1. Laser assisted Corneal normalization in Ectatic disorders
D. Alexopoulos MD,DO
LASEREYE PC

2. The presenter has no financial or other interest in the equipment or methods presented

3. Laser and CXL PTK combined with CXL Topoguided PRK combined with CXL
CWFG Transepithelial PRK combined with CXL

4. PTK and CXL The idea is that the epithelium is thinner over the cone
Fulll thickness ablation of the epithelium should partially ablate some corneal stroma in the steepest area
Moderate results are shown ,with a variable but in some cases significant flattening effect

5. Topo guided PRK and CXL
Introduced by J. Kanellopoulos (Athens Protocol)
Uses a specific Excimer Laser platform that follows a corneal topography by the Pentacam (Oculus)
The depth of stromal ablation is limited to 50μ with an OZ of 5,5 to 6mm.
Accelerated CXL follows
Very good results are shown in most cases with marked improvement in keratometric properties

6. Limiting factors of the Athens protocol
The inability to control the static and dynamic torsion of the eye, during ablation leads to lack of reliable and precise registration of the planed ablation on the cornea
The assumption of Pentacam of the corneal surface shape (best fit sphere –maps change with fitting)
The compensatory role of the corneal epithelium is not used to our benefit
The flying spot size may be too large (0,78) mm for HOA treatment
Have all led to good but variable results

7. CWFG Trans PRK and Accelerated CXL
Performed since 2013
Utilizes a particular Excimer Laser platform (Amaris –Swind) ,followed by accelerated CXL (30mW/cm2)
Concentrates on removing mainly the HOA of the ectatic cornea
Uses a large 6,5 to 7mm OZ and a max. stromal ablation depth of 60μ
Accelerated CXL follows
Excellent and consistent results in all forms of KCN

8. Data aquisition
The Keratron (Optikon) corneal topography uses the arc step algorithm , calculating both curvature and height corneal maps ,independently from each other
This arc step calculated Corneal topography is decomposed into Zernike polynomial up to the 7th order.
Users can select individual Zernike components and the pupil size and can move off-pupil-centre on the resulting OPD map

9. EXCIMER TREATMENT
The Amaris plarform uses a static & dynamic torsion control up to 12,5 degrees) and has a 6D eye tracker Also the dual fluence ,0,54mm flying spot of the platform, coupled with the 750 or 1050HZ operation frequency and the fast and reliable eye tracker are ideal for higher order aberrations treatment

10. CXL treatment Accelerated CXL consists of
10’ Dextrane free Riboflaving soaking
8’ UV “on-off” irradiation 30mW/cm2 , 9mm diam.
Our observations and published studies show a max. of μ of stromal crosslinking

11. Advantages of Corneal Wavefront maps
1. Show the cornea in terms of its optics
2. Allow analysis and selection of individual aberrations
3. Allow simulations of vision, PSF, MTF
4. Allow comparison with aberrometers

12. Why not just topo guided treatment ?
The topographic astigmatism (as presented by Placcido or Scheimphlung ) “contains” a variable amount of coma
The commonly observed difference between the topographic and topographic astigmatism is ,at least partially, due to coma.
Spherical aberration influences the spherical equivalent of the refraction (i.e. + SA refracts as hyperopia)
Sph. Aber. (C4) increases exponentially with pupil diameter . This cannot be addressed with topoguided

13. Approach in detail Multiple topographic images with the Keratron Scout
Selection of the best topographies
Conversion of topography to HOA (Zernike polynomials)
Digital transfer of the above and the eye image to the Amaris hardware
Evaluation of the HOA (Zernike polynomials pyramid)
Selection of the|” significant”HOA to be treated
Estimation of the desired ablation depth (any, but max. 90μ in KCN)
Torsion control (max 3 degr.off)
Treatment with continuous torsional control

14. Tips No need for all HOA to be treated
Only SA(C3) and Coma (C4) are practically important
Coma treatment alone addresses a variable but significant amount of astigmatism
Reducing the spherical component of the ablation doesn’t always minimize the ablation depth. Experiment on site!
The refractive result varies but there is always a reduction of astigmatism
We don’t aim towards full correction of the astigmatism but rather normalization of it

15. Case examples

16. KCN

18. KCN corneal wavefront

19. KCN Treatment plan

20. HOA selection for treatment

21. KCN topo change

22. Pre to post op topography difference compared to pre op CWF

23. KCN treatment refractive data
Pre op /-3.50 x (SE ) 6/10
Post op /-1.50 x 45 ( SE -4.50) 10/10+2

24. Peripheral cone/pellucid corneal wavefront

25. Peripheral cone/pellucid treatment plan

26. Peripheral cone/pellucid

27. Refractive data Pre op Post op pl/- 5.00 x 90 9/10-

28. Coma only treatment plan

29. Coma only treatment

30. Coma only treatment

31. Refractive data Pre op -1.50/-1.50 x 160 4/10+ Post op
pl/-1.25 X /10 -

32. Series of 42KCN patients 3,5 yrs follow up

33. Tips No need for all HOA to be treated
Only SA(C3) and Coma (C4) are practically important
Coma treatment alone addresses a variable but significant amount of astigmatism
Reducing the spherical component of the ablation doesn’t always minimize the ablation depth. Experiment on site!
The refractive result varies but there is always a reduction of astigmatism
We don’t aim towards full correction of the astigmatism but rather normalization of it

34. Limitations The cornea must be optically clear (no hydrops ,scars)
The RSD must be at least 340μ (thinnest point)

35. CONCLUSIONS
CWFG Trans epithelial PRK combined with accelerated CXL is probably the most effective means for reshaping the keratoconic cornea No reccurence of KCN has been seen so far No significant corneal haze is observed All our patients can now wear soft CL or glasses with very good vision