brief note on lasers usedin ophthalmology.

1. MODERATOR: DR. S. KALPANA
PRESENTER: DR. ANJALI

2.  Introduction.
 History .
 Laser physics.
 Classification .
 Laser tissue interactions.
 Uses – therapeutic.
- diagnostic.
 Complications.

3. 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.

4.  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 LIGHT
 Stimulated emission
 Monochromatic.
 Highly energized
 Parallelism
 Coherence
 Can be sharply focussed.
 Spontaneous emission.
 Polychromatic.
 Poorly energized.
 Highly divergence
 Not coherent
 Can not be sharply
focussed.

6.  Coherency
 Monochromatism
 Collimated
 Constant Phasic Relation
 Ability to be concentrated in short time interval
 Ability to produce non linear effects

7.  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 ???

9. Contd. …

11. Pulsed – energy delivered in brief
bursts, more power
Examples: Nd YAG, Excimer lasers
Continuous – Argon, krypton lasers, diode
lasers, and dye lasers

12.  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)

14.  Haemoglobin:
 Argon Green are absorbed , Krypton yellow. These
laser are found to be useful to coagulate the blood
vessels.
 Xanthophyll:
 Present in inner and outer plexiform layers of macula.
 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

17.  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.

18. LASER VARIABLE:
 Wavelength
 Spot Size
 Power
 Duration
TISSUE VARIABLE:
 Transparency
 Pigmentation
 Water Content

19. This is the amount of power delivered to a
unit area of tissue.
To prevent creating very intense burn.
Decrease in the spot size should be
accompanied by decrease in power.

20. LASER
TISSUE
Thermal
Effect
Photo-
chemical
Ionizing
Effect
 Photocoagulation  Photoradiation
 Photodisruption  Photoablation
 Photovaporization

21. (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.

22. (2) Photodisruption:
 Mechanical Effect:
 Laser Light
Optical Breakdown
Miniature Lightening Bolt
Vapor
Quickly Collapses
Thunder Clap
Acoustic Shockwaves
Tissue Damage
Contd. …

23. (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. …

24.  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

25. 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

26. 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. …

27.  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

28. iridotomy

29.  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

30.  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.

31. Transpupillary: - Slit lamp
- Laser Indirect
Ophthalmoscopy
Trans scleral : - Contact
- Non contact
Endophotocoagulation.

32. Most commonly employed mode for
anterior and posterior segment.
 ADVANTAGES:
Binocular and stereoscopic view.
Fixed distance.
Standardization of spot size is more
accurate.
Aiming accuracy is good.

33.  Advantages :
 Wider field(ability to reach periphery).
 Better visualization and laser application in
hazy medium.
 Ability to treat in supine position.(ROP/EUA)
 Disadvantage : difficulty in focusing.
 Difficulty to standardize spot size.
 Expensive.
 Un co-operative patient.
 Learning curve.

34. THERAPEUTIC.
DIAGNOSTIC.

35. CORNEA:
Laser in Keratorefractive 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.

36. High energy UV laser.
Excited dimer.
Argon fluoride(193nm) most commonly
applied for corneal surgeries.
Photoablation.

37. Laser removes approximately 0.25microns
of corneal tissue with each pulse.
Amount of tissue to be ablated derived
from ―munnerlyn equation”
Central ablation depth in microns=diopters
of myopia*(ablation zone diameter in mm)2
3

38. PRK LASIK

39. 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
 Costly

40. Contd. …

41.  Laser Iridotomy.
 Laser Trabeculoplasty (LT)
 Selective Laser Trabeculoplasty
 Trabecular ablation
 Gonioplasty (Iridoplasty, Iridoretraction)
 Pupilloplasty
 Sphincterotomy
 Iridolenticular Synechiolysis
 Goniophotocoagulation
 Goniotomy

43. Peripheral Iridectomy Argon Laser
IridoplastyArgon Nd:YAG
Light Irides Dark Irides
Spot size (μm) 50 50 Fixed 200–500
Spot duration (seconds) 0.2 0.02–0.05 Fixed
(nanoseconds)
0.2–0.5
Power (mW) 1000 1000 3–8 mJ 200–400
Number of spots per
quadrant
15–25 25–100 1–5 shots (each
burst consists of
1–3 pluses)
4–10
Wavelength Argon green Argon green 1064 nm Argon green
Contact lens Abraham Wise Abraham, Wise,
or Lasag CGI
Goldmann
Pretreatment Pilocarpine
and
apraclonidine
or
brimonidine
Pilocarpine
and
apraclonidin
e or
brimonidine
Pilocarpine and
apraclonidine or
brimonidine
Pilocarpine

45. PUPILLOPLASTY
2-3 rows of burns
circumferentially 1mm
away from the pupillary
margin.
Innermost row:8spots,
200micron size, 200-
400mW.
Outer row:10-
12spots,400micron
size,300-500mW

46. Laser parameters are
same for photomydriasis.
Burns are placed along
the inferior margin.

47. ARGON LASER TRABECULOPLASTY
Mechanism of
action:Mechanical.
Biological.

48. Parameters Argon laser trabeculoplasty
Spot size (μm) 50
Spot duration (seconds) 0.1
Power (mW) 200–800
Number of spots per
quadrant
20–25
Wavelength Argon green
Contact lens Goldmann
Anesthetic Topical
Pretreatment Apraclonidine or brimonidine
Argon laser trabeculoplasty

50.  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. …

51. SCLEROSTOMY

52. AB INTERNO SCLEROSTOMY

53.  Posterior capsulotomy
 Laser phacoemulsification
 Phacoablation.
 Laser in Lacrimal Surgery:
 Laser DCR.
LASER IN VITREOUS
 Vitreous membranes
 Vitreous traction bands

54.  Diabetic Retinopathy
 Retinal Vascular Diseases
 Choroidal Neovascularization (CNV)
 Clinical Significant Macular Edema (CSME)
 Central Serous Retinopathy (CSR)
 Retinal Break/Detachment
 Tumour

55.  ARMD
 Retinal Vein Occlusion
 Eale’s Disease
 Coats Disease
 Peripheral Retinal Lesion
 Retinopathy of prematurity.
Contd. …

56. Patient should be explained about the
possible complications to avoid legal
problems to the treating physician later.

57.  Light : Barely visible retinal blanching
 Mild : Faint white retinal burn
 Moderate : Opaque dirty white retinal burn
 Heavy : Dense white retinal burn

64. TYPE OF RETINOPATHY THERAPY
Background
Control of diabetes, regular
review
Maculopathy
CSME
Focal photocoagulation
Diffuse leakage around macula Grid laser
Circinate Focal photocoagulation
Pre-proliferative Retinopathy Frequent review
Proliferative retinopathy Pan retinal photocoagulation
Advanced diabetic eye disease
Vitreoretinal surgery with
photocoagulation
Contd. …

66. Step 1
Step 2

67. Step 3
Step 4

69. Laser settings
Wavelength :argon
green, Nd YAG,dye
yellow red , diode.
Duration :0.1-
0.2seconds.
Retinal spot size: 200-
500microns.
Intensity : moderate
retinal whitening

70.  Indication:
Photocoagulation
technique.
Initial destruction of the
surrounding choroidal
blood supply-1-2rows -
200-500 microns 0.5-
1sec-intense burn.
Direct tumour
photocoagulation-low
energy burns long
duration5-30sec.

71.  Visudyne (Verteporfin)
 Selective Damage
of SRNVM.
 Costly.

72. 1. Dye dose = 6 mg/m2 body surface area
2. Intravenous infusion over 10 min
3. Treatment at 15 min after start of dye
infusion
4. Laser light wavelength of at 689 nm,
irradiance of 600 mW/cm2
and fluence of 100 J/cm2

73.  Thermotherapy can involve using
 ultrasound, microwave, or infrared radiation to
deliver heat to the eye.
 Retinoblastoma -application of diode (infrared)
laser to the tumor surface in regions of disease
activity.
 Goal- 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.

74. Retinoblastoma after
thermotherapy

75. Lens Uses Image
Spot
Magnificatio
n
Field of view
Goldmann
Macula
Equator
Periphery
Virtual
Erect
1.08 360
Volk
Supermacul
a 2.0
Macula
Real
Inverted
2.15 700
Mainster
High
Magnificatio
n
Macula
Real
Inverted
1.34 750
Volk Area
Centralis
Macula
Equator
Real
Inverted
1.13 820

76. Lens Uses Image
Spot
Magnificatio
n
Field of
view
Mainster
Standard
Macula
Equator
Real
Inverted
1.03 900
Panfundusc
opic
Equator
Periphery
Real
Inverted
0.76 1200
Volk
Transequat
or
Equator
Periphery
Real
Inverted
0.75 1220
Mainster
Wide Field
Equator
Periphery
Real
Inverted
0.73 1250

77. Lens Uses Image
Spot
Magnificatio
n
Field of
view
Volk
QuadrAsph
eric
Equator
Periphery
Real
Inverted
0.56 1300
Mainster
Ultra Field
PRP
Equator
Periphery
Real
Inverted
0.57 1400
Volk
SuperQuard
160
Equator
Periphery
Real
Inverted
0.56 1600

78.  The PASCAL Photocoagulator is an integrated semi-
automatic pattern scan laser photocoagulation system
designed to treat ocular diseases using a single shot or
predetermined pattern array.
 Laser source :Nd:YAG laser.
 Delivery device: slit lamp or laser indirect
ophthalmoscope (LIO)
 Control system for selecting power and duration
 Method for selecting spot size
.

80. Scanning Laser Ophthalmoscopy
 allows for high-resolution, real-time motion
images of the macula without patient
discomfort.
 SLO angiography: to study retinal and
choroidal blood flow.
 May be used to perform microperimetry, an
extremely accurate mapping of the macula’s
visual field.

81. Uses diode laser light in the near-infrared
spectrum (810 nm) to produce high-
resolution cross-sectional images of the
retina using coherence interferometry.

84.  General complications:
 Pain
 Seizures.
 Anterior segment complications:
 Elevated IOP.
 Corneal damage.
 Iris burns.
 Crystalline lens burns.
 IOL and PC damage.
 Internal opthalmoplegia.

85. Choroidal detachment and exudative RD.
Choroidal ,subretinal and vitreous
hemorrhage.
Thermal induced retinal vascular damage.
Preretinal membranes.

86. Ischaemic papillitis.
Paracentral visual field loss and scotoma.
Photocoagulation scar enlargement.
Subretinal fibrosis.
Iatrogenic choroidal neovascularisation.
Accidental foveal burns.

87.  Save a child’s eye as in Retinoblastoma.
 Change a personality as in LASIK.
 Cure a middle aged person with Glaucoma.
 Restore Vn. in a person with After-Cataract.
 Preserve & Retain Vn. in pts. with DR & ARMD
 The possibilities are endless…...

88. YANOFF AND DUKER
OPHTHALMOLOGY- 3rd edition.
LASERS IN OPTHALMOLOGY
A practical guide-AIIMS.
LASER SURGERY OF THE POSTERIOR
SEGMENT- Steven M. Bloom

89. Thank you