bio medical optics by jai

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Bio Medical Optics

ByD.Jayakumar M.Sc., M.Tech.,Optical EngineerResearch & Development Division (Optics and Laser)Appasamy Associates, Chennai, India.


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Propertiesof Human

Eye

Radii of surfaces (mm)

Anterior cornea 7 . 80

Posterior cornea 6 . 50

Anterior lens 10 . 20

Posterior lens - 6 . 00

Refractive indices

Cornea 1 . 3771

Aqueous humor 1 . 3374

Lens 1 . 4200

Vitreous humor 1 . 3360

Optical Power


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Role of Optics

Replacement for Nature

Intra Ocular Lenses for CATRACT

Diagnosing tool Optical Coherence Tomography Retinal

diseases


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Cataract


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Definition of cataract Opacity of the lens, which occurs when fluid gathers between

the lens fibers.When eyes work properly:

Light passes through the cornea and the pupil to the lens.

The lens focuses light & producing clear, sharp images on the

retina. As a cataract develops, the lens becomes clouded, which

scatters the light and prevents a sharply defined image fromreaching retina. As a result, vision becomes blurred.


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HOW DOES A CATARACTAFFECT VISION?

Simulated CataractVision Simulated NormalVision

Photos courtesy of the NationalEye Institute

Gradually, visionbecomes dimmerObjects lose their

color


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Who gets CATRACT? And Difficulty

Almost everyone sooner or later but half of all peoplebetween the ages of 40s and 50s. Younger people too!!!

Certain diseases such as diabetes.

Personal behavior such as smoking and alcohol use.

The environment such as prolonged exposure to sunlight.

Difficulty

Seeing in the distance or reading.

Distinguishing road signs and Driving at night

Recognizing colors.


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DETECTING A CATARACT

Visual acuity test Slit lamp examination


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Visual acuity test


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Slit lamp examination


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TODAYS CATARACTSURGERY

Greatly improved technology

Usually no hospital stay or long recovery period

Safer, faster and more comfortable

than ever

THE CATARACT PROCEDURE

The clouded natural lens is removed

A man-made lens is inserted The new lens is an intraocular lens

(IOL)


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Replacement for NatureIntra Ocular Lenses


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Multifocal lens for Near, Middle and FarVision.

Induce negative Spherical Aberrationswith the lens to compensate for positivecorneal Spherical Aberrations

Aspheric Optics. Apodization for Glare and Halo reduction

Design Objective


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Spherical aberration occurs when lightrays areover-refracted at the periphery of a

lens system,

The Problem SphericalOptics

SphericalAberratio

n

MarginalRays

ParaxialRays

LightRays

Spherical IOL

*Smith,G.,AtchinsonD.A.,(1997)TheEyeandVisualOpticalInstruments.CambridgeUniversityPress,Cambridge,UnitedKingdom,pp.667.


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AsphericSurface

Aspheric optics align the light rays tocompensate for positive cornealspherical aberration, resulting in

enhanced image quality.

The Solution AsphericOptics

*Smith,G.,AtchinsonD.A.,(1997)TheEyeandVisualOpticalInstruments.CambridgeUniversityPress,Cambridge,UnitedKingdom,pp.667.

LightRays

Aspheric IOL


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Anatomy of the Apodized

Diffractive Technology13.0 mm

AnteriorApodizedDiffractiveOptic

6.0 mm6.0 mm

SymmetricBiconvex

AnteriorAspheric Optic


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Anatomy of the Apodized

Diffractive TechnologyCentral 3.6 mmapodized diffractivestructure

Step heightsdecreaseperipherally from1.3 0.2 microns

Outer refractivezone

Anterior

aspheric

optic


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Gradual reduction orblending

of the diffractive stepheights.

Optimally manages

light energy deliveredto the retina as itdistributes the

appropriate amount

Apodization

1.3 micronstep


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Technology of the AcrySofReSTOR IOL in Human

Terms Thickness of a Human

Hair

= 60 microns

Thickness of a RedBlood Cell= 7 microns


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AcrySof ReSTORAspheric IOL

(SN6AD3) Specifications13.0 mm

6.0 mm

OPTICS

Multifocal Apodized Diffractive Optic

Compensation for PositiveCorneal Spherical Aberration

Aspheric Optic

Optic Type Proprietary Symmetric Biconvex

Optic Diameter 6.0 mm

Overall Length 13.0 mm

MATERIAL

Optic/Haptic Material AcrySof Hydrophobic Acrylic

Light Filtration UV and High-Energy Blue

DESIGN

IOL Design Single-Piece

Haptic Design STABLEFORCE Modified-L

SPECIFICATIONS

Diopter Range +10 D +30 D in 0.5 D increments+31 D +34 D in 1.0 D increments


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Diagnosing toolOptical Coherence Tomography

(OCT)


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OCT in non-invasive

diagnostics Ophthalmology

diagnosing retinaldiseases.

Dermatology skin diseases, early detection of skin

cancers. Cardio-vascular diseases

vulnerable plaquedetection.

Endoscopy (fiber-optic

devices) gastroenterology gynecology

Embryology/Developmental biology

Functional imaging Doppler OCT (blood flow) spectroscopic OCT (absorption,

high speed) optical properties Polarization Sensitive-OCT

(birefringence).

Guided surgery

delicate procedures brain surgery, knee surgery


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Optical Coherence Tomography

Measuring the echo timedelay and magnitude of

backscattered light. Non-invasive three-

dimensional imagingtechnique with the

resolution of 1-15 m


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l a t e r a l ( X )s c a n n i n gm i r r o r

n e g a t i v e l e n s

a x i a l( Z - a x i s )

s c a n

p h o t o d e t e c t o r

videomonitor

electronics

A SCAN

B SCAN

OCT using fiber optics


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OCT using fiber optics

electronics

photodetector

SLD

sample

referenc

e

D l t f S t S


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RF

Generator

SLD

Driver

SLD FC/PC AOT

F

CCD

computer

L1

L2

Reference

Sample

Development of Swept-SourceOCT System

BS

Swept-Source FDOCT


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Swept Source FDOCT

swept

laser

fixed refmirror

inverseFouriertransfor

m

electronics

1/

I

Distance


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ophthalmology

Normalpatient

Patient with impaired vision(20/80):The cause is a macular hole

Patients other eye (vision20/25):Impending macular hole, whichcan be treated

http://rleweb.mit.edu/Publications/currents/cur11-2/11-


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1,000 Ascans. 17

images/sec

Fundusimage

from 3D

data

Volumetric3D image(5.7 sec)


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Glaucoma


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Non Contact Tonometer


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Slit Lamp


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Diabetic retinopathy

Normal Retina


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Fundus Camera

bio medical optics by jai

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