myppt for pentacam

1. C L GUPTA EYE INSTITUTE
CORNEAL TOPOGRAPHY

2. C L GUPTA EYE INSTITUTE
THE SCHEIMPFLUG PRINCIPLE
• The Scheimpflug principle, It is a geometric rule that
describes the orientation of the plane of focus of an
optical system (such as a camera) when the lens plane
is not parallel to the image plane
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3. C L GUPTA EYE INSTITUTE
THE DEVICE
•The light source - UV-free blue LED’s
(wavelength=475 nm).
2 cameras
1 st -Located in the center for the purposes of detection
of the size and orientation of the pupil and to control
fixation.
• 2 nd - Mounted on rotating wheel to capture images
from the anterior segment. This rotating process
supplies pictures in three dimensions and also allows
the center of the cornea to be measured precisely.
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5. C L GUPTA EYE INSTITUTE
Assessment of Corneal Surface

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Corneal topography
 Measurements with a keratometer is insufficient and
limited to the central 3 mm.
 Its provides us with a detailed description of various
curvature and shape characteristics of the cornea.
 Provides helpful information for the illustration of
astigmatism, detection of corneal pathologies and
perfection of contact lens fitting.
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Anderson D, Kojima R. Topography: A clinical pearl. Optom Manag 2007 Feb;42(2):35

7. C L GUPTA EYE INSTITUTE
CLINICALAPPLICATION
1. Pachymetry
2. Scheimpflug Imaging in LASIK
3. Topography and contact lenses.
4. Topography in RK.
5. Post keratoplasty astigmatism.
6. Keraoconus screening
7. Corneal Pathologies
8. Anterior Chamber implantation of phakic IOLs
9) Glaucoma Screening
• a) Effect of pilocarpine on anterior chamber depth and anterior
chamber volume in eyes with narrow angle and open angles
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8. C L GUPTA EYE INSTITUTE
PENTACAM
• The OCULUS Pentacam/Pentacam HR is a rotating
Scheimpflug camera.
• The rotational measuring procedure generates Scheimpflug
images in three dimensions
The Pentacam calculates a 3-dimensional model of the anterior
eye segment from as many as 25.000 (HR: 138.000) true
elevation points.
• It takes a maximum of 2 seconds to generate a complete image
of the anterior eye segment.

9. C L GUPTA EYE INSTITUTE
Review of Pentacam main Page
• This page should be displayed with the four main
Refractive maps
– Anterior sagittal curvature map,
– Anterior and posterior elevation maps and
– Thickness map
• Belin/Ambrosis Enhanced ectasia maps
• Topography maps for Keratoconus indices

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ANTERIOR SAGITTAL MAP
Steep areas hot colours (red and orange), while flat
areas cold colours (green and blue).
Normally, the inferior (I) point has a higher value than
the superior (S) one, and the I-S difference should be <
1.5 D.
The superior point may rarely have a higher value than
the inferior one ,the S-I difference should be < 2.5D
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12. C L GUPTA EYE INSTITUTE
CON
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15. C L GUPTA EYE INSTITUTE
Classification of various patterns on axial map of placido based topography. Top A, round;
B, oval; C, superior steepening; D, inferior steepening; E, irregular; F, symmetric bow tie; G,
symmetric bow tie with skewed radial axes; H, asymmetric bow tie with inferior
steepening (AB/IS); I, asymmetric bow tie with superior steepening; J, asymmetric bow tie
with skewed radial axes (AB/SRAX

16. C L GUPTA EYE INSTITUTE
• K1 or Rf: Horizontal curvature power
of the cornea in the central 3 mm
circle expressed in diopters
• K2 or Rs: Vertical curvature power of
the cornea in the central 3 mm
expressed in diopters.
• Km: Mean curvature power of the
cornea in the central 3 mm
expressed in diopters.
• Rh: Horizontal curvature radius of
the central 3 mm expressed in mm.
• Rv: Vertical curvature radius of the
central 3 mm expressed in mm.
• Rm: Mean curvature radius of the
central 3 mm expressed in mm.
• Qs: “Quality specification” should be
displayed “OK”

17. C L GUPTA EYE INSTITUTE
Important figures:
• when taking the decision—that any anterior K readings
should not be more than 47D on the front sagittal curvature
map. Recently, with the availability of thin flap technology,
the power 49D became acceptable. More than 49D is risky
regardless of the patient’s refractive error.
• Corneal astigmatism on either surface should not be higher
than 6D; otherwise it is a risk factor.
• Against the rule astigmatism is considered suspicious.

18. C L GUPTA EYE INSTITUTE
ELEVATION MAPS
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19. C L GUPTA EYE INSTITUTE
Elevation Map
• The computer considers all points above the reference surface
as elevations, being displayed as positive values, and considers
all points below the reference surface as depressions, being
displayed as negative values (in microns)
• The elevation maps are more accurate than curvature maps in
evaluating both surfaces of the cornea. They are less affected
by tear film disturbance and use of contact lenses

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• The elevation values on the front
surface map should not exceed +12 μ.
• Values between +13 μ and +15 μ are
suspected,
• and any value > +15 μ is considered a
risk factor.
• The elevation values on the back
surface map should not exceed +17 μ.
• Values between +18 μ and +20 μ are
suspected, and
• Any value >+20 μ is considered a risk
factor.

21. C L GUPTA EYE INSTITUTE
Important considerations
• Be careful when any value of the central 4 mm of the elevation
maps is more than +15 μ for the anterior surface, and more
than +20 μ for the posterior surface.
• Be careful when the “back-front” difference is more than +5 μ
at the same point.
• Be careful when there is an isolated island on either surface

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CORNEAL THICKNESS MAP

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• Pachy apex: Corneal thickness at the
apex. The computer considers the apex as
the origin of the coordinates, X for the
horizontal and Y for the vertical
Therefore, zero is displayed in both
squares of pachy apex coordinates.
• Pupil center: Corneal thickness in the
pupil center. The Xand Y-coordinates
show the position of the pupil center from
the apex. The two coordinates differ
according to pupil medriasis or miosis,
because the pupil center is often shifted
superotemporally when dilated.
• Thinnest location: Thinnest point in the
cornea. It is the most important in the
decision procedure

24. C L GUPTA EYE INSTITUTE
• Cornea volume: studies are carried out to
realize the relaSome tionship between
cornea volume and ectatic changes.
• Chamber volume: Volume less than 100
mm3 should alert us to check the patient
for angle closure glaucoma.
• AC depth (Int.): Central anterior chamber
depth, measured from the inner surface of
corneal endothelium to the iris.
• It is important for phakic IOLs. It should
not be less than 2.8 mm to keep the corneal
endothelium intact.
• KPD: The average value of keratometric
power deviation. The normal value is less
than +0.75. When the value is more than
+1.5, it is abnormal indicating an abnormal
cornea
.

25. C L GUPTA EYE INSTITUTE
How to start reading Pentacam Refractive Map

26. C L GUPTA EYE INSTITUTE
Based on severity of curvature
• Mild - <45D in both meridian
• Moderate 45 – 52D in both meridian
• Severe - >52D in both meridian
• Advanced - >62D in both meridian
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