Thus, LASIK reduces corneal structural integrity both by reducing overall available load bearing tissue and by shifting the load bearing responsibility to the structurally weaker posterior corneal stroma.

1. Post LASIK Ectasia
Dr/Marwa Abdellah , MD
Lecturer of ophthalmology
Sohag University
Beware of the
Monster !!!
Dr/ Marwa Abdellah

2. The cornea
c,
The cornea :
*protect the eye,
*contain the intraocular pressure,
*Provide a smooth optical surface.
These functions can be affected
by a variety of diseases including immunologi
infectious, metabolic, genetic, and traumatic
disorders
Dr/ Marwa Abdellah

3. But , We deal with the
cornea as a mechanical
cture
*The cornea is a dynamic structure.
* It is a biological system under
constant remodeling.
*Several chemical compounds may
affect its extracellular matrix
homeostasis
Dr/ M
s
arw
t
a Ar
bdeu
llah

4. *We stretch it with ring segment
*sculpt it with excimer,
*cut it with femtosecond and
*blades in order to reshape and correct its
refractive power
Dr/ Marwa Abdellah

5. Corneal Ectasia
Dr/ Marwa Abdellah
Corneal ectasia is a rare serious
complication of refractive surgery.
It is progressive steepening and
thinning of the
Cornea after corneal refractive
surgery .

6. When ??
Dr/ Marwa Abdellah
*Time to Diagnosis:
The median time to
diagnosis of postoperative
LASIK ectasia was 13
months (6 to 20 months).

7. Incidence
Dr/ Marwa Abdellah
The incidence of
progressive corneal
ectasia after LASIK has
been estimated to be 0.2%

8. Risk Factors !!!!!
Dr/ Marwa Abdellah

9. •Forme Fruste keratoconus
•Asymmetric
Bowtie
Preoperative Topographic
pattern
Dr/ Marwa Abdellah

10. •Inferior Steep/Skewed Radial Axis
•I/S ratio > 1.4
Dr/ Marwa Abdellah

11. RESIDUAL STROMAL BED
THICKNESS
Dr/ Marwa Abdellah
Recent biomechanical studies have reinforced the importance of
RSB thickness after LASIK. Both stress-strain analysis and
cohesive tensile strength analysis indicate:
that corneal strength is significantly
greater in the anterior 40% of the corneal
stroma than in the posterior 60%.

12. RESIDUAL STROMAL BED
THICKNESS
Dr/ Marwa Abdellah
Further, the corneal flap contributes minimally to the
tensile strength of the cornea after LASIK.
Thus, LASIK reduces corneal structural integrity
both by reducing overall available load bearing tissue
and by shifting the load bearing responsibility to the
structurally weaker posterior corneal stroma.

13. It is clear, however that RSBof 250microns does not
absolutely discriminate between eyes that will develop
ectasia and those that will not.
Dr/ Marwa Abdellah
RSB seems to be a continuous variable,
with the risk of ectasia increasing with
decreasing RSB.

14. AGE
Young patient age has been identified as significant
risk factor for ectasia in eyes without other generally
accepted risk factors.
This may be partially explained
by the fact that corneal tensile
strength increases with age,
Dr/ Marwa Abdellah

15. CORNEAL THICKNESS
CT, degree of myopia, and RSB are inter-related.
Low CT has been found to be a risk factor
for ectasia in every published case-control analysis,
Since keratoconic corneas are thinner
than normal corneas
Dr/ Marwa Abdellah

16. Thin corneas may be an indicator of early
keratoconus,
thinner corneas are at higher risk for low RSB
thickness owing to variability in microkeratome
function.
However, preoperative CT alone appears to
be only a weak indictor for increased risk of
ectasia
Dr/ Marwa Abdellah

17. DEGREE OF MYOPIA
Dr/ Marwa Abdellah
High myopia leads to deep ablation
with low residual stromal bed thickness
Even with expected RST > 250
um………..myopia > 8 D is a high risk
factor

18. Ectaisa Scoring System
Dr/ Marwa Abdellah

19. Postoperative risk factors ???
Dr/ Marwa Abdellah

20. Role of Pregnancy
*The role of pregnancy in corneal ectasia may be incidental,
circumstantial, or causal.
Relaxin hormone increases during pregnancy.
inhibit collagen remodeling .
may affect the collagen integrity of
ligaments and wound healing
The increase in the level of relaxin hormone during
pregnancy may contribute to changes in the physiochemical
properties of corneal collagen leading to ectasia (Royce
et al., 2009; Cooney et al., 2009; Kapila et al., 2009
Dr/ Marwa Abdellah

21. Adenoviral
keraratoconjuctivitis
Dr/ Marwa Abdellah
Adenoviral inflammation of the corneal interface may lead to
upregulation of inflammatory cytokines and metalloproteinases
leading to collagen loss and further weakening of the corneal
stroma.
With time, there is apoptosis of the corneal stromal keratocytes
which may contribute to a decrease in corneal collagen
synthesis and further weakening of the corneal stroma

22. Choric Eye Trauma ( eye
rubbing )
Dr/ Marwa Abdellah

23. Dr/ Marwa Abdellah

24. How to diagnose post
LASIK ectasia???
Dr/ Marwa Abdellah

25. r
Randleman et al ( 2008 )defined corneal
ectasia as:
Inferior topographic steepening of 5 D o
more compared with immediate
postoperative appearance
loss of 2 or more lines of Snellen acuity,
change in manifest refraction of 2 D or
more of either sphere or cylinder
Dr/ Marwa Abdellah

26. Dr/ Marwa Abdellah

27. Histopathology of ectatic
cornea
Dr/ Marwa Abdellah
Histopathologic studies suggest that intermellar and
interfibrillar biomechanical slippage occurs when the cornea
becomes ectatic after LASIK or PRK in the
post-operative stress-bearing regions of the corneal stromal
Composite
sciences classify this chronic biomechanical failure process
as interfiber fracture

28. Reassure of the patient that there are
many treatment options
Aim of the treatment :
To restore vision
To prevent progression
Management of PostLasik
Ectasia
Dr/ Marwa Abdellah

29. Corneal Crosslinking
Dr/ Marwa Abdellah

30. Intracorneal Rings
Dr/ Marwa Abdellah

31. keratoplasty
Dr/ Marwa Abdellah

32. Good preoperative
evaluation prevents many
problems
Dr/ Marwa Abdellah
Avoids you to meet the
monster !!!

33. Dr/ Marwa Abdellah