1. Advances for Characterizing and Understanding the Irregular Cornea
Renato Ambrósio Jr., MD, PhD

2. Financial Disclosure Allergan: B Alcon: B Moria: B Oculus: A, B
Reichert: B

3. Evolution in Corneal Imaging
KERATOMETRY
(Central Corneal Power) CORNEAL TOPOGRAPHY
(Corneal Surface Shape; Regularity)

4. Corneal Topography: Evolution from Keratometry
Anterior corneal evaluation: anterior surface has convex mirror properties
Reflection of virtual image whose size is determined by the radius of curvature
True elevation is NOT measured, but CALCULATED
Classic Keratometry (Kt): two orthogonal axes based on Helmholtz's assurances that the central cornea is a spherocylindrical surface
Keratoscopes: Qualitative evaluation
Computerized videokeratoscopy or Corneal Topography (S. Klyce, PhD ’s)

5. Corneal Topography for Screening Refractive Candidates
1% of candidates were diagnosed with corneal ectasia and advised not to have the surgery
These cases can have normal general eye exam and 20/20 or better BSCVA
Less than ½ of these cases have any sign of ectasia at slit lamp examination

6. Oculus Topometric Indices (8mm surface Curvature)

7. Oculus Topometric Indices (8mm surface Curvature)
Clinical Study: 226 Normals X 88 Keratoconus
KK Indices: 7% False Negatives: 93% Sensitivity
KK Indices: 13% False Positives: 87% Specificity
Clinical Study: 226 Normals X 88 Keratoconus
Average Q at 30º: Cut off: -0.33
Average Q at 30º : 79% Specificity and Specificity
Superior Q at 30º: Cut off: -0.56
Superior Q at 30º: 88.3% Specificity and 92% Specificity

8. Corneal Topography
Unquestionable improvement in Sensitivity to detect Ectasia
Problems related to “false keratoconus” due to irregular corneal surface and not ectasia
BUT it is NOT the most sensitive test to detect “earlier” or more sub-clinical cases

9. Asymmetric Keratoconus
Placido (Axial): Absolute Scale

10. Pachymetry: Clinical Relevance
Ultrasound (20 or 50 MHz) CCT
(Central Corneal Thickness): Gaussian Distribution in normal population
Central Thickness helps diagnosing ectatic disease (thinning)
Mann-Whitney U Test
P<0.0001
Cut off: 513µm
Sens: 85%
Spec: 87%
AUROC:0.925

11. Evolution in Corneal Imaging
KERATOMETRY
(Central Corneal Power) CORNEAL TOPOGRAPHY
(Corneal Shape; Regularity)
CORNEAL TOMOGRAPHY
3D Architecture (Pachymetry)

12. Pachymetry Map: CCT and TP
Indentification of the TRUE Thinnest Pont and its Location; Pachymetric Distribution

13. Thinnest Point performs statistically better than Central (apex)Thickness (N=226; KC=88)
Cut off: 503µm
Sens: 88.6%
Spec: 90%
AUROC: 0.945
Cut off: 513µm
Sens: 85%
Spec: 87%
AUROC: 0.925

14. Pentacam: Corneal Thickness Profile: CTSP & PTI average of the thickness in the points within maginary circles centered on the Thinnest Point with increasing diameters

15. Ambrósio’s Relational Thinnest (ART)
Cut-off
Sensitivity
Specificity
ART-Max
338.7
0.989
0.969
ART-Ave
426.4
0.943
0.978 TP
502
0.875
0.912
RPI Mid
1.15
0.932
RPI Max
1.51
0.947

16. Cut-Off for Ectasia Susceptibility
ART-Avg = 485 μm
ART-Max = 400 μm
Based on cases with very asymmetric keratoconus
Cases who developed ectasia after LASIK with no risk factors
Cases who progressed naturally to keratoconus

17. Elevation Tomography: Concept of Enhanced BFS (Belin)
Standard reference sphere- BFS
New reference shape- (enhanced BFS)- best fits to the peripheral corneal area excluding the central area with 4mm in diameter centered on the thinnest point
Michael W. Belin, MD
Standard-BFS
New-BFS pronounces the cone

18. Enhanced Elevation (Belin) will not change much in normal

19. Enhanced Elevation (Belin) will highlight ectasia

20. Corneal Characterization
ARCHITECTURE or GEOMETRICAL
CHARACTERIZATION (3D - TOMOGRAPHY)
BIOLOGICAL PROPERTIES OF
CORNEAL TISSUE
Cindy Roberts, Ph.D.
Corneal Wound Healing
Corneal Physical Properties
(Biomechanics)

21. Reichert ORA: First Clinical Instrument for Assessing Corneal Biomechanics

22. ORA Parameters CH: P1-P2 CRF: P1- (k* P2) IOPg: (P1 + P2)/2
IOPcc: K1*(P *P1) + K2

23. What is true about Corneal Hysteresis?
Reduced in Keratoconus and in Fuchs compared to normal (Luce, JCRS 2005)
Reduced after LASIK and Surface Ablation (Luce, JCRS 2005; Pepose, AJO 2006)
Primary open-angle glaucoma patients with diabetes have significantly higher CH values than those without diabetes (Castro, J Glaucoma 2009)
Negative Correlation with Age (Kotecha, et al., IOVS 2006)
No Change after Collagen Crosslinking (Goldich , Cornea 2009)

24. Need to Go Beyond Hysteresis
Biomechanical characteristics of the ectatic cornea.
Kerautret J, Colin J, Touboul D, Roberts C.
J Cataract Refract Surg Mar;34(3):510-3.

25. 2 Clinical Examples (different patients)
Normal Thin CCT: 503 µm; TP: 499 µm;
RPI-Mid:0.8; RPI-Max:1.14
ART-Mid:624 µm
ART-Max: 438 µm
Keratoconus
CCT: 545 µm; TP: 536 µm
RPI-Mid:1.66; RPI-Max:2.19
ART-Mid:322 µm
ART-Max: 244 µm

26. Normal Thin Cornea CCT: 503µm
Keratoconus:
CCT: 545 µm

27. Conclusions
Enhanced Screening increases both sensitivity and specificity
Current approach is based on Pentacam Tomography and ORA Biomechanics
Topogrphy (Placido) is still relevant!
Epithelial and stromal profile (Reinstein, VHF US and FD-OCT)
Other indices will come…
New biomechanical tests and models

28. Wavefront-Guided Ablation for Improving Vision after Previous Refractive Surgery
Mounir Khalifa, MD, PhD
Prof of Ophthalmology, Tanta University
Horus Vision Correction Center, Alexandria
Clear Vision Center, Cairo
Tanta Laser Center, Tanta
Egypt
I have the following financial interests or relationships to disclose:
WaveLight AG C

29. Diagnostic tools Slit lamp biomicroscopy Refractometry
Topography:* Anterior surface only.
*Anterior and posterior surfaces ( Orbscan)
Aberrometers
Pentacam: Anterior and posterior surfaces (Scheimpflug Imaging System)

30. 2) Irregular astigmatism 3) Increased ocular aberrations.
Many patients, who received LVC, RK, or PKP complain from lost lines of BCVA, haloes, glare, star bursting, and reduced contrast sensitivity.
Possible Problems in Management:
1) Difficult refraction
2) Irregular astigmatism
3) Increased ocular aberrations.
4) LASIK flap may give way at the RK scars
5) PRK is likely to result in corneal haze

31. Recommended Plan of Management
1) Surgical approache:
PRK with MMC or LASIK
2) Ablation pattern:
a) Wavefront – guided :
+ve Reliable WF map
b) Conventional ( Optimized/ F-CAT to improve spherical aberration)
-ve reliable WF map & reliable MR &regular cornea
c) Topography – guided:
-ve reliable WF map & reliable MR & irregular cornea; one stage
-ve reliable WF map & -ve reliable MR & irregular cornea; 2 stages

32. LASIK Advantages Disadvantages Fast visual rehabilitation
RK scars may give way during flap cutting or elevation
Intersection of cuts may induce new surface irregularities which leads to refractive errors and HOA’s.

33. LASIK vs PRK in RK Cases
A retrospective comparative study was done to evaluate the efficiency of wavefront guided ablation in correcting ocular aberrations in RK cases. All the included eyes of 2 groups had reliable WF mapping using Wave Scan, and WF guided ablation using Visx Star S4. Gp A included LASIK using Moria M2 for 130 microns flap making, and Gp B included PRK with MMC cases ( 0.02% for sec.).
Mean follow up time : 3.5 months(1-8 ).

34. Demographic Data Group A ( LASIK Gp)
21 Eyes (14 patients: 9 females, 5 male)
Previous RK ( 8 incisions or less):
13 ys (10 ys – 19 ys)
Age: 41.5 ys ( ys)
Mean of manifest sphere -3.73D(±3.57) and cylinder D (±2.1)
Group B ( PRK Gp)
18 Eyes (11 patients: 7 females, 4 males)
Previous RK ( 8 incisons or more):
7 ys (6 ys – 9 ys)
Age: 32.5 ys (25 – 36 ys)
Mean of manifest sphere -2.92D
(±2.87) and cylinder -1.9 D (±2.4)

35. Efficacy and Safety Indices*
No significant difference between both groups in efficacy.
*Significant difference ( p<0.05) in favour of LASIK in safety, may be due to 12% haze ( 2 eyes) with PRK.

36. Mean HOA RMS TotalHOA Coma Trefoil Sph. Aber.
Significant improvement of Total HOA’S, coma, trefoil, and spherical aberration in both groups. Spherical aberration showed shift to negative side ( prolating the oblate cornea).
Trefoil reduction was significant with PRK compared to LASIK (P<0.01)

37. Pre and postoperative HOA’s after wavefront-guided treatment of RK case.

38. Wavefront-Guided Ablation to Correct Ocular Aberrations After LASIK,RK,or PKP
Prof.Dr. MOUNIR KHALIFA
Tanta University
HORUS VISION CORRECTION CENTER
ALEXANDRIA,EGYPT

39. This prospective study was done to evaluate the efficiency of wavefront guided LASIK in correcting ocular aberrations in LVC, RK, and PKP cases.

40. Preoperative Mean Refraction Group A
Sph Cyl.
Manifest D(±0.35) D(±0.71)
Cycloplegic D (±0.21) D (±0.63)
Wave Front D (±0.42) D (±0.83)

41. Preoperative Mean Refraction Group B
Sph Cyl.
Manifest D(±2.57) D (±2.1)
Cycloplegic D (±1.89) D (±1.96)
Wave Front D (±1.87) D (±1.77)

42. Preoperative Refraction Group C
Sph Cyl.
Manifest D D X 15
Cycloplegic D D X 12
Wave Front D D X 19

43. All the eyes of the 3 groups received WF mapping using Wave Scan, and WF guided LASIK using Visx Star S4. In gp.A; 8 eyes with cutting a new flap (previous LASIK >2 years), and 44 eyes with flap left.
Mean follow up time after WF: 3.5 months(1-8 ).

44. Group A : PSF testing in LASIK patients before and after wavefront

45. Group B : PSF testing in RK patients before and after wavefront

46. Group C : PSF testing in PKP patient before and after wavefront
Note : The Corneal Scar is at the medperiphery
of the ablation bed

47. Note : The Corneal Scar is at the medperiphery
Group C : Acuity difference map in PKP patient before and after wavefront
Note : The Corneal Scar is at the medperiphery
of the ablation bed
Note the corrected Coma

48. Topography- Guided Ablation

49. -ve WF& reliable MR & irregular cornea ( 0ne stage) ( Visx Custom Cap)
37 Ys. Lady
RK on 1997
Pre-Custom Cap:
MR X 20
UCVA: 20/80
BCVA: 20/40
Post-Custom Cap:
MR X 30
UCVA 20/30
BCVA 20/20

50. Topography-guided ablation (Visx Custom Cap)
Pre-op
Post-op

51. Allegro
topolyzero
T-CAT
Allegro
oculyzero
Oculink
Allegretto Eye-Q

52. Conclusions
Wavefront guided ablation proved to be a useful tool to correct the unsatisfied previous corneal refractive surgery patients.
Significant correction of the disturbing HOA’s can result in a significant improvement of visual performance and patient satisfaction.

53. Conclusions
Previously LASIKed patients rendered the most satisfying results using this modality.
Previous RK and PKP patients were very satisfied, in spite of the fact that corneal scars still limiting the ablation depth and the end visual performance.

54. Recommendation for managing previously operated cornea with refractive errors
Regular cornea + clear pupillary area + BSCVA 6/6 → reliable wavefront map → Wavefront-guided PRK + MMC or LASIK (if incisions <=6)
Regular cornea + BSCVA < 6/6 + unreliable wavefront map + a reliable MR→
Optimized PRK + MMC or LASIK
Irregular cornea + reliable refraction → Topography-guided ablation (one stage)
Irregular cornea + -ve reliable MR →
Topography-guided ablation ( 2 stages)

55. Grossly irregular cornea + unreliable topography map → no refractive surgery (PKP may be the only solution)