A DETAILED USAGE OF LASERS IN RETINAL DISORDERS. DIABETIC RETINOPATHY/RETINAL OCCLUSIVE DISEASES

1. RETINAL LASERS
DR SHREYA TYAGI
PG RESIDENT
GMC, BHOPAL

2. LASER
LIGHT AMPLIFICATION BY STIMULATED
EMISSION OF RADIATION.
Two main properties: 1. Monochromatic : single
wavelength/ frequency. ( No chromatic aberrations.)
2. Coherent : Similar phase of all photons emitted.
( Limited divergence)
Coherence

3. LASER VS LIGHT
LASER LIGHT
STIMULATED EMISSION
MONOCHROMATIC
HIGHLY POLARISED
PARALLELISM
COHERENCE
CAN BE SHARPLY FOCUSSED
SPONTANEOUS EMISSION
POLY- CHROMATIC
POORLY ENERGISED
HIGHLY DIVERGENCE
NOT COHERENT
CAN NOT BE SHARPLY FOCUSSED

4. LASER TISSUE INTERACTION
THERMAL EFFECT PHOTOCHEMICAL EFFECT IONISING EFFECT
Photocoagulation Photo- vaporisation Photo ablation Photo- radiationPhoto- disruption
Argon
Krypton
Freq- doubled
ND-YAG
CW Nd-YAG
Long pulsed
Nd: YAG
Dye
Diode(810nm)
Carbon- dioxide
Excimer Arf/KRF
FREQ- Quad Nd- YAG
Holmium : YAG
Freq- doubled dye
Dye
Gold vapor
Diode (689nm)
Q- switched Nd- YAG
Mode- locked Nd- YAG
Nd- YAG
Er- YAG
Holmium: YAG
Er YLF

5. MECHANISM OF ACTION
PHOTO- VAPORISATION: Higher irradiation than photo- coagulation.
PHOTO- ABLATION: No tissue temperature rise at short wavelengths.
Tissue simply disappears with no charring. Layer by layer removed. Ex
- excimer.
PHOTO- RADIATION: Hemotoporphyrin - tumor tissues(irradiated
with 630nm, red light, diode). Verteporfin in CNV (irradiated with
diode at 689nm). Singlet oxygen. Thrombosis and occlusion.
PHOTO- DISRUPTION: Temp increase from 37 - 15000 degrees.
Electrons move out of atom, create a plasma state and bubble,
formation of hydro- dynamic and acoustic shock wave, mechanically
tears the tissue.

6. LASER PARAMETERS
POWER: No of photons emitted each second. Expressed in
watts .
EXPOSURE TIME: The duration in seconds the photons are
emitted from the laser in each burn.
SPOT SIZE: Diameter of the focussed laser beam. Expressed
in microns. Depends upon 1. LSMF of the laser lens 2. Spot
size selected in slit lamp 3.Refraction of the eye under
treatment.
Energy : No of photons emitted during an exposure of any
duration. Expressed in Joules. ( J = W * Second ).

7. LASER DELIVERY
1.SLIT LAMP
BIOMICROSCOPY : Most
common. Laser parameters can
be changed.
2.LASER INDIRECT
OPHTHALMOSCOPE:
Argon green and Diode lasers(fibre- optic
cables).
3.ENDO - LASER: Intra- operative
during vitrectomy( Argon and Diode ).

8. Photo - coagulation
MOA : Increases the temp from 37 to 50 degrees –
conformational changes,resulting in enzyme
inactivation, loss of structural integrity, cell necrosis,
haemostasis and coagulation.
MELANIN: Absorbs light spectrum ( 400- 700 nm).
Principle absorber in TM, Co- absorber in RPE AND
CHOROIDS.
XANTHOPHYLL : Absorb blue light more than green.
Present in OPL AND IPL of macula.Avoid in macular
photo- coagulation.
HAEMOGLOBIN: Absorbs red/ blue and
yellow( maximum). Red is totally unabsorbed.

9. LASERS IN PHOTOCOAGULATION
1.CW GREEN LASER:(514.5nm) : Suitable for PC of
RPE, choroids and blood vessels.
FREQ- DOUBLED Nd- YAG LASER/ KTP (532nm):
pea- green. considerably safe in macular treatment.
KRYPTON RED LASER( 647nm): Not absorbed by HB
and Xanthophyll in macular area. Suitable for macular
PC ;and sub- retinal neo- vascular membrane.
DIODE LASER(810nm): Most important semi-
conductor. No direct flash of light but more painful.

10. Do not use blue laser in:
Macular photo- coagulation
Old people with lenticular opacities: lens
absorbs, more scattering.

11. Grades of laser burn
Depending upon opacities, laser beam
may get reflected or scattered or may get
absorbed.
Power to cause optimum burn has to be
given
GRADE CHORIO- RETINAL COAGULATION
1/LIGHT Barely visible blanching of RPE
2/MILD Hazy, faint whiteRC
3/
MODERATE
Opaque, dirty white RC
4/ HEAVY Dense white/ chalky RC

12. Classification of lasers
SOLID : Ruby, Nd- YAG, Erbium - YAG
GAS: Argon , helium- neon , CO2, Krypton , ION
METAL VAPOR: Cu, Gold
DYE : Rhodamine
EXCIMER : Argon flouride, Krypton Fluoride, Krypton
chloride
DIODE : Gallium- alluminium- arsenide( Ga- Al- As)

13. PRP/SCATTER LASER IN DIABETIC
RETINOPATHY
GOLD STANDARD in DR and veinous
occlusions.
Pre- requisite- BS and lipid levels should be
controlled.

14. INDICATIONS OF PRP
1.MODERATE TO SEVERE NVD
2. Mild NVD with pre - retinal hmgh or vit hmgh.
3. NVE with pre - retinal/ vitreous hmg.
4. Rubeosis of iris/angle
5. Signs of extensive retinal ischaemia.
6. Severe PDR in other eye.
7. Both eye approaching HRPDR.
8. HRPDR
9Pregnancy/post- renal transplantation- PPDR/PDR.

15. PROPOSED THORIES
Injured RPE cells : thinning and anoxia of the
outer retina.
More oxygen available to inner retina and
vitreous. Decreased stimulus for neo-
vascularisation.
Also, PRP converts ischaemia to anoxia, no
VEGF.

16. LENSES IN PRP LASER
GOLDMANN 3- MIRROR :
MAINSTER PRP 165
VOLK SUPER QUAD 160
MAINSTREAM WIDEFILED : Better for posterior
pole
VOLK QUADRA SPHERIC : Better for mid-
periphery
Virtual, erect image
More effective in
periphery
Comes with anti-
reflective coating
Argon/ diode/krypton
lasers
Better for
periphery.

18. Technique - PRP
3 sessions, 1-2 week apart, 800 - 1600 burns
recommended( 1800- 2200)
Avoid major vessels, vortex veins, vitreous hmgh
and chorio- retinal scars. Also within papillo-
macular bundle.
Krypton red and diode much better in case of
reduced retinal visibility viz vit. hmgh/ lental
opacity. But these are painful.
Session 1:
Spot size: 100- 200
Exposure : 0.05- 0.2
sec
Power: 100- 400
mW
(Intensity- GR3)
PATTERN : 1- 1.5
spot size
NVD : confluent
burns
Session 2/3
Spot size : 300- 500um
Duration : 0.1- 0.2 sec
Power : 400- 800 mW
(Intensity grd -3)
Pattern : 1 spot size

19. FOCAL/ GRID PHOTO-
COGULATION
INDICATIONS:
ME from diabetes or BRVO
ROP
Focal ablation of extra- foveal choroidal neovascular
membrane
Retinal Breaks and Detached areas.
Focal treatment of pigment abnormalities such as RPE
leakage in CSR.
Ocular tumors (Malignant melanoma / Retino - blastoma etc)
Posterior hyaloidotomy in large sub- hyaloid haemorrhage.

20. Focal photo- coagulation
Location :
Indications : CME : Focal points of leakage >= 500/ 300-
500um from macula leading to hard exudates or macular
thickening
Target in CSME : leaks including micro- aneurysm and IRMA.
END POINT: Whitening/ darkening of micro - aneurysm
1.GOLDMANN 3-
MIRROR(ARGON/ DIODE)
2.MAINSTER STANDARD
3.MAINSTER HIGH
MAGNIFICATION
4.OCULAR PDT 1.6 *(High
magnification
And resolution
5.VOLK AREA CENTRALIS
LENSES USED Parameters
Spot size= 50- 100 um
Exposure; 0.1 sec
Power - 100 to 400 mw

22. Newer RPE replaced .
PC causes existing RPE cells to absorb more
fluid.
Stimulates endothelial proliferation (better
integrity ) of blood - retinal barrier.

23. Grid photo- coagulation
Location : extends arcade to arcade leaving
500 um around macular centre and 500
um of the optic disc margin. Usually placed
in papillo- macular bundle.
Direct photo- coagulation of micro-
aneurysm not done.
Indication in CME :
Modified GRID PHOTO- COAGULATION:
PARAMETERS:
SPOT SIZE: 50- 200um
Exposure: 0.1 s
Power: start with 50- 100mw,
Gradually increase.
No of burns: 100- 200, 1 burn apart)

25. Photo- coagulation in Retinal
Veinous Occlusion
BRVO
Indications : (at least 3 months duration)
GRID LASER: ME<6/12 with intact
peri- foveolar capillary network
GRID :Intensity grd 1. Over capillary leak and
Papillo- macular bundle.
PRP : NVE/ NVD
Intensity:200-500um/o.1sec/moderate/ 1 burn apart

26. CRVO
Indications :
PROMT/IMMEDIATE : NVI/ NVA/ NVE/ NVD
PROPHYLACTIC: Close follow up not possible
High risk : 1 month symptom/VA<6/60/extensive areas of
capillary non- perfusion.
Only PRP done.(0.1-0.5sec/500-1000um/moderate intesity-
1 to 1 1/2 spot size.)
No of spots : 1200- 2000

27. RETINOPATHY OF PREMATURITY
Indication : threshold ROP (Stage 3, Zone 1
or 2 , Extent 5 contagious or 8 cumulative).
Plus disease ;RUSH disease(Fulminant variety):
Technique :PC avascular area anterior to
the mesenchymal ridge upto ora
serrata.Photo- coagulation over and
posterior to the mesenchymal ridge
should be avoided.
LASER USED: DIODE (810nm) through
BIO ( binocular indirect ophthalmoscope )
with + 20D/ +28D.

28. PARAMETERS
Spot size: 100 um
Exposure : 0.3 sec
Power : 300mW
Intensity - grd 2
Pattern : Nearly confluent or 1/2
burn width apart.
Complications
Hyphaema
Iris burn
Retinal detachment
Accidental burn over mesenchymal ridge
And posterior to it.
Corneal haziness(argon)
Systemic- apnea, Brady, seizures and arrhythmia

29. Peripheral Retinal
Degenerations/ Breaks
DEGENERATIONS:
Parameters: 500-800UM/0.1- 0.2 SEC/ 400- 600mw(more in
periphery)/
Pattern : solitary, linear, single row, 1/2 spot size. 1 DD away from
degeneration.
Anterior most periphery first than posterior.
BREAKS.
Parameters: 500- 1000um/0.2-0.5sec/400- 600 um.
Pattern same as degenrations with 1/4 the spot size.

32. Photo- dynamic Therapy(PDT)
DYE : VERTEPORFIN
• 1. Classic sub- foveal
CNV in wet AMD
• 2.Idiopathic CNV
• High myopia
• Traumatic rupture of
choroids
• Ocular histoplasmosis
syndrome
• Angiod streaks
• Drusens of the optic
nerve
• THE SIZE >=
5400MICRONS
INDICATIONS CONTRA
INDICATIONS
1.DRY AMD
2. SIZE< 5400 MICRONS
SYSTEMIC:
1. Hypersensistivity to verteporfin
2. Porphyria
3. Severe hepatic disorder
4. Relative: uncontrolled HTN,
Unstable cardiac disorder

33. Special precaution : No extra- vasation of blood .
POST- LASER : Avoid sunlight exposure(fully covered body with
protective sun- glasses, stay indoors for 5 days, no hair dye)
PARAMETERS:
Spot size: 500um
Size of beam: 1000um+ greatest linear dimension of lesion
Exposure : 83 secs
Intensity : 600mW/cm2
Total Laser Energy : 50 J/cm2
Dose of dye : 6mg/ m2

34. Trans-pupillary Thermo-
Therapy(TTT)
Alternative to PDT for sub- foveal CNV secondary to
wet AMD.
INDICATIONS:
1. Occult sub- foveal/Juxta- foveal CNV in wet AMD.
2. Retinoblastoma(upto 4mm basal diam and 2mm in
thickness) without vitreous / sub- retinal seeding.
3. Choroidal Hemanigioma
4. Choroidal Melanoma
TIMING : Done within 72 hrs post recent FFA.

35. FEATURES PDT TTT
LASER AND
WAVELENGTH
Diode,689 nm Diode, 810nm
LASER TISSUE
INTERACTION
Photo- radiation Photo- thermal
INDICATIONS Classic sub -foveal CNV As discussed
TEMPERATURE RISE
( Intra-lesional)
2 degree C 10 degree C
EXPOSURE 83 secs 60 secs
POST - LASER Avoid photo- toxicity NIL
SIDE- EFFECTS
Inj site extra- vacation,
back pain etc
NIL
TOLERANCE Not so well tolerated Well- tolerated
TREATMENT COST Expensive In expensive

36. THANK YOU.

37. Ido :Suitable for photocoagulation of retinal breaks, degenerations,
lasers in the periphery in cases rubeosis iridis, PDR, Post - CRVO ,
ROP. Not suitable for focal/ macular grid lasers.
Ideal for photocoagulation in eyes with small pupil, lenticular opacities and intra- ocular
gas.
Spot size change : condensing lens used, lever. More in hypermetropes, lesser in myopes.
Endo- laser : Ideal for photo- coagulation in NVE, peripheral retinal breaks and
degenerations after air- fluid exchange in vitrectomy. And giant retinal tear.
Ideal for photo- coagulation in NVE, peripheral retinal breaks and degenerations after air-
fluid exchange in vitrectomy. And giant retinal tear.
Prior SRF removal needed. Prior SRF removal needed.

38. To do
Lasers intro read
Sequence of scatter lasers
PHOTONS AND POLARISM

39. Doubts
Spot size depends upon
Ido : spot size why more in hypermetropes
Which laser do we use here for PRP
HRPDR
States of laser.. solid/ gas
What is CW?
Why to use diode in ROP?
ZONES OF PRP