1Dr.ashokKumar Ophthalmology Laser

8/2/2019 1Dr.ashokKumar Ophthalmology Laser

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LASER IN OPHTHALMOLOGY

~: Moderator :~

DR. (MRS.) B. DEVI

Professor & Head

DEPARTMENT OF OPHTHALMOLOGY,

ASSAM MEDICAL COLLEGE & HOSPITAL, DIBRUGARH

~: Presenter :~

DR. ASHOK KUMAR

Postgraduate Trainee


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INTRODUCTION

LASER is an acronym for:

L : Light

A : Amplification (by) S : Stimulated

E : Emission (of)

R : Radiation

Term coined by Gordon Gould.

Lase means to absorb energy in one form and to emita new form of light energy which is more useful.


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PROPERTIES OF LASER LIGHT

Coherency

Monochromatism

Collimated

Constant Phasic Relation

Ability to be concentrated in short time interval

Ability to produce non linear effects


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LASER PHYSICS

Light as electromagnetic waves, emitting radiant energy in

tiny package called quanta/photon. Each photon has a

characteristic frequency and its energy is proportional to

its frequency.

Three basic ways for photons and atoms to interact:

Absorption

Spontaneous Emission

Stimulated Emission

HOW LASER WORK ???


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HOW LASER WORK ???

Contd.


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LASER Vs. LIGHT

LASER LIGHT

Simulated emission

Monochromatic.

Highly energized

Parallelism

Coherence

Can be sharplyfocussed.

Spontaneous emission.

Polychromatic.

Poorly energized.

Highly divergence

Not coherent

Can not be sharplyfocussed.


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CLASSIFICATION OF LASER

Solid StateRubyNd.Yag

Erbium.YAGMolmium.YAG

GasIonArgon

KryptonHe-NeonCO2

Metal VapourCu

Gold

DyeKiton RedDCM

Rhodamine Excimer

Argon FluorideKrypton FluorideKrypton Chloride

DiodeGallium-Aluminum

Arsenide (GaAlAs)


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LASER TISSUE INTERACTION

LASER VARIABLE:

Wavelength

Spot Size

Power

Duration

TISSUE VARIABLE:

Transparency

Pigmentation

Water Content


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THREE TYPE OF OCULAR PIGMENT

Haemoglobin: Argon Green are absorbed, depending on its

oxygenation , Krypton yellow. These laser arefound to be useful to coagulate the blood vessels.

Xanthophyll: Macular area, Lens Maximum absorption is blue. Argon blue is not

recommended to treat macular lesions.

Melanin: RPE, Choroid Argon Blue, Krypton Pan Retinal Photocoagulation, and Destruction of

RPE


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LASER TISSUE INTERACTION

LASER

TISSUE

ThermalEffect

Photo-chemical

IonizingEffect

Photocoagulation Photoradation

Photodisruption Photoablation

Photovaporization


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THREE BASIC LIGHT TISSUE INTERACTIONS

(1) Photocoagulation:

Laser Light

Target TissueGenerate Heat

Denatures Proteins

(Coagulation)

Rise in temperature of about 10 to 20 0C will cause

coagulation of tissue.


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THREE BASIC LIGHT TISSUE INTERACTIONS

(2) Photodisruption:

Mechanical Effect:

Laser Light

Optical Breakdown

Miniature Lightening BoltVapor

Quickly CollapsesThunder Clap

Acoustic ShockwavesTissue Damage

Contd.


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PHOTOVAPORIZATION

Vaporization of tissue to CO2 and water occurs when

its temperature rise 60100 0C or greater.

Commonly used CO2

Absorbed by water of cellsVisible vapor (vaporization)

Heat Cell disintegration Cauterization Incision


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PHOTOCHEMICAL EFFECT

PHOTORADIATION (PDT):

Also called Photodynamic Therapy

Photochemical reaction following visible/infrared lightparticularly after administration of exogenous chromophore.

Commonly used photosensitizers:

Hematoporphyrin

Benzaporphyrin Derivatives

e.g. Treatment of ocular tumour and CNV


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PHOTODYNAMIC THERAPY


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PHOTOCHEMICAL EFFECT

Photon + Photosensitizer in ground state (S)3S (high energy triplet stage)

Energy Transfer Molecular Oxygen Free Radical

S + O2 (singlet oxygen) Cytotoxic Intermediate Cell Damage, Vascular Damage , Immunologic Damage

Contd.


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IONISING EFFECT

Highly energized focal laser beam is delivered ontissue over a period of nanosecond or picosecondsand produce plasma in target tissue.

Q Switching Nd.YagIonization (Plasma formation)Absorption of photon by plasmaIncrease in temperature andexpansion of supersonic velocityShock wave production Tissue Disruption


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THREE BASIC COMPONENTS

A Laser Medium

e.g. Solid, Liquid or Gas

Exciting Methods

for exciting atoms or molecules in the medium

e.g. Light, Electricity

Optical Cavity (Laser Tube)

around the medium which act as a resonator


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MODES OF LASER OPERATION

Continuous Wave (CW) Laser: It deliver their energy in acontinuous stream of photons.

Pulsed Lasers: Produce energy pulses of a few tens of

micro to few mili second. Q Switches Lasers: Deliver energy pulses of extremely

short duration (nano second).

A Mode-locked Lasers: Emits a train of short duration

pulses (picoseconds). Fundamental System: Optical condition in which only one

type of wave is oscillating in the laser cavity.

Multimode system: Large number of waves, each in a slight

different direction ,oscillate in laser cavity.


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TYPES OF OPHTHALMIC LASERS


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LASER INSTRUMENTATION

Three Main Components

Console: It contain laser medium and tube, powersupply and laser control system.

Control Panel: It contain dials or push buttons forcontrolling various parameters. Contain a standbyswitch as a safety measure.

Delivery System:

Slit Lamp Microscope

Indirect Ophthalmoscopes

Endophotocoagulation


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ACCESSORY COMPONENT

Aiming Beam

Laser Switch

Safety Filter

Corneal Contact Lenses for Laser use

Cleaning of the Contact Lens


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ACCESSORY COMPONENT

Slit Lamp Laser Delivery lenses:

Single mirror gonio lens

Abraham or wise iriditomy lens

Goldman style 3-mirror lens

Panretinal lenses

e.g. Rodenstock, Mainster, Volk-Quadrispheric

Indirect Fundus Lenses for Indirect Ophthalmoscopes

Contd.


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LASER SAFETY

Class-I : Causing no biological damage.

Class-II : Safe on momentary viewing but chronicexposure may cause damage.

Class-III : Not safe even in momentary view.

Class-IV : Cause more hazardous than Class-III.

LASER SAFETY REGULATION:

Patient safety is ensured by correct positioning.

Danger to the surgeon is avoided by safety filter system.

Safety of observers and assistants.


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CLINICAL USE OF LASER

DIAGNOSTIC USE:

Laser Interferometry

Scanning Laser Ophthalmoscopy (SLO)

Laser Flare Cell Photometry

Optical Coherence Tomography (OCT)


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Optical Coherence Tomography (OCT):

It is non invasive, non contact imaging system thatuses super luminescent diode uses laser to give high

resolution cross sectional real time tomographicimage of retina.

OCT produces light resolution upto 10. Interpretation of OCT Images:

Red-yellow colours represent areas of maximaloptical reflection and back scattering.

Blue-black colours represent area of minimalsignals.

Contd.


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THERAPEUTIC USES: Laser in Lacrimal Surgery:

Laser DCR.

Skin: Removal of Small Lid Lesion

e.g. Seborrhoeic keratitis Removal of Capillary Haemangiomas Blepharoplasty

Aseptic Phototherapy Pigmentation lesion Laser Hair Removal Technique Tattoo Removal Resurfing

Contd.


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LASER IN ANTERIOR SEGMENT

CORNEA:

Laser in Keratorefractive Surgery:

Photo Refractive Keratectomy (PRK)

Laser in situ Keratomileusis (LASIK)

Laser Subepithelial Keratectomy (LASEK)

Epi Lasik

Laser Thermal KeratoplastyCorneal Neovascularization

Retrocorneal Pigmented Plaques

Laser Asepsis


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PRK LASIK


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LASER IN GLAUCOMA

Laser Iridotomy, Laser Iredectomy

Laser Trabeculoplasty (LT)

Selective Laser Trabeculoplasty

Trabecular ablation

Gonioplasty (Iridoplasty, Iridoretraction)

Pupilloplasty

Sphincterotomy

Iridolenticular Synechiolysis

Goniophotocoagulation

Goniotomy


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LASER IRIDOTOMY


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PUPILLOPLASTY


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ARGON LASER TRABECULOPLASTY


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LASER IN GLAUCOMA

Laser Filtration Procedures (sclerostomy):

Ab Externosclerostomy (Holmium)

Ab Internosclerostomy (Nd.YAG) Contact Non-contact

Cyclodestructive Procedures (cyclophotocoagulation)

Transscleral Cyclophotocoagulation

Trnaspupillary Cyclophotocoagulation

Diode Laser Endophotocoagulation

Contd.


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SCLEROSTOMY


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AB INTERNO SCLEROSTOMY


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LASER IN GLAUCOMA

Laser Sinusotomy:

Procedure of unroofing the canal of schlemm,

allowing aqueous humour to percolate into

subconjunctival space.

Laser Bleb Revision and Remodeling

Iris Cyst

Displaced Pupil

Contd.


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LASER IN LENS

Posterior capsulotomy

Laser phacoemulcification

Phacoablation

LASER IN VITEROUS

Viterous membranes

Viterous traction bands


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LASER TREATMENT OF

FUNDUS DISORDERS

Diabetic Retinopathy

Retinal Vascular Diseases

Choroidal Neovascularization (CNV)

Clinical Significant Macular Edema (CSME)

Central Serous Retinopathy (CSR)

Retinal Break/Detachment

Tumour


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LASER TREATMENT OF

FUNDUS DISORDERS

ARMD

Retinal Vein Occlusion

Eales Disease

Coats Disease

Peripheral Retinal Lesion

Drainage of Subretinal Fluid

Laser Scleral Buckling for Retinal Detachment

Contd.


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CLASSIFICATION OF

CHORIORETINAL BURN INTENSITY

Light : Barely visible retinal blanching

Mild : Faint white retinal burn

Moderate : Opaque dirty white retinal burn

Heavy : Dense white retinal burn


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DIABETIC RETINOPATHY

Diabetic Macular Edema:

Indication:

Presence of CSME or any of the following: Retinal thickening at or within 500 micron of the

foveal centre.

Retinal thickening 1500micron or larger size any part

of which is within 1500microns of the foveal centre. Hard exudate at or within 500 micron of the foveal

centre if associated with thickening of the adjacentretina.


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Focal thickening/leakage: Focal Photocoagualation

Diffuse thickening/leakage: Macular gridphotocoagulation

Treat all avascular zones 500-3000 microns from thefoveal centre.

Laser Parameter:

50-100 micron spot size, 0.05-0.1 sec( for focal spotsize 50micron, for grid 100-200 micron)

Spots must be atleast one burn width apart.

Contd.


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Contd. TYPE OF RETINOPATHY THERAPY

BackgroundControl of diabetes, regularreview

MaculopathyCSME

Focal photocoagulation

Diffuse leakage around macula Grid laser

Circinate Focal photocoagulation

Pre-proliferative Retinopathy Frequent review

Proliferative retinopathy Pan retinal photocoagulation

Advanced diabetic eye diseaseVitreoretinal surgery withphotocoagulation


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PASCAL

PATTERN SCAN LASER:(Pascal)

Offering multiple, patterned burns in a single-session

procedure.

Improved precision

Safety

Patient comfort

Significant reduction in treatment time.


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FEMTOSECOND LASER

ADVANTAGES:

Flap are more accurate and uniform in thickness.

Centration of flap is easier. Better adherence to underlying stroma.

Patient are more comfortable.

DISADVANTAGES: Suction break

Cost ly


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FEMTOSECOND LASERContd.


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FUGO (plasma) BLADE

Dr. Daljit Singh

Iris claw lens

1stUS FDAclear plasma incision device for use in eye

Portable

USES Anterior capsulotomy (yr 2000)

Trance ciliary filtration (singh filtration yr 2004)

Peripheral iridotomy ( yr 2005 )

Eyelid surgery.


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IN THE DEPARTMENT

ARGON GREEN LASER (IRIDEX)


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IN THE DEPARTMENT

Nd :YAG LASER (CARL ZEISS)


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LASER HAZARDS

EYE

Small lesion to extensive haemorrhage

Disruption of retina and choroid

Immediate loss of vision

Epiretinal membrane formation

Macular hole,gliosis

SKIN Erythema

Carcinogenesis


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PREVENTION OF LASER HAZARDS

Engineering Control Measure: Increasing laser

safety by designing of laser housing to prevent

free access , provision of filters and shutter for

safe observer viewing

Personal protective devices, like protective eye

wear or goggles with side shields, protective

clothes may be included Administrative and procedural controls, which

help by implementation of laser safety program

under laser safety officer.


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COMPLICATION OF LASER TREATMENT

Increased IOP

Corneal Damage

Iris Burn

Cataract

Internal Ophthalmoplegia

Pain

Seizure

CD & RD

Foveal Burn


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CONCLUSION

In a relatively brief period , laser have evolved from an

obscure research novelty to an invaluable clinical

instrument.

The continual refinement of existing laser types, as

well as the introduction of new laser technology, mark

this area of ophthalmology as one of its most

energetic and dynamic fields.


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HAVE A NICE DAY


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HAVE A NICE DAY.

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1Dr.ashokKumar Ophthalmology Laser