All about Pan Retinal Photocoagulation.pptx

This PPT is about Pan Retinal Photocoagulation

1. PAN RETINAL PHOTOCOAGULATION

2. LASER : - Light Amplification by the Stimulated Emission of Radiation which describes emission process by which an intense beam of electromagnetic radiation is generated. LASER coined by Gordon Gould. Charles Towns & Arthur Schawlow produced maser(microwave amplification by stimulated emission of radiation). Argon laser was discovered in 1964 by William Bridges. Xenon arc laser was developed in the 1950s by Carl Zeiss Lab. Ophthalmology was the 1 st medical speciality to utilize lasers with the 1 st report utilizing a Ruby laser to treat ocular lesions.

3. CLASSIFICATION OF LASER :- Solid state :- Ruby,Nd -YAG, Erbium YAG Gas ion :-Argon, Krypton,He -Neon, Carbon dioxide Metal vapour :-Cu, Gold Dye :- Rhodamine Excimer :-Argon Fluoride, Krypton Fluoride, Krypton Chloride Diode :-Gallium-Aluminium-Arsenide( GaAlAs )

4. LASERS can be classified into distinct categories (based on their M.O.A.) :- Thermal interaction Photodisruption Plasma induced ablation 3 basic ways for photons & atoms to interact: - Absorption Spontaneous emission Stimulated emission

5. LASER coined by Gordon Gould Charles Towns & Arthur Schawlow produced maser Argon laser was discovered in 1964 by William Bridges.

6. PAN RETINAL PHOTOCOAGULATION

7. PHYSICS & BIOLOGICAL INTERACTIONS: - Light from the laser is absorbed by RPE & underlying choroid. It is a photothermal reaction.
Absorption of light by the target tissue results in a temp rise of 20 to 30 degree centigrade, causing denaturation of proteins.
PRP remains the mainstay of t/t for PDR. For PRP, typically yellow, green OR red laser light is used.

8. PHYSICS & BIOLOGICAL INTERACTIONS(Cont.): - Thermal burns denature tissue protein which leads to local retinal cell death & coagulative necrosis. These areas of thermally damaged tissue eventually scar & become more heavily pigmented, leaving visible laser scars at the level of RPE. Classically,1000 to 2000micron burns are made on the retina. PRP reduces the area of ischemic tissue, which in turn reduces total VEGF production in the eye & thereby reducing the impetus for neovascularization. PRP is typically delivered through either a slit-lamp system OR laser IDO.

9. Lasers in ophthalmology:-

10. Modes of laser operation:- Contineous wave Pulsed laser Q switched lasers A mode locked laser TISSUE EFFECTS:- Induces moderate sterile inflammation. Creates bio-adhesion Collagen shrinkage Membrane shrinkage

11. Laser tissue interactions:- Photocoagulation Photodisruption Photoablation Photochemical reaction Photovaporization

12. PHOTOCOAGULATION:- Protein denaturation Rise in temp. of about 10degree to 20degree will cause coagulation of tissue.

13. Laser delivery systems:- Slit-lamp Laser Indirect Ophthalmoscope(LIO) Endo laser

14. LASER PARAMETERS:-

15. PREREQUISITES:- Pain medication Contact lens placement Depends on the contact lens. PRP:-200 to 400 micrometer Focal/Grid laser:-50 to 100 micrometer Ideal spot size:-

16. Grade of burns:- Grades 1 Just visible , barely visible retinal whitening 2 Faint white 3 Opaque Dirty white 4 Chalky white DURATION:- Pascal Conventional 20ms 150ms Up to 25spots in one shot Single spot Time to complete PRP lesser Time to complete PRP more

17. Focal laser Grid laser Laser removes unhealthy RPE cells, replaced by viable RPE cells. Stimulates existing RPE cells & absorb more fluid. Destroys outer photoreceptors reducing oxygen consumption. Stimulates vascular endothelial cell proliferation & improve inner BRB. Direct t/t of focal fluorescein leaks. 50-100 microns spot size. 0.1sec. Duration.

18. Sectoral Laser Photocoagulation Barrage Laser ROP Laser:- APROP/Classic threshold ROP stage 3, Zone 2plus. Anterior to Ridge with grade 3, confluent Burns till Ora .

19. TYPICAL LASERS WITH PHOTOCOAGULATION EFFECT :- Krypton red (647nm) :- Well absorbed by melanin Can pass through Hb For t/t of subretinal neovascular membrane Low intraocular scattering with good penetration through media opacity or edematous retina. Ability to coagulate choriocapilaries & choroid. Argon blue –green Laser :- 70% blue(488nm) & 30% green (514nm) It coagulates tissues between the choriocapilaries & inner nuclear layer. A/E :- High intraocular scattering Macular damage in photocoagulation near the fovea Choroidal neovascularization Frequency double Nd:Yag Laser (532nm) :- Highly absorbed by Hb , melanin in RPE & Trabecular meshwork. Used either continuously OR in pulsed mode. Ex:- PASCAL(Pattern Scan Laser)

20. Pascal(Pattern Scan Laser) Uniform Laser spots, evenly spaced & less intense. Semi-automated pattern generation technique. Multi-spot pattern array 25 spots. Allows rapid delivery of laser in predetermined sequence. PRP in sitting. Less pain.

21. Short duration treatment:- Delivers a pattern of multiple burns in the same OR less amount of time. Speed of delivery allows newer lasers to reduce the pulse duration to 10 to 30milliseconds per spot. Provides patients with more comfort. Long duration typical treatment (Conventional):- The oldest & most conventional form of PRP. Highest levels of patient discomfort. Pulse duration of 100milliseconds Large spot size(200 to 500 micron) Power:-200 to 250mW

22. PRP techniques:-

23. INDICATIONS:- PDR Retinal vascular occlusion CSME Choroidal neovascular membrane Polypoidal choroidal vasculopathy Retinal breaks Symptomatic peripheral retinal degeneration Retino choroidal tumours

24. Adverse effects :- Vasovagal attack Macular edema Peripheral visual field loss Decrease in colour & night vision. Choroidal detachment & Exudative Retinal detachment Pre- retinala membranes Small “pinching” sensation with each burn created in the affected eye. ( PRP divided into several sessons ) After the procedure,it is normal for patients to have mild headaches.

25. Navigated Retinal Laser( navilas ) :- Works by tracking retinal eye movements in real time using assistance of computers. Imaging techniques include:- Infrared, colour & FA of the fundus, which minimizes the amount of light that patients are exposed to. Doesn’t use a contact lens with current machines,d /t various imaging processes involved. Solid state-Diode 532nm & 577nm yellow Combines high-definition multimodal imaging along with planned Laser delivery system in real time.

26. Sub-threshold micropulse laser:- 577nm yellow-outside absorption spectrum of retinal xanthophylls . Low ontensity ,high density therapy. Inner retinal temp. remains below the threshold of coagulative damage(Maintain natural transparency) Originally targeted towards combating DME. Recently been hypothesized to counter PDR.

27. Laser Posterior Hyaloidotomy :- Double frequency Yag 532nm Valsalva retinopathy Short pulse,High energy burns. Selective Laser therapy-closure of choroidal neo-vascular process Leaves healthy retinal tissue unharmed Verteporfin dye used-Photosensitizing agent Photodynamic therapy( pdt ):-

28. Transpupillary thermotherapy( ttt ):- Diode (810nm) Long Pulse- 60sec of a alarge spot(1.2- 3 mm) at low irradiance. Uses:- Choroidal hemangioma Choroidal melanoma Retinoblastoma Extrafoveal CNVM Chronic CSCR

29. THANK YOU