1. ROLE OF LASERS IN OPHTHALMOLOGY
Presenter : Dr. Ajay Gulati

2. HISTORY
 Dates to 400 BC, when Plato described the dangers of direct sun
gazing during an eclipse
 Czerny and Deutschmann, in 1867 and 1882, respectively,
focused sunlight through the dilated pupils of rabbits
 Meyer-Schwickerath undertook the study of retinal
photocoagulation in humans in 1946 using the xenon arc lamp
 The first functioning laser was demonstrated by Maiman in
1960. The active laser material was a ruby which emitteda
radiation of 649 nm (red light) pulsed with a xenon flash lamp
 First clinical ophthalmic use of a laser in humans was reported
by Campbell et al. in 1963 and Zweng et al. in 1964
 Argon laser was developed in 1964, L’Esperance conducted the
first human photocoagulation with it
 He also introduced the frequency-doubled neodymium:yttrium-
aluminum-garnet (Nd:YAG) and krypton lasers in 1971 and 1972,
respectively
 Q-switched , mode-locked , tunable dye laser , semiconductor
infrared diode laser were other sequential discoveries

3. INTRODUCTION
 LASER stands for Light Amplification by Stimulated
Emission of Radiation
 The basic laser cavity consists of an active medium in a
resonant cavity with two mirrors placed at opposite ends.
One of the mirrors allows partial transmission of laser
light out of the laser cavity, toward the target tissue. A
pump source introduces energy into the active medium
and excites a number of atoms. In this manner,
amplified, coherent, and collimated light energy is
released as laser energy through the mirror that partially
transmits. The various lasers differ mainly in the
characteristics of the active medium and the way this
active medium is pumped

6. Properties of laser light that make it
useful to ophthalmologists
 Monochromaticity
 Spatial coherence
 Temporal coherence
 Collimation
 Ability to be concentrated in a short time
interval
 Ability to produce nonlinear tissue effects

7. Laser physics

8. TYPES
Carbon Dioxide
Neon
Helium
Krypton
Argon
Gas
Nd Yag
Ruby
Solid State
Gold
Copper
Metal
Vapour
Argon Fluoride
EXCIMER Dye Diode
LASERS

9. Tissue Interactions
Carbon Dioxide
(Photo vaporisation)
Neon
Helium
Krypton
(Photo coagulatn)
Argon
(Photo coagulatn)
Gas
Nd Yag
(Photo coagulatn)
(Photo disruption)
Ruby
(Photo coagulatn)
Solid State
Gold
(Photo dynamic)
Copper
Metal
Vapour
Argon Fluoride
(Photo ablation)
EXCIMER Dye
(Photo coag.)
(Photo dynamic)
Diode
(Photo coag.)
LASERS

10. DELIVERY SYSTEMS
 Slit-lamp biomicroscope : most common, delivery is
transcorneal, with or without the aid of contact
lenses
 Indirect ophthalmoscope : condensing lens ,
transcorneal
 Endolaser probes : fiber-optic probes used within
the eye
 Exolaser probes : fiber-optic probes used trans-
sclerally

11. PARAMETERS AND TECHNIQUES
 Wavelength: choice of optimal wavelength
depends on the absorption spectrum of the target
tissue
 PRINCIPAL WAVELENGTHS OF COMMONLY USED LASERS
 193 nm - Excimer (Cornea)
 488 - 514 nm - Argon (Retina)
 532nm - Frequency doubled Nd:YAG
 694.3 nm - Ruby
 780 - 840 nm - Diode
 1064 nm - Nd Yag (Capsule)
 10,600 nm - Carbon dioxide (Skin)

13. Other Parameters
 Power
 Exposure Time
 Spot Size

14. TISSUE EFFECTS OF LASER

15. PHOTORADIATION (PDT):
 Also called Photodynamic Therapy
 Photochemical reaction following visible/infrared light
particularlyafteradministration ofexogenous chromophore.
 Commonly used photosensitizers:
 Hematoporphyrin
 Benzaporphyrin Derivatives

16.  Photon + Photosensitizer in ground state (S)

high energy triplet stage

Energy Transfer
 
Molecular Oxygen Free Radical
S + O2 (singlet oxygen), Cytotoxic Intermediate
 
Cell Damage, Vascular Damage , Immunologic
Damage

17. Photoablation:
 Breaks the chemical bonds that hold tissue
together essentially vaporizing the tissue, e.g.
Photorefractive Keratectomy, Argon Fluoride (ArF)
Excimer Laser.

18. Photocoagulation:
Laser Light

Target Tissue

Generate Heat

Denatures Proteins
(Coagulation)
Rise in temperature of about 10 to 20 0C will cause
coagulation of tissue.

19.  Photovaporization
 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

20. Photodisruption:
Mechanical Effect:
Laser Light

Optical Breakdown

Miniature Lightening Bolt

Vapor

Quickly Collapses

Thunder Clap

Acoustic Shockwaves

Tissue Damage

21. MODES OF OPERATION
 Continuous Wave (CW) Laser: It deliver the energy
in a continuous stream of photons.
 Pulsed Lasers: Produce energy pulses of a few tens
of micro to few mili second.
 Q Switched Lasers: Deliver energy pulses of
extremely short duration (nano second).
 Mode-locked Lasers: Emits a train of short
duration pulses (picoseconds) to femtoseconds
 Pulsed pumping

22. Safety
Lasers are usually labeled with a safety class number, which identifies
how dangerous the laser is
 Class I/1 is inherently safe, usually because the light is contained
in an enclosure, for example in CD players.
 Class II/2 is safe during normal use; the blink reflex of the eye will
prevent damage. Usually up to 1 mW power, for example laser
pointers.
 Class IIIa/3R lasers are usually up to 5 mW and involve a small
risk of eye damage within the time of the blink reflex. Staring into
such a beam for several seconds is likely to cause damage to a spot
on the retina.
 Class IIIb/3B can cause immediate eye damage upon exposure.
 Class IV/4 lasers can burn skin, and in some cases, even scattered
light can cause eye and/or skin damage. Many industrial and
scientific lasers are in this class.

23. Warning symbol for lasers

24. USES
 DIAGNOSTIC  THERAPEUTIC

25. DIAGNOSTIC
 Scanning Laser Ophthalmoscopy
 Laser Interferometry/ Optical Coherence Tomography
 Wavefront Analysis

26. Scanning Laser Ophthalmoscopy
 In the scanning laser ophthalmoscope (SLO), a 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. Media
opacities, such as retinal hemorrhage, vitreous hemorrhage,
and cataract, also affect the amount of light transmitted back
to the observer. Because the SLO uses laser light, which has
coherent properties, the retinal images produced have a much
higher image resolution than conventional fundus
photography.
 study retinal and choroidal blood flow
 microperimetry, an extremely accurate mapping of the
macula’s visual field.

28. Tests Performed on the Scanning Laser
Ophthalmoscope
 Scanning Laser Acuity Potential (SLAP) Test: The letter E
corresponding to different levels of visual acuity (ranging from
20/1000 to 20/60) is projected directly on the patient’s retina. The
examiner directs the test letters to foveal and/or extrafoveal locations
within the macula, and determines a subject’s potential visual acuity.
This is especially helpful in individuals who have lost central fixation
but still possess significant eccentric vision.

30.  Microperimetry / Scotometry : The SLO could visualize a
particular area of the retina and test its sensitivity to visual stimuli,
thereby generating a map of the seeing and non-seeing areas.

31.  Hi-Speed FA / ICG
 Fluorescein and Indocyanine Green Angiography (FA/ICG) performed
using the SLO is recorded at 30 images per second, producing a real-
time video sequence of the ocular blood flow

32. Optical Coherence Tomography
 diode laser light in the near-infrared spectrum (810 nm)
 partially reflective mirror used to split a single laser beam into two, the
measuring beam and the reference beam
 measuring beam is directed to the retina , laser beam passes through the neurosensory
retina to the retinal pigment epithelium (RPE) and the choriocapillaris. At each optical
interface, some of the laser light is reflected back to the OCT’s photodetector
 reference beam is reflected off a reference mirror at a known distance from the beam
splitter, back to the photodetector. The position of the reference mirror can be adjusted to
make the path traversed by the reference beam equal to the distance traversed by the
measuring beam to the retinal surface. When this occurs, the wave patterns of the measuring
and reference beams are in precise synchronization, resulting in constructive interference.
This appears as a bright area on the resulting cross-sectional image. However, some of the
light from the measuring beam will pass through the retinal surface and will be reflected off
deeper layers in the retina. This light will have traversed a longer distance than the reference
beam, and when the two beams are brought back together to be measured by the
photodetector, some degree of destructive interference will occur, depending on how much
further the measuring beam has traveled. The amount of destructive interference at each
point measured by the OCT is translated into a measurement of retinal depth and graphically
displayed as the retinal cross-section.
 OCT images are displayed in false color to enhance differentiation of retinal structures. Bright
colors (red to white) correspond to tissues with high reflectivity, whereas darker colors (blue to
black) correspond to areas of minimal or no reflectivity. The OCT can differentiate structures
with a spatial resolution of only 10 μm

34. Wavefront Analysis and Photorefractive
Keratectomy
 Lasers are used in the measurement of complex
optical aberrations of the eye using wavefront
analysis
 Hartmann-Shack aberrometer

37. Therapeutic Uses
• Lids and Adnexae
• Anterior Segment & Posterior Segment

38. Lids and Adnexae
Skin: (usually CO2 laser)
 Lid Tumors : carbon dioxide laser ,benign and malignant
,bloodless but scarring, lack of a histologic specimen, and
inability to assess margins.
 Blepharoplasty (carbon dioxide or erbium:YAG laser )
 Xanthalesma ( green laser)
 Aseptic Phototherapy
 Pigmentation lesion
 Laser Hair Removal Technique
 Tattoo Removal
 Resurfing

39. Lacrimal Surgery
 Endoscopic Laser Dacryocystorhinostomy

40. Anterior Segment
 Conjunctival / Corneal Growths,
Neovascularization
 Refractive Surgery
 Laser in Glaucoma
 Laser in Lens

41. Refractive Surgeries
 Photorefractive keratectomy
 Laser subepithelial keratomileusis (LASEK)
 Laser-assisted in situ keratomileusis (LASIK)

42. Photorefractive keratectomy
 low myopia (up to 6D)
and low hyperopia (up to 3D)

43. LASIK jjj
 2 to 9 D
 lamellar dissection with the microkeratome
 refractive ablation with the excimer laser
 IntraLASIK/Femto-LASIK or
All-Laser LASIK ( corneal flap is made with
Femtosecond laser microkeratome)

44. Suction Ring Microkeratome Flap Removed
LASIK Flap replaced Post operative

45. Femto lasers in cataract surgery
 LenSx Lasers (ALCON)
 new level of precision and reproducibility
 The Laser creates
a) Corneal incisions with precise dimensions and geometry.
b) anterior capsulotomies with accurate centration and
intended diameter, with no radial tears.
c) lens fragmentation (customized fragmentation patterns)

46. Lasers in Glaucoma
 Laser treatment for internal flow block
 Laser treatment for outflow obstruction
 Miscellaneous laser procedures

47. Laser treatment for internal flow block
 Laser peripheraLiridotomy
&
 Laser iridopLasty (GoniopLasty)

48. Laser peripheraLiridotomy

49.  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.

50.  Argon or Solid-State Laser iridotomy:
Photocoagulative (lower energy & longer exposure)
Iris color (pigment density) is the most imp factor
Iris color can be divided into three categories:
a) light brown : 600–1000 mW with a spot size of 50 µm and a
shutter speed of 0.02–0.05 second
b) dark brown: 400–1000 mW , spot size of 50 µm and a shutter
speed of 0.01 second
c) blue iris: 200- µm spot, 200–400 mW, 0.1
Second to anneal the pigment epithelium to the stroma , Then the
spot size reduced to 50 µm and power increased
to 600–1000 mW at 0.02–0.1 second to perforate

51. Complications of Laser iridotomy
 Iritis
 Pressure elevation
 Cataract
 Hyphema
 Corneal epithelial injury
 Endothelial damage
 Failure to perforate
 Late closure
 Retinal burn

52. Laser Iridoplasty (Gonioplasty)
 Plateau iris &
Nanophthalmos:
100–200- µm spot
size , 100–30 mW
at 0.1 second ,
10- 20 spots evenly
distributed over
360º

53. Laser treatment for outflow
obstruction
 Laser Trabeculoplasty
 Excimer Laser Trabeculostomy
 Laser Sclerostomy

54.  Laser trabeculosplasty (LTP) :
a) Argon laser trabeculoplasty (ALT) : 50 µm spot size
and 1000-mW power for 0.1 second , 3–4° apart
20–25 spots per quadrant
b) 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

56.  COMPLICATIONS
Iritis
Pressure elevation
Peripheral anterior synechiae
Hyphema

57. Excimer Laser Trabeculostomy((ELT)
 precise and no thermal damage to surrounding
tissues
 ab-interno (used intracamerally) : 308-nm xenon-
chloride (XeCl) excimer laser delivers photoablative
energy

59. 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 .
 Ab-externo : probe applied to the scleral surface
under a conjunctival flap.
 Ab-interno : through a goniolens

63. Miscellaneous laser procedures
 Cyclophotocoagulation
 Laser suture lysis (LSL)
 Reopening Failed Filtration sites
 Laser synechialysis
 Goniophotocoagulation
 Photomydriasis (pupilloplasty)

64. Cyclophotocoagulation
 Trans-scleral Cyclophotocoagulation
A) Noncontact Nd:YAG laser cyclophotocoagulation
B) Contact Nd:YAG laser cyclophotocoagulation
C) Semiconductor diode laser trans-scleral
cyclophotocoagulation
 Endoscopic cyclophotocoagulation (ECP)

68. Laser suture lysis (LSL)
When lasering sutures, the flange of
the Hoskins laser suture lens holds up
the lid. The suture is located under the
laser slit lamp
lens is pressed steadily against the
conjunctiva, displacing edema until a
clear image of the suture is seen . The
suture usually is treated near the knot.
The long end of the suture will then
retract into the sclera

70.  Laser synechialysis : lyse iris adhesions
 Goniophotocoagulation: anterior segment
neovascularization , rubeosis , fragile vessels in a
surgical wound
 Photomydriasis (pupilloplasty) : enlarge the
pupillary area by contracting the collagen fibers of
the iris

71. Lasers In Lens
 Posterior Capsular Opacification : (Nd:YAG) laser
posterior capsulectomy

72. Laser posterior capsulectomy
Cruciate pattern Circular pattern

73. Posterior Segment
 Laser in vitreous
 Laser in Retinal vascular diseases
 Other Retinal diseases

74. Laser in vitreous
 Vitreolysis in cystoid macular edema
 Viterous membranes & traction bands

75. Laser Photocoagulation In Vascular Diseases
 Panretinal Laser Coagulation
a) Full Scatter Panretinal Laser Coagulation
b) Mild Scatter Panretinal Laser Coagulation
 Focal Laser Application
 Subthreshold Laser Coagulation for Retinal
Disease

76. Full Scatter Panretinal Laser
Coagulation
 Diabetes : four accepted indications for a dense (full
scatter) panretinal laser coagulation are
a) Presence of vitreous or preretinal hemorrhage
b) Location of new vessels on or near the optic disk (NVD)
c) Presence of new vessels “elsewhere” (NVE)
d) Severity of new vessels (proliferation area greater
than one-fourth of the optic disk size)
exposure times 100–200 ms ,a spot size of 500 μm. The laser
application should lead to a mild white retinal lesion. The
distance between the laser spots 0.5–1 laser spot. range of laser
spots varies between 1,000 and 2,000 . It is recommended to
apply laser lesions in Two to four sessions, 2 weeks apart ,
Regression expected after 4–6 weeks

77.  Central Retinal Vein Occlusion: main
complications of a central vein occlusion apart from
macular edema are neo-vascularizations of the retina
and of the iris
 no effect of prophylactic pan-retinal laser
coagulation to prevent neovascularizati-ons of the
iris. But if neovascularizations of the retina or of the
iris exist,the treated eyes clearly benefit from full
scatter panretinal laser coagulation

78.  Branch Retinal Vein Occlusion: characterized by
macular edema and vitreous hemorrhage from retinal
neovascularizations
 Retinal laser coagulation done not earlier than 3–6
months.
 done only if retinal hemorrhage has significantly cleared.
 For the treatment of macular edema, exposure times of
100 ms and a spot size of 100 μm are recommended. The
distance of 2–3 spot diameters. The area of the edema
should be treated in a dense grid. After occurrence of
neovascularizations a sector retinal laser coagulation is
indicated.

79. Mild Scatter Panretinal Laser
Coagulation
 For Non-proliferative diabetic retinopathy
 risk factors for treating non PDR
 The 4:2:1 rule
a) If either intraretinal bleeding occurs in 4 quadrants
b) Or if venous beading occurs in at least 2 quadrants
c) Or if intraretinal microvascular abnormalities
(IRMA) occur in at least one quadrant
600 laser spots of 500 μm ,exposure times 100–200
ms spots more spaced than full scatter.

81. Focal Laser Application
 Clinically significant macular edema (CSME)
 It is present and should be treated by focal laser
coagulation if:
a) There is a clinical retinal thickening within 500 μm
distance from the center of the macula
b) There is hard exudation within 500μm distance from the
center of the macula with retinal thickening in the
bordering retina
c) There is a retinal thickened area by the size of at
least one papilla diameter within the distance of one
papilla diameter from the center of the macula

82.  Placement of the laser coagulation spots has to be
decided by fluorescein angiography
 exposure times 100ms and a spot size of 100 μm with
beginning power of 70–80 mW.
 leads to a mild gray retinal lesion.

83. Subthreshold Laser Coagulation for
Retinal Disease
 Selective treatment of the RPE
 Diabetic macular edema
 Central serous retinopathy (CSR)
 Drusen in age-related macular degeneration (AMD)

84. Focal diabetic macular edema before treatment by
SRT

85. The same fundus 2h after SRT–the lesions are visible
only in the fluorescein angiogram and show the pattern of treatment

86. Fundus image 6 months after SRT. The hard exudates
have resolved

87. Photodynamic therapy (PDT)

89. Indications
 CNVs due to age-related macular degeneration,
pathologic myopia, angioid streaks and presumed
ocular histoplasmosis syndrome
 Retinal capillary hemangioma
 Vasoproliferative tumor
 Parafoveal teleangiectasis

90.  For age-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: light dose of 100 J/cm2 over an
interval of 166 s

94. Other Uses Of Lasers in Post. Segment
 Drainage of subretinal fluid / haem

95.  Retinal Breaks or Tears

96.  Intraocular tumors (RB , Melanomas )

97. THANK YOU