1. Evaluation of Long-Term Keratoconus Progression Using Scanning-Slit Topography First Author: David Galarreta, MD Contributing Authors: Nestor Cortes, MD, Fernando Sanchez- Mannarelli, MD, Alejandro Portero, MD, Belen Carrasco, MD, Jesus Merayo-Lloves, MD Hospital Clinico Universitario Valladolid (Spain) IOBA. Universidad de Valladolid (Spain) The authors have no financial interest in the subject matter of this poster VI World Cornea Congress, Boston 7-9th April 2010

2. Purpose  To evaluate the long term changes and predictor factors of evolution in keratoconus using corneal elevation topography parameters measured by scanning-slit topography system

3. Methods  Retrospective study  Ninety three eyes from 52 keratoconic patients were evaluated by scanning-slit topography system.  Diagnosed by slit lamp findings and by corneal topography  Minimum follow up of 3 years was required with topography examinations at least twice.  Tenets of the Declaration of Helsinki were followed and local medical ethics comitee approved the study.

4. Methods  Age at onset and at analysis  Sex  Quantitative topographic parameters analyzed  Keratoconus topographical pattern  Minimum mean simulated keratometry (minSimK)  Maximum mean simulated keratometry (maxSimK)  Maximum keratometry reading (Kmax)  Posterior and anterior best-fit sphere (BFS)  Posterior/Anterior BFS ratio (P/A BFS)  Thinnest and central pachymetry point

5. Results  Age 26,46 years  9,51 (SD) at onset (diagnosis). 39,12 years  10,4 (SD) at analysis.  Sex: 53,84% male  Follow up: 3,91 y1,94 (SD). Topographical patternsCasesPercentage Asymmetric bow tie with skewed radial axis (ABT/SRAX) 2425,8% Asimetric bow tie inferior77,5% Asimetric bow tie superior66,5% Central nipple99,7% Central oval11,1% Inferior steepening3335,5% Irregular11,1% Pellucid like88,6% Simmetric bow tie22,2% Simmetric bow tie with skewed radial axis22,2% Total93100%

6. Results  Whole keratoconus group (n=93) MaxSimK: 49,63D to 50,40D (p=0,006) MinSimK: 44,94D to 45,94D (p<0,001)  ABT/SRAX pattern group (n=24) Posterior BFS: 54,06D to 54,62D (p=0,042) MaxSimK:48,55D to 49,47D (p=0,01) MinSimK: 43,67 to 45D (p=0,01) Kmax: 51,66D to 52,46D (p=0,03)  Inferior steeping pattern group (n=33) Anterior BFS: 43,87D to 44,42D (p=0,004) Posterior BFS: 54,59D to 55,41D (p=0,006) MinSimK: 45,12D to 46,14D (p=0,017) Kmax: 53,24D to 54,99D (p=0,006)  No changes detected in other patterns (low n bias)

7. Results  Age at onset (percentile 50th= 31,26 years) Younger patients (<31,26 years)  MaxSimK: 50,05D to 51,23D (p=0,022)  MinSimK: 44,83D to 46,48D (p<0,001)  Posterior BFS: 54,86D to 55,70D (p=0,002)  Kmax: 53,52D to 55,45D (p<0,001) No changes detected in older patients (p>0,05)

8. Results  Kmax groups <47D  MaxSimK: 45,16D to 46,35D (p=0,04) 47D-50D  Posterior BFS: 54,23D to 55,01D (p=0,011)  MinSimK: 43,78D to 44,78D (p=0,028) 50D-53D  MaxSimK: 51,15D to 52,22D (p=0,025)  MinSimK: 46 to 47,56D (p=0,012) >53D: Showed no pregression Nor difference in age at onset nor at follow up

9. Results  Thinnest pachymetry (p50th=432 microns) Thinner pachymetry (<432 microns)  MaxSimK: 51,37D to 52,06D (p=0,02)  MinSimK: 46,6D to 47,9D (p<0,001) Thicker pachymetry (>433 microns)  Anterior BFS: 43,4D to 43,87D (p<0,001)  Posterior BFS: 52,82D to 53,66D (p<0,001)  Central pachymetry: 501 microns to 493 microns (p=0,016)  Thinnest pachymetry: 480,6 microns to 470,7 microns (p=0,019)  MaxSimK 47,88D to 48,78D (p=0,021)

10. Results  Posterior BFS (p50th=54,5D) <54,5D  Posterior BFS: 52,22D to 52,74D (p=0,013)  Central Pachymetry: 481 microns to 476 microns (p=0,04)  MaxSimK: 46,9D to 47,83D (p=0,027)  MinSimK: 43D to 43,69D (p=0,038) >54,5D  MinSimK 46,96D to 48,28D (p<0,001)

11. Results  Posterior/Anterior BFS (p50th=1,24) <1,24  Posterior BFS: 52,89D to 53,37D (p=0,002)  Central Pachymetry: 481 microns to 473 microns (p=0,022)  Thinnest pachymetry: 460 microns to 451 microns (p=0,021)  MaxSimK: 48D to 48,8D (p=0,04)  Posterior/anterior BFS: 1,20 to 1,21 (p=0,03) >1,24  MinSimK 46,1D to 47,39D (p<0,001)

12. Conclusions  Younger age at onset increased the probability of progression of topographical parameters in keratoconus.  Topographical patterns of keratoconus (Asymmetric bow tie with skewed radial axis and inferior steepeninig) provide information about a higher risk of progression.  Very high K readings, thinner corneas, high power in posterior BFS,and high posterior/anterior BFS showed less progression of keratoconus topographical parameters. These variables normally correlates with an advanced keratoconus.  Low K readings, thicker corneas, low power in posterior BFS, and low posterior/anterior BFS can potentially showed a wide margin for advance in keratoconus