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METODOLOGIE DI CALCOLO
Giacomo Savini
Studio Oculistico d’Azeglio – Bologna
ICCRS Fondazione GB Bietti – Roma
METODOLOGIE DI CALCOLO
Condizioni necessarie per un calcolo accurato
1) Strumentazione (biometria) aggiornata
2) Formule aggiornate
3) Costanti ottimizzate
Giacomo Savini
BIOMETRIA
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ULTRASUONI
OTTICA
BIOMETRI AD ULTRASUONI
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Tecnica ad immersione
Ottimizzazione costanti
Stessa accuratezza della biometria ottica
BIOMETRI AD ULTRASUONI
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Confronto Immersione - Tomey - Topcon
Campione = occhi con SN60WF
Criteri di esclusione
Stafiloma
Mancanza di misurazioni con 1 dei 3
metodi
CDVA postop <5/10
BIOMETRI AD ULTRASUONI
Giacomo Savini
Totale = 217 occhi (Aprile 2011-Giugno 2018)
107 occhi con misurazioni disponibili per tutti
i 3 metodi
Immersione Aladdin OA-2000
Lunghezza 24.13 +/-1.52 24.20 +/-1.56 24.21 +/-1.56
< 22 2 (1.9%)
22-24.5 73 (68.2%)
24.5-26 22 (20.6%)
>26 10 (9.3%)
BIOMETRI AD ULTRASUONI
Giacomo Savini
Median Absolute Error = differenza fra refrazione
predetta e refrazione postoperatoria (D)
Friedman’s test
(nonparametric
ANOVA)
p = 0.6036
Friedman’s test
(nonparametric
ANOVA)
p = 0.7680
Friedman’s test
(nonparametric
ANOVA)
p = 0.8044
Friedman’s test
(nonparametric
ANOVA)
p = 0.5578
BIOMETRI AD ULTRASUONI
Giacomo Savini
BIOMETRI AD ULTRASUONI
Giacomo Savini
Percentuale di occhi con
errore di predizione ≤0.5 D
BIOMETRI AD ULTRASUONI
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BIOMETRI AD ULTRASUONI
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Conclusioni:
No differenze significative fra biometria
ad immersione e biometria ottica
Vantaggi biometria ottica
maggiore velocità, minore invasività
formule di Barrett e Olsen
Vantaggi biometria ad immersione
Sum-of-segments
BIOMETRI AD ULTRASUONI
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BIOMETRI OTTICI
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Haag-Streit
LenStar
Haag-Streit
EyeStar 900
Movu
Argos
Nidek
AL-Scan
Oculus
Pentacam AXL
Heidelberg
Anterion
Zeiss
IOLMaster 700
Ziemer
Galilei G6
Tomey
OA-2000
Topcon
Aladdin
BIOMETRI OTTICI
Giacomo Savini
Non esistono prove che un biometro sia più
( o meno) accurate degli altri
Uniformità misurazioni (K, ACD, AL) per
poter usufruire delle costanti ULIB
Giacomo Savini
BIOMETRI OTTICI
Aladdin OA-2000 Galilei G6
Giacomo Savini
Haigis Hoffer Q Holladay SRK/T Barrett
Tomey OA-2000 85.9% 87.9% 91.9% 87.9% -
Topcon Aladdin 85.0% (86.7%)
82.6% (84.8%)
82.6% (84.8%)
86.8% (86.1%)
- (89.4%)
Ziemer
Galilei G6 83.8% 83.8% 80.1% 82.3% 85.3%
Prediction Error ≤0.50 D
BIOMETRI OTTICI
Red = published data
Blue = larger (n=151), updated, unpublished data
CALCOLO IOL PER CHIRURGIA
REFRATTIVA DELLA CATARATTA
Giacomo Savini
Avvisare sempre i pazienti che nel 5-10%
dei casi può essere necessario un ritocco
laser per migliorare la refrazione.
LA SCELTA DELLA FORMULA
Olsen Holladay 1
Hoffer H5
SRK/T
SRK II
Haigis
Holladay 2
EVO
Hoffer Q
?
Giacomo Savini
Barrett UII
Hill-RBF Panacea
CHOOSING THE FORMULA
Giacomo Savini
FORMULE TEORETICHE L’approssimazione “Thin-lens”
La cornea ed il
cristallino sono
infinitamente sottili
Giacomo Savini
Vergenza dei
raggi dalla IOL
alla retina
Vergenza dei
raggi dalla
cornea alla IOL
LA SCELTA DELLA FORMULA
Le formule “thin-lens” differiscono
principalmente per il metodo con cui predicono
la posizione della IOL
Hoffer Q < K, AL
Holladay 1 < K, AL
SRK/T < K, AL
Haigis < ACD, AL
Holladay 2 < K, AL, ACD, LT, WTW
Giacomo Savini
LA SCELTA DELLA FORMULA
Giacomo Savini
Lunghezza assiale
<22 mm Hoffer Q
22-24,5 mm Media 3 formule
24,5-26 mm Holladay 1
>26 mm SRK/T
Haigis: valida in tutti i gruppi
Holladay II: valida ma superflua
SRK e SRKII: mai!
Linee guida Hoffer
LA SCELTA DELLA FORMULA
Confronto Haigis-Hoffer Q negli occhi corti
Attenzione all’ACD
ACD >2.40 mm: no differenza fra Haigis e Hoffer Q
ACD <2.40 mm: Haigis più accurata di Hoffer Q
Giacomo Savini
LA SCELTA DELLA FORMULA
Evitare la SRK/T negli occhi con K o piatto
Melles et al Ophthalmol 2018
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LA SCELTA DELLA FORMULA
Attenzione a ACD e LT
Melles et al Ophthalmol 2018
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LA SCELTA DELLA FORMULA
Nuove formule
Barrett Universal II
Olsen
Hill-RBF
EVO
Panacea
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LA SCELTA DELLA FORMULA
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Barrett Universal II
Formula «thin-lens» (non pubblicata)
Gratis su www.apacrs.org
ELP predetto da AL, K, ACD
LT e WTW = optionals
LA SCELTA DELLA FORMULA
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Olsen (C-constant)
Basata sul ray-tracing
Posizione IOL predetta da LT e
ACD
LA SCELTA DELLA FORMULA
Giacomo Savini
Hill-RBF 2.0 (Radial Basal Function)
www.rbfcalculator.org
Basata su intelligenza artificiale, no formule ottiche
Database aumentato da 3.445 a 12.419 occhi
Potere fino a -5 D
Target Rx diversa da zero
LA SCELTA DELLA FORMULA
Giacomo Savini
EVO (Emmetropia Verifying Optical) Formula
www.evoiolcalculator.com
Thick-lens formula (non pubblicata) sviluppata in Singapore da
T.K. Yeo, MD
Basata su K, AL e ACD (no LT)
LA SCELTA DELLA FORMULA
Giacomo Savini
Panacea
Thin-lens formula (non pubblicata), basata sulla formula di
vergenza standard, sviluppata da D. Flikier in Costarica
www.panaceaiolandtoriccalculator.com
Predizione ELP da K, AL, ACD, LT
Il potere corneale include informazioni sul rapporto A/P e Q-
value
Disponibile gratuitamente come app
LA SCELTA DELLA FORMULA
Giacomo Savini
Intraocular lenspower formulaaccuracy:
Comparison of 7formulas
Jack X. Kane, MBBS, Anton Van Heerden, MBChB, FRANZCO, Alp Atik, MBBS,
ConstantinosPetsoglou, MBBS, MMed(Clin.Epi), FRANZCO
PURPOSE: Toassesstheaccuracyof 7intraocular lens(IOL) power formulas(Barrett Universal II,
Haigis, Hoffer Q, Holladay1, Holladay2, SRK/T, andT2) usingIOLMaster biometryandoptimized
lensconstants.
SETTING: Public hospital ophthalmologydepartment.
DESIGN: Retrospectivecaseseries.
METHODS: Data from patients having uneventful cataract surgery with Acrysof IQSN60WFIOL
implantationover 5yearswereobtainedfromthebiometryandpatient charts. Optimizedlenscon-
stantswerecalculatedfor eachformulaandusedtodeterminethepredictedrefractiveoutcomefor
each patient. This was compared with theactual refractive outcometo givetheprediction error.
Eyeswereseparatedintosubgroupsbasedonaxial length(AL) asfollows:short (%22.0mm),me-
dium(>22.0 to<24.5mm), mediumlong(R 24.5 to<26.0mm), and long(R 26.0mm).
RESULTS: Thestudy included3241patients. TheBarrett Universal II formulahad thelowest mean
absolutepredictionerror over theentireALrange(P<.001, all formulas) aswell as in themedium
(P<.001, all formulas), medium-long(P<.001, except Holladay1andT2), andlongAL(P<.001,
except T2) subgroups. Nostatisticallysignificant differencewasseenbetweenformulas in theshort
AL subgroup. Overall, the Barrett Universal II formula resulted in the highest percentage of eyes
withpredictionerrorsbetweenG0.25diopter D, G0.50D, andG1.00D.
CONCLUSION: IneyeswithanALlonger than22.0mm, theBarrett Universal II formulawasamore
accuratepredictor of actual postoperativerefraction than theother formulas.
Financial Disclosure: Noneof theauthorshasafinancial or proprietary interest inanymaterial or
methodmentioned.
JCataract Refract Surg2016; 42:1490–1500Q 2016ASCRSandESCRS
Ongoing advances mean that cataract surgery is
now arefractiveoperation and not simply an extrac-
tion procedure. Changes in surgical technique have
resulted in amorepredictablepostoperativeintraoc-
ular lens(IOL) position,1 and partial coherenceinter-
ferometry (PCI) has increased the precision of
preoperative measurements, leading to improved
postoperativerefractiveresults.2New IOL power for-
mulas have attempted to improve the accuracy of
their refractive outcome predictions, predominantly
by increasing the number of variables they assess.
Thenumber of variablesassessed rangesfrom2(Hol-
laday 1,3 Hoffer Q,4,5 SRK/ T,6T27) up to7(Holladay
2A). Theoretically, increasing thenumber of relevant
variables assessed should increase the accuracy in
predicting postoperative refraction, but many of
these newer formulas have not been adequately
assessed.
Few studieshaveevaluated asubstantial number of
eyesacross theentireaxial length (AL) range. Aristo-
demou et al.8 tested the Hoffer Q, Holladay 1, and
SRK/ T formulas in 8108 eyes (the largest IOL power
formula study) and found that theHoffer Q was the
most accurate formula for ALs below 21.0 mm (in 1
of the2IOLsstudied), theHolladay 1trended toward
thehighest accuracy ineyesfrom23.5mmto26.0mm,
and in longeyes(O26.0mm) theSRK/ Twasthemost
accurateformula. Narvaez et al.9 studied 643eyesus-
ing theHolladay 2, Hoffer Q, Holladay 1, and SRK/ T
formulasand found no significant differencebetween
any of them. In 2043eyes, Olsen et al.10 found no dif-
ference between the Haigis, Hoffer Q, Holladay 1,
Q 2016 ASCRSand ESCRS
Published by Elsevier Inc.
1490 http://dx.doi.org/10.1016/j.jcrs.2016.07.021
0886-3350
ARTICLE
Comparison of 9 intraocular lenspower
calculation formulas
David L. Cooke, MD, Timothy L. Cooke, BA
PURPOSE:Toevaluatetheaccuracyof 9intraocular lens(IOL) calculationformulasusing2optical
biometers.
SETTING: Privatepractice, Saint Joseph, Michigan, USA.
DESIGN: Retrospectiveconsecutivecaseseries.
METHODS: NineIOL power formulapredictions with observed refractions after cataract surgery
werecomparedusing1 IOLplatform. Theperformanceof each formulawas ranked for accuracy
bymachineandbyaxial length(AL). TheOlsenwasfurther dividedbyapreinstalledversion(Olse-
nOLCR)andapurchasedversion(OlsenStandalone).TheHolladay2wasdividedbywhetherarefraction
wasentered(Holladay2PreSurgRef) or not (Holladay2NoRef). TheOLCRdeviceusedinthestudywas
theLenstar L5900andthePCI device, theIOLMaster.
RESULTS: Theformulaswererankedby thestandarddeviationof thepredictionerror (optical low-
coherence reflectometry [OLCR], partial coherence interferometry [PCI]) as follows: OlsenStandalone
(0.361, 0.446), Barrett Universal II (0.365, 0.387), OlsenOLCR (0.378, not applicable), Haigis (0.393,
0.401), T2 (0.397, 0.404), Super Formula(0.403, 0.410), Holladay 2NoRef (0.404, 0.417), Holladay
1(0.408,0.414),Holladay2PreSurgRef (0.423,0.432),HofferQ(0.428,0.432),andSRK/T(0.433,0.44).
CONCLUSIONS:Theformulasgavedifferentresultsdependingonwhichmachinemeasurementswere
used.TheOlsenformulawasthemostaccuratewithOLCRmeasurements,significantlybetter thanthe
best formulawithPCI measurements. TheOlsenwasbetter, regardlessof AL. If onlyPCI measure-
ments(without lensthickness)wereavailable,theBarrettUniversal IIperformedthebestandtheOlsen
formulaperformedtheworst. Thepreinstalledversionof Olsenwas not as goodas thestandalone
version. TheHolladay2formulaperformedbetter whenthepreoperativerefractionwasexcluded.
Financial Disclosure: Neither author has a financial or proprietary interest in any material or
methodmentioned.
JCataract Refract Surg2016; 42:1157–1164Q 2016ASCRSandESCRS
Several intraocular lens (IOL) power calculation for-
mulas are in use today. Many have been compared
with each other. In a previous paper,1 we compared
6 formulas to determine which formulas were better
“out of thebox” on 2different optical biometers. This
study broadens the topic to include formulas that
werenot availableon thesebiometersat the time the
first study was performed. The discussion section of
thispaper isorganized by each of thesenew formulas.
Thefollowing6formulaswerepreviouslyevaluated
on our dataset of 1079 eyes: Haigis,2 Holladay 1,3
Hoffer Q,4–6 Sanders-Retzlaff-Kraff/ Theoretical
(SRK/ T),7 SRK II,8 and Olsen.9 These formulas came
preinstalled on the IOLMaster (Carl Zeiss Meditec
AG) or theLenstar LS900 (Haag-Streit AG), theonly
optical biometersavailable in theUnited Stateswhen
this study was initiated. The IOLMaster is based on
partial coherenceinterferometry (PCI) and theLenstar
on optical low-coherence interferometry (OLCR).
The SRK II has been shown to bemarkedly worse
than other formulas.1 It wasthusexcluded from anal-
ysis in thisstudy. Theadditional formulasused were
the purchased (standalone) version of the Olsen for-
mula, Holladay 2,A T2,10 Super Formula,11 and the
Barrett Universal II.B
We present predictions from 9 formulas in this
study. However, some tables present up to 12 for-
mulas. This isbecausewepresent 2 distinct forms of
3formulas. Welisted themasthough they weresepa-
rate formulas because each gave distinctly different
Q 2016 ASCRSand ESCRS
Published by Elsevier Inc.
http://dx.doi.org/10.1016/j.jcrs.2016.06.029 11570886-3350
ARTICLE
LA SCELTA DELLA FORMULA
Giacomo Savini
Confronto di 7 formule (3241 pazienti)
Occhi corti (n=
156): no differenze
fra le 7 formule
Occhi lunghi (n= 77):
Barrett
SRK/T
Haigis
Kane et al. JCRS 2016
LA SCELTA DELLA FORMULA
Giacomo Savini
Confronto di 9 formule (1454 pazienti):
Barrett e Olsen = formule migliori
IOLMaster
Barrett = migliore
Lenstar
Olsen = migliore
LA SCELTA DELLA FORMULA
Giacomo Savini
Un errore di predizione entro 0.5 D può essere ottenuto nel
70-80% dei casi
LA SCELTA DELLA FORMULA
Giacomo Savini
La percentuale cala al 60% negli occhi corti (<22 mm) ed in
quelli lunghi (>26 mm)
OTTIMIZZAZIONE COSTANTI
Giacomo Savini
Le costanti fornite dai costruttori di IOL
dovrebbero essere usate solo nei primi casi,
quando non si conosce ancora la Rx postop
L’ottimizzazione della constante ci permette
di eliminare errori sistematici fra la refrazione
predetta e quella postop (azzerare l’errore di
predizione)
OTTIMIZZAZIONE COSTANTI
Giacomo Savini
OTTIMIZZAZIONE COSTANTI
Giacomo Savini
Come si ottimizzano le costanti
Metodo più semplice: software biometri
Metodo tradizionale: ULIB website
Metodo più accurato: Excel
ESEMPIO
Giacomo Savini
IOL impiantata = 24.5 D
Rx postop = 0 D
IOL TORICHE
Considerate sempre l’astigmatismo
corneale posteriore
Giacomo Savini
IOL TORICHE
Giacomo Savini
Il meridiano posteriore più curvo è quasi
sempre orientato verticalmente. 1-4
Questo allineamento genera un
astigmatismo contro regola, che si
somma a quello anteriore.
1 - Ho et al. AJO 2009
2 - Koch et al. JCRS 2012
3 - Savini et al. JCRS 2014
4 - Tonn et al. IOVS 2015
IOL TORICHE
Giacomo Savini
Anteriore Posteriore
Esempio
Esempio
IOL TORICHE
Giacomo Savini
Correlazione significativa (p<0.001, r2=0.5683) fra astigmatismo
corneale posteriore ed anteriore
Giacomo Savini
IOL TORICHE
Giacomo Savini
Quali sono i risultati?
Giacomo Savini
IOL TORICHE
Giacomo Savini Giacomo Savini
Keratometric astigmatism
(D)
Total corneal astigmatism
(D)
WTR -0.59 +/-0.34 -0.13 +/-0.42
ATR 0.32 +/-0.42 0.07 +/-0.59
Curvital power
Negative = overcorrection
Positive = undercorrection
ERA = Error in Refractive astigmatism
(difference between predicted and measured astigmatism)
Sovracorrezione
Sottocorrezione
IOL TORICHE
Giacomo Savini
Quali sono i risultati?
Giacomo Savini
IOL TORICHE
Giacomo Savini Giacomo Savini, MD
64 eyes Mean absolute error (MAE)
in astigmatic power
% of eyes with absolute
error ≤0.5 D
KA (Keratron) 0.70 ±0.39 D 26.56%
TCA (Pupil / Zone) 0.69 ±0.40 D 39.06%
TCA (Pupil / Ring) 0.73 ±0.51 D 43.75%
TCA (Apex/ Zone) 0.73 ±0.48 D 40.63%
TCA (Apex/ Ring) 0.75 ±0.48 D 37.50%
TCA Sirius 0.64 ±0.38 D 43.75%
Barrett 0.55 ±0.32 D 56.25%
Abulafia-Koch 0.62 ±0.48 D 54.69%
Næser-Savini
Optimized KA
0.52 ±0.33 D 57.81%
IOL TORICHE
Giacomo Savini Giacomo Savini
Næser/Savini Optimized KA
Optimized KA = 0.103 + 0.836 * Measured KA + 0.457 *cos(2*α)
https://www.soiweb.com/toric-calculator/
Giacomo Savini Giacomo Savini
GRAZIE
Giacomo Savini
www.studiodazeglio.it
www.biometria-bologna.it