IC-16_Pallikaris_Handout
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Transcript IC-16_Pallikaris_Handout
Evolution of surface treatments for the
correction of ametropias
PRK
Epithelial injury
FDA approval:1995
Risk of corneal ectasia
Unpredictable
flap induced aberrations
ADVANCED SURFACE
ABLATIONS
Postoperative pain
Late visual recovery
Risk of Haze
Intrastromal incision
LASIK
In a deep plane
FDA approval:1999
in the stroma
Advanced Surface Ablations
The term “advanced surface ablations”:
was coined as a way to explain the evolution in
surface ablation techniques from the earlier PRK days
covers several techniques such as:
PRK with the intraoperative use of mitomycin-C (MMC)
(PRK-MMC)
epipolis LASIK (Epi-LASIK)
laser epithelial keratomileusis (LASEK)
Advanced Surface Ablations
Advanced surface ablation techniques offer
several advantages over conventional PRK
such as:
increased quality of vision
reduced postoperative pain
minimized corneal haze
Advanced Surface Ablations
Reasons for selecting a surface treatment:
Thin corneas for attempted correction (residual bed
thickness < 300μm)
Preoperative Dry Eye
Epithelial basement membrane dystrophies
Flat or steep corneas
No risk of flap-related complications
No risk of flap-induced aberrations
Epithelial Removal
The epithelium can be removed with several
ways:
Mechanical removal of the epithelium with a blade
or newly a rotating brush
Epithelial removal with the use of alcohol
(LASEK)
Epi-LASIK
Epithelial removal with the laser (transepithelial)
Evolution of
Advanced Surface Ablations (I)
Introduction of MMC for the control of
corneal haze:
Therapeutic use globally accepted (selected
complicated cases)
Intraoperative prophylactic use after PRK
(PRK-MMC)
Evolution of
Advanced Surface Ablations (II)
Introduction to the retained epithelial flaps
(LASEK, Epi-LASIK):
Allow for decreased incidence of haze
Offer with better tolerance of patients
Mechanical epithelial separation provides
with the benefit of avoiding alcohol toxicity
PRK-MMC
0.02% for up to 1.5 min depending on the attempted
correction (delay in epithelial healing at 2 min)
Reduction of myofibroblast activity / haze (compared to
corticosteroids)
Faster visual recovery and confocal microscopic
normalization
Safety up to about 10 yrs max experience
LASEK
A dilute solution (20%) is used on the eye in a
holding cup (8.5mm diameter) for approximately 30
seconds in order to loosen the epithelium and creates
a complete epithelial flap
After the loosened epithelium is slid to the side and
the stromal surface is treated with the laser
The epithelium is replaced or can be directly removed
Epi-LASIK
Surface ablation (epi-polis superficial)
Epithelium is separated as a sheet and replaced on the
ablated stroma
Special device (Epikeratome) - automated procedure
No use of alcohol
Dealing with drawbacks of PRK (postoperative pain/
discomfort, late visual recovery, haze) and avoiding
risks of LASIK
Suitable for thin corneas