Limitations of corneal topography . Not mine but shared by a friend .

1. Case A: Blurred Vision After LASIK, Causes
Unknown. An Epithelial Ingrowth Is Present
but It Is Located Superiorly and Far From
Visual Axis.
•Scan unsuccessful
due to no data point
being collected
from visual axis.
•Mono-camera
system is more
prone to optical
artifact due to
surface irregularity
arising from
adjacent corneal
elevation/opacities.

2. Case B: Ghost Image After LASIK, Causes
Unknown.
•Scan
shows flat
but
otherwise
normal
cornea.

3. Case C: Post LASIK, Poor BCVA, Causes
Unknown.
•Scan shows central
flattening (but within
normal limits), inferior
flattening, and
posterior vaulting.
Is it real? Can suchIs it real? Can such
ectasia occur in aectasia occur in a
cornea with normalcornea with normal
thickness of 573um?thickness of 573um?
Does the inferiorDoes the inferior
flattening affect theflattening affect the
validity of the data?validity of the data?

4. Case D: Poor BCVA s/p PRK, With Anterior
Stromal Haze, Should We Do PTK On The 313
um Cornea?
•The “thinned” cornea
is actually an aberrant
reading (ultrasound
showed 520um).
•Mono-camera systems
are prone to
artifactual pachymetry
and posterior surface
reading, when there is
incomplete penetration
of light due to corneal
haze.

5. Case D con’t: the contralateral eye
•The same thing, s/p
PRK with haze
which affects the
optical pachymetry,
giving an
aberrantly thin
pachy reading (321
um, ultrasound
showed 515um).

6. Case E: s/p High Myopic Treatment, Flat
Cornea, Over-Corrected, Should We Enhance
On This 253 um Cornea?
•Ultrasound actually
showed 480 um. The
artifactual pachy
reading is due to the
flatness of the
cornea which affects
the accuracy of
mathematical
reconstruction
(intra/extrapolation)
of posterior surface
and pachy, which is
necessary in a
mono-camera
system

7. Case E: s/p High Myopic Treatment, Flat
Cornea, Over-Corrected, Should We Enhance
On This 253 um Cornea?
•Ultrasound actually
showed 480 um. The
artifactual pachy
reading is due to the
flatness of the
cornea which affects
the accuracy of
mathematical
reconstruction
(intra/extrapolation)
of posterior surface
and pachy, which is
necessary in a
mono-camera
system