lasers in ophthalmology

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lana ahmed    on Sep 04, 2013 Says :

very nice.would it be possible to have acopy for apurpose of teatching
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2 : 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 emit a new form of light energy which is more useful.
3 : PROPERTIES OF LASER LIGHT Coherency Monochromatism Collimated Constant Phasic Relation Ability to be concentrated in short time interval Ability to produce non linear effects
4 : HISTORY 1960 : The first laser was built by Theodore Maiman using a ruby crystal medium. 1963 : The first clinical ophthalmic use of laser in humans. 1968 : L Esperance developed the argon laser. 1971 : Neodymium yttrium aluminum garnet (Nd.YAG) and Krypton laser develop. 1983 : Trokel developed the eximer laser.
5 : 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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7 : HOW LASER WORK ??? Contd. …
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9 : LASER Vs. LIGHT LASER LIGHT Simulated emission Monochromatic. Highly energized Parallelism Coherence Can be sharply focussed. Spontaneous emission. Polychromatic. Poorly energized. Highly divergence Not coherent Can not be sharply focussed.
10 : CLASSIFICATION OF LASER Solid State Ruby Nd.Yag Erbium.YAG Molmium.YAG Gas Ion Argon Krypton He-Neon CO2 Metal Vapour Cu Gold Dye Kiton Red DCM Rhodamine Excimer Argon Fluoride Krypton Fluoride Krypton Chloride Diode Gallium-Aluminum Arsenide (GaAlAs)
11 : LASER TISSUE INTERACTION LASER VARIABLE: Wavelength Spot Size Power Duration TISSUE VARIABLE: Transparency Pigmentation Water Content
12 : THREE TYPE OF OCULAR PIGMENT Haemoglobin: Argon Green are absorbed, depending on its oxygenation , Krypton yellow. These laser are found 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
14 : THREE BASIC LIGHT TISSUE INTERACTIONS (1) Photocoagulation: Laser Light ? Target Tissue ? Generate Heat ? Denatures Proteins (Coagulation) Rise in temperature of about 10 to 20 0C will cause coagulation of tissue.
15 : THREE BASIC LIGHT TISSUE INTERACTIONS (2) Photodisruption: Mechanical Effect: Laser Light ? Optical Breakdown ? Miniature Lightening Bolt ? Vapor ? Quickly Collapses ? Thunder Clap ? Acoustic Shockwaves ? Tissue Damage Contd. …
16 : THREE BASIC LIGHT TISSUE INTERACTIONS (3) Photoablation: Breaks the chemical bonds that hold tissue together essentially vaporizing the tissue, e.g. Photorefractive Keratectomy, Argon Fluoride (ArF) Excimer Laser. Usually - Visible Wavelength : Photocoagulation Ultraviolet Yields : Photoablation Infrared : Photodisruption Photocoagulation Contd. …
17 : PHOTOVAPORIZATION Vaporization of tissue to CO2 and water occurs when its temperature rise 60—100 0C or greater. Commonly used CO2 ? Absorbed by water of cells ? Visible vapor (vaporization) ? ? Heat Cell disintegration ? ? Cauterization Incision
18 : PHOTOCHEMICAL EFFECT PHOTORADIATION (PDT): Also called Photodynamic Therapy Photochemical reaction following visible/infrared light particularly after administration of exogenous chromophore. Commonly used photosensitizers: Hematoporphyrin Benzaporphyrin Derivatives e.g. Treatment of ocular tumour and CNV
20 : 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. …
21 : IONISING EFFECT Highly energized focal laser beam is delivered on tissue over a period of nanosecond or picoseconds and produce plasma in target tissue. Q Switching Nd.Yag ? Ionization (Plasma formation) ? Absorption of photon by plasma ? Increase in temperature and expansion of supersonic velocity ? Shock wave production ? Tissue Disruption
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23 : 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
24 : MODES OF LASER OPERATION Continuous Wave (CW) Laser: It deliver their energy in a continuous 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.
26 : LASER INSTRUMENTATION Three Main Components – Console: It contain laser medium and tube, power supply and laser control system. Control Panel: It contain dials or push buttons for controlling various parameters. Contain a standby switch as a safety measure. Delivery System: Slit Lamp Microscope Indirect Ophthalmoscopes Endophotocoagulation
27 : ACCESSORY COMPONENT Aiming Beam Laser Switch Safety Filter Corneal Contact Lenses for Laser use Cleaning of the Contact Lens
28 : 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. …
29 : USING THE OPHTHALMIC LASER PREPARATION OF THE PATIENT FOR SURGERY: Investigation Local Anaesthetic Position of the patient at Slit Lamp THE SURGEON: Comfortable position at Slit Lamp Semi-darkened Room Appropriate Contact Lens
30 : LASER SAFETY Class-I : Causing no biological damage. Class-II : Safe on momentary viewing but chronic exposure 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.
31 : CLINICAL USE OF LASER DIAGNOSTIC USE: Laser Interferometry Scanning Laser Ophthalmoscopy (SLO) Laser Flare Cell Photometry Optical Coherence Tomography (OCT)
32 : CLINICAL USE OF LASER Optical Coherence Tomography (OCT): It is non invasive, non contact imaging system that uses super luminescent diode uses laser to give high resolution cross sectional real time tomographic image of retina. OCT produces light resolution upto 10?. Interpretation of OCT Images: Red-yellow colours represent areas of maximal optical reflection and back scattering. Blue-black colours represent area of minimal signals. Contd. …
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34 : CLINICAL USE OF LASER 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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37 : 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 Keratoplasty Corneal Neovascularization Retrocorneal Pigmented Plaques Laser Asepsis
39 : 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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45 : 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. …
48 : 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. …
49 : LASER IN LENS Posterior capsulotomy Laser phacoemulcification Phacoablation LASER IN VITEROUS Viterous membranes Viterous traction bands
50 : 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
51 : LASER TREATMENT OF FUNDUS DISORDERS ARMD Retinal Vein Occlusion Eale’s Disease Coats Disease Peripheral Retinal Lesion Drainage of Subretinal Fluid Laser Scleral Buckling for Retinal Detachment Contd. …
52 : 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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55 : 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 adjacent retina.
56 : DIABETIC RETINOPATHY Focal thickening/leakage: Focal Photocoagualation Diffuse thickening/leakage: Macular grid photocoagulation Treat all avascular zones 500-3000 microns from the foveal centre. Laser Parameter: 50-100 micron spot size, 0.05-0.1 sec( for focal spot size 50micron, for grid 100-200 micron) Spots must be atleast one burn width apart. Contd. …
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60 : PASCAL PATTERN SCAN LASER:(Pascal) Offering multiple, patterned burns in a single-session procedure. Improved precision Safety Patient comfort Significant reduction in treatment time.
61 : 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
63 : FUGO (plasma) BLADE Dr. Daljit Singh Iris claw lens 1stUS FDA clear 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.
66 : 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
67 : 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.
68 : COMPLICATION OF LASER TREATMENT Increased IOP Corneal Damage Iris Burn Cataract Internal Ophthalmoplegia Pain Seizure CD & RD Foveal Burn
69 : 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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lasers on becoming an indispensible part in ocular ds management
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