Lecture about Ferrara Ring New Nomogram by Dr. Paulo Ferrara on January 23-24, 2015 at Le Meridien Jeddah Madina Road, Jeddah, Kingdom of Saudi Arabia

1. Ferrara Ring
New Nomogram
PAULO FERRARA, MD, PHD
Paulo Ferrara Eye Clinic
Ferrara Ophthalmics
Belo Horizonte – MG - Brasil

2. Declaration of Conflict of Interest
•Ferrara Ophthalmics
•Ferrara e Hijos
•AJL
•Intacs

3. SELECTION OF THE RING BASED ON
CORNEAL ASPHERICITY

4. Corneal Eccentricity (E-value)
Define the shape of the cornea (conic section)
(Q= - e2)
Behavior of the Asphericity
Healthy and ectasic cornea

5. • Corneal Asphericity (Q) – shape of the
cornea;
• Oblate …………………….Prolate;
• “Normal”: lightly prolate
• Keratoconus: hiperprolate cornea;
• Normal Value of Q: - 0.231
Asphericity
1. Yebra-Pimentel E, González-Méijome JM, Cervino A, et al. Asfericidad corneal en una
poblácion de adultos jóvenes. Implicaciones clínicas. Arch Soc Esp Oftalmol 2004: 79:385-392

6. Spherical Surface (Q = 0)
Several focal points (More light bean refracted at the
periphery than in the center)
Behavior of the Asphericity
Healthy and ectasic cornea
SA = +0.30 µm

7. Behavior of the Asphericity
Healthy and ectasic cornea
Prolate Surface (Q < 0)
Single focal point (reduction of spherical aberration)
e2 > 0
SA ≈ 0.0 µm

8. Behavior of the Asphericity
Healthy and ectasic cornea
Oblate surface (Q > 0)
Many focal points (Increase in spherical aberration)
e2 < 0
SA > 0.30 µm

9. •High reproducibility between the same devices
but poor reproducibility between different devices
!
•Different topographers can provide different
values in the same patient. (each unit has its own
reference point)
Asphericity

10. Retrospective Study
165 eyes operated between January and July of 2013. (Dr. Paulo Ferrara Eye Clinic)
Groups (keratoconus grade*)
Group I – Grade I keratoconus (Km < 48 D)
Group II – Grade II keratoconus (48 < Km < 52 D)
Group III – Grade III keratoconus (52 < Km < 58 D)
Group IV – Grade IV keratoconus (Km > 59 D
Evaluation of SimK. Maximun keratometry and corneal asphericity at 20º, 25º, 30, 35º e 40º.
(Pentacam)
Behavior of the Asphericity
Healthy and ectasic cornea
*Ferrara-Amsler

11. Results
Behavior of the Asphericity
Healthy and ectasic cornea
Mean corneal asphericity
n = 38 EYES
-0.60
-0.50
-0.40
-0.30
-0.20
-0.10
0.00
20 25 30 35 40
Normal Corneas

12. Results
Behavior of the Asphericity
Healthy and ectasic cornea
Mean corneal asphericity
Km < 48 D
n = 54 EYES
-0.63
-0.61
-0.59
-0.57
-0.55
-0.53
-0.51
-0.49
-0.47
-0.45
20 25 30 35 40
KCN 1
KCN 1

13. Results
Behavior of the Asphericity
Healthy and ectasic cornea
Mean corneal asphericity
48 < Km < 52 D
n = 43 EYES
-1.20
-1.10
-1.00
-0.90
-0.80
-0.70
-0.60
20 25 30 35 40
KCN 2
KCN 2

14. Results
Behavior of the Asphericity
Healthy and ectasic cornea
Mean corneal asphericity
52 < Km < 58 D
n = 38 EYES
-1.55
-1.45
-1.35
-1.25
-1.15
-1.05
-0.95
-0.85
20 25 30 35 40
KCN 3
KCN 3

15. Results
Behavior of the Asphericity
Healthy and ectasic cornea
Mean corneal asphericity
Km > 58 D
n = 7 EYES
-1.80
-1.70
-1.60
-1.50
-1.40
-1.30
-1.20
-1.10
-1.00
20 25 30 35 40
KCN 4
KCN 4

16. Results
Behavior of the Asphericity
Healthy and ectasic cornea
Asphericity: Healthy vs ectasic cornea
-1.80
-1.60
-1.40
-1.20
-1.00
-0.80
-0.60
-0.40
20 25 30 35 40
Corneas Normais
KCN 1
KCN 2
KCN 3
KCN 4

17. CLINICAL CASE
R.S.C. female, 29 y.o.

18. CLINICAL CASE
-0.9
-0.8
-0.7
-0.6
-0.5
-0.4
-0.3
-0.2
-0.1
0
20º 25º 30º 35º 40º

19. CLINICAL CASE
R.M.B., male, 26 y.o..
Inferior keratoconus

20. CLINICAL CASE
-0.25
-0.2
-0.15
-0.1
-0.05
0
0.05
0.1
20º 25º 30º 35º 40º
Inferior keratoconus

21. CLINICAL CASE
R.S.O.C., female, 17 y.o.

22. CLINICAL CASE
-2.15
-2.05
-1.95
-1.85
-1.75
-1.65
-1.55
20º 25º 30º 35º 40º
RSOC
RSOC

23. Selection of the segment based on corneal
asphericity

24. GENERAL RULES FOR RING SELECTION
FERRARA RING NOMOGRAM
IT MUST BE DETERMINED:
1. The corneal asphericity (Q):
The selected ring for implantation may induce asphericity changes with a
final result close to “normal” values (- 0.23 ± 0.08)

25. GENERAL RULES FOR RING SELECTION
FERRARA RING NOMOGRAM
IT MUST BE DETERMINED:
2. The pachymetry at the corneal steepest axis and probable ring track
(5 mm optical zone)
Incision (80% depth):
1 segment: at 900 axis – the tip of the ring at the steepest axis
2 segments: at the steepest axis

26. Keratoconus (KC) Phenotypes
Central KC:
Hiperprolate (nipple)
High regular astigmatism (bow-tie)
Paracentral KC (oval)
Morphological Classification
KC Classification for ICRS

27. Other ectasias Phenotypes
Pellucid Marginal degeneration (DMP)
Pelucid “Like”
Morphological Classification
KC Classification for ICRS

28. In order to choose the proper segment or pair of segments one have to define
. The thinnest point of the cornea in the ring track (5.0 MM OPTICAL ZONE)
. The ring thickness cannot exceed half thickness of the cornea in its path ,
. Check the Q value and find in the graph which segment or pair of segments is
appropriate
. Check konus type to decide the arch lengh
REMEMBER
.The incision MUST be 80% of the cornea thickness at the site of the incision
. If one segment the incision can be placed at 90 meridien and the tip of the ring
at the steepest axis
.If two segments the incision is placed at the steepest meridien
NOMOGRAM

29. Q variation according to the ring thickness
Q

30. Km variation according to the ring thickness
Diopters

31. The segment or pair of segments
SHOULD not turn the expected
postoperative cornea asphericity
(Q) significantly above -0.23.
If this happens so it is advisable
to choose a pair of segments that
fits this condition even if the
achieved KERATOMETRIC
correction is smaller
than the desired one.
AVOID
POSTOPERATIVE OBLATE
CORNEAS !
Q (asphericity) =
Quality of vision

32. CLINICAL CASE
CDVA OD post op: + 0,50 - 1,00 x 95º
02/02/2012
17/01/2014
CDVA OD pre op: plano - 4,50 x 90º 20/40

33. CLINICAL CASE
Pre Post op
Behavior of corneal asphericity
pre and post Ferrara ring implantation
-2.1
-1.9
-1.7
-1.5
-1.3
-1.1
-0.9
-0.7
-0.5
-0.3
-0.1
20º 25º 30º 35º 40º
Pre op
Pos op

34. CLINICAL CASE
CDVA LE post op: + 0,50 // -1,25 x
125º 20/30
02/02/2012
17/01/2014
CDVA LE pre op: +3,00 // -5,00 x
90º 20/70 +

35. CLINICAL CASE
Pre op Post op
-2.1
-1.9
-1.7
-1.5
-1.3
-1.1
-0.9
-0.7
-0.5
-0.3
-0.1
20º 25º 30º 35º 40º
Pre op
Pos op
Behavior of corneal asphericity
pre and post Ferrara ring implantation

36. VIII . CASOS CLÍNICOS
20/200 -6.00-2.50x10
SURGICAL PLANNING ?
PREOP
POSTOP
20/40 pl-5.00 x50
AF 150/160
AF 250/160

37. VIII . CASOS CLÍNICOS
20/200
SURGICAL PLANNING ?
PREOP
POSTOP
20/40 -2.50-1.50x45
AF 200/160

38. VIII . CASOS CLÍNICOS
Nipple
20/60 -8.50-1.50x140
SURGICAL PLANNING ?
PREOP
POSTOP
20/40 - 0.50-1.50x40
AF 250/210

39. VIII . CASOS CLÍNICOS
< 20/400
SURGICAL PLANNING ?
PREOP
POSTOP
20/60 -5,50 -2,00 x 105
AF 200/140
AF 250/140

40. VIII . CASOS CLÍNICOS
20/400 +3.00-6.00x85
Cataract + PMD
SURGICAL PLANNING ?
PREOP
POSTOP
20/30 +0.50-3.00x85
AF 150/140
3 mo después: Phaco+ IOL: 20/30 +2.00-3.00x85

41. CONCLUSION
• THIS NEW NOMOGRAM INCREASES THE
UNDERSTANDING OF THE CORNEAL BEHAVIOR
• INCREASES THE PREDICTABILITY OF THE
DESIRED RESULTS
• FACILITATE THE SELECTION OF THE RING
SEGMENTS

42. Thank You