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 www.ophtalmique.ch

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 ►► ►► ►►

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.

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

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*

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

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

K-max and repeatability

Repeatability vs disease severity

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

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