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