Downloaded 147 times
More Related Content
Similar to Lasers in ophthalmology
Lasers in ophthalmology
- 1. LASERS IN OPHTHALMOLOGY By- PriyankaRaj Moderator- Dr. Bharti Nigam
- 2. • LASER isan 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. 2
- 3. LASER v LIGHT LASERLIGHT • Stimulated emission • Monochromatic. • Highly energized • Parallelism • Coherence • Can be sharply focussed. LIGHT ▪ Spontaneous emission. ▪ Polychromatic. ▪ Poorly energized. ▪ Highly divergence ▪ Not coherent ▪ Can not be sharply ▪ focussed. 3
- 4. PROPERTIES OF LASERLIGHT 1. Coherency 2. Monochromatism 3. Collimated 4. Constant Phasic Relation 5. Ability to be concentrated in short time interval 6. Ability to produce non linear effects 4
- 5. LASER PHYSICS 1. Lightconsists of electromagnetic waves, emitting radiant energy in tiny package called ‘quanta’/photon. 2. Each photon has a characteristic frequency and its energy is proportional to its frequency. 3. When light is passed through certain kinds of materials, these photons excite electrons around atoms into the next higher energy level 5
- 6. Three basic waysfor photons and atoms to interact: ▫ Absorption ▫ Spontaneous Emission ▫ Stimulated Emission 6
- 7. Absorption 1. A photonof the “right” energy gets absorbed and “bumps” an electron into a higher energy level. 7
- 8. Spontaneous Emission 1. Anexcited electron falls back to its lower energy level, releasing a photon in a random direction 8
- 9. Stimulated Emission A photonstrikes an excited electron. The electron falls to its lower energy level, releasing a photon that is going in the same direction and in exact phase with, the original photon. Note that only one photon strikes the atom but two photons leave it—the original photon plus the emitted photon 9
- 10.
- 11. Laser Construction 1. Apump source or exciting medium 2. A gain medium or laser medium. 3. An optical resonator or laser tube. 11
- 12. TYPES OF OCULARPIGMENTS Effective retinal photocoagulation depends on ▫ • how well light penetrates the ocular media ▫ • how well the light is absorbed by pigment in the target tissue Ocular pigments • Hemoglobin: ▫ Blue ,Green and yellow light are absorbed and red light is passed. ▫ RED laser is used to treat blood vessels below hemorrhage . • Xanthophyll: ▫ Present in inner and outer plexiform layers of macula. ▫ Maximum absorption is blue. Yellow and red light are passed ▫ Argon blue is not recommended to treat macular lesions. • Melanin: ▫ Present in RPE and Choroid ▫ Blue ,green and yellow light are absorbed and red light is passed ▫ Argon Blue, Krypton yellow and ,double frequency YAG lasers used for Pan Retinal Photocoagulation, and Destruction of RPE 12
- 13. CLASSIFICATION • Solid State •Ruby • Nd.Yag • Erbium.YAG • Gas • Ion • Argon • Krypton • He-Neon • CO2 • Metal Vapour • Cu • Gold • Dye • Rhodamine • Excimer • Argon Fluoride • Krypton Fluoride • Krypton Chloride • Diode • Gallium-Aluminum • Arsenide (GaAlAs) 13
- 14. 14 LASER WAVELENGTH Diode 810nm Krypton red 647 nm Krypton yellow 568nm Frequency doubled Nd YAG 532 nm Argon green 514 nm Argon blue 485 nm
- 15. LASER TISSUE INTERACTION •LASER VARIABLE: • Wavelength • Spot Size • Power • Duration ▪ TISSUE VARIABLE: ▪ Transparency ▪ Pigmentation ▪ Water Content 15
- 16.
- 17. Photocoagulation: • Laser Light • •Target Tissue • • Generate Heat • • Denatures Proteins • (Coagulation) 17
- 18. 1. Rise intemperature of about 10 to 20 0C will cause coagulation of tissue. Frequency-doubled Nd:YAG lasers (wavelength 532 nm) are used for pan-retinal photocoagulation in patients with diabetic retinopathy. Argon and krypton lasers were used previously, 18
- 19. Photodisruption: Laser Light Optical Breakdown MiniatureLightening Bolt Vapor Quickly Collapses Thunder Clap Acoustic Shockwaves Tissue Damage 19
- 20. 1. Neodymium-doped YttriumAluminum Garnet is a crystal that is used as a lasing medium for solid-state lasers and photodisruption. 2. Nd:YAG lasers typically emit light with a wavelength of 1064nm, in the infrared range. Used for posterior capsulotomy in capsular opacification and Peripheral iridotomy in patients with acute angle closure glaucoma 20
- 21. Photoablation: 1. Breaks thechemical bonds that hold tissue together essentially vaporizing the tissue, e.g. Photorefractive Keratectomy, Argon Fluoride (ArF) Excimer Laser. 2. Usually - ▫ Visible Wavelength : Photocoagulation ▫ Ultraviolet Yields : Photoablation ▫ Infrared : Photodisruption ▫ Photocoagulation 21
- 22. Photovaporization • Vaporization oftissue to CO2 and water occurs when its temperature rise is 60 to 100°C or greater. • • Commonly used CO2 Absorbed by water of cells Visible vapor (vaporization) Heat Cell disintegration Cauterization Incision 22
- 23. PHOTOCHEMICAL EFFECT 1. 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 23
- 24. Photon + Photosensitizerin ground state (S) 3S (high energy triplet stage) Energy Transfer Molecular Oxygen Free Radical Cell Damage, Vascular Damage , Immunologic Damage 24
- 25. IONISING EFFECT Highly energizedfocal laser beam is delivered on tissue over a period of nanosecond or picoseconds and produce plasma in target tissue. 1. 25
- 26. 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 26
- 27. THREE BASIC COMPONENTS ALaser 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 27
- 28. MODES OF LASEROUTPUT 1. Continuous Wave (CW) Laser: Delivery of energy in a continuous stream of photons. 2. Pulsed Lasers: Produce energy pulses of a few tens of micro to millisecond. 3. Q Switches Lasers: Delivery of energy pulses is of extremely short duration (nanosecond). 4. A Mode-locked Lasers: Emits a train of short duration pulses (picoseconds). 5. Fundamental System: Optical condition in which only one type of wave is oscillating in the laser cavity. 6. Multimode system: Large number of waves, each in a slight different direction ,oscillate in laser cavity. 28
- 29. DELIVERY SYSTEMS • Transpupillary:- Slit lamp - Laser Indirect Ophthalmoscopy • Trans scleral : - Contact - Non contact • Endophotocoagulation. 29
- 30. SLITLAMP BIOMICROSCOPIC LASERDELIVERY 1. Most commonly employed mode for anterior and posterior segment. ADVANTAGES: 1. Binocular and stereoscopic view. 2. Fixed distance. 3. Standardization of spot size is more accurate. 4. Aiming accuracy is good. 30
- 31. 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
- 32. USES ▪ DIAGNOSTIC ▪THERAPEUTIC 32
- 33. DIAGNOSTIC USES 1. ScanningLaser Ophthalmoscopy 2. Laser Interferometry/ Optical Coherence Tomography 3. Wavefront Analysis 33
- 34. Scanning Laser Ophthalmoscopy •narrow laser beam illuminates the retina one spot at a time, and the amount of reflected light at each point is measured. • The amount of light reflected back to the observer depends on the physical properties of the tissue, which, in turn, define its reflective, refractive, and absorptive properties 34
- 35. • Because theSLO uses laser light, which has coherent properties, the retinal images produced have a much higher image resolution than conventional fundus photography. • Used to study 1. SLAP test 2. retinal and choroidal blood flow (Hi-Speed FA / ICG) 3. Microperimetry/ scotometry 35
- 36. Optical Coherence Tomography(OCT) •Uses diode laser light in the near-infrared spectrum (810 nm) to produce high resolution cross-sectional images of the retina using coherence interferometry 36
- 37. Wavefront Analysis andAberrometery 1. Lasers are used in the measurement of complex optical aberrations of the eye using wavefront analysis 2. Hartmann-Shack aberrometer 37
- 38. THERAPEUTIC USES • Lidsand Adnexa • Anterior Segment • Posterior Segment 38
- 39. LIDS AND ADNEXAE Skin:(usually CO2 laser) 1. Lid Tumours : carbon dioxide laser ,benign and malignant ,bloodless but scarring, lack of a histologic specimen, and inability to assess margins. 2. Blepharoplasty (carbon dioxide or erbium:YAG laser ) 3. Xanthalesma ( green laser) 4. Aseptic Phototherapy 5. Pigmentation lesion 6. Laser Hair Removal Technique 7. Tattoo Removal 8. Resurfacing Lacrimal Surgery Endoscopic Laser Dacryocystorhinostomy39
- 40. 40 ANTERIOR SEGMENT ▪ ConjunctivalGrowths and Neovascularization ▪ Laser in cornea. ▪ Laser in Glaucoma ▪ Laser in Lens
- 41. CORNEA • Laser inKeratorefractive Surgery: ▫ Photo Refractive Keratectomy (PRK). ▫ Laser in situ Keratomileusis (LASIK). ▫ Laser Sub epithelial Keratectomy (LASEK). ▫ Epi Lasik. • Laser Thermal Keratoplasty . • Corneal Neovascularization. • Retrocorneal Pigmented Plaques. 41
- 42. Refractive Surgeries 1. Photorefractivekeratectomy 2. Laser subepithelial keratomileusis (LASEK) 3. Laser-assisted in situ keratomileusis (LASIK) 4. Epi LASIK 42
- 43.
- 44. Lasers Used inkeratorefractive surgeries EXCIMER • HiExcited dimer. • Argon fluoride(193nm) most commonly applied for corneal surgeries. • Photoablation. • Laser removes approximately 0.25microns of corneal tissue with each pulse. • Amount of tissue to be ablated derivedfrom ―munnerlyn equation” • gh energy UV laser. FEMTOSECOND LASER ADVANTAGES: • Flap are more accurate & uniform in thickness. • Centration of flap is easier. • Better adherence to Underlying stroma. • Patient are more comfortable. DISADVANTAGES: ▪ Suction break ▪ Costly 44
- 45. LASER IN GLAUCOMA •Lasertreatment for internal flow block – Laser peripheral iridotomy – Laser iridopLasty (Gonioplasty) • Laser treatment for outflow obstruction – Laser Trabeculoplasty – Excimer Laser Trabeculostomy – Laser Sclerostomy • Miscellaneous laser procedures – Cyclophotocoagulation – Laser suture lysis (LSL) – Reopening Failed Filtration sites – Laser synechialysis – Goniophotocoagulation – Photomydriasis (pupilloplasty) 45
- 46.
- 47. ND:YAG Laser iridotomy: • Q-switched Nd:YAG lasers (1064 nm) • 2–3 shots/burst using approximately 1–3 mJ/burst • opening of at least 0.1 mm. 47
- 48. Argon or Solid-StateLaser Iridotomy: • Photocoagulative (lower energy & longer exposure) • Iris color (pigment density) is the most imp factor • Iris color can be divided into three categories: 48 IRIS COLOUR LIGHT BROWN DARK BROWN BLUE To anneal pigment To perforate ENERGY 600-1000Mw 400-1000mW 200-400mW 600-100mw SPOT SIZE 50 μm 50 μm 200 μm 50 μm SHUTTER SPEED 0.02-0.05 sec 0.01 sec 0.1 sec 0.02- 0.1 sec
- 49. Place your screenshothere Laser Iridoplasty (Gonioplasty) Plateau iris & Nanophthalmos: • Spot size-100–200μm • Power-100–300 mW • duration -0.1 second • Number -10- 20 spots evenly distributed over360º 49
- 50. Laser trabeculosplasty (LTP) Argonlaser trabeculoplasty (ALT) • 50 μm spot size • 1000-mW power • 0.1 second • 3–4° apart • 20–25 spots per quadrant Selective Laser trabeculopLasty (SLT) • Q-switched, frequency-doubled 532-nm Nd:YAG laser • 400-μm spot • 0.8 mJ • 180° with 50 spots or 360° with 100 spots • 3–10 ns 50
- 51. Excimer Laser Trabeculostomy(ELT) • Precise and no thermal damage to surrounding tissues • Ab-interno (used intracamerally) : 308-nm xenonchloride (XeCl) excimer laser delivers photoablative energy 51
- 52. Laser Sclerostomy Nd:YAG laser,the dye laser, 308-nm XeCl excimer laser, argon fluoride excimer laser, erbium:YAG laser, diode lasers, the holmium:YAG laser etc . are used • • Ab-externo : probe applied to the scleral surface under a conjunctival flap. • • Ab-interno : through a goniolens 52
- 53. Cyclophotocoagulation 1. Trans-scleral Cyclophotocoagulation •Noncontact Nd:YAG laser cyclophotocoagulation • Contact Nd:YAG laser cyclophotocoagulation • Semiconductor diode laser trans-scleral cyclophotocoagulation 2. Endoscopic cyclophotocoagulation (ECP) 53
- 54. Other 1. Suture lysis 2.Laser synechialysis : lyse iris adhesions 3. Goniophotocoagulation: anterior segment neovascularization , rubeosis , fragile vessels in a surgical wound 4. Photomydriasis (pupilloplasty) : enlarge the pupillary area by contracting the collagen fibers of the iris 54
- 55. Pupilloplasty • 2-3 rowsof burns circumferentially 1mm away from the pupillary margin. • Innermost row: 8spots, 200micron size, 200-400mW. • Outer row:10-12spots, 400micron size, 300-500mW 55
- 56. LASER IN LENS 1.Posterior capsulotomy 2. Laser phacoemulsification 3. Phacoablation. 56
- 57. Femto laser incataract surgery Femtosecond laser technology systems use Neodymium:glass 1053 nm (near-infrared) wavelength light 57
- 58. 58 POSTERIOR SEGMENT ▪ Laserin vitreous ▪ Laser in Retinal vascular diseases ▪ Other Retinal diseases
- 59. LASER IN VITREOUS 1.Vitreolysis of anterior vitreous tag in PC rent to avoid traction and cystoid macular edema 2. Vitreous membranes & traction bands 3. Vitreous floaters 4. Retinoblastoma seeds 59
- 60. LASER TREATMENT OFFUNDUS DISORDERS CLASSIFICATION OF CHORIORETINAL BURN INTENSITY 1. • Light : Barely visible retinal blanching 2. • Mild : Faint white retinal burn 3. • Moderate: Dirty white retinal burn 4. • Heavy : Dense white retinal burn 60
- 61. TYPES OF RETINALLASER 1. Panretinal Laser Coagulation a) Full Scatter Panretinal Laser Coagulation b) Mild Scatter Panretinal Laser Coagulation 2. Focal Laser Application 3. Subthreshold Laser Coagulation for Retinal Disease 61
- 62. Focal and Gridlaser 62 FOCAL GRID SPOT SIZE 50 to 100u size 50 to 200u DURATION 0.05 to 0.1sec. 0.05 to 0.1 sec INTENSITY Moderate Light to medium POWER 70 to 100 mW 70 to 100 mW. WAVELENGTH argon green, db.fq. YAG green, dye yellow or diode red AREA OF TREATMENT within 500um of center of macula avoiding the fovea LENS USED area centralis, meinster standar,goldman 3 mirror
- 63. Indication of Focalor grid photocoagulation 1. Macular edema from diabetes or BRVO 2. Retinopathy of prematurity(ROP) 3. Closure of retinal microvascular abnormalities such as microaneurysms, telangiectasia or angiomas 4. Focal ablation of extrafoveal choroidal neovascular membrane 5. Creation of chorioretinal adhesions surrounding retinal breaks and detached areas. 6. Focal treatment of pigment abnormalities such as RPE leakage in CSR 7. Treatment of ocular tumours 8. Posterior hyloidotomy in large sub hyloid haemorrhage 63
- 64. 64 Laser to ischemicareas in ROP Modified grid laser in dme Laser barrage around retinal tear. 3 rows of laser burns given .
- 65. PAN RETINAL PHOTOCOAGULATION 1.Number - 2000-3000 spots distributed in 3 to 4 sittings 2. Spot size- 500 mm size with goldmann lens and 200-300 mm size with panfunduscopic lens. 3. Duration- 0.05-0.10 sec. 4. Intensity- moderate intensity laser burns 5. Wavelength– argon green, db.fq. YAG green, dye yellow or diode red. 6. Lens used – PRP 165 or goldman 3 mirror lens 7. Pattern- Scatter pattern PRP. Place laser spots in the peripheral retina for 360 degrees sparing the central 30 degrees of the retina. 8. Laser spots are given 1 spot apart 1 DD away from the disc nasally , 2DD away from macula temporally and beyond the arcades superiorly and inferiorly65
- 66.
- 67. INDICATIONS OF PRP 1.Proliferative diabetic retinopathy with high risk characteristics 2. Severe non proliferative diabetic retinopathy associated with-poor compliance for follow up or before cataract surgery or renal failure Or one eyed patient or pregnancy 3. Central retinal vein occlusion and branch retinal vein occlusion with nvd or nve or nvi 4. Sickle cell retinopathy, 5. Eales disease and IRVAN (idiopathic retinal vasculitis, aneurysms, and neuroretinitis ) 6. Retinopathy of prematurity (ROP) 7. Coats Disease 8. Radiation retinopathy 9. Neovascularisation of iris in ocular ischaemic syndrome 67
- 68. COMPLICATIONS General : ▫ Pain,Seizures. Anteriorsegment • Elevated IOP. • Corneal damage. • Iris burns. • Crystalline lens burns. • IOL and PC damage. • Internal ophthalmoplegia. POSTERIOR SEGMENT : • Choroidal detachment and exudative RD. • Choroidal ,subretinal,vitreous hemorrhage. • Thermal induced retinal vascular damage. • Preretinal membranes. • Ischaemic papillitis. • Paracentral visual field loss and scotoma. • Photocoagulation scar enlargement. • Subretinal fibrosis. • Iatrogenic choroidal neovascularisation. • Accidental foveal burns. 68
- 69. TRANSPUPILLARY THERMOTHERAPY 1. Thermotherapyinvolves using ultrasound, microwave, or infrared radiation to deliver heatto the eye. 2. It involves application of diode (infrared) laser to the tumor surface or in regions of CNVM activity. 3. Retinoblastoma It cause tumor cell death by raising the temperature of tumor cells to above 45°C for ~1 min., thus reducing blood supply and producing apoptosis. 4. Classic subfoveal or extrafoveal choroidal neovacular membrane 69
- 70. Transpupillary thermotherapy (TTT) •Retinoblastoma before thermotherapy ▪ Retinoblastoma after ▪ Thermotherapy 70
- 71. Photodynamic Therapy • Forage-related macular degeneration and pathologic myopia : i.v Verteporfin at 6mg/m2 BSA over 10 mins. Five minutes after the cessation of infusion, light exposure (laser emitting light of 692 nm) with an irradiance of 600 mW/m2 is started, delivering 50 J/cm2 within 83 s . • Angiod Streaks and CSR light dose of 100 J/cm2 over an interval of 166 s 71
- 72. Indications of PDT 1.Classic CNVs due to ▫ – age-related macular degeneration ▫ – idiopathic polypoidal choroidal vasculopathy, ▫ – pathologic myopia, ▫ – angioid streaks ▫ – presumed ocular histoplasmosis syndrome 2. Retinal capillary hemangioma 3. Vasoproliferative tumor 4. Parafoveal teleangiectasis 5. CSR with subfoveal leak 72
- 73.
- 74.