Three steps to successful outcomes:
(Important to have keratometric, posterior, anterior and
thickness views)
STEP 1
Verify cone, identify type and evaluate displacement of
cone using keratometric map and
posterior float
-
Centered Cone
PEARL:
If more than 50% of the primary conal anomaly identified on
the posterior float is inside the 3mm zone then use
similar Intacs sizes.
-
De-centered Cone
PEARL:
If more than 50% of the primary conal anomaly identified on
the posterior float is outside the 3 mm zone, use
different sizes to pull the cone centrally. Larger Intacs size where
greater pull is desired.
STEP 2
Identify steep meridian to determine incision placement
-
Verify and correlate steep meridian
refraction to the maximum K on topographical axis.
- Use Manifest Refraction to
help determine:
- Steepest refractive
axis. Verify by comparing to topographical Max K axis.
- The "I" denotes steep
axis for incision placement.
PEARL:
If Steep refractive meridian is more than 20 degrees off
from topographical then re-refract patient on apex of cone.
And if you cannot get a refraction, use Steep meridian on
topography.
Note:
Steepest refractive axis does not always correlate with the
topographical axis - Make sure the patient isn't "adjusting" to
his/her best viewing angle during the refraction. Steep axis
incision placement appears to maximize outcomes. Like the
uniqueness in each manifestation of keratoconus, each procedure
is customized for the presenting corneal topography. It
appears to achieve maximum reduction in cylinder and eliminates
inducement of astigmatism in standard myopia.
STEP 3
Determine Intacs Size based on spherical equivalent and nomogram
- Calculate manifest
refraction spherical equivalent (MRSE)
PEARL:
Use Swanson nomogram and don't deviate from
Prolate System Steps
Types of
Ectasia and Unstable Cornea's
Pre & Post Operative Examples
Form Fruste
| Irregular |
Central |
Pelluid
| Pellucid "Like"
| Intacs & Lasik
Post Lasik
