medical optics

8/2/2019 Medical Optics

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Bio Medical Optics

Jayakumar D Swamy M.Sc., M.Tech.,

Optical Engineer


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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 & producingclear, sharp images on theretina.

As a cataract develops, the lens becomes clouded, whichscatters the light and prevents a sharply defined image fromreaching retina. As a result, vision becomes blurred.


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Causes of cataract

Old age (commonest)

Ocular & systemic diseases

DM

Uveitis

Previous ocular surgery

Systemic medication

Steroids

Phenothiazines

Trauma & intraocular foreign

bodies Ionizing radiation

X-ray

UV

Congenital

Dominant

Sporadic

Part of a syndrome

Abnormal galactosemetabolism

Hypoglycemia

Inherited abnormality

Myotonic dystrophy

Marfans syndrom

Rubella

High myopia


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Cataract

Divided to :

Acquired cataract

Age - related cataract

Presenile cataract

Traumatic cataract

Drug induced cataract

Secondary cataract

Congenital Cataract

Systemic associationNon-systemic association


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Age -related cataract

It is the Most commonly occurred.Classified according to:

Morphological Classification

Nuclear

Cortical

Subcapsular

Christmas tree uncommon

Maturity classification

Immature Cataract

Mature Cataract

Hypermature Cataract


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Nuclear cataract Most common type

Age-related

Occur in the center of the lens. In its early stages, as the lens changes theway it focuses light, patient may becomemore nearsighted or even experience atemporary improvement in reading vision.Some people actually stop needing their

glasses. Unfortunately, this so-called 2nd sightdisappears as the lens gradually turns moredensely yellow & further clouds vision.

As the cataract progresses, the lens mayeven turn brown. Advanced discoloration

can lead to difficulty distinguishing betweenshades of blue & purple.


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Cortical cataract

Occur on the outer edge of the lens (cortex).

Begins as whitish, wedge-shaped opacities or streaks.

Its slowly progresses, the streaks extend to the center and

interfere with light passing through the center of the lens.

Problems with glare are common with this type of cataract.


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Symptoms

A cataract usually developsslowly, so:

Causes no pain.

Cloudiness may affect only asmall part of the lens

People may be unaware of anyvision loss.

Over time, however, as thecataract grows larger, it:

Clouds more the lens

Distorts the light passingthrough the lens.

Impairs vision

Reduced visual acuity (near

and distant object)

Glare in sunshine or with

street/car lights.

Distortion of lines.

Monocular diplopia.

Altered colours ( white

objects appear yellowish) Not associated with pain,

discharge or redness of the

eye


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Signs

Reduced acuity.

An abnormally dim red reflex is seen when the eye is viewedwith an ophthalmoscope.

Reduced contrast sensitivity can be measured by the

ophthalmologist. Only sever dense cataracts causing severely impaired visioncause a white pupil.

After pupils have been dilated, slit lamp examination shows thetype of cataract.


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Gradual loss of vision

DDX:

1. Cataract

2. Glaucoma

3. Diabetic retinopathy4. Hypertensive retinopathy

5. Age related macular degeneration

6. Retinitis pigmentosa

7. Trachoma8. Onchocerciasis (river blindness)

9. Vitamin A deficiency


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Treatment

Glasses: Cataract alters the refractive power of the natural lens

so glasses may allow good vision to be maintained.

Surgical removal: when visual acuity can't be improved with

glasses.

Surgical techniques

Phacoemulsification method.

Extracapsular method. Intracapsular method


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Pre-op assesments

General health evaluation including blood pressure check

Assessment of patients ability to co-operate with theprocedure and lie reasonably flat during surgery

Instruction on eye drop instillation

The eyes should have a normal pressure, or any pre-existingglaucoma should be adequately controlled on medications.

An operating microscope is needed, in order to reach the lens,a small corneal incision is made close to the limbus for the

phaco-probe. It is important to appreciate anterior chamber depth and to

keep all instruments away from the corneal endothelium in theplane of the iris.


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Pupil conjugate plane

Lamp

Aperture

45 mirror

Practical Retinal Illumination System


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Retinal Imaging System


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stop in pupil planeconjugate

circular aperturein stop

opticaxis

SUBJECT


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opticaxis

observers pupil inconjugate pupil plane

SUBJECT

OBSERVER


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FIRST ATTEMPT AT BINOCULAR VIEW

Obs. L eye

Obs. R eye

Ss eye

Combine L and R eye views

Observers eyes have to be too close


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OPHTHALMOSCOPE MAGNIFICATION


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20 DlensRI

60 Deye

OPHTHALMOSCOPE MAGNIFICATION

Mag of RI

Peye

Plens=

60 D

20 D

= 3.0M =


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42

40 mm

50 mm

20 D

1 mm dia exit pupil

2.0 mm

MONOCULAR FIELD OF VIEW


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20 D

40

Area of binocular view

BINOCULAR FIELD OF VIEW

GTT 04


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Clear Aperture: CLAP

Working Distance: WD CLAP2

WD

54.72 mm

51.04 mm

= 24 mm

47 mm

CLAPWD= tan-1 ( (

= 23.7 FOV = 47.4 = 25.2 FOV = 50.3 = 25.2 FOV = 50.3

Example: OI Maxlight 20 DCLAP = 48 mmWD = 47 mmFOV = 50

ESTIMATING FIELD OF VIEW


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Complete binocular

Indirect

ophthalmoscope


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GTT 05


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hole in 45o mirror


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camera or CCD

Fundus camera


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3. Optical Coherence Tomography (OCT)

h f h


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coherent incoherent

partially coherent

Coherence of Light Waves


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Laser Beam Coherence

Laser

coherence

length


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fixedmirror

movable

mirror

laser

negative lens

screen

interferencefringes

beam-splittingprism

L1

L1

L2

Michelson Interferometer

reference arm

sample arm


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screen

plane wavesfrom fixedmirror

plane wavesfrom movablemirror

Interference Fringes in Michelson Interferometer


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low coherence length

long coherence length

Mi h l I t f t O ti l C h T h


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movable

mirror

laser

negative lens

fixedmirror

Michelson Interferometer Optical Coherence Tomography

photodetector

electronics

video monitor


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lateral (X)scanningmirror

negative lens

axial(Z-axis)

scan

photodetector

sample

video monitor

electronics

reference arm

sample arm


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Fringes form when reference mirror path length matches path

length of a reflective piece in the tissue in the sample arm.

Fringes only form when the path difference is within the

coherence length of the light source.

IN MICHELSON INTERFEROMETER


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lateral (X)scanningmirror

negative lens

axial(Z-axis)

scan

photodetector

video monitor

electronics

A SCAN

B SCAN

OCT using fiber optics


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electronics

photodetector SLD

sample

reference


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GTT/98


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MICROSCOPES

ANGULAR MAGNIFICATION


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Apparent size of object depends on angle it subtends at eye.

100 m

100 m

10 m

10 m


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25 cm

On average, an object cannot be closer than 25 cm from the eye to be seen clearly.

Average distance of

most distinct vision

ANGULAR MAGNIFICATION


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25 cm

f

h

25 cm

f

h

tanh

25

tan hf

Angular Magnification =tan

tan h25

h

f= =

25

f

virtual image

cm

(cm)


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Eye

Eyepiece

Objective

Object f

Real imagef

objective

eyepiece

BASIC MICROSCOPE

magnifier

real image

magnification


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M1

=Im

Ob

M2

=25

f

Mtotal

=Im

Ob

25

f

X

MICROSCOPE MAGNIFICATION

OBJECTIVES


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anw.d.

D

NA = sinn a

a= 14

n = 1.00 (air)

EXAMPLE

NA = 1.00 x sin(14 )

NA = 0.24

OBJECTIVESNumerical Aperture (NA)

Light gathering ability Resolution

OBJECTIVES


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a = 28n =1.00

NA = 0.46

a = 35n =1.00

NA = 0.57

a = 60n =1.52 (oil)

NA = 1.32

OBJECTIVES

N.A. Examples

EYEPIECES


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converging

rays from

objective

Real image

Real image

parallel rays from

eyepiece

Huygens RamsdenEYEPIECES

(OCULARS)

D


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Specimen

Objective

Real image

REAL MICROSCOPE

EXPERIMENT 4


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EXPERIMENT 4

Basic Microscope

onion skin

real image

on card

f

Produce real image of onion skin on card.

Mark distance of real image on base.

irisdiaphragm

EXPERIMENT 4--CONTINUED


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View real image with magnifier (eyepiece)

real

image

plane

f

Adjust iris diaphragm. How does image change?

What is the total magnification? Mtotal=

Im

Ob

25

fX


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Slit-lamp Biomicroscope


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The slit-lamp biomicroscope

begins with a microscope.

Objective

Specimen

Eyepiece

turned on its side


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.turned on its side

subjectobjective

Huygens

eyepiece

.fundamental slit-lamp biomicroscope

.change specimen, objective & eyepiece

image

plane

B ild i ifi ti h ith t h i ki


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Build in magnification change without changing working

distance

fobj

Galilean

telescope to

change mag

working

distance

no image in

image plane

B ild i ifi ti h ith t h i ki


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Build in magnification change without changing working

distance

fobj

Galilean

telescope to

change mag

working

distance

no image in

image planeD


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..add lens to form image in eyepiece image plane

astronomical

telescope

D

Porro* prism


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F

F

p

2 right-angle prisms

1800 image rotation

reduce length of

telescope

displace image

horizontally

Porro -Abbe


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Slit-lamp with folded optical path

D


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D


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binocular slit-lamp viewing system


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Anatomy of the ApodizedDiffractive Technology

Central 3.6 mm apodized

diffractive structure

Step heightsdecrease peripherally from

1.3 0.2 microns

A +4 D at lens plane

equaling +3.2 at spectacle

plane

Outer refractive zone

Anterior

aspheric

optic


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Anatomy of the ApodizedDiffractive Technology

13.0 mm

Anterior

Apodized

Diffractive Optic

6.0 mm6.0 mm

Symmetric

Biconvex

Anterior Aspheric

Optic


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Gradual reduction or blendingof the diffractive step heights.

Optimally manages light energy

delivered to the retina as itdistributes the appropriateamount of light to near anddistant focal points, regardlessof the lighting situation.

Designed to improve imagequality while minimizing visualdisturbances.

Apodization

1.3 micron

step


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Technology of the AcrySofReSTORIOL in Human Terms

Thickness of a Human Hair= 60 microns

Thickness of a Red Blood Cell= 7 microns

Step Height at periphery ofthe diffractive portion of theAcrySof ReSTOR AsphericIOL = 0.2 microns


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Design considerations for the AcrySof

ReSTOR Aspheric IOL:

Induce negative Spherical Aberrationswith the lens to compensate for positive

corneal Spherical Aberrations

Design Objective


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Spherical aberration occurs when light rays areover-refracted at the periphery of a lens system,resulting in a region of defocused light which candecrease image quality.

The Problem Spherical Optics

Spherical

Aberration

Marginal Rays

Paraxial Rays

Light Rays

Spherical IOL

*Smith, G., Atchinson D.A., (1997) The Eye and Visual Optical Instruments. Cambridge University Press, Cambridge, United Kingdom, pp. 667.


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Aspheric

Surface

Aspheric optics align the light rays to compensate for positivecorneal spherical aberration, resulting in enhanced imagequality.

The Solution Aspheric Optics

*Smith, G., Atchinson D.A., (1997) The Eye and Visual Optical Instruments. Cambridge University Press, Cambridge, United Kingdom, pp. 667.

Light Rays

Aspheric IOL


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AcrySof ReSTOR Aspheric IOL(SN6AD3) Specifications

13.0 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 mmOverall Length 13.0 mm

MATERIAL

Optic/Haptic Material AcrySofHydrophobic Acrylic

Light Filtration UV and High-Energy Blue

DESIGN

IOL Design Single-Piece

Haptic Design STABLEFORCEModified-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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Surgical Loupe


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OCT: Basic Principles

Three-dimensional imaging technique with highspatial resolution and large penetration depth even

in highly scattering media

Based on measurements of the reflected light fromtissue discontinuities

e.g. the epidermis-dermis junction.

Based on interferometry

interference between the reflected light and the reference

beam is used as a coherence gate to isolate light from

specific depth.


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1 mm 1 cm 10 cm

Penetration depth (log)

1 mm

10 mm

100 mm

1 mm

Resolution (log)

OCTConfocal

microscopy

Ultrasound

Standard

clinical

High

frequency

OCT vs. standard imaging

OCT in non invasive


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OCT in non-invasive

diagnostics

Ophthalmology diagnosing retinal diseases.

Dermatology skin diseases,

early detection of skin cancers.

Cardio-vascular diseases vulnerable plaque detection.

Endoscopy (fiber-optic devices) gastroenterology

gynecology

Embryology/Developmentalbiology

Functional imaging Doppler OCT (blood flow)

spectroscopic OCT (absorption, highspeed)

optical properties

Polarization Sensitive-OCT(birefringence).

Guided surgery

delicate procedures

brain surgery,

knee surgery

OCT: Principle of operation


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OCT: Principle of operation

OCT is analogous to ultrasound imaging

Uses infrared light instead of sound

Interferometry

is used to measuresmall time delays

of scattered photons

Human skin

5 mm wide x 1.6 mm deepSpatialResolution: 10-30 m

Time resolution: 30fs!!!

Speed of sound ~ 1480 m/sec (in water)

Speed of light 3x108 m/sec


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Good OCT sources have small coherence length and large bandwidth

Axial resolution


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Axial resolution

The axial resolution is

notice that D is the 3dB-bandwidth!

The broader the bandwidth the shorter the

coherence length and the higher the resolution

2 2

0 02 ln 2 1 2 ln 2

0.44c

cl

D D D


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Lateral resolution: Decoupled from


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axial resolution

xD

2 xD4 f

xd

D

Lateral resolution

Dz

Dz

Dz

High NA

Low NA

xDb Dz

Lateral resolution similar to that in a standard microscope

f=focal length

d= lens diameter

Light sources for OCT


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Continuous sources SLD/LED/superfluorescent fibers,

center wavelength;

800 nm (SLD),

1300 nm (SLD, LED),

1550 nm, (LED, fiber), power: 1 to 10 mW (c.w.) is sufficient,

coherence length;

10 to 15 mm (typically),

Example

25 nm bandwidth @ 800 nm12 mm coherence length (in air).

S l i t di d (SLD )


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Superluminescent diodes (SLDs)Definition: broadband semiconductor light sources based on

superluminescence(Acronym: SLD)

Superluminescent diodes (also sometimes called superluminescence diodes or

superluminescent LEDs) are optoelectronic semiconductor devices which are

emitting broadband optical radiation based on superluminescence. They are

similar to laser diodes, containing an electrically driven p-n junction and an

optical waveguide, but lack optical feedback, so that no laser action can occur.Optical feedback, which could lead to the formation ofcavity modes and thus

to pronounced structures in the spectrum and/or to spectral narrowing, is

suppressed by means of tilting the output facet relative to the waveguide, and

can be suppressed further with anti-reflection coatings.

Superluminescence: amplified spontaneous emission

http://www.rp-photonics.com/superluminescent_diodes.html

http://www.rp-photonics.com/superluminescence.htmlhttp://www.rp-photonics.com/laser_diodes.htmlhttp://www.rp-photonics.com/waveguides.htmlhttp://www.rp-photonics.com/lasers.htmlhttp://www.rp-photonics.com/cavity_modes.htmlhttp://www.rp-photonics.com/anti_reflection_coatings.htmlhttp://www.rp-photonics.com/anti_reflection_coatings.htmlhttp://www.rp-photonics.com/anti_reflection_coatings.htmlhttp://www.rp-photonics.com/anti_reflection_coatings.htmlhttp://www.rp-photonics.com/cavity_modes.htmlhttp://www.rp-photonics.com/lasers.htmlhttp://www.rp-photonics.com/waveguides.htmlhttp://www.rp-photonics.com/laser_diodes.htmlhttp://www.rp-photonics.com/superluminescence.html


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Pulsed lasers mode-locked Ti:Al2O3 (800 nm),

3 micron axial resolution (or less).

Scanning sources tune narrow-width wavelength over entire spectrum,

resolution similar to other sources,

advantage that reference arm is not scanned,

advantage that fast scanning is feasible.

Construction of image


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Construction of image

Source of contrast: refractive

index variations

Image reconstructed by

scanning

Applications in ophthalmology


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Normal patient

Patient with impaired vision (20/80):

The cause is a macular hole

Patients other eye (vision 20/25):

Impending macular hole, which can be

treated

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

Applications in cancer detection


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Applications in cancer detection

Loss of organization

Columnar epithelium: crypts

Squamous epithelium


Applications in developmental biology


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pp p gy

Ey=eye; ea=ear; m=dedulla; g=gills; h=heart; i=intestine

Ultra high resolution OCT


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Ultra-high resolution OCT

Image through the skin of a living frog tadpole

Resolution: 3 mm


Ultra-high-resolution-OCT


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mm

mm

versus commercial OCT

W. Drexler et al., Ultrahigh-resolution ophthalmic optical coherence

tomography, Nature Medicine 7, 502-507 (2001)

3-D Reconstruction: In vivo images of human eyeusing spectral-domain OCT


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using spectral domain OCT

RPE

NFL

I

T

N

S

I

S

TN

N. A. Nassifet al., Opt. Express 12, 367-376 (2004)


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Applanation tonometry

Theoretical Basis


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Applanation tonometry is based on the Inbert-Fick

principle.

Which states that for an ideal sphere the pressure (P)

inside the sphere is equal to the force (F) required to

applanate (flatten) its surface, divided by the area (A)

of flattening:P = F/A or F = PA.

The ideal sphere is dry, thin-walled, and readily

flexible.

The cornea, which is not even a true sphere, is none of

these three. Because of this, there are two other

significant forces at work.


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The force of capillary attraction (T) between the

tonometer head and the tear film is additive tothe external force.

In addition, a force (C), independent of IOP, is

required to flatten the relatively inflexible

cornea. Thus,

F = PA , becomes

F + T = PA + C , orP =( F + T - C) / A

The A is actually on the interior surface of the


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The A, is actually on the interior surface of the

cornea.

The Goldmann applanator is designed so that Ais equal to 7.35 mm 2.

To achieve this, the diameter of flattening of the

cornea is 3.06 mm.

With this value for A, the opposing forces of

capillary attraction and corneal inflexibility

cancel out.P = F / 7.35 mm 2


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In addition, with this value for A the IOP in

millimeters of mercury (mmHg) is equal to tentimes the force applied to the cornea in grams,

which is a convenient conversion.

Since only 0.5 m{mu} is displaced from the eyeand the additional increase in pressure induced

in the eye from its steady state by the

tonometer tip is negligible, applanation

tonometery is not significantly affected by

ocular rigidity.

Slit Lamp Imaging


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Slit Lamp Imaging


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UC Berkeley Retinal Reading Program


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Diabetic Retinopathy Screening with EyePACS

Program Manual

10/07

EyePACS

Anatomy of the Retina


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Optic Disc

Macula

Superior temporal artery and vein

Inferior temporal artery and vein

MaculaSuperior temporal

artery and vein

Inferior temporal artery

and vein

RIGHT EYE

RIGHT EYE


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GLAUCOMA

Sneak Thief of Sight

GLAUCOMA


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GLAUCOMA

13% of the blind in India have been

blinded due to Glaucoma

It may be


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YOU


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GLAUCOMA

PATIENT EDUCATION

Glaucoma: The Disease


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Caused by increased pressure of fluid in theeye

The fluid is known as aqueous humor.

Aqueous humor is not same as tears, whichbathe the outside of the eye.

Aqueous humor maintains the normal shapeof the eyeball and nourishes its internalstructure



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Normal Drainage

Picture

The Trabecular meshwork is

the eyes drain

The Ciliary Bodyis the eyes faucet

or tap where fluid is made

When this drainage of the fluid gets blocked, excess

pressure is formed leading to Glaucoma

Lens

Glaucoma: Symptoms


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y p

Most patients with Glaucoma, especially Primary Open Angle Glaucoma

are asymptomatic i.e. without any symptoms, until late in the course ofdisease. However, certain patients may have symptoms such as pain,redness, halo vision, blurred vision.


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Tunnelvision

Red eye, pain in theeye,

Halo around lights

Blurred vision

Visionloss

SYMPTOMS
http://www26.brinkster.com/cowjam/photos/red%20eye.jpg


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Glaucoma: Symptoms


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Glaucoma: Symptoms

Normal vision

Reduced side vision,

central vision intactTunnel

vision

How common is glaucoma and who gets it?


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Any one at any age can get glaucoma,

but the older you are the more likely

you are to get it.

People above 45 years are more likely

to get Glaucoma.

Who is most likely to get glaucoma?


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y g g

You are more likely to get glaucoma if you:

Have family members with glaucoma

Are over 45 years of age

Have poor vision

Have diabetes

Take steroid medication Previous eye injury.

Glaucoma: Types of Glaucoma


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Chronic or

Primary Open

Angle Glaucoma

Clogged Drainage holes

The angle between the iris and the cornea is normal,

but the drainage holes get clogged from the inside.

Lens

Glaucoma: Types of Glaucoma


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Acute Angle

Closure Glaucoma

Blocked Drainage holes

The angle is narrower than normal. If fluid cant flow

easily through the opening in the pupil, the iris pushes

forward and blocks the drainage holes.

Lens

How can I find out if I have glaucoma?


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A series of test performed by your eye doctor

will help to determine whether you have

glaucoma or likely to develop glaucoma.

Glaucoma: Diagnosis


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1st History and General Examination

Glaucoma: Diagnosis


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5th PerimetryActual measurement of visual field looking for any

dark areas in field of vision

Treatment Options


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Eye drops

Pills

Laser surgery Eye operations

Combination

method

Glaucoma: Treatment


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MEDICAL

Drugs increase conventional outflow.

Lens

Glaucoma: Treatment


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Drugs reduce production of fluid in the eye.

LensMEDICAL


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The purpose of treatment is to

prevent further loss of vision.

This is important because loss of

vision due to glaucoma is

irreversible.

Glaucoma: Treatment


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SURGERY

Trabeculectomy

New Drain

Sclera

Lens

Glaucoma: Treatment


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SURGERY

Trabeculoplasty

Lens

Open Drainage hole

Laser

Glaucoma: Treatment


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SURGERY

Iridotomy

Laser

Lens

Making a tiny opening in theiris with a laser allows fluid to

drain freely

Will I go blind because of glaucoma?


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If glaucoma is left untreated, damage increases,

which may eventually lead to blindness.

Therefore, you should have


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Regular eye examinations Regular intake of medications as

instructed by the ophthalmologist

Dos and Donts of Glaucoma


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Stock the medicine before they run out; it isimportant to continue medication on schedule

If more than one drug is used, wait for 10 minutes

between drops

Do not increase the number or amount of

medication taken at one time.

Do not stop taking medication just because you

have no obvious symptoms

Dos and Donts of Glaucoma


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Take all prescribed doses.

Remember to take medications with you when

you travel

Learn how to take eye drops properly ask yourdoctor for help

Maintain a record with your medication schedule

and lists of treatments and doctors

Remember


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Treatment for glaucoma requires a team made up of bothyou and your doctor (ophthalmologist)

Your doctor can prescribe treatment for glaucoma, but only

you can make sure to put your eye drops regularly

Do not stop taking or changing your medications withoutfirst consulting your doctor (ophthalmologist)

Frequent eye examinations and tests are critical to monitor

your eyes for any changes

Remember,

It is your vision, and therefore its your responsibility to maintain it

Diagram of the Canon CR6-45NM


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FocusKnob

Monitor

Setting

Switches

Power

Lamp

Shutter Button

JoystickHeight Adjusting Dial

View SwitchingButtonFixation Target Button

Platform LockingKnob

Diagram of the Canon CR6-45NM


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Small Pupil KnobInfrared Ray Knob

Lamp Knob

Power SwitchFuse Holders

Power Connector

Forehead Rest

HeightAdjustment Mark

Objective Lens

Chin RestHeight AdjustmentRing

RS422A Connector

Focus Knob

High Correction Sleeve

Fundus Reflex Photographs and 3 Standard FieldsFirst Set: The Right Eye Invert if using Canon DGi

External: Fundus Reflex


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Field 1: Macula

Field 2: DiscPosition the optic disc at the center. Use the

Fixation Target to position the optic disc (2 stops left

from default).

Position the macula to the far left of the optic

disc.Field 3: Temporal to Macula

Position the optic disc to the far right until it has

disappeared from the screen. Use the Fixation Target

to position the optic disc off to the left (3 stops right

from default).

Position the macula a little lower and a little off to

the right of the center.

High correction sleeve on right side of camera is pulled out;

set S.P. setting to on; F-stop set to F-1; head is positioned 1

inch from head rest bar; focus on iris detail.

High correction sleeve on right side of camera is pushed in;

set S.P. setting to off , F-stop set to ~F-4 F-5

The Optic Disc and Macula should be about equal

distances from the center. This is the default position of

the camera when it is turned on.


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Using EyeScapeOnce finished taking photos click End Procedure


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g p

Review your photos. Discard any poor quality photos by highlighting the photo tab and

clicking the Delete button. Once you have the best photos in order, click the Save all button.

Upload Instructions(continued)Step Five: Uploading is not complete until you see the View Case Details page with thumbnail images

of the retinal images you captured


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of the retinal images you captured.

Depth of focus


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D Wilson 2002

The effects of a smaller pupil

O'

O''

O'''

I'''

I''

I'

Blur

circles

Screen

p

The pupil & aberrations


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p p

Spherical aberration and coma are reduced by the

eyes pupil

D Wilson 2002

E

E (entrance pupil)

The pupil & spectacle

magnification


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magnification

Spectacle magnification will occur at all positions

except at the entrance pupil

D Wilson 2002

E

E (entrance pupil)

The pinhole & myopia


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Lewis Williams 2002

Myopia

With pinhole

Without pinhole

Pinhole

aperture

Blur circles

The pinhole & hyperopia


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Lewis Williams 2002

Blur circles

With pinhole

Without pinhole

Hyperopia

Pinhole

aperture

The effects of the pinhole


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Without pinhole aperture

With pinhole aperture

F or P?

Lewis Williams 2001

The future of vision


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Super

vision



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Can we improve on creation?Yes



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Aberrations and the eye

The eye is subject to wavefront aberrations

These affect all eyes but are more significant incases of:

Keratoconus

Larger pupils

Corneal surgery (eg refractive surgery)



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It is possible to correct these aberrations in the

laboratory but not yet clinically

Work is currently underway to correct the

aberrations for real subjects using:

The excimer laser to custom ablate (wavefront

guidance)Customised, aberration correcting, contact lenses

but they may change the corneal curvature



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What are the optical limits?

Diffraction

Changing aberrations with changing accommodation

Changing aberrations with changing direction of gaze

Changing aberrations with the ageing eye

Chromatic aberration



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Are there other limits?

Image transmission

The cones are 0.5' of arc apart, meaning we have digital

vision!

So, the image may be too detailed for the receptors

creating the familiar TV tweed coat effect



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Restoration of natural vision

Insert for ametropia

Accommodating

IOL


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Radiation WavelengthsSURYA


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193 nm - Excimer (Cornea)

488 - 514 nm - Argon (Retina)

694.3 nm - Ruby

780 - 840 nm - Diode

1064 nm - Nd Yag (Capsule)

10,600 nm - Carbon dioxide (Skin)

UsesSURYA


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Diagnostic Therapeutic

Diagnostic UsesSURYA


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Laser Fluorescence Spectroscopy

Scanning Laser Ophthalmoscopy

Laser Interferometry

Fundus Fluorescein Angiography

Ffa PIC

Therapeutic UsesSURYA


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Widely Used -

Extra-ocular adnexae Anterior Segment

Posterior Segment



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LASIK

Suction Ring Microkeratome Flap Removed



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LASIK

LASIK Flap Replaced Post - Op.

Therapeutic Uses

B Anterior SegmentSURYA


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B. Anterior Segment



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What is Glaucoma ?

Therapeutic Uses

B Anterior SegmentSURYA


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iv. Reopen failedfiltering blebs

v. Iridoplasty,

Gonioplastyvi. Iris cyst,Pupilloplasty

B. Anterior Segment

Therapeutic Uses

B. Anterior SegmentSURYA


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vii. Posterior Capsular Opacification

B. Anterior Segment

Therapeutic UsesC. Posterior Segment

SURYA


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C. Posterior Segment

What is Diabetic Retinopathy ?



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p y




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i. Diabetic Retinopathy



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i. Diabetic Retinopathy



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Focal Grid Panretinal



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ii. Retinal Haemorrhage



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iii. Retinal Breaks or Tears



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iv. Subretinal neovascularisation

v. Central serous retinopathy


Therapeutic Uses

C. Posterior SegmentSURYA


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vi. Vitreolysis in cystoid macular edema

g

Therapeutic Uses

C. Posterior SegmentSURYA


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vii. Vitreous traction bands, to freeencapsulated foreign bodies

g

Therapeutic Uses

C Posterior SegmentSURYA


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viii. Drainage of subretinal fluid / haem.


Therapeutic UsesC. Posterior Segment SURYA


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ix. Intraocular tumors (RB)

Therapeutic UsesC. Posterior Segment SURYA


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ix. Intraocular tumors (Choroidal Melanoma)



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x. Laser scleral buckling


Therapeutic Uses

D Mi ll U

SURYA


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i. Neovascular stimulation

ii. Aseptic phototherapy for pre-op

preparationiii. Laser asepsis for diagnosed infectious

corneal ulcers

iv. Endonasal DCR

D. Miscellaneous Uses

What is the Latest ?

PDT (Photo Dynamic Therapy)SURYA


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PDT (Photo Dynamic Therapy)

TTT (Transpupillary Thermo Therapy)

What is ARMD ?SURYA


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Two types -

Dry ARMD

Wet ARMD

What is ARMD ?SURYA

W t ARMD


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Wet ARMD -

Rare

More devastating

Drusen

SRNVM

What is ARMD ?SURYA

Drusen


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Drusen

What is ARMD ?SURYA

SRNVM


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SRNVM

What is ARMD ?SURYA

Vision in ARMD


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Vision in ARMD

What is PDT ?SURYA


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Visudyne (Verteporfin) Smart Bomb for wet ARMD

Selective Damage

of SRNVM

Costly

Rear Mirror

NEODYMIUM YAG LASER


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Rear Mirror

Adjustment Knobs

Safety Shutter Polarizer Assembly (optional)

Coolant

BeamTube

AdjustmentKnob

OutputMirror

BeamBeam Tube

Harmonic

Generator (optional)

Laser Cavity

PumpCavity

Flashlamps

Nd:YAGLaser Rod

Q-switch(optional)

Laser-Professionals.com

Light Detection - The Retina


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Layer of light sensitive cells on inner surface

of the eye

Fovea

Retina

Blind Spot

Optic Nerve


There are two types of photoreceptor cells in the retina:


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There are two types ofphotoreceptor cells in the retina:

cones and rods. The cones are responsible for sharpcolour vision in daylight. The rods provide vision in dim

light.

Near the centre of the retina is a small depressionabout 0.3 mm in diameter which is called thefovea. It

consists entirely ofcones packed closely together. Each

coneis about 2min diameter. Most detailed vision is

obtained on the part of the image that is projected onthefovea. When the eye scans a scene, it projects the

region of greatest interest onto thefovea.


The region around thefovea contains both cones and


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g f

rods. The structure of the retina becomes more coarseaway from thefovea. The proportion ofconesdecreases until, near the edge, the retina is composedentirely ofrods.

In thefovea, each cone has its own path to the opticnerve. This allows the perception of details in theimage projected on thefovea.

Away from thefovea, a number ofreceptors are

attached to the same nerve path. Hence the resolutiondecreases, but the sensitivity to light and movementincreases.

Light Detection - The RetinaWith the structure of the retina in mind, let us examinehow we view a scene from a distance of about 2 m


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how we view a scene from a distance of about 2 m.

From this distance, at anyone instant, we can see mostdistinctly an object only about 4 cm in diameter. Anobject of this size is projected into an image about thesize of the fovea. Objects about 20 cm in diameter areseen clearly but not with complete sharpness. The

periphery of large objects appears progressively lessdistinct.

Thus, for example, if we focus on a person's face 2 maway, we can see clearly the facial details, but we can

pick out most clearly only a subsection about the sizeof the mouth. At the same time, we are aware of thepersons arms and legs, but we cannot detect, forexample, details about the persons shoes.



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Receptors


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Sensitivity:


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Summary of Properties of Cones


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Cones Colour receptors (three types red, blue & green)

Respond in high illumination (daylight)

About 6.5 million per eye, concentrated at thefovea (i.e., high resolution in this region)

In the fovea, each cone connects to one nerve

fibre. Elsewhere, several to one fibre

Overall peak response at ~ 550 nm

Summary of Properties of Rods


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Rods Respond to intensity only (monochrome)

Respond to low illumination (night vision)

About 120 million per eye, their highest concentration is at about 20 from the fovea

Hundreds of rods connect to each nerve fibre, hence low resolution

Peak response at 510 nm

Resolution of the Eye

So far in our discussion of image formation we


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have used geometric optics, which neglects thediffraction of light.

Geometric optics assumes that light from a pointsource is focused into a point image. This is not

the case. When light passes through an aperturesuch as the iris, diffraction occurs, and the wavespreads around the edges of the aperture.

As a result, light is not focused into a sharp pointbut into a diffraction pattern consisting of a disksurrounded by rings of diminishing intensity.

Diffraction from a circular aperture (Airy disc)


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Diffraction Intensity from a square aperture


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If light originates from two point sources that are closetogether their image diffraction disks may overlap


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together, their image diffraction disks may overlap,making it impossible to distinguish the two points.An optical system can resolve two points if theircorresponding diffraction patterns are distinguishable.

This criterion alone predicts that two points are

resolvable if the angular separation between the linesjoining the points to the centre of the lens is equal to orgreater than a critical value given by sin = 1.22/dwhere is the wavelength of light and d the diameter ofthe aperture.

For an iris diameter of 0.5 cm and green light (500nm),

= 1.22x10-4 radians.


Experiments have shown that the eye does not


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p y

perform this well.Most people cannot resolve two points with anangular separation of less than 5 x10-4 radians.

Clearly there are other factors that limit theresolution of the eye.

Imperfections in the lens system of the eyecertainly impede the resolution. But perhapseven more important are the limitationsimposed by the structure of the retina.

Resolution of the EyeThe cones in the closely packedfovea are about 2 m indiameter. To resolve two points, the light from each pointmust be focused on a different cone and the excited cones


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must be focused on a differentcone and the excited cones

must be separated from each other by at least one conethat is not excited.Thus at the retina, the images of two resolved points areseparated by at least 4 m. A single unexcited conebetween points of excitation implies an angular resolution

of about 3 x 10-4

radians (using nodal point 15mm fromretina).Some people with acute vision do resolve points with thisseparation, but most people do not. We can explain thelimits of resolution demonstrated by most normal eyes if

we assume that, to perceive distinct point images, theremust be three unexcited cones between the areas ofexcitation. The angular resolution is then, as observed, 5 x10-4 radians.


Let us now calculate the size of the smallest detail that


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the unaided eye can resolve. To observe the smallestdetail, the object must be brought to the closest pointon which the eye can focus. Assuming that thisdistance is 20 cm from the eye, the angle subtendedby two points separated by a distancexis:

tan-1(/2) = (x/2)/20.

If is very small, this becomes = x/20. Because thesmallest resolvable angle is 5 x 10-4 radians the

smallest resolvable detail x is 0.1 mm (5 x 10-4

x 20).Using the same approach facial features such as thewhites of the eye are resolvable from as far as 20m.

Sensitivity of the Eye


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The sensation of vision occurs when light is absorbedby the photosensitive rods and cones.

At low levels of light, the main photoreceptors are

the rods. Light produces chemical changes in the

photoreceptors which reduce their sensitivity.For maximum sensitivity the eye must be kept in the

dark (dark adapted) for about 30 minutes to restore

the composition of the photoreceptors.


Under optimum conditions, the eye is a very sensitive


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detector of light.The human eye, for example, responds to light from a

candle as far away as 20 km.

At the threshold of vision, the light intensity is so small

that we must describe it in terms of photons.

Experiments indicate that an individual photoreceptor

(rod) is sensitive to 1 quantum of light. This, however,

does not mean that the eye can see a single photonincident on the cornea. At such low levels of light, the

process of vision is statistical.


In fact, measurements show that about 60quanta must arrive at the cornea for the eye to


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quanta must arrive at the cornea for the eye toperceive a flash.

Approximately half the light is absorbed orreflected by the ocular medium.

The 30 or so photons reaching the retina arespread over an area containing about 500 rods.

It is estimated that only 5 of these photons areactually absorbed by the rods.

It seems, therefore, that at least 5photoreceptors must be stimulated to perceivelight.


The energy in a single photon is very small.


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gy g p y

For green light at 500 nm, it is (using E=hc/)

4 x 10-19 Joules

This amount of energy, however, is sufficient to

initiate a chemical change in a single molecule

which then triggers the sequence of events that

leads to the generation of the nerve impulse

Vision

Vision cannot be explained entirely by the physicaloptics of the eye.


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optics of the eye.

There are many more photoreceptors in the retina thanfibres in the optic nerve. It is, therefore, evident thatthe image projected on the retina is not simplytransmitted point by point to the brain.

A considerable amount of signal processing occurs inthe neural network of the retina before the signals aretransmitted to the brain.

The neural network "decides" which aspects of theimage are most important and stresses thetransmission of those features


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Limits of Detection


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Lower limit of illumination about 30 photons spread over about 500 rods

Resolution

Diffraction effects and structure of retina limitresolution to about 8mm under optimal conditions

Blind Spot

Caused by region where nerve fibres enter the

optic nerve - edited out by the brain


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Understanding VisionDistanceVision

The Human Eye = The Camera


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The cornea & lens work together tofocus images in the eye

Cornea

Lens

FocalPoint

Understanding VisionYour eye focuses on what you are looking directly at

Central vision is sharp & clear peripheral vision blurred


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Your eye is continually refocusing as you look from far to near Near vision focusing is called ACCOMMODATION

Near

Normal AccommodationIntermediate Vision


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Lens shape fordistance vision

When looking at arms length, the lens changesshape & moves forward to focus images

Near imagesfocus behind retina

Intermediate vision is clearDistance & near vision out of focusLens changesshape & position

Intermediate imagesfocus on retina

Normal AccommodationNear Vision

Near vision is clearDistance vision


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Lens shape fordistance vision

When looking at near objects, the lens continues tochange shape & move forward to focus image

Near imagesfocus behind retina

Lens changesshape & position

Near imagesfocus on retina

out of focus

The Ageing EyeNear Vision


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The ageing lens loses its ability to change shapeReading glasses or bifocals are required

Loss of Accommodation is called PRESBYOPIA

Lens unableto focus image

FocalPoint

IF YOU HAVE A CATARACT, YOURE NOT

ALONE


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2.5 million cataract surgeries per year

Number-one therapeutic surgical procedure

for Americans over 65

TODAYS CATARACT SURGERY


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Greatly improved technology

Usually no hospital stay or long recovery

period

Safer, faster and more comfortable

than ever

WHAT IS A CATARACT?


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The lens focuses light on the retina

As we age, the lens hardens and cant

focus at close distancesAs we continue to age, the lens may

become cloudy

The cloudiness is the cataract

HOW DOES A CATARACT AFFECTVISION?


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A cataract scatters light in the eye

instead of focusing it

The cloudier the lens,

the more light isscattered

HOW DOES A CATARACT AFFECTVISION?

Simulated Cataract Vision Simulated Normal


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Vision

Photos courtesy of the NationalEye Institute

Gradually, visionbecomes dimmerObjects lose their

color

PEOPLE WITH CATARACTS HAVE DIFFICULTY:


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Seeing in the distance or reading

Distinguishing road signs at dusk

Recognizing colors

Recognizing friends and family at

a distance

Driving at night

WHO GETS CATARACTS?


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Almost everyone sooner or later

Half of all people between the ages

of 52 and 64*

Younger people, due to injury, excessive

sunlight, metabolic changes, or drugs

*American Academy of Ophthalmology

DETECTING A CATARACT


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Visual acuity testSlitlamp examination

Glare test

TREATING A CATARACT


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Is vision impaired?

Is quality of life affected?

The eye care practitioner andthe patient decide:

TODAYS CATARACT SURGERY


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A marvel of medical technology

Outpatient procedure

Local anesthesia

Tiny incision heals rapidly

Little of no discomfort

THE CATARACT PROCEDURE


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The clouded natural lens is removed

A man-made lens is inserted

The new lens is an intraocular lens

(IOL)

CHOICES FOR RESTORING VISION


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Todays technology offers two

different types of intraocular

lenses (IOLs)

Monofocal ReZoom

MONOFOCAL


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MONOFOCAL


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Good vision at one distance

usually far

Most people need glasses for close-upactivities like reading or crafts

Good vision when you go to aballgame or read road signs

The ReZoom Multifocal Lens


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The ReZoom and Crystalens IOL


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Designed for gooddistance vision

and near vision

Can reduce the need forglasses in activities like

reading, watching

television, or watching a

movie

ReZoomRANGE OF VISION EXAMPLES


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If youre golfing, you may be able tosee where your drive lands, sink your

putt, and write down the score,

without glasses

When shopping, you may be able to

read the aisle signs and the package

labels, and count your change,without glasses

EQUAL SAFETY FOR BOTH IOL TYPES


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Identical surgical procedures

The real difference is the type of vision

ReZoomBalanced View Optics

Technology


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Pictorial representation

ReZoomTM IOL Spectacle Independence

%


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Source: Product labeling.

93% 93%

81%

0%

20%

40%

60%

80%

100%

Distance Intermediate Near

ReZoom IOL

ReZoom IOL Visual Outcomes


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PatientBrochure


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Which Lens Is Best For You?We will help you decide which lens is the bestalternative for your specific refractive need


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Not everyone is a candidate for CrystaLens VisionEnhancement Surgery

Lifestyle

Expectations

A thorough examination will be performedMultiple diagnostic tests will be performed

Expectations

All surgery involves risk


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Not everyone responds to the surgery in the sameway

Other medical & eye diseases may influence yourability to seeclearly &/or accommodate

Vision After Accommodative Surgery

1 to 10 days after surgery


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Distance vision is typically excellent in the

majority of patients

Near & intermediate vision may be excellentafter surgery, however varies from patient to

patient

Typically continues to improve over time

Vision After Accommodative Surgery

One year after surgery*


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98.4% were able to drive, watch TV, participate in sports &

perform normal activites

98.0% were able to work on their computer, read product

labels & read the speedometer

98.4% were able read newspapers, magazines, recipes; sew

& dial their cell phone

*FDA Clinical Study

Without Glasses73.5% do not depend on glasses atall or wear them only occasionally

Are You A Candidate Forcrystalens Vision Enhancement?

Schedule a eye examination


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Talk with people who have had cataract surgery

Research lens replacement after lens removal surgery

Find a qualified & certified crystalens

VisionEnhancement Surgeon

Non- Contact Tonometers


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- Invented by Dr. Bernie Grolman in the 1960s (American Optical)

- To enable ODs in the USA to perform tonometry

- Introduced in 1971

- Uses rapid air pulse technology

- Easy to use

- Strong Goldmann correlation

- Objective: no operator bias

- No anesthetic required

- No risk of cross-contaminationModern NCT - AT555

NCT Traditional Method of Operation


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Method of Operation


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Applanation Signal Plot


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Definitions

H t i


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HysteresisThe phenomenon was identified, and the term coined, by

Sir James Alfred Ewing in 1890.

Hysteresis is a property of physical systems that do not

instantly follow the forces applied to them, but reactslowly, or do not return completely to their original state.

Corneal Hysteresis

The difference in the inward and outward pressure

values obtained during the dynamic bi-directionalapplanation process employed in the Ocular Response

Analyzer, as a result of viscous damping in the cornea.


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medical optics

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