Modeling the Eye as an Optical System

Advanced Optics for OphthalmologyJim Schwiegerling, PhDOptical SciencesOphthalmology & Vision SciencesUniversity of Arizona1Accommodation

Relaxed ciliary muscle pulls zonules taut an flattens crystalline lens. Constrict ciliary muscle releases tension on zonules and crystalline lens bulges. Presbyopiasolidsmack.com/cad/the-mystery-of-the-disappearing-solidworks-drawing-view/visionhelp.wordpress.com/2012/07/21/presbyopia-old-man-look-at-my-life/presbyopia2/

Presbyopia

Your ability to accommodatereduces steadily with age.Typically, you dont noticethe effects until it affects yourability to read comfortably.This is presbyopia. 4Scatter

Scatter creates a large haloaround light sources andreduces contrast of a scene.Tom van den Berg Netherlands Institute for Neuroscience Cataract

http://webeye.ophth.uiowa.edu/eyeforum/cases/128-Posterior-Polar-Cataract.htm

Cataracts are an opacification of the crystalline lens in the eye. Early stages cause reduce light levels and scatter. Advanced stages cause (preventable) blindness.

Cataract extraction with intraocular lens implantation is the most widelyperformed surgery in the US. Roughly 20 million blind people worldwide due to cataracts.Couching

telemedicine.orbis.org &Wellcome Library London

Cataract Extraction

1735 The French oculist Jacques Daviel (16931762) developed a method for the removal of cataracts from the eyewww.daviddarling.info/encyclopedia/S/science_in_the_eighteenth_century.htmlAphakia

http://www.righttosightandhealth.org/senegal-pictures-2011/

Harold Ridley

Ridley noticed that shards from the canopy (PMMA)of RAF pilots lodge in their eyes did not get rejectedby the bodys immune system. Proposed making animplantable lens out of the material.

Intraocular Lenses (IOLs)

Reading Glasses

Conventional IOLs fix cataracts,but not presbyopia.Still need reading glasses to see up close.Multifocal IOLsNearFarMultifocal come in a variety of forms,but the basic concept is to have two different powers simultaneously on asingle lens. One power allows for distance vision, while the other allowsfor near vision.

Variations in zone size, number ofzones, power distribution, progressives,aspherics and diffractives all exist.

Simulated Images

Multifocal LensSingle Vision LensDistance VisionNear VisionRefractive Multifocal

Diffraction Grating

Diffractive Lens+10Addition of refractive lenscauses light to converge totwo pointsDiffractive Multifocal

http://www.midlandseyespecialist.comDiffractive IOLsRefractive IOLs tend to have more visual artifacts compared to diffractive lenses.Most multifocal IOLs today are diffractive lenses.These lenses are also limited because they give two distinct planes of focus.

Trifocal Diffractive Lens+20Alternating step heightscauses light to converge tothree points+1Diffractive IOLsBifocal Diffractive

Trifocal Diffractive

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Accommodating IOL

Accommodating IOL

Cataract Treatment EvolutionLens displacement or removal Blindness to light perception.Aphakic Spectacles Vision, limited field of view.IOL Normal distance vision.Multifocal IOL Distance and reading vision.Trifocal IOL Distance, intermediate and reading vision.Accommodating IOL Can focus at all ranges, like young healthy eye (in progress).Whats Needed in General76 million baby boomers.An understanding that people want normal or even enhanced abilities in their medical devices and treatments.Communication between physicians, scientists and engineers.Time & Support.

Whats NeededMaterials which are biocompatible and mechanical properties can be defined. (e.g. curvature changing IOL and phaco ersatz).Chemistry & Biochemistry, BME, AME.

Whats NeededNew imaging modalities to visualize crystalline lens in vivo. e.g. OCT, High-frequency Ultrasound, MRI.Medical Imaging, Optical Sciences, ECE

Whats NeededMiniature electronics, batteries, wireless recharging, solar power.ECE, Material Science, Optical Sciences

Whats NeededDrugs which slow the formation of cataracts, or reduce the scatter from cataracts after they have formed.Biochemistry, Pharmacology

Whats NeededPortable diagnostics & treatments.Telemedicine, ECE, Optical Sciences

SummaryThin slice of cataracts and their treatment, but many other medical conditions can be analyzed in the same way.Many of the solutions are multidisciplinary. How to communicate needs and capabilities?Strong and flexible Tech Transfer to work with medical device companies.