accommodating iols
DESCRIPTION
By Alan Glazier, ODTRANSCRIPT
Challenges and New Technologies forAccommodating Intra-Ocular Lenses
in Presbyopia
Alan N. Glazier, OD, FAAO2013
Binocular Accommodation• Six components of Accommodation • Mechanics of Each Function Together to Provide Human
Physiologic Binocular Accommodation• Four components recognized as vital
– increased convexity of the lens – anterior movement of the lens – miosis of the pupil– convergence of the eyes
• Two additional components; – pupillary compression– Gestalt (the “brain factor”)
• No one component of accommodation can account for binocular near vision/All six must function
Importance of Accommodative Amplitude
• Accommodative Amplitude – Latent and Manifest Ability of Ciliary Muscle to Exert and Sustain Effort on Ocular Lens at the Spectacle Plane
• “Pushing” does not equal “Sustaining”• Sheard’s Criterion – Standard for Determining Sufficient Amplitude for Near Vision Sustenance;
– One-Third to One-Half of the Accommodative Amplitude Needs to be Left in Reserve in Order to Allow for Sustained Near-Point Activity. (A patient able to achieve 2.5 D with an accommodative IOL should only be able to sustain use of perhaps 1.25 D freely - 2.5 D of accommodative amplitude does not equate with a 2.5-D bifocal add but more like a 1.25-D bifocal Add)
• Most Current Technologies Have Demonstrated Abilities of Slightly More Than 1.75 Diopters of Add Max• Reading Comfortably at 33 cm Would Require 3 D of Power at Spectacle Plane (4.5
to 6 D of Accommodative Amplitude - Leaving 1/3 of Accommodation Left in Reserve).
Hinged Accommodating IOLs
Tetraflex
Kellan Tetraflex IOL• Small-Incision (2.5mm) Single-Optic
Accommodative IOL. • Hydroxymethylmethacrylate• Has a 5.75- millimeter equiconvex optic and a
square-edged design to inhibit posterior capsular opacification
• Approved in Europe, Australia and the Middle East since 2003
• U.S. Trials are Beginning, With About 50 lenses Implanted to Date. On Sale in US
Crystalens (Bausch & Lomb)
Crystalens (Eyeonics)
• The Crystalens is a modified, hinged, plate-haptic silicone lens with polyimide loops. The lens has a high refractive index of 1.43 with a UV filter. The length of the lens plate is 10.5 mm, with a total IOL length of 11.5 mm. The lens optic is biconvex with a diameter of 5 mm. The IOL offers near and intermediate focal ranges by way of anterior displacement of the lens optic due to fluctuating pressures within the vitreous cavity as the ciliary body contracts
Crystalens• Extra Power Provided by the CrystaLens May Not be
Sufficient/May Still Require a Reading Add (Reading Add Still Required in About ½ of Patients)
• Small Optic - Issue With Patients With Large Pupils/Significant Pupillary Dilation in Dim Light - More Prone to Edge Glare
• Mean Accommodative Amplitude 1.79 diopters (Dell, Steven, MD) 96% percent of eyes had a change in distance acuity of ? ±1.0 D
ICU Akkommodative(Human Optics)
ICU Akkomodative
• Foldable, Single-Piece IOL with an Optic Diameter of 5.5 mm and an Overall length of 9.8 mm.
• Hydrophilic Acrylic material with a refractive index of 1.46.
• Biconvex, Square-Edged Optic and Four Flexible Haptics that Bend When Constricted in the Capsular Bag After Ciliary Body Contraction.
ICU Akkomodative• Accommodating Mechanism Can Play Role in Capsule Fibrosis,
Likely to Reduce Amplitude of Device as Patient Ages• Clinical Studies Report That Accommodation Amplitudes, 6 Months
After the Operation, Mean Value Between 1.7 D and 1.9 D• Approximately 1.80 D of Accommodation Occurs Per 1 mm of
Anterior Movement of the Lens Optic. (Langerbucher et al )• Mean Accommodative Amplitude Produced 1.8D (Kuchle et al)
Fibrosis – The Curse for Hinged Accommodating IOL’s
• Short and long term study results show that capsule bag reduces accommodative powers of the eye through shrinkage and fibrotic processes
• Often leads to IOL dislocation and explantation due to hinge optic designs. (Binder et al., Obertshausen, Germany)
• If Lens Doesn’t Move as Expected it Results in Diminished Accommodative Capacity or Myopia at Distance (Blur)
• Long-Term Stability of the Hinge and Accommodative Refractive Effect are not Known
• Fibrosis Likely to Reduce Amplitude of Device Further as Patient Ages
Other Challenges
• Increased Rate of CME Associated With Sulcus-Bag Placement of Haptics.
• Effects of Vitrectomy on Accommodative Performance of “Movable” IOL’s are unknown.
• Lower Powers → Less Accommodation• Capsular Contraction → Distortion and
Decentration• Wound Leaks → Unexpected Myopia
Dual Optic
Sarfarazi Elliptical IOL (Bausch &Lomb)
Synchrony (AMO)
Synchrony
• Designed With an Anterior High-Plus-Powered Lens and a Posterior Minus Lens
• Pseudophakic Accommodation Occurs When Zonular Tension is Released During Ciliary Body Contraction Resulting in a Compression of the Optic and Spring Haptic.
• Currently in Clinical Studies in the U.S. and Recently Received CE Mark in Europe
Synchrony Dual-Optic Accommodating IOL (Visiogen)
• Model Calculated Approximately 2.20 D of Accommodation
• Amplitude Measured at +2.50 (Burkhardt Dick, Cataract and Ref. Surgery, July 2004)
• Mean Accommodative Amplitude 2.55 D ( study by Ossma-Gomez, Ivan MD)
• Mean Monocular Amplitude of Accommodation : 3.17D
NuLens
NuLens
• Compressible Polymer Between Fixed Plates On Accommodative Effort Polymer Bulges Through Aperture in the Anterior Fixed Plate, Resulting in an Increase in the Steepness of the Anterior Surface.
• Still in Animal Studies
NuLens• Progressive Capsular Contraction Following
Cataract Extraction With Subsequent IOL Power Changes
• Difficult Distance (contracted ciliary body) IOL Power Calculations
• Optical Aberrations From Peripheral Portions of the IOL Not Undergoing Dynamic Power Changes
• Accommodation Not Governable• Elderly Average Remaining Ciliary “Strength”
Insufficient to Take Advantage of Amazing Accommodative Potential of Technology
SmartIOL
SmartIOL (Formerly SmartLens) (Medennium)
• Hydrophobic Acrylic Made Into a Stable 2mm Rod that can be inserted Into the Capsular Bag and Forms a Full-Size Lens
• Optic-9.5 by 3.5-mm – Same as Human Crystalline Lens
SmartIOL• Difficult to Determine How Much Gel to Inject to
Predictably Control Resulting Lens Power. • Capsulorhexis Must Be Small, So That It Can Be Sealed to
Confine the Gel. This May Require New Surgical Technologies.
• Control Needed to Get the Critical Optical Interface in the Central Location of the Capsulorhexis
• To Minimize Energy Consumption in Accommodation the Intracapsular Pressure Built Up By Lens Epithelial Cells has to be Restored By the Refill Procedure. Only Then Can the Exchange of Potential Elastic Energy Between the Lens Capsule and the Lens Matter Work. (Haefliger, E., Binningen, Switzerland)
The Fluid Lens (PowerVision)
• Redistributes Peripheral Fluid Centrally on Accommodation Increasing the Plus Power of the Optic
• Drives Fluid of a Polymer-Matched Refractive Index From the IOLs Soft Haptics Thru Channels to a Fluid-Driven Activator
• Causes an Accommodative Increase in the Anterior Curvature of the Lens
• Curvature Change Has Been Shown to be As High as 8D
• 6 Month Study on 30 Eyes Showed 5D Max
Quest Vision (AMO)
• Has Myopic Configuration in the Resting State and an Anterior Position in the Accommodative State
Electro-Active Accommodating IOL(Elenza – Roanoke, VA)
• Switchable Liquid Crystal Diffractive Lens• Electrical Control of the Refractive Index of a Nematic Liquid
Crystal Sandwiched Between A Photolithographically Defined Transparent Electrode
• Hydrophobic IOL with Hermetically Sealed Circuitry• Microsensors Detect Physiologic Changes in Light Triggered
by Accommodative Effort• Lithium Ion Power Cells Charged Weekly by an Inductive
Charging Element
LiquiLensVision Solutions Technologies
LiquiLens• Bi-Fluidic IOL• Gravity Based Mechanism Shifts Focal Plane on Down-
Gaze by Altering Interplay of Fluids Against One Another
• Capable of Providing Any Desired Spectacle Plane Addition
• Prototype Investigations Demonstrated 20D IOL Providing 13 Additional Diopters on Downgaze
• Can Be Designed With Any Desired Accommodation, from +1.00 D to +40 D
• Action Independent of Ciliary Mechanism
LiquiLens Challenges in Presbyopia
• Too Powerful for Young Presbyopes• No Mid-Range (Computer) Vision• Large Incision Required Currently
Multifocality
Mean Accomodative Amplitude (D)
Equivalent Add at
Spectacle Plane (D)
Optic Diameter
(mm)
Incision Size (mm)
Dependence on Ciliary
Mechanism
LiquiLens Bifocal As Desired As Desired 6-7 None
Crystalens Multifocal 1.79 Approx. 1.00 4.5 3.5 Total
ICU Akkomodative
Multifocal 1.7-1.9 Approx. 1.00 5.5 3.5-3.7 Total
NuLens Multifocal 10 Variable ? 5 Total
Synchrony Multifocal 2.55 – 3.17 1.50 5.5 3.6 Total
ReStor Multifocal Above 4 3.2 6 2.5 None
ReZoom Multifocal Above 4 2.75 6 2.5 None
SmartIOL Multifocal ? ? 9.5 3 Total
Sarfarazi Multifocal 7-8 (animal) ? 5 2-3 Total
PowerVision Multifocal ? ? ? ? Total
Quest Multifocal ? 3.00 ? ? Total
Kellan Tetraflex
Multifocal 2.4 1.2 5.75 2.5 Total
Other Experimental Technologies in Development
• Aspheric Multifocal M-Flex Lens • Asymmetric Diffactive Twin-Set IOL• Binderflex Lens Design (sulcus) designed to transmit the contractions of
the ciliary body directly onto the IOL in order to eliminate negative effects of the shrinking capsular bag on the accommodation process
• Presbyopic Ablation• Corneal Inlay• Laser Assisted Sclerectomy• PresView Scleral Implants• Femtosecond Interlenticular Surgery (Presbyopic Lentotomy) (Gerten,
MD, Augenklinik am Neumarkt , Koln, Germany ) • Pseudo Accommodative Advanced Surface Ablation• PHAKO ERSATZ
Phaco Ersatz (Lens Refilling Surgeries)
• Introduced by Julius Kessler in 1966.
• Jean-Marie Parel coined the term Phaco Ersatz at Bascom Palmer Eye Institute 1970’s.
• Extraction of the lens contents through a sub-1 mm mini-rhexis • Silicon polymers have been shown to have the adequate biocompatibility and optical properties
to restore accommodation in monkeys.
• Current efforts involve the development of safer polymers that can be cured in situ after lens refilling and avoiding the need of UV light. (Light Adjustable IOLs)
• PCO prevention remains a major hurdle
• Research is required for practical purposes as deciding the precise amount of refilling required. (Barraquer, R, Institut Universitari Barraquer, Barcelona, Spain)