LASERS USED IN OPHTHALMOLOGY

1. LASERS IN OPHTHALMOLOGY
PRESENTOR-
DR. ROHIT AGRAWAL
MODERATOR-
DR. SUNE SIR
CONDUCTOR-
DR. CHANDAK SIR
23/APR/2018

2. Contents
• Introduction
• Lasers in skin
• Lasers in anterior chamber
• Lasers in lens
• Lasers in vitreous
• Lasers in retina

3. INTRODUCTION
• LASER stands for Light Amplification by Stimulated Emission of
Radiation.
• PROPERTIES OF LASER-
• Monochromatic- emit only one wave length
• Coherence- all in step with one another-improves focusing
• Polarized-in one plane- easy to pass through media
• Collimated- in one direction & non spreading
• High energy- Intensity measured by Watt (J/s)
• Due to all these properties Laser light can deposit a lot of energy
within a small area hence it is more hazardous than ordinary light

4. • 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.

5. Classification of lasers-
(on the basis of active medium)
• Metal Vapour
• Cu
• Gold
• Dye
• Rhodamine
• Excimer
• Argon Fluoride
• Krypton Fluoride
• Krypton Chloride
• Diode
• Gallium-Aluminum Arsenide
(GaAlAs)
• Solid State
• Ruby
• Nd.Yag
• Erbium.YAG
• Gas
• Ion
• Argon
• Krypton
• He-Neon
• CO2

6. Ruby Laser
• This is a pulsed laser.
• It was the first laser to be demonstrated.
• It is a crystalline sapphire with a small percentage of chromium
• It is usually excited by being pulsed with a xenon flash lamp with
emission
• Wavelength- 694 nm

7. Nd:YAG laser
• The active element is a triply ionised neodymium ion that is
incorporated in small fractions in a glass or in a crystal structure.
• The Nd:YAG laser is optically pumped either:
• By the flash lamp (for pulsed operation)
Or
• By a continuous arc lamp (for continuous wave operation).
• It is the most commonly used solid state laser.

8. CO2 Laser
• In a CO2 laser, although the active medium is CO2, there are usually
two other gases in the mixture, viz., nitrogen and helium.
• The output is in the infrared range between 9000 and 11,000 nm.
• The water in cellular tissues is rapidly vaporised by energy from the
CO2 laser, thereby creating a wound in an explosive fashion.
• Excellent haemostasis is produced and this is the major
intraoperative advantage of CO2 laser produced incisions.

9. Excimer Laser
• The term ‘excimer’ stands for ‘excited dimer’.
• It is used in a broad sense to include any diatomic molecule in
which the component atoms are bound in the excited state but are
not bound in the ground state.
• The most attractive excimer molecules are rare gas halides, e.g.:
• Argon fl uoride (193 nm)
• Krypton chloride (222 nm)
• Krypton fl uoride (249 nm)

10. Dye Laser
• A dye laser consists of a fluorescent organic compound (a dye)
dissolved in a liquid solvent which is then optically pumped by
either a laser or a flash lamp.
• Dye laser can emit laser radiation over a wide range of wavelengths
• The output wavelength can be changed by varying the tuning
element.

11. Diode Laser
• Recent advances in semiconductor technology have led to the
development of diode laser (gallium-aluminium-arsenide, Ga Al As).
• These emit continuous wave monochromatic coherent laser light in
the near infrared region with wavelength from 780 to 840 nm.
• Compared to argon laser, only 20% of diode laser light incident on
the retina is absorbed by the retinal pigment epithelium.

12. Modes of Laser operation
• 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.

13. Lenses for Laser Delivery
• Corneal Contact Lenses for Laser use
• Single mirror goniolens for goniotomy
• Abraham lens and wise lens for capsulotomy and iridotomy
• Goldman style 3-mirror lens for photocoagulation (PRP) lenses
• Volk-Superquad and pan 165 for PRP
• Mainster and Area centralis for focal and grid laser
• Indirect Fundus Lenses (20 D) for Indirect laser delivery

14. Laser Tissue Interaction
LASER
TISSUE
THERMAL
EFFECT
PHOTO
COAGULATION
PHOTO
DISRUPTION
PHOTO
VAPORISATION
PHOTO
CHEMICAL
EFFECT
PHOTO
RADIATION
PHOTO
ABLATION
IONIZING
EFFECT

15. LASERS USED IN OPHTHALMOLOGY
LASER WAVELENGTH (nm) CLINICAL APPLICATION
1. Nd:Yag (Neodymium-
Yttrium-Aluminium-
Garnet)
1064 Posterior capsulotomy, iridotomy,
vitreolysis
2. Frequency
doubled Nd:Yag
532 Retinal photocoagulation,
cyclophotocoagulation
3. Argon Green 514 Trabeculoplasty, iridoplasty,
pupillomydriasis, retinal photocoagulation
4. Diode Laser 800 Retinal photocoagulation
5. Eximer Laser
(Argon fluoride)
193 Refractive surgeries
6. Femtosecond
Laser (neodymium-
glass)
1053 Femtosecond laser assisted cataract
surgery, femtosecond Lasik, lamellar and
full thickness corneal transplant

16. LASERS IN LID & ADNEXA
• Skin:
• Lid Tumors : carbon dioxide laser
• Blepharoplasty (carbon dioxide or erbium:YAG laser )
• Xanthalesma ( green laser)
• Lacrimal Surgery:
• Endoscopic Laser Dacryocystorhinostomy

17. LASERS IN ANTERIOR SEGMENT:
• Laser Asepsis
• Refractive surgery
• Lasers in glaucoma
• Lasers in lens

18. Laser Asepsis
• In this procedure, a known organism in microbial keratitis is allowed
to conjugate with topical drops on cornea that contain an antibody
to that organism tagged with fluorescein.
• The antibody–organism complex is then irradiated with a non-
focused argon laser beam.
• The fluorescein absorbs the laser energy and converts it to heat
energy which in turn leads to the death of the organism and healing
of corneal ulcer.

19. Refractive Surgery-
• Photorefractive keratectomy
• Laser subepithelial keratomileusis (LASEK)
• Laser-assisted in situ keratomileusis (LASIK)
• Femto lasers in cataract surgery

20. Lasers in Glaucoma-
• Laser treatment for internal flow block
• Laser treatment for outflow obstruction

21. Laser treatment for internal flow block:
• Laser peripheral iridotomy
• Laser iridoplasty (Gonioplasty)

22. Laser iridotomy-
• INDICATIONS-
• Acute angle closure glaucoma
• Aphakic or pseudophakic pupillary block
• Chronic angle closure with PAS
• ACIOL implant
• Incomplete surgical iridectomy
• Subluxated crystalline lens

23. • ND:YAG LASER IRIDECTOMY:
• Q-switched Nd:YAG lasers are used
• 2–3 shots/burst using approximately 1–3 mJ/burst is used
• Opening of at least 0.1 mm is made

24. • ARGON OR SOLID-STATE LASER IRIDOTOMY:
• Photocoagulative (lower energy & longer exposure)
• Iris colour (pigment density) is the most imp factor.
• 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: 200–400 mW, 200- μm spot, 0.1 second

25. Laser Iridoplasty (Gonioplasty)
• It is done using contraction burns.
• 100–200- μm spot size
• 100–30 mW energy
• 0.1 second
• 10- 20 spots evenly distributed over 360º
• Done in cases of Plateau Iris and Nanophthalmos
• When each burn is placed, there is contraction of iris stroma which
leads to separation of contact between iris and trabecular
meshwork.

26. Laser treatment for outflow
obstruction
• Laser Trabeculoplasty
• Excimer Laser Trabeculostomy
• Laser Sclerostomy

27. Laser Trabeculoplasty (LTP)
• Argon Laser Trabeculoplasty (ALT) : 50-μm spot size and 1000-mW
power for 0.1 second , 3–4° apart 20–25 spots per quadrant.
The laser beam is focused through a goniolens at the junction of the anterior
non-pigmented and the posterior pigmented edge of trabecular meshwork.
• 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.
The aiming beam is centred over the trabecular meshwork and straddles the
entire TM.

29. Excimer Laser Trabeculostomy(ELT)
• Precise and no thermal damage to surrounding tissues
• ab-interno (used intracamerally) : 308-nm xenon chloride (XeCl)
excimer laser delivers photo ablative energy.
Paracentesis
Fiber optic is
advanced
through AC
Placed in
contact with
trabecular
meshwork
Ablation hole is
created through
trabecular
meshwork and
inner wall of
schlemm’s canal

30. Laser Sclerostomy
• Can be done using following lasers:
• Nd:YAG laser
• Dye laser
• 308-nm XeCl excimer laser
• Argon fluoride excimer laser
• Erbium:YAG laser
• Diode lasers
• Holmium:YAG laser

31. • 2 methods for laser Sclerostomy-
• Ab-externo : probe applied to the scleral surface under a
conjunctival flap.
• Ab-interno : through a goniolens OR a laser probe

32. Lasers in Lens-
• Posterior Capsular Opacification : (Nd:YAG) laser posterior
capsulotomy
Cruciate pattern Circular pattern

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

34. • CYCLO-PHOTOCOAGULATION
1. Trans-scleral Cyclophotocoagulation
• Non contact Nd:YAG laser cyclophotocoagulation
• Contact Nd:YAG laser cyclophotocoagulation
• Semiconductor diode laser trans-scleral Cyclophotocoagulation
2. Endoscopic cyclophotocoagulation (ECP)

35. Tip of G-probe is placed 1.2mm posterior to limbus
to allow direct treatment of ciliary body
Semiconductor diode
laser trans-scleral
Cyclophotocoagulation

36. Endoscopic CycloPhotocoagulation (ECP)

37. • LASER SUTURE LYSIS (LSL)
• Hoskins laser suture lens is used
• This lens is pressed on the conjunctiva to displace the edema till the suture
is visible
• Then suture can be easily cut with 50 μm spot size with 400mW energy for
0.1 sec.

38. • 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 fibres of the iris

39. LASERS IN POSTERIOR SEGMENT
• Laser in vitreous
• Laser in Retinal vascular diseases
• Other Retinal diseases

40. Lasers in Vitreous
• Vitreolysis of anterior vitreous tag in PC rent to avoid traction and
cystoid macular oedema
• Vitreous membranes & traction bands
• Vitreous floaters
• Retinoblastoma seeds

41. CLASSIFICATION OF CHORIO-RETINAL BURNS
• Light : Barely visible retinal blanching
• Mild : Faint white retinal burn
• Moderate : Opaque dirty white retinal burn
• Heavy : Dense white retinal burn

42. Lasers in Retinal 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

43. 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-third of the optic disk size)
• Exposure time- 100–200 ms
• 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- 1,000 and 2,000
• Apply laser lesions in Two to four sessions, 2 weeks apart
• Regression expected after 4–6 weeks

44. • Central Retinal Vein Occlusion:
• Main complications of a central vein occlusion apart from macular
oedema are neo-vascularisations of the retina and of the iris.
• If neovascularisations of the retina or of the iris exist, the treated
eyes clearly benefit from full scatter panretinal laser coagulation

45. MILD SCATTER PANRETINAL LASER COAGULATION
• For Non-proliferative diabetic retinopathy
• It is done when one of the following is present (The 4:2:1 rule)
• If either intraretinal bleeding occurs in 4 quadrants
• if venous beading occurs in at least 2 quadrants
• 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

46. STEPS OF PRP (PAN RETINAL PHOTOCOAGULATION)-
OUTSIDE
INFERIOR
ARCUATE
FIBRES
OUTSIDE
SUPERIOR
ARCUATE
FIBRES
NASAL TO
THE DISC
2 DISC
DIAMETER
TEMPORAL
TO MACULA

47. FOCAL LASER APPLICATION
• Classically done for CSME
• Placement of the laser coagulation spots has to be decided by
fluorescein angiography
• Exposure times 100ms and a spot size of 100 μm
• Power of 70–80 mW.
• Leads to a mild gray retinal lesion.

48. SUBTHRESHOLD LASER COAGULATION FOR
RETINAL DISEASE
• Selective treatment of the RPE
• Diabetic macular oedema
• Central serous retinopathy (CSR)
• Drussen in age-related macular degeneration (AMD)

49. Photodynamic therapy (PDT)
• PRINCIPLE-
Administration of
intravenous
photosensitive
agent
(VERTIPORFIN)
Distribution and
accumulation of
photosensitizing
agent in the body
(EYE-TARGET
TISSUE)
Light application
on the target
tissue
Damage to the
cell membranes
endothelium
Thrombogenic
factors increases
PHOTO-
THROMBOSIS

50. • Dye dose = 6 mg/m2 body surface area
• Intravenous infusion over 10 min
• Treatment at 15 min after start of dye
infusion
• Laser light wavelength of at 689 nm
• Energy of 600 mW/cm2
• INDICATIONS
• CNVs due to age-related macular degeneration
• pathologic myopia
• Retinal capillary haemangioma
• Vasoproliferative tumour
• Parafoveal telangiectasis

51. PAttern SCAn Laser (PASCAL)
• The PASCAL Photo coagulator is an integrated semiautomatic
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

52. SCANNING LASER OPHTHALMOSCOPY
• It is a diagnostic laser procedure
• Allows for high-resolution, real-time motion images of the macula
without patient discomfort
• 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.

53. • USES-
• SLO angiography- 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
• Microperimetry- 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.
• High resolution fundus photos
• SLAP Test

54. Scanning Laser Acuity Potential (SLAP) Test-
• The letter E corresponding to different levels of visual acuity 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.

55. LASER safety
• Lasers are usually labelled 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/3A 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.

56. Safety precautions before using lasers-
• Protective shutters built into the equipment
• Filters incorporated into the slit-lamp biomicroscope
• Divergence of the beam at the exit optics
• Accessory lenses should have Anti Reflective Coating
• Reflected laser light should be within nominal hazard zone
• When a hand lens is used in place of biomicroscopy, precautions must be
taken to minimize the chance of specular reflection from instruments
and lens.
• Personal protective devices, like protective eye wear or goggles with side
shields, protective clothes may be included
• Warning signs listing the laser’s type and class should be posted at all
entrances to the laser suite.

57. THANKYOU....

58. Next PG Activity on 24/04/2018-
• Case presentation
• Presenter- Dr. Vishal
• Moderator- Dr. Lohiya sir
• Conductor- Dr. Nagpure madam