with thin cornea.
Disadvantages:
 May cause more pain and discomfort
than LASIK.
 Longer recovery time than LASIK.

29. Non laser procedures
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 Inter corneal ring :- ultra thin PMMA ring is
implanted on 2/3 of stromal depth
 Flattening depend on thickness of ring
 Radial keratotomy :- uses knives ( diamond,
ruby) special blades
 Central cornea get flatter as peripheral bulged out
following radial incision
 -1.00 - -6.00 D will have best result

30. Intrastromal Corneal Implants
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Used to treat
 Myopia. -1.00 - -1.50
 Keratoconus.
 It has two semicircular rings made of PMMA.
Advantages:
 Easily removable.
 Small incision.
Disadvantages:
 Vision disorder.
 Problem with night vision.

31. Conductive Keratoplasty (CK)
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 This technique uses a fine conducting needle to deliver
radiofrequency energy into the peripheral cornea in set
patterns.
 This shrinks corneal collagen fibers, thereby reshaping
the cornea.
 CK can be used in low hyperopes or in presbyopes in
order to sharpen near vision. The latter technique helps
to reduce a presbyope’s dependence on reading glasses by
creating monovision.

32. References:
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 Basic and Clinical Science Course, Section 8:
External Disease and Cornea. San Francisco:
American Academy of Ophthalmology; (updated
annually).
 www.aao.org National Eye Institute,
 www.nei.nih.gov LASIK.com
 www.allaboutvision.com

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