A.H. MirfendereskiTehran University of Medical Sciences

Optometry Department

Pre-IOL era : Patients traded in their cataractous lenses for “Coke bottle

bottom” spectacles. Problems :

Prismatic effect and ring scotoma between 40 and 60 degrees.

Markedly constricted visual field. Lack of stereopsis. Spherical aberrations. False orientation.

As early as the 1760s, ophthalmologists had explored the idea of an artificial replacement for the cataractous lens.

Around 1795, Casamata inserted a glass lens into an eye, but it immediately sank back toward the posterior pole.

IntroductionIntroduction

Sir Harold Ridley was the first to successfully implant an intraocular lens in 1949. The procedure was performed on a 45-year-old woman at St Thomas Hospital at London.

That first IOL was manufactured by the Rayner company from PMMA.

The surgery was an anatomic success, but the patient was left highly myopic.

Her postoperative visual acuity was 6/18, requiring a refractive correction of -18.0 -6.0 × 120. There was clearly an error in the calculation.

Baron designed and implanted the first Anterior Chamber IOL (ACIOL) in 1952.

IntroductionIntroduction

Clinical history MethodClinical history Method

Before 1975 the power of an IOL was calculated by the use of this equation :

P = 18 + ( 1.25 × Ref )

Errors exceeding 1 diopter occurred in over 50% of cases.

These large errors were caused by the difficualty of determining the patients' refractive error,

Power Calculation FormulasPower Calculation Formulas

Basic opticsBasic optics

Basic opticsBasic optics

In a two-lens System, the object for the second lens is the image for the first lens.

cL

nP

cv

n

cKnn

cL

nP

Original Theoritical FormulasOriginal Theoritical Formulas

Required Measurements : L : The Axial Length in millimeters. C : The estimated postoperative anterior chamber depth (ACD) in millimeters. K: The corneal power in diopters. r : The corneal radius of curvature.

Original Regression FormulasOriginal Regression Formulas

Regression formulas are derived empirically from retrospective computer analysis of data accured on a great many patients. A regression formula is based on this equation :

P = A – BL – CK L: Axial Length (millimeters)

K: Corneal Power (diopters)

A,B,C: Constants

SRK I is the most popular

original regression formula :

P = A – 2.5L – 0.9K

Modified FormulasModified Formulas

100005.0336.1

336.1

05.0

1336

C

RKCL

P

133605.00125.1

1

05.0)23(1.0

1336

CK

CLLP

Modified FormulasModified Formulas

)4)((

)4(1336

CRCL

LRP

KLAP 9.05.21

Modified FormulasModified Formulas

Estimated Lens Position (ELP)Estimated Lens Position (ELP)

Estimated Lens Position (ELP)Estimated Lens Position (ELP)

(1/23.45)12.5Length AxialAG

)]4/1)((AGR[R0.56aACD

SaACDELP222

3.595-0.9704) value(ACDfactor S

65.60-0.5663)constant-(Afactor S

The Haigis FormulaThe Haigis Formula

)()(

position lens effective the

210 ALaACDaad

d

Measuring The Axial LengthMeasuring The Axial Length

A-SCANA-SCAN

A-SCANA-SCAN

Community Eye Health Journal Vol. 19 No. 60 DECEMBER 2006 www.cehjournal.org

J Emmetropia 2011; 2: 210-216 ©2011 SECOIR - Sociedad Española de Cirugía Ocular Implanto-Refractiva

A-SCANA-SCAN

IOL MasterIOL Master

IOL MasterIOL Master

IOL Master

IOL Master

LenstarLenstar

1.1. IOL Power CalculationsIOL Power Calculations, H. John Shammas, , H. John Shammas, SLACK Incorporated, 2004 SLACK Incorporated, 2004

2.2. Intraocular Lenses in Cataract and Intraocular Lenses in Cataract and Refractive SurgeryRefractive Surgery, , Dimitri T. Azar. W.B. Dimitri T. Azar. W.B. Saunders Company 2001Saunders Company 2001

3.3. Lens Implant Power CalculationLens Implant Power Calculation, John A. , John A. Retzlaff, Slack Incorporated, 1990Retzlaff, Slack Incorporated, 1990

4.4. IOL PowerIOL Power, , Kenneth J Hoffer, Slack, 15 Mar Kenneth J Hoffer, Slack, 15 Mar 20112011