1. Precision of the Pentacam HR device in patients with keratoconus: clinical implications
Dr Ciara Bergin, PhD
Dr Ivo Guber, Dr Kate Hashemi, Dr Francois Majo
The authors have no financial interests to disclose

2. Pentacam Topographic Images:
A series of 25 images of the anterior segment are taken using a Scheimflug rotating camera
These images are used to create a 3D grid of the surfaces in the anterior segment
This grid is used to estimate parmeters such as corneal curvature and Pachmetry
The device provides heat maps of height maps of each surfaced derived to highlight surfaces with deviations from smooth surfaces ►► ►► ►►

3. Clinical uses for the Pentacam device
Do you use the pentacam device to monitor keratoconus?
What parameters do you monitor?
How do you take the decision to do CXL?
Official guideline is that if the difference in K-max is greater than 1D (or three times the limits of repeatability)
► Keratoconus progression has occurred.

4. Repeatability of Pentacam HR device in normal subjects:
Investigative Ophthalmology & Visual Science, September 2011, Vol. 52, No. 10

5. Repeatability of the Pentacam HR device in Keratoconus patients
Ophthalmology 2014, accepted for publication:
Reduced precision of the Pentacam HR ® in eyes
with mild to moderate keratoconus
Kattayoon Hashemi, Ivo Guber, Ciara Bergin*, François Majo*

6. Retrospective review ►Representive of clinical environment
All the data from the Pentacam HR device was exported
Pairs of images
taken on the same patient
the same day,
within the same sitting
Only images with over 85% of the data validated
248 pairs of image in 248 eyes of 197 keratoconus eyes met the inclusion criteria
Corneal curvature ranges from 45D to 72D
►Representive of clinical environment
► Large cohort
► Large range of corneal curvature values

7. Patient Demographics All TKC 1 TKC 2 TKC 3 TKC 4 No. eyes 248 27 90
101 30
Age, years
35.3
36.3
36.1
34.8
33.8
K-max, D
55.3
47.7
52.6
57.8
61.7
Km front, D
47.5
44.0
46.3
48.8
50.0
Pachy Apex
476
510
489
464
448
Pachy Min
458
492
475
445
419
BAD D
8.8
4.4
6.6
10.5
13.9

8. K-max and repeatability

9. Repeatability vs disease severity

10. Summary table repeatability
TKC 1
TKC 2
TKC 3
TKC4
Number of eyes 27 90
101 30
Anterior
K1, D
0.48
0.59
0.97
1.91
K2, D
0.47
0.58
1.44
Astigmatism
1.51
3.78
4.54
4.23
Asphericity
0.12
0.14
0.31
0.39
Elevation, μm
0.03
0.09
0.19
Posterior
0.36
0.57
0.17
0.22
0.37
0.28
0.25
0.44
0.66
0.07
0.08
0.15
0.27
Summary data
Maximum corneal curvature
0.7
1.3
1.78
2.4
Central corneal thickness
12.69
12.33
16.55
24.53
Thinnest corneal thickness
11.9
12.19
19.37
29.69
BAD D
1.06 1
2.23
3.73

11. Conclusions
Repeatability limits become wider with more advanced disease stage/ higher corneal curvature
The average of repeated measures can reduce noise in line with normative limits
The more advanced the disease the less reliable the measures taken with the Pentacam device, limiting clinical usefulness in these eyes