Phacoemulsification some Basic Ideas… Khalid M. Al-Arfaj, MD Dammam University

1-Quiz … 2- lecture … 3-Vedio …

Basic Phaco Settings

Basic Phaco Settings Sculpting 60 / 80 / 24 US, Vac, Asp.

Quadrant Removal/Burst 45 / 400 / 37 BW 50 - 120

Quadrant Removal/Pulse 45 / 376 / 35 PR 6

Horizontal Choping

Vertical Choping Courtesy of David Chang, MD

Evolution of IOL Calculation Formulas Clinical History Formula Used before 1975 Simple formula to calculate IOL power P = 18 + (1.25 x Ref) Poor accuracy >50% had >1D error “9 D surprise” – some huge errors due to the inaccuracy of calculating refractive error prior to cataract formation

Formulas and Their Derivations Regression Formulas Derived from retrospective computer analysis of postoperative data from a large number of patients SRK Formula P = A – 2.5L – 0.9K Derived by Sanders, Retzlaff and Kraff1 Required measurements L – Axial length (mm) K – Corneal power (D) A – A Constant 1 Sanders DR, Retzlaff J, Kraff MC. Arch Ophthalmol 1983;101:965-967

Formulas and Their Derivations SRK and early Theoretical formulas fairly accurate for eyes of moderate length Inaccuracies occurred at extremes of axial length

Modern Theoretical Formulas Most important concept is postop Anterior Chamber Depth is related to IOL placement in the eye, not to preop ACD All have a personalizable factor to improve accuracy of calculations Holladay/Holladay 2 S factor – personalized surgeon factor SRK/T A constant – based on multiple variables (IOL manufacturer, implant style, surgeon’s technique, etc.) Hoffer Q Personalized ACD value

Modern Theoretical Formulas All based on Thin Lens Optics

Modern Theoretical Formulas Found to be more accurate than older formulas All basically the same in predicting IOL power in average eyes Differences occur at extremes of AL and K’s Personalized factors based on optimal cases (PCIOL, intact capsule) Must change when surgical plan changes (Sulcus PCIOL or ACIOL)

Axial Length Measurement Current methods Contact A Scan Biometry Optical Biometry Partial Coherence Interferometry

A Scan Biometry Use of A scan ultrasound to measure axial length Contact

Normal Phakic Contact A Scan C1 – Anterior surface of Cornea C2 – Posterior surface of Cornea L1 – Anterior surface of Lens L2 – Posterior surface of Lens R – Retina

Optical Coherence Biometer IOL Master Fine beam of infrared laser used to measure axial length

ultrasound vs. optical biometry Ultrasound A-Scan 10MHz sound wave IOLMaster 780nm laser beam ILM RPE averaging across foveal cup reflection at Bruch's membrane Foveal thickness is about 150µ (±20) from ages 10 to 80 years. The parafoveal area is between 0.10 mm and 0.16 mm thicker.

alignment precision: ultrasound vs. optical Ultrasound A-Scan 10MHz sound wave A-scan US does not measure to the exact center of the fovea, but samples an area around it due to the broad angle of the U/S beam and fixation light. ? fixation blob IOLMaster 780nm laser beam IOLMaster uses a point fixation light, measures along visual axis to the RPE at foveal center and then adds back the foveal thickness. fixation point

Comparison of three methods myopia hyperopia partial coherence interferometry non-contact laser device phakic, pseudophakic, phakic IOLs posterior staphyloma, silicone oil not limited by wavelength or retinal thickness variations -0.5 0.0 0.5 myopia hyperopia applanation A-scan falsely short axial length variable corneal compression corneal micro-abrasions highly operator dependent source of IOL power errors -2.0 -1.0 0.0 1.0 2.0 90% 80% 70% 60% 50% 40% 30% 20% 10% 90% 80% 70% 60% 50% 40% 30% 20% 10% spherical equivalent prediction error (D) Data courtesy of Warren E. Hill, MD, FACS

Pearls and Pitfalls Measure axial length of both eyes Take multiple readings of each to assure accuracy Compare eyes Shouldn’t be a significant disparity in axial lengths unless a significant difference in refraction Axial Length measure too short - myopic surprise measure too long - hyperopic surprise Normal Eye: 1.0 mm error  2.5 to 3.0 D surprise Short Eye: 1.0 mm error  7.5 D surprise Keratometry 1D curvature error  1D surprise

What is your target postop refraction? IOL Power Selection What is your target postop refraction? Examine patient data Discuss with patient Match other eye? Monovision? Binocular distance? Binocular near?

How do you choose IOL? Material Configuration Delivery system Silicone IOL Choices How do you choose IOL? Material Silicone Acrylic PMMA Configuration One piece Three piece Delivery system Fold vs. Inject

Basic IOL Design Features Haptic Edge Optic

Basic IOL Design Features Haptic 1-piece 3-piece diameter Edge Optic

Haptic Design 1 13.0

Basic IOL Design Features Haptic Edge square rounded Optic

Square Rounded anterior reduced PCO reduced PCO dysphotopsias? Edge Design Square reduced PCO dysphotopsias? Rounded anterior reduced PCO reduced internal reflections

Optic Design Material Focality/Sphericity Diameter Rigid Foldable PMMA Foldable acrylic silicone collamer Focality/Sphericity Monofocal spheric toric wavefront aspheric Multifocal accomodative pseudoaccomodative Diameter 5.0 to 7.0 mm 6.0

Consider matching IOL design features with individual patient needs Which lens? Consider matching IOL design features with individual patient needs

High myopia Considerations: IOL size, power Lens choice High myopia Considerations: IOL size, power longer haptic span, larger optic diameter low power

High hyperopia Considerations: IOL size, power Lens choice High hyperopia Considerations: IOL size, power smaller haptic span, smaller optic diameter high power IOL

Presbyopia Considerations: spectacle independence Lens choice Presbyopia Considerations: spectacle independence multifocal IOL (accomodative, pseudoaccomodative) monovision using two monofocal IOLs

Astigmatism (corneal) Lens choice Astigmatism (corneal) Considerations: correct corneal astigmatism Toric IOL

Improved functional vision Lens choice Improved functional vision Considerations: maximize contrast sensitivity aspheric

Macular degeneration Considerations: block toxic UV light Lens choice Macular degeneration Considerations: block toxic UV light blue blocking chromophore

Pseudoexfoliation Considerations: Long term zonular stability Lens choice Pseudoexfoliation Considerations: Long term zonular stability avoid silicone material (capsular phimosis)

Crystalens “ Accommodating” Lens –single optic

Crystalens

Crystalens

The good Less capsule issues The Multifocals ReZoom & ReSTOR The good Less capsule issues Known material Good near vision The Bad: Unwanted photopsia Contrast sensitivity

ReZoom

AcrySof® ReSTOR® Apodized Diffractive IOL

Anatomy of the Apodized Diffractive IOL Step heights decrease peripherally from 1.3 – 0.2 microns Central 3.6 mm diffractive structure A +4.0 add at lens plane equaling +3.2 at spectacle plane

Patient Selection Pre-operative Exclusion Criteria Subjective Exclusion Hypercritical patients Patients with unrealistic expectations Occupational night drivers Medical Exclusion >1.0 D of corneal astigmatism? Pre-existing ocular pathology Previous refractive patients

Patient Satisfaction Crystalens, ReZoom, and ReSTOR all have clinical studies extolling the level of spectacle independence, excellent near, intermediate, and far vision of patients with these lenses.

Future Technology The HumanOptics IOL ( 1CU) is a single optic accommodative lens continuing in clinical trials in Europe. (Image courtesy of HumanOptics, Ophthal Clinics of N. Amer. March 2006.)

Future Technology Accommodative intraocular lenses with two optics. Gross photographs showing the injection of the Synchrony lens (Visiogen). Source: Liliana Werner, M.D., Ph.D. and Nick Mamalis,M.D.

Sarfarazi Lens Reproduced from Ophthal Clinics of N. Amer. March 2006 courtesy of Bausch & Lomb The Sarfarazi IOL, currently licensed by Bausch & Lomb, is comprised of a minus-powered optic positioned posteriorly to a positive-powered optic joined by compressible bridges.

Other Technology Lens replacement with flexible polymers injected into the capsular bag.