Ferrara Ring Correction Guide

Ferrara Ring (ICRs)
A-Z
PAULO FERRARA, MD, PHD
Paulo Ferrara Eye Clinic
Ferrara Ophthalmics
Belo Horizonte – MG - Brasil

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

1950 - Barraquer, J., Intracorneal implants
1966 - Blavatskaya - Corneal rings from corneal tissue
1986 - Simon, G. - Silicon Rings
1987 - Fleming - Adjustable rings
HISTORY

SHAPE ?
SIZE?
OPTICAL ZONE?
DEPTH?
TOLERANCE?
INFLAMATORY RESPONSE?
STABILITY?
RANGE OF CORRECTION?
SURGICAL TECHNIQUE ?
QUESTIONS TO BE ANSWERER 1985

FERRARA RING
1986
Pocket incision

Intra Corneal Ring Segments Research
ICRS: Well Tolerated in the Deep Stroma

1
2
3
3
2
1
ICRS: Well Tolerated in the Deep Stroma

Reversibility

Superficial stroma
Deep stroma
Localization: 80% corneal
thickness
Why deep?

MYOPIA CORRECTION
Remove tissue of the center of the cornea;
Add tissue to the periphery of the cornea.
HYPEROPIA CORRECTION
Add tissue to the center of the cornea
Remove tissue from the periphery of the
cornea
BARRAQUER’s THICKCESS LAW

The larger (diameter) the ring
the lesser the correction
The thicker the ring
the greater the correction
BLAVATSKAYA’S LAW

6
6,5
7
7,5
8
8,5
9
9,5
10
10,5
11
1,3
2
2,7
3,4
4,1
0
2
4
6
8
10
12
14
200 250 300 350 400 450
Diopters
Ferrara
(OZ 5)
Intacs
(OZ 7)
More ThicKCess
More Correction
250 
100 D
150 D
300 D
ICRS ThicKCess
Less ThiKCess
Less Correction
150 
Blavastkaya

FERRARA RING
1991
Lamellar keratectomy
One piece ring

FERRARA RING
1994
TUNELIZATION INCISION

Ferrara Ring Nomogram
(Myopia)
 RING THICKCESS SPHERICAL EQ
AF5/15 µ -2 to -4
AF5/20 µ -4 to -6
AF5/25 µ -6 to -8
AF5/30 µ -8 to -10
AF5/35 µ -10 to -12
AF = Ferrara Ring 5 = Ring Diameter
µ = micra

1994 Ferrara ring 350°
For high myopia
(First Generation)

MYOPIC GROUP
Very high
myopic correction
Poor previsibility

FERRARA RING NOMOGRAM
First generation (1997 - 2003): spherical equivalent
Eye 1 Eye 2
Refraction: -10.00 D Refraction: -10.00 D
Are these the same?
NO !
cornea hypercorrection in axial myopia

THE RING AS A PRIMARY REFRACTIVE
PROCEDURE SHOWED LOW PREVISIBILITY
DESPITE LONG TERM STABILITY AND
GOOD VISUAL PERFORMANCE.
SAFETY AND LONG TERM STABILITY
IN DIFFICULT CASES SUGGESTED THEIR
APPLICATION IN CONTACT LENS
INTOLERANT KERATOCONUS PATIENTS
1995
MOVING TO OTHER APPLICATIONS...

1995
Ferrara ring as an orthopedic procedure

FERRARA RING
FOR KERATOCONUS
1996

I.M.S. Pre Op.
SURGERY: 08/20/1996
AF5.60.160/25 RE.
UCVA: 20/400
BSCVA: 20/40
Refraction: –5,50 –1,00 x 10
keratometry: 46,00 / 46,50

Material PMMA
YELLOW FILTER
Apical Diameter 5mm
Triangular cross section =
PRISMATIC EFFECT
FLAT BASIS WIDTH 0,6 MM
Variable arch lengh segments
Hole in each extremity
FERRARA RING
CHARACTERISTICS

SECOND
GENERATION
TWO RING
SEGMENTS

IMPROVED SURFACE QUALITY AND FINISHING
INCLUSION OF A HOLE IN EACH EXTREMITY
DEFINITION OF A NOMOGRAM ON A
STATISTICAL BASIS

The flat basis is responsible for the induction of the astigmatism

Evaluation of ring segments
position in the corneal stroma
with respect to the visual axis
and its depth, and thus providing
a better underestanding of the
results
2004

Indications
 Primary or Orthopedic indication
 Corneal irregularities
 Keratoconus
 Pellucid Marginal Degeneration
 IATROGENIC
 PKP
 PRK; LASIK; RK
 TRAUMA
 SECUNDARY
 REFRACTIVE

Indications
GOALS:
• Stabilize the evolution and/or progression
• Reduce corneal asymmetry
• Preparing for optical treatment with stable cornea

Keratoconus
Prevalence: 1:2000*
*Siganos., 2002

Inclusion Criteria
• Young patients
• Contact lens intolerant keratoconus
• Evidence of evolution of the corneal ectasia,
despite CL tolerance
• Reduce CL dependency

Inclusion Criteria
Patients with good CDVA, good pachymetry and low asymmetry
Refractive purpose (best cases)
Patients with bad CDVA, reasonable pachymetry and asymmetry
Regularize corena
Patients with bad CDVA, pachymetry and asymmetry, corneal
scars
Lamellar keratoplasty

Exclusion Criteria
• Hidropsia
• Severe corneal opacities
• Ocular or sistemic disease (vernal keratoconjuntivitis,
Severe dry eye(Steven Johnson, Sjogren syndrome, etc)
• Young patients presenting VA ≥ 20/40 CDVA.
• These patients need to be observed every three
months to detect the progression of the condition.

Patient Selection
• Assessment of visual function
• Assessment of CDVA, pH VA plus spheric refraction
• Ectasia classification
• Management

G.M., male, 16 y.o.
1st. Visit 04/01/2011
Ferrara ring RE
LE KC III ( CXL)
Bad visual acuity LE
Ferrara ring implantation LE 07/11/2011 (manual technique)
Clinical Case

CDVA 20/60 CDVA20/30 21/08/201431/03/2011

I.R.G., male, 15 yo
1st. Visit 01/07/2008
CDVA 20/25 both eyes
KC in evolution RE operated in 01/17/2008 (manual technique)
RE UDVA 06 y.o. POST OP 20/20
Last Visit in 08/08/2014
KC in evolution LE operated in 08/08/2014 ( FEMTOSECOND)
LE UDVA post op IMMEDIATE 20/30
Clinical Case

CDVA Pre op20/25 UDVA Post op20/20
ICRS implant in 01/17/2008 (manual technique)
Clinical Case

ICRS implant in 08/08/2014 (Femtosecond)
Comparative Topometric Map 2008 and 2014
Clinical Case

Preop CDVA20/30 Post op CDVA20/20

Clinical Case
Pellucid Marginal Degenration ( PMD)
E.B.,male, 62y.o.
PMD ICL
Visit 04/03/2010
RE +3,50-6,00 x 85 20/400
LE +3,00-4,50 x 95 20/40-

Clinical Case
Pellucid Marginal Degenration ( PMD)
Ferrara ring implant in RE (04/03/2010)
CDVA in 07/04/2010 (33º DPO)
RE -1,50-5,00 x 95º 20/80-
Phaco + LIO in RE
15/06/2010
CDVA in 07/04/2010 (22º DPO)
RE +0,50-3,50 x 85º 20/30

Clinical Case
Pellucid Marginal Degenration (PMD)
+1,50 -1,00 x 95º 20/30+3,50 -6,00 x 85 20/400
10/09/2010

Clinical Case
Pellucid Marginal Degenration ( DMP)
Last Visit
18/02/2013
RE +1,75-4,25 x 85º 20/20
LE +3,75-2,75 x 95º 20/20

Clinical Case
Post RK ring implantation
Y.A.P.,male, 53y.o.
Underwent RK 1992
Lasek 1998
KC 4 years later
AF surgery LE (14/06/2011)

Clinical Case
Pre op

CDVA 08/08/2011 (53º DPO)
LE -3,00 -2,50 x 85º 20/60
CDVA in 14/06/2011
LE -2,50 -5,00 x 90 20/80
Ferrara ring LE (14/06/2011)
Clinical Case

Clinical Case
-2,50 -5,00 x 90 20/80 -3,00 -2,50 x 85º 20/60
53º
DPO

Clinical Case
High astigmatism post PKP

Clinical Case
M.V.T.P.,female, 32y.o.
ICLK
PKP LE followed by
Ferrara ring implantation
1996
Ferrara ring for corneal
irregularities

Clinical Case
18 years AFTER
Phaco+ Lio LE
Post op
CDVA 20/25

Clinical Case
Ferrara ring and ICL
Combination of Techniques
N.O.R.,female, 23y.o.
ICL
Ferrara ring implantation 1 year post op RE
VA RE -8,50 -1,00 x135 20/30+2

15/05/2014
AV preop -8,50 -1,00 x 135 20/30+2
AV post op Plano 20/40
ICL Implantation after FR in RE 07/04/2014
Clinical Case
Ferrara ring and ICL

Ferrara ring Implatation
pH VA: RE 20/100 LE 20/80
UCVA: RE<20/400 LE<20/100

Imediate post op
UCVA RE 20/100 LE 20/80

Nomogram Based on Corneal
Astigmatism

0%
25%
33%
50%
Mapa
Distribution of
the ectasia
Description
Entire ectasia is located on
one side of the cornea
75%
75% of the ectasia is
located on one side of the
cornea
66% of the ectasia is
located on one side of the
cornea
50%
The ectasia is symmetrically
distributed over the cornea
100%
66%

G.M.H.S.,male, 19 y.o.
UCVA RE 20/20
LE< 20/400
20/80 (PH)
biomicroscopy
Grade II KC LE
WHAT TO DO?
LC RGP ???
CXL?
RINGS???
TYPE

NOMOGRAM
Segmentosasimétricos
25/75%
up para 2,00 D 01 segt of 15
2,25 TO 4,00D 01 segt of 20
4,25 TO 6,00D 01 segt of 25
6,25 TO 8,00D 01 segt of 30
8,25 TO 10,00D 02 segts 15/25
10,25 TO 12,00D 02 segts 20/30
.

FERRARA RING
01 SEGMENT 160/25
INCISION 90
DEPTH 450 µm
surgery: 06/26/2008
Last visit (09/26/08):
UCVA 20/80
BSCVA 20/40
MANIFEST Rx:
+0.50 -1.50 x 105

L.F.A., female, 28 y.o
KC III LE
TYPE 3
Pre op Data 06/09/2008
MANIFEST Rx
LE: -14.00 -2.50 x 180
BSCVA
LE: 20/80

NOMOGRAM
Asymmetric Astigmatism
33/66%
Up TO 2,00 D 01 segt 15
2,25 TO 4,00D 02 segts 15/20
4,25 TO 6,00D 02 segts 20/25
6,25 TO 8,00D 02 segts 25/30

SURGICAL STRATEGY
2 AFR 160/20
160/25
Incision 75º
Depth 480 µm

L.F.A., female, 28 y.o.
KC III LE
TYPE 3
Post op Data 09/30/2008
MANIFEST Rx
LE: -9.00 sph
BSCVA
LE: 20/40

F.B.S., male, 19 y.o.
KC II
TYPE 4
Pre op data 07/31/2007
UCVA 20/200
BSCVA 20/200
MANIFEST Rx
IMPOSSIBLE

Central
Symmetric Bow-tie
Up to 1,00D 02 segts of 15
1,25 to 2,00D 02 segts of 20
2,25 to 3,00D 02 segts of 25
3,25 to 4,00D 02 segts of30

Surgical Strategy
2 AFR 160/20
Incision 60º
Depth 440 µm

F.B.S., male,
19 y.o.
KC II
TYPE 4
Post op data
09/30/2008
UCVA 20/20

A.M.A, 30 y.o., male
Ectasia Post PRK
Pre op date 23/04/2008
BSCVA = <20/400
MANIFEST Rx+1.00 -6.50 X 140
Contact lens intolerant
NIPPLE TYPE

Central
nipple
210 Segments
Up to 2,50 D 01 segt of 15
2,75 to 4,00 D 01 segt of 20
4,25 to 5,75 D 01 segt of 25
6,00 to 8,00 D 01 segt of 30
3,79
5,79
8,01
2,52
-
1,00
2,00
3,00
4,00
5,00
6,00
7,00
8,00
9,00
Segm
ento
15
Segm
ento
20
Segm
ento
25
Segm
ento
30

Surgical Strategy
01 SEGMENT 210/25

A.M.A 30 yo male
Post op data (04/08/2008)
MANIFEST Rx-0.50 -2.50 x 90
BSCVA = 20/30

FERRARA RING NOMOGRAMA
Third generation (2006 - 2009):Topografic astigmatism
Eye1 Eye2
Keratometry: 42.00 x 47.00 D
Are the same?
NO !
Same topografic astigmatism- different changes after the ICRS implantation
Keratometry: 52.00 x 57.00 D

PAULO FERRARA, MD, PhD
LEONARDO TORQUETTI, MD, PhD
GUILHERME FERRARA, MD
JESUS MERAYO-LLOVES, MD,PhD
PAULO FERRARAEYE CLINIC
BELO HORIZONTE – MG
Comparison of clinical Results after implantation of
ring segments using two different NOMOGRAMS:
Corneal topographic astigmatism vs asphericity

Results
Preoperative and post operative BCVA, according to
keartoconus stage
TA = parapograficoastigmatismo - Q = Asfericidad

Results
TA Q
Preop Postop p Preop Postop p
Asphericty (Q) -0.88 -0.35 0.000 -0,77 -0,13 0.000
Keratometry (D) 49.18 45.72 0.000 48,91 45,54 0.000
Pachymetry (μm) 448 465 0.000 447 465 0.000
160 arc ring

Results
TA Q
Preop Post op p Preop Post op p
Asphericity(Q) -1.17 -0.56 0.000 -0,89 -0,40 0.000
Keratometry(D) 51.92 48.10 0.000 52,82 48,87 0.000
Pachymetry (μm) 418 435 0.000 423 445 0.000
210 arc ring

There’s a tendency to implant less tissue to achieve the
same (or better) correction than the past;
Value of Q = Quality of the vision
NOMOGRAM

SELECTION OF THE RING BASED ON
CORNEAL ASPHERICITY

Corneal Eccentricity (E-value)
Define the shape of the cornea (conic section)
Center of the cornea flattening to the periphery
(Q= - e2)
Behavior of the Asphericity
Healthy and ectasic cornea

What is prolate, and oblate?
Radius of curvature
Sphere: Same radius of curvature
Prolate surface (negative Q), periphery radius > center
radius
Oblate surface (positive Q), periphery radius < center
radius

•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. Asfericidadcornealen una
poblácion de adultos jóvenes. Implicaciones clínicas. ArchSocEspOftalmol 2004: 79:385-392

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

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

Spherical Surface (Q = 0)
Several focal points (More light bean refracted at the
Periphery than in thecenter)
e2 = 0
SA = +0.30 µm

Prolate Surface(Q < 0)
Single focal point (reduction of spherical aberration)
e2> 0
SA ≈ 0.0 µm
e2≈+0.60

Oblate surface (Q > 0)
Many focal points (Increase in spherical aberration)
e2< 0
SA > 0.30 µm

•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

Retrospective Study
165 eyes operated between january and luly 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
Group V –Control
Evaluation of SimK. Maximunkeratometry and conrealasphericity at 20º, 25º, 30, 35º e40º.
(Pentacam)
BehavioroftheAsphericity
Healthyandectasiccornea
*Ferrara-Amsler

Results
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

Results
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

Results
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

Results
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

Results
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

Results
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

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

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

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

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

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

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

Selection of the segment based on corneal
asphericity

CLINICAL CASE
CDVA OD post op: + 0,50 - 1,00 x 95º 2
02/02/2012
17/01/2014
CDVA OD pre op: plano - 4,50 x 90º 20/40

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

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

CLINICAL CASE
Preop 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

160 arc = (“standard” ring)
- negative Q (prolate to hiperprolatecornea)
-HighvaluesofK
-Highastigmaitisms

140 arc = PMD
- Q 0 or positive
- Low values of K
- High astigmatism

210 arc = Nipple
- Q negative (hiperprolatecornea)
- High values of K
- Low astigmatism

Variationof K (Keratometry) according to the
thickness of the ring
0.1 1 10
250-250
200-200
150-200
250
150
5.300000191
6.269999981
5.650000095
3.859999895
4.349999905
3.400000095
2.74000001
1.820000052
0.779999971
Diopters

Variationof Q (asphericity) according
To the thickess of the ring
-1.20
-1.00
-0.80
-0.60
-0.40
-0.20
0.00
150 200 250 150-150 150-200 150-250 200-200 200-250 250-250
-0.07
-0.310000002
-0.340000004
-0.569999993
-0.730000019
-0.800000012
-0.860000014
-1.019999981
-0.99000001
Q

Clinical Case
20/200 -6.00-2.50x10
SURGICAL PLANNING ?
PREOP
POSTOP
20/40 pl-5.000x50
AF 150/160
AF 250/160

Clinical Case
20/200
SURGICAL PLANNING ?
PREOP
POSTOP
20/40 -2.50-1.50x45
AF 200/160

Clinical Case
20/400 +3.00-6.00x85
Cataract + PMD
SURGICAL PLANNING ?
PREOP
POSTOP
20/30 +0.50-3.00x85
AF 150/140
3 months after: Phaco+ IOL: 20/30 +2.00-3.00x85

Clinical Case
Nipple
20/60 -8.50-1.50x140
SURGICAL PLANNING ?
PREOP
POSTOP
20/40 --0.50-1.50x40
AF 250/210

Clinical Case
Nipple
20/60 -8.50-1.50x140
SURGICAL PLANNING ?
PREOP
POSTOP
20/40 -5.50
AF 200/210

CLINICAL CASE
Q = 0,13
Cil = -5.2 D
K1 = 39.8 D
K2 = 44.9 D
PREOP
SURGERY
STRATEGY?

CLINICAL CASE
AF 150/140
Q = 0,08
Cil = -2.2 D
K1 = 40.7 D
K2 = 42.9 D
POSTOP
IF THE astigmatism WAS USED IN THE SELECTION OF
SEGMENT (160/250):
Oblate CORNEA
overcorrection

CLINICAL CASE
Ambliopia
BCVA: 20/80
-2.50-4.50x20
Q = -0.31
Cil = -3.5 D
K1 = 41.2 D
K2 = 44.7 D
PREOP
Surgical
Strategy??

CLINICAL CASE
AF 150/140
BCVA: 20/30
-3.50
Q = -0.26
Cil = -1.5 D
K1 = 41.4 D
K2 = 43.0 D
FOLLOWED BY
CORRECTION
OF
AMETROPIA BY
PRK
POSTOP

• Normal Value of Q: - 0.23 1
•Corneal asphericity in KC:
The target of the correction is - 0.23
OR
The Q value of the unaffected fellow eye
Asphericity
1. Yebra-Pimentel E, González-Méijome JM, Cervino A, et al. Asfericidadcornealen una
poblácion de adultos jóvenes. Implicaciones clínicas. ArchSocEspOftalmol 2004: 79:385-392

SURGICAL TECHNIQUE
Manual
Femtosecond

1-Pachymetryat thesteepestaxisofthecornea (manual technique) (ZO 5 mm)
OR thethinnestpointonthepathofthering (Femtosecond)
2- Incision 80% depth of the thickness of the cornea at site of the incision
(if manual technique)
The incision is always performed at the steepestaxis
AND
Incision 80% depth of the thickness of the cornea at thinnest point
onthepathofthering (Femtosecond)
SURGICAL TECHNIQUE

RING SELECTION BASED ON THE
NOMOGRAM
SURGICAL TECHNIQUE
-1.20
-1.00
-0.80
-0.60
-0.40
-0.20
0.00
150 200 250 150-150 150-200 150-250 200-200 200-250 250-250
-0.07
-0.310000002
-0.340000004
-0.569999993
-0.730000019
-0.800000012
-0.860000014
-1.019999981
-0.99000001

SURGICAL TECHNIQUE
ADVANTAGES FEMTO ADVANTAGES MANUAL
TECHNIQUE
Easytoperform Cheap
Reproducible Portability
Less trauma
Fast visual recovery
Long termresults are thesame

ICRS IN COMBINED SURGERIES
PAULO FERRARAEYECLINIC
PAULO FERRARA

KERATOCONUS
Highand irregular keratometricvalues
Associateornottohighametropia
Needforsurgicalassociationoftechniquesto
obtainresults more satisfactory

Phakic IOL’s
ICL
CACHET
ARTISAN …
FERRARA RINGS + CXL…
PSEUDO PHAKIC LENS

SAFETY AND EFFICACY ANALYSIS OF A LARGE
SAMPLE OF EYES IMPLANTED WITH INTRASTROMAL
CORNEAL RING SEGMENTS
GUILHERME FERRARA, MD
LEONARDO TORQUETTI, MD, PhD
JESUS MERAYO-LLOVES, MD,PhD
PAULO FERRARA, MD, PhD
PAULO FERRARA EYE CLINIC

•Sample: 1073 eyesof 810 patientsoperatedconsecutivelybetweenJanuary2006
and July 2008
•Twogroups (TYPE OF RING IMPLANTED):
Group I - patientsimplantedwith 160-degreearch (n = 972)
Group II - patientsimplantedwitharcsof 210 degreesofarch (n = 101)
•Parametersstudied:
Uncorrected visual acuity (UCVA)
Best corrected visual acuity (BCVA)
Keratometry (K)
Asphericity (Q)
Cornealthickcess at thethinnestpointofthe cornea
METHOD

•Average of age: 29.2 ± 9.4 (grupo I) and 30.2 ± 8.7 (grupo II);
• Follow-up: 23.8 ± 12.2 (groupI) y 22.9 ± 15.1 months (groupII).
Allpatientscomplited at least 6 monthsoffollow-up
• Statistical analysis: tStudent´s Test for paired data- SPSS software
(SPSS, Chicago, IL).
METHOD

grupo I grupo II
Preop Postop p Preop Postop p
UCVA 20/220 20/80 0.000 20/350 20/130 0.001
BCVA 20/100 20/40 0.000 20/110 20/60 0.000
Sph. Eq. (D) -3.99 -2.26 0.000 -8.52 -4.14 0.000
Asphericity -0.88 -0.35 0.000 -1.17 -0.56 0.000
Keratometry(D) 49.18 45.72 0.000 51.92 48.10 0.000
Pachymetry (m) 448 465 0.000 418 435 0.000
RESULTS

UCVA pre y post op
210
60
220
80
250
100
400
200
0
50
100
150
200
250
300
350
400
I II III IV
Preop
Postop
I II III IV
RESULTS

I II III IV
60
35
94
40
400
55
800
90
0
100
200
300
400
500
600
700
800
I II III IV
Preop
Postop
BCVA pre y post op
RESULTS

Complicatios (treatment) ojos (%)
Undercorrection (implantationofadditional segment) 16 (1.49)
Overcorrection (segmentremovalfollowed by reimplantation) 11 (1.02)
Extrusion (removal of the segment) 6 (0.56)
Malposition (repositioning of the segmento) 4 (0.37)
KC progression (keraparaplasty) 2 (0.18)
Neovascularization (bevacizumab) 2 (0.18)
TOTAL 41 (3.82%)
RESULTS

• RELATED TO SURGICAL TECHNIQUE
• RELATED TO THE NOMOGRAM
• RELATED THE RING
COMPLICATIONS

- Extrusion 0.1%
- Infection 0.08%
- Descentration of the segment
- Migration
- Rotation
-Deviation or asymmetry of the segments
RELATED TO SURGICAL
TECHNIQUE

Shallow tunnelExtrusion
EXTRUSION

(Corneal biomecanics)
1 - Hipocorrection
2 - Overcorrection
RELATED TO THE
NOMOGRAM

Halos and Glare
Peri ring deposits
Neovascularization
RELATED TO THE RING

Preoperative 1 month 1 year 2y.o. 3y.o. 4y.o. 5y.o.
KMAX
52.95 ± 6.78 49.36 ± 6.66 47.69 ± 5.43 47.77 ± 5.26 47.81 ± 5.87 48.07 ± 6.26 48.09 ± 5.92
KMIN
47.86 ± 5.19 45.27 ± 5.39 44.03 ± 4.52 44.29 ± 4.46 44.04 ± 4.85 44.82 ± 5.57 44.45 ± 5.97
KMEAN
50.36 ± 5.68 47.29 ± 5.91 45.79 ± 4.85 45.96 ± 4.65 45.83 ± 5.08 46.44 ± 5.90 46.24 ± 5.89
UCVA 0.12 ± 0.14 0.25 ± 0.19 0.33 ± 0.23 0.29 ± 0.18 0.34 ± 0.23 0.42 ± 0.31 0.31 ± 0.23
BCVA 0.41 ± 0.24 0.56 ± 0.24 0.67 ± 0.25 0.68 ± 0.24 0.63 ± 0.21 0.65 ± 0.19 0.59 ± 0.19

Calculated exponential cell loss rate over the mean
interval of follow-up (4y.o.):
1.4% per year
Endothelial Cell Loss (per year) in:
Young normal ojos: 1.1%
Old normal ojos: 0.6%
después cataract surgery: 2.5%
después PKP: 4.2-9.4%

The mean BCVA increased from 20/125para20/55 (p=0.0001)

Preoperative Posparaperative
UCVA 20/185 20/66 p = 0.005
BCVA 20/125 20/40 p = 0.008
Apex Pachymetry 457.7 466.2 p =0.025
Asfericidad (Q) -0.95 -0.23 p = 0.006
Queraparametría (K) 45.41 42.88 p = 0.000

Take home message
• Identify the KC
• Central
• Eccentric -inferior
• Corneal Asphericity: Nomogram for ring size and
thicKCess
• One or two
• ThicKCess
• Incision on steep meridian at 80% depth

Conclusions
• Improve UCVA and BCVA
• Reduce Rx measurements
• Reduce Avg Ks and increase asphericity
• Mechanically stabilize cornea
• Improve CL tolerance and/or spectacle use

Conclusions
•Restore of Functional Vision
Functional Refraction with Soft, Soft-Toric, or Rigid Contact
Lenses
•Post-Surgical Recovery
Immediate Visual Improvement
•High Potential to Avoid Corneal Transplant

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