This document describes a retrospective study that aimed to create corneal graft tissues with parallel faces using excimer laser and microkeratome. 15 donor corneas were used. The corneas were first regularized to a uniform 550um thickness using excimer laser ablation guided by optical tomography. Then a 400um thick stromal flap was cut using a microkeratome, leaving a 150um thick endothelial lenticule. Histological analysis found the lenticules had the intended thicknesses. The study concluded the procedure successfully created graft tissues with parallel faces and uniform thicknesses.

1. DSAEK GRAFTS WITH PARALLEL
FACES : IS THE FUTURE?
Luca Avoni
IV ivis suite user meeting
Innsbruck, 6 July 2013

2. Grafts with parallel faces
Purpose:
 avoid hyperopic shifts post DSAEK

obtain a thin graft with a uniform
thickness from one side to the other in
order to reduce the incidence of postoperative detachment

3. Retrospective observational study
15 donor corneas not suitable for transplantation, for
morphological abnormalities or donor is not suitable for
medical history, according to the following protocol :
1.
Corneal pachymetry with corneal optical tomography
2.
Setting pachymetry to a constant thickness of 550 um with
excimer laser
3.
Acquisition of corneal pachymetry
4.
Cut of stromal flap with microkeratome for a thickness of 400 um
5.
Acquisition of corneal pachymetry
6.
Histological analysis of the cross section of stromal and
endothelial flap

4. Retrospective observational
study: Instruments
1. Optical
tomography
2. Software for customized ablation.
3. Excimer laser.
4. Microkeratome
5. Ophthalmic microscope

5. Retrospective observational study
Software for the regularization of the corneal stroma to a
desired thickness by a customized ablation with excimer
laser

6. OBJECTIVES:



Realization of stromal lenticule with uniform
thickness of 550 μ by a customized ablation with
excimer laser
Realization of endothelial lenticule with uniform
thickness of 150 µ
To evaluate the safety and effectiveness of this
procedure

7. ITER
Step 1
Evaluation of the cornea by microscope according to the
traditional criteria of the EYE Bank (cell density, margins,
morphology and mortality)
Morphological evaluation of corneal endothelium
Density
Mortality
Cell/mm2
%
N =13
N =13
Mean
σ
Interval
Morphological evaluation of corneal
endothelium
Margins
N=13
Homogenous
1461.538
3.53%
CI 95%
94.23
1000 ÷1900
0.07
0÷30
Partially Homogenous
CI 95%
Irregular
CI 95%
Morphological evaluation of corneal
endothelium
Morphology
N=13
Polymorphism
Moderate
7/13
46.67%
(19.22 74.87 )
6/13
Polymorphism
CI 95%
53.33%
(25.13 80.78 )
CI 95%
3/13
26.67%
(5.04 53.81 )
9/13
66.67%
( 38.57 90.91)
1/13
13.33 %
( 0.19 36.03)

8. ITER
Step 2
Optical Corneal tomography with and study of the pachymetry
map with high repeatability
Optical pachimetry examination of the cornea
Min Pachimetry [ µ ]
Max Pachimetry [ µ ]
N=13
N=13
Mean
σ
Interval
612.08
13.17
568 ÷ 680
697,08
21.78
629 ÷ 767

9. ITER
STEP 3
Set up a Customized ablation to regularize the
stroma to a constant residual thickness of 550
microns

10. ITER
STEP 4
Customized ablation with laser in order to obtain a regular stroma
lenticule of 550 microns thickness

11. ITER
STEP 5
Optical corneal tomography to assess the pachymetry
Optical Pachimetry after the laser regularization of the Cornea
Pachimetry [ µ ]
N=13
Mean
σ
CI 95%
Left point
549.77
4.78
547.17 552.37
Center point
561.61
5.62
558.56 564,67
Right point
573,46
7,21
569.54 577.38
Target
550 ±25 µ

12. ITER
STEP 6
Cut of the stromal flap with a microkeratome 400 micron-head to obtain a
endothelial lenticule of 150 micron thickness.

13. ITER
STEP 7
Pachymetry of endothelial lenticule. Thickness of stromal lenticule
is obtain by the difference between the pre-cut pachymetry and
post-ablation pachymetry.
Optical Pachimetry after the 400 microns cut with microcheratomy of the endothelium lenticule
Target
Pachimetry[ µ ]
N=13
Pachimetry of stromal lenticule after the 400 microns cut
(Difference between optical corneal pachimetry and optical endothelium optical
pachimetry )
Target
Pachimetry [ µ ]
N=13
150 ±50 µ
Mean
σ
CI
95%
Left point
142.1
Center point
156.05
Right point
170
1.82
141.11 143.09
3.202
154.31 157.79
5.56
166.98 173.02
Mean
Left point
549.77 – 142.1 =
407.67
Center point
561.61 - 156.05
= 405, 56
Right point
573,46 - 156.05 =
417,41
400 ± 25 µ

14. ITER
STEP 8
Evaluation of the endothelial lenticule by microscope according to the
traditional criteria of the EYE Bank (cell density, margins, morphology and
mortality)
Morphological evaluation of corneal endothelium
Density [Cell/mm2]
N =13
Mean
σ
Delta (Mean
pre – Mean
post)
Target
1353.85
122.69
Reduction 107.69
7.37 %
Reduction < 10%
Mortality [ % ]
N =13
16.68%
0.48
Increase
13.15 %
Not Defined
Morphological evaluation of corneal endothelium
Delta (Mean pre – Mean post)
Morphology
N=13
Polymorphic
CI 95%
Moderate
Polymorphic
CI 95%
7/13
46.67%
(19.22 74.87 )
6/13
53.33%
(25.13 80.78 )
No change
No change
Morphological evaluation of corneal endothelium
Delta (Mean pre – Mean post)
Margins
N=13
Homogenous
CI 95%
Partially
Homogenous
CI 95%
Irregular
CI 95%
3/13
26.67%
(5.04 53.81 )
9/13
66.67%
( 38.57 90.91)
1/13
13.33 %
( 0.19 36.03)
No change
No change
No change

15. ITER
STEP 9
Histological evaluation of endothelial lenticule (thickness and morphology)
and the stromal lenticule (thickness and morphology.)
Histological Thickness evaluated at 4 months after procedure execution
Endothelium lenticule [ µ ]
Stromal lenticule [ µ ]
N=13
N=13
Target
Measured value
Mean
σ
CI 95%
Left point
139.4
8.80
134.62
144.18
Center point
161.7
14.89
153.60
169.80
Right point
204
26.52
189.58
218.42
150 ±50 µ
Measured value
Center
Left point
point
508,7
522,7
23.67
25.25
495.83
508.97
521,57
536,43
Target
Right
point
540,1
18.28
530.16
550.04
400 ±25 µ

16. CONCLUSIONS
This clinical study showed that the
procedure of regularization of the
cornea thickness with the excimer
laser IRES is effective and safe as
shown in the following endpoints.

17. Histological evaluation




Paraffin embedding
Staining with
hematoxylin and
eosin
Scanner digital slides
Measurement with
morphometro

Fate clic per
modificare il formato
del testo della
struttura
−
Secondo livello
struttura

Terzo livello
struttura
− Quarto livello
struttura

Quinto

18. Endothelial and stromal
lenticules

19. CONCLUSIONS
Endpoint 1 –Stromal regularization:
The pachymetry after the customized
ablation of the stromal lenticule has
shown that the average thickness of
550 ± 25 micron has been achieved
successfully

20. CONCLUSIONS
Endpoint 2 – Endothelial lenticule:
The pachymetry after the microkeratome cut of the
endothelial lenticule has shown that the average thickness
of 150 ± 50 micron has been achieved successfully
In addition to optical pachymetry, histological analysis,
performed at the Pathology Department of Ospedale
Maggiore-Bologna in October 2012, provided a further
confirmation of the results.

21. CONCLUSIONS
Endpoint 3 – Stromal Lenticule:
The difference between the pachymetry performed before
and after the customized ablation of the stromal lenticule
has shown that the average thickness of 400 ± 50 micron
has been achieved successfully.
The histological analysis has shown in this last case a
stromal lenticule of 508,7 μm thickness of the left side,
522,7 μm of the center and 540,1 μm of the right side.
Probably, this inconsistency is due to the delay of more
than four months from the date of execution of the
procedure and the date of execution of the histological

22. Thank you