LASERS IN OPHTHALMOLOGY Presentation .pptx

Lasers in ophthalmology

1. LASER IN OPHTHALMOLOGY MODERATOR: DR. DIMPLE SHAKEET DR. JYOTI GARHWAL

2. INTRODUCTION LASER is an acronym for: L:- light A:-amplification by S:- stimulated E:- emission of R:- radiation Termed coined by Gordon gould .

3. LASER VS LIGHT LASER LIGHT Stimulated emission Spontaneous emission monochromatic polychromatic Highly energized Poorly energized parallelism Highly divergent coherence Non coherent Can be sharply focused Can not be sharply focused

4. PROPERTIES OF LASER LIGHT Coherency Monochromatism Collimated Constant phasic relation Ability to concentrated in short time interval Ability to produce non linear effects

5. LASER PHYSICS Light as electromagnetic waves, emitting radiation energy in tiny package called photon. Each photon has a characteristic frequency and its energy is proportional to it frequency Three basic ways for photons and atoms to interact: Absorption Spontaneous emission Stimulated emission

6. CLASSIFICATION OF LASER SOLID Ruby Nd:yag 2. GAS Ion Argon Krypton he-neon Co2 3. METAL VAPOUR Cu Gold 4. DYE Rhodamine 5. Excimer argon fluoride krypton fluoride krypton chloride 6. Diode Gallium-aluminum arsenide ( GaAIAs )

7. Nd:YAG laser Neodymium- doped yttrium aluminum garnet is a crystal that is used as lasing medium for solid state laser Nd:YAG laser typically emit light with a wavelength of 1064nm, in infrared APLLICATIONS Correct posterior capsule opacification Peripheral iridotomy in patient with angel closure glaucoma Frequency doubled Nd:YAG laser (532nm) are used for pan retinal photocoagulation in patient with diabetic retinopathy.

8. WAVELENGTHS OF LIGHT

9. LASER SAFETY CLASS 1 :- causing no biological damage CLASS2 :- safe on momentary view but chronic exposure cause damage CLASS3 :- not a safe even in momentary view CLASS4 :- cause more hazardous than class 3 LASER SAFETY REGULATION Patient safety is ensured by correct positioning Danger to surgeon is avoided by safety filter system Safety of observers and assistants

10. LASER TISSUE INTERACTION THERMAL EFFECT Photocoagulation Photodisruption Photovaporization PHOTO CHEMICAL Photoradiation Photoablation 3. IONIZING EFFECT

11. PHOTOCOAGULATION Laser light Target tissue Generate heat Denatures proteins (coagulation) Rise in temperature of about 10 to 20degree Celsius will cause coagulation of tissue Visible wavelength used for photocoagulation

12. PHOTODISRUPTION Ionized the electrons of target tissue Produce physical state called plasma This plasma expand with momentary pressure as high as 10kilobars Produce cutting and incising effect Work based on infrared light

13. PHOTOABLATION Breaks the chemical bonds that hold tissue together essentially vaporizing the tissue E.g. photorefractive keratectomy, argon fluoride excimer laser Works based on ultraviolet rays

14. PHOTOVAPORIZATION Vaporization of tissue to CO2 and water occurs when its temperature rise 60-100 degree Celsius Commonly used CO2 Absorbed by water of cells Visible vapor heat& cauterization cell disintegration& incision e.g. femtosecond laser

15. PHOTORADIATION Also called photodynamic therapy(PDT) Photochemical reaction following visible/infrared light particularly after administration of exogenous chromophore commonly used photosensitizers are: Haematoporphyrin Benzaporphyrin derivatives e.g. treatment of ocular tumor and CNV

16. Photon + photosensitizer in ground state (S) 3S (high energy triplet stage) Energy transfer molecular oxygen free radical s +o2 (singlet o2) cytotoxic intermediate cell damage, vascular damage immunologic damage

17. IONISING EFFECT Highly organized focal laser beam 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

18. VARIOUS LASER AND APPLICATION IN OPHTHALMOLOGY

19. DELIVERY SYSTEMS Transpupillary :- slit lamp laser indirect ophthalmoscopy Trans scleral:- contact Non contact 3. Endophotocagulation

20. USES DIAGNOSTIC Scanning laser ophthalmoscopy Laser interferometry Optical coherence tomography THERAPEUTIC Extra ocular adnexa Anterior segment Posterior segment

21. Extra ocular adnexa Removal of lid masses Orbitotomies Blepharoplasty Aesthetics Capillary hemangioma

22. LASER IN ANTERIOR SEGMENT CORNEA: LASER IN KERATOREFRACTIVE SURGERY Photo refractive keratectomy(PRK) Laser in situ keratomileusis (LASIK) Laser subepithelial keratectomy(LASEK) Corneal neovascularization

23. LASER IN GLAUCOMA Laser iridotomy Laser trabeculoplasty Selective laser trabeculoplasty Trabecular ablation Goniotomy Gonioplasty Sphincterotomy

24. LASER IRIDOTOMY Performed using Nd:YAG laser Opening should be at least 150-200 microns in size In mid peripheral iris, at 1 or 11 0’clock position Depending on the thickness of iris power varies from 3 to 6 mJ Post operatively steroid and anti glaucoma medication given to prevent inflammation and rise in intraocular pressure

25. LASER TRABECULOPLASTY Its hypotensive effect by increasing outflow facility, possibly by producing collagen shrinkage on the anterior aspect of trabecular meshwork and opening intratrabecular space. Done by 50 spots on anterior half of trabecular meshwork over 180 degree. Done by using argon laser or diode laser Decrease 12-16mmhg iop

26. Selective laser trabeculoplasty Targets only selectively pigmented trabecular meshwork cells without causing thermal or collateral damage to non pigmented cells or structure Performed using double frequency Nd:YAG laser With pulse duration of 3ms Spot size is 400microne Energy setting 0.8mj Pressure lowering effect similar to LT

27. LASER IN LENS Posterior capsulotomy Laser phacoemulsification LASER IN VITREOUS Vitreous membranes Vitreous traction bands

28. LASER IN FUNDUS DISORDER Diabetic retinopathy Retinal vascular diseases Choroidal neovascularization(CNV) Clinical significant macular edema(CSME) Central serous retinopathy (CSR) Retinal break/detachment Tumour ARMD

29. Diabetic retinopathy and laser Laser light absorb by melanin in RPE Photoreceptor destruction & Decrease oxygen consumption Oxygen flux from choroid to inner retina

30. Improved oxygenation of inner retina Decreased VEGF autoregulatory constriction of retinal Production arterioles and increased resistance decrease hydrostatic pressure capillaries and venules Constriction of retinal venules and capillaries Decreased neovascularization decreased edema formation

31. PANRETINAL PHOTOCOAGULATION PRP place laser spots in the peripheral retina for 360 degree sparing the central 30 degree of the retina 1200 to 1600 burns of moderate intensity, 500um in size For 0.1 sec duration For at least two session by using argon, krypton or double frequency Nd:YAG laser

32. Indications Proliferative diabetic retinopathy Neovascularisation over iris Sever non proliferative diabetic retinopathy associated with Poor compliance for follow up, before cataract surgery, renal failure One eyed patient Central retinal vein occlusion Branch retinal vein occlusion

33. FOCAL OR GRID PHOTOCOAGULATION Macular edema from diabetic retinopathy or branch vein occlusion Retinopathy of prematurity Closure of retinal microvascular abnormalities such as microaneurysm, telangiectasia and perivascular leakage Focal ablation of extrafoveal choroidal neovascular membrane Creation of chorioretinal adhesion surrounding retinal breaks and detached areas Treatment of ocular tumors

34. Focal and grid laser settings 50-100 micron spot size, 0.05-0.1 sec (for focal spot size 50micron, for grid laser 100-200 micron) Spots must be at least one burn width apart Seal specific leaking blood vessels in a small area of the retina , usually near the macula

35. DIAGNOSTIC USES Scanning laser ophthalmoscopy Allow for high resolution, real time motion image of the macula without patient discomfort Can be used to perform microperimetry, an extremely accurate mapping of the macula’s visual field Optical coherence tomography Use diode laser light in the near infrared spectrum(810 nm) to produce high resolution cross section images of the retina using coherence interferometry

36. complications General complication Pain Seizures Anterior segment complications Elevated IOP Corneal damage Iris burn Crystalline lens burns IOL and PC damage

37. Choroidal detachment and exudative RD Choroidal, subretinal and vitreous hemorrhage Thermal induced retinal vascular damage Preretinal membranes Paracentral visual field loss and scotoma Subretinal fibrosis Accidental foveal burns

38. THANK YOU!!!!