Ferrara Ring New Nomogram - 1st Red Sea Ophthalmology Symposium

Ferrara Ring

New Nomogram

PAULO FERRARA, MD, PHD

Paulo Ferrara Eye ClinicFerrara Ophthalmics

Belo Horizonte – MG - Brasil

Declaration of Conflict of Interest

•Ferrara Ophthalmics

•Ferrara e Hijos

•AJL

•Intacs

SELECTION OF THE RING BASED ON

CORNEAL ASPHERICITY

Corneal Eccentricity (E-value)

Define the shape of the cornea (conic section)

(Q= - e2)

Behavior of the Asphericity

Healthy and ectasic cornea

• Corneal Asphericity (Q) – shape of thecornea;

• 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

Spherical Surface (Q = 0)

Several focal points (More light bean refracted at the

periphery than in the center)



SA = +0.30 µm



Prolate Surface (Q < 0)

Single focal point (reduction of spherical aberration)

e2 > 0

SA ≈ 0.0 µm



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 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)



*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, 26 y.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

-1.5520º 25º 30º 35º 40º

RSOC

RSOC

Selection of the segment based on corneal

asphericity

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)

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

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

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

Q variation according to the ring thickness

Q

Km variation according to the ring thickness

Diopters

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

CLINICAL CASE

CDVA OD post op: + 0,50 - 1,00 x 95º 20/30

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 pre op: +3,00 // -5,00 x

90º 20/70 +

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

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


20/200

SURGICAL PLANNING ?

PREOP

POSTOP

20/40 -2.50-1.50x45

AF 200/160


Nipple

20/60 -8.50-1.50x140

SURGICAL PLANNING ?

PREOP

POSTOP

20/40 - 0.50-1.50x40

AF 250/210


< 20/400

SURGICAL PLANNING ?

PREOP

POSTOP

20/60 -5,50 -2,00 x 105

AF 200/140

AF 250/140


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

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

Thank You

Ferrara Ring New Nomogram - 1st Red Sea Ophthalmology Symposium

Health & Medicine

Transcript of Ferrara Ring New Nomogram - 1st Red Sea Ophthalmology Symposium