Lasers are widely used in ophthalmology to treat various eye conditions. The main types of laser-tissue interactions are photothermal, photochemical, and photoionizing effects. Different laser wavelengths are absorbed selectively by tissues like melanin, haemoglobin, and macular xanthophyll, allowing targeted treatment. Common lasers used in retina include argon, frequency-doubled Nd:YAG, krypton red, and diode lasers. Therapeutic applications include treating retinal tears, diabetic retinopathy, and choroidal neovascular membranes. Precise laser delivery systems like slit lamps and indirect ophthalmoscopes allow treatment of anterior and posterior segment diseases.

1. L A S E R S I N O P T H A L M O L G Y
E . K A R O L I N E K E R S I N
A S S I S TA N T P R O F E S S O R

2. OPTHALMOLOGY
• Ophthalmology was the first medical specialty to utilize laser energy in patient
treatment, and it still accounts for more laser operations than any other specialty.
• The main use of ophthalmic lasers was to treat various intraocular conditions.
• The transparency of the optical media allows laser light to be focused upon the
intraocular structures without the need for endoscopy.
• Lasers are now used in many other areas of ophthalmic practice, including refractive
surgery, cosmetic eyelid surgery, and diagnostic imaging of ocular structures.
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3. LASER- TISSUE INTERACTION
Photothermal
Photochemical
Photoionizing effects
• Laser-tissue interactions can occur in several ways, depending on the power, pulse-
duration and wavelength indices chosen.
• They are broadly grouped under following categories
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4. PHOTOTHERMAL EFFECTS
• Photothermal effects include photocoagulation and photovaporization-
photocarbonization.
• In the first instance, absorption of light by the target tissue results in a
temperature rise, which causes denaturization of proteins.
• Typically, argon and krypton lasers, with wavelengths in the visible
spectrum, are used in photocoagulation and cautery.
• Photovaporization occurs when higher energy laser light is absorbed by the
target tissue, resulting in vaporization of both intracellular and extracellular
water.
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5. PHOTOCARBONIZATION
• When the local store of water is vaporized, photocarbonization occurs.
• The advantage of this type of tissue response is that adjacent blood vessels are also
treated, resulting in a bloodless surgicalfield.
• The carbon dioxide laser, with its wavelength in the far infrared, uses this method of
action and is used primarily for bloodless incisions.
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6. PHOTOCHEMICAL EFFECTS
• Photochemical effects include photoradiation and photoablation.
• In the former, intravenous administration of hematoporphyrin derivative, which is
taken up by the target tissue, causes sensitization of the target tissue.
• Exposure of this sensitized tissue to red laser light induces the formation of cytotoxic
free radicals.
• Thinnable dye lasers are used for this purpose.
• Photoablation occurs when high-energy laser wavelengths in the far ultraviolet ( < 350
nm) region of the spectrum are used to break long-chain tissue polymers into smaller
volatile fragments.
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7. • In contrast to the photoradiation effect, where relatively long exposure times (minutes)
are necessary to produce the cytotoxic free radicals, the exposure times in the
photoablation process must be much shorter (nanoseconds) compared with diffusion
times necessary for heat conduction into surrounding tissue (milliseconds).
• Excimer lasers, using this mechanism of action, are being used experimentally to
produce precise cuts in corneas2 and to disrupt intravitreal membranes
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8. PHOTOIONIZATION EFFECTS
• Photoionization occurs when high-energy light is deposited over a short interval to
target tissue, stripping electrons from the molecules of that tissue.
• This cloud of electrons and ionized molecules constitutes a "plasma," which then
rapidly expands, causing an acoustic shock wave that disrupts the treated tissue.
• The ND:YAG laser uses this "photodisruptive" mechanism in lysing secondary cataract
membranes and vitreous membranes
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9. LASER INTERACTION
LASER interaction Mechanism of Action Clinical Effect Example
PHOTOTHERMAL
(Photocoagulation and
Photovapourisation)
Coagulation of Tissue burns Argon, Nd: YAG laser
PHOTOABLATION Breakage of
interatomic bonds
Tissue etching Excimer
PHOTORADIATION Generation of cytotoxic
free radicals
Oxidative tissue
damage
Photodynamic therapy
PHOTODISRUPTION Stripping of electrons
from atoms, the
formation of plasma/
shock wave
Cuts tissues Nd:YAG laser (Q
switched)
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10. LASER-TISSUE ABSORPTION IN THE RETINA
Melanin
• Found mainly in the RPE (Retinal
pigment epithelium) and choroid, and
absorbs mainly wavelength between
400-700 nm.
• The longer the wavelength of light, the
more the melanin is penetrated.
• For example, Diode laser with
wavelength of 810 nm can penetrate
deeply into the choroid.
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11. Macular
xanthophyll
• Located in the inner and outer
plexiform retinal layers.
• It protects the photoreceptors
from short-wavelength light
damage, but can be damaged
by blue light which is why
Argon green is preferred in
macular photocoagulation
over Argon blue.
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12. Haemoglobin
• Absorption varies
according to oxygen
saturation.
• It absorbs yellow, green,
and blue wavelengths,
but red light is absorbed
poorly.
• Thus, macular lasers
uncommonly, damage
retinal vessels. 12

13. LASER TYPES IN RETINA
Argon blue-green laser (70% blue (488 nm) and 30% green(514nm))
Absorbed selectively at retinal pigment epithelial layer (RPE), hemoglobin pigments,
choriocapillaries, inner and outer nuclear layer of the retina.
 It coagulates tissues between the choriocapillaris and inner nuclear layer.
The main adverse effects of these lasers are high intraocular scattering, macular
damage in photocoagulation near the fovea, and choroidal neovascularization
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14. Frequency-doubled Nd-YAG Laser (532 nm)
 Highly absorbed by hemoglobin, melanin in retinal pigment epithelium and trabecular
meshwork. It can be used either continuously or in pulsed mode.
 PASCAL (Pattern Scan Laser) is one such type of laser that incorporates semi-Automated multiple
pattern, short pulse, multiple shots with precise burn in very short duration using frequency-
doubled Nd-YAG Laser (532 nm).
 It is commonly used nowadays in treatment of many retinal conditions (proliferative diabetic
retinopathy, diabetic macular edema, vein occlusions etc.).
 It has many advantages when compared with conventional single spot laser, as it is produced at
a very short duration (10-20 msec) compared to (100-200 msec) of conventional single spot one
which leads to less collateral retinal damage.
 Other advantages include relatively stable scar size, less destructive same efficiency. It also
permits the application of different patterns that gives more regular spots on retina with less
duration.
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15. Krypton red (647 nm)
Well absorbed by melanin and can pass through hemoglobin which makes it suitable
for treatment of subretinal neovascular membrane.
It also has low intraocular scattering with good penetration through media opacity or
edematous retina and has ability to coagulate the choriocapillaries and the choroid.
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16. Diode laser (805-810 nm)
It is well absorbed by melanin.
The near to infrared spectrum (near invisible) makes it more comfortable to use due to
absence of flashes of light.
It has very deep penetration through the retina and choroid making it the laser of
choice in treatment of Retinopathy of Prematurity (ROP) and some types of retina
lesions.
It is also used via trans-scleral route to treat the ciliary body in some cases of refractory
glaucoma.
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17. LASER DELIVERY SYSTEMS
Slit lamp
• It is the most popular and common delivery system.
• Laser settings such as power, spot size and exposure time can be changed easily.
Indirect ophthalmoscope
• Commonly used via a fiberoptic cable to deliver diode or argon lasers. It is ideal in
treatment of peripheral retina e.g. peripheral breaks and cases of retinopathy of
prematurity.
• The spot size is altered by the dioptric effect of the condensing lens used.
• It may even vary depending on the refractive status of the eye (i.e. in hyperopic eyes
the spot size will be smaller, and in myopic eyes it will be larger).
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18. Endophotocoagulation
• It delivered mainly argon green and diode lasers.
• Often used during retinal detachment repair following pars plana vitrectomy and
extrusion of the subretinal fluid or in the surgical treatment of proliferative diabetic
retinopathy.
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19. Micropulse laser therapy
• Micropulse laser describes a method of retinal laser delivery and can be applied with
lasers of different wavelengths, such as 532 nm, 577 nm, or 810 nm.
• This type of delivery essentially divides the treatment into repeated microsecond
impulses with intervals separating these where the retinal tissue is allowed to cool
down.
• The laser power is set to a low level, and in general, the spots are not visible on the
retina; the intention is to treat the retina on a subclinical basis while avoiding thermal
damage to the underlying retina that can occur with conventional photocoagulation.
• While this type of laser therapy appears to be safe, its efficacy continues to be
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20. THERAPEUTIC USES
ANTERIOR SEGMENT
Cornea
Glaucoma
cataract
POSTERIOR SEGMENT
• Retinal neovascular diseases
• Retinal tears and retinal detachment
• Choroidal neovascular diseases
• Intraocular tumors
• Anomalous blood vessels and
macular edema
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21. • CORNEA: Lasers have been utilized in procedures for refractive error correction like
LASIK, epi-LASIK, LASEK, PRK, and therapeutic procedures such as phototherapeutic
keratectomy (PTK) for the removal of surface irregularities, small corneal opacities.
• CATARACT: Thelaser is utilized to assist cataract surgeries like Femto laser-assisted
cataract surgeries (FLACS) and post-cataract surgery for removal of capsular
opacification as in Nd: YAG posterior capsulotom
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22. GLAUCOMA
•
NATOMICAL
SITE
LASER
PROCEDURE
INDICATION TYPE OF LASER
IRIS Peripheral
iridotomy (PI)
Angle closure
glaucoma
Occludable
angles
Nd:YAG or Argon-
YAG
Laser iridoplasty Plateau iris
Unresponsive
angle closure
glaucoma
Prior to ALT
Argon
Laser
pupilloplasty
Breaking
peripheral
anterior
synaechiae (PAS)
Relieve
appositional angle
closure
Adjust the
position of a
Argon
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23. SCLERA Laser scleroplasty Primary open angle
glaucoma (POAG)
Holmium YAG
Laser suture lysis After trabeculectomy to
increase filtration
ANGLE Laser trabeculoplasty
(ALT)
Refractory POAG
Pigment dispersion
Pseudoexfoliation
syndrome
Argon
Selective laser
trabeculoplasty (SLT)
Argon
CILIARY BODY Cyclophotocoagulation
(CPC : transscleral/
trans pupillary/
endoscopic)
Refractory glaucoma
like:
Neovascular glaucoma
(NVG)
Uveitis glaucoma
Traumatic glaucoma
Congenital glaucoma
Diode
Nd: YAG
ANTERIOR
VITREOUS FACE
Laser vitreolysis Malignant glaucoma Nd: YAG
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24. RETINAL NEOVASCULAR DISEASES
• These include Diabetic retinopathy, Central and Branch vein occlusion, Sickle cell
retinopathy, etc. PATHOGENESIS: The aim of laser treatment in these cases is to
eliminate hypoxia retina so as to eliminate the stimulus for neovascularization. This is
called Pan retinal photocoagulation. Argon or Krypton laser may be used for the same
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25. RETINAL TEARS AND RETINAL DETACHMENT
• Retinal tears and small retinal detachments may be treated with Focal laser
photocoagulation. Here many small burns are applied to the attached retina around
the tear or localized detachment in an attempt to “weld” the retina.
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26. CHOROIDAL NEOVASCULAR DISEASES:
• Conditions such as age-related macular degeneration, choroidal neovascularization
secondary to trauma, angioid streaks, etc can be treated with Argon or krypton laser
photocoagulation
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27. INTRAOCULAR TUMORS
• Tumors like Retinoblastomas, melanomas, and retinal angiomas can be treated with
focal Argon or Krypton lasers.
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28. ANOMALOUS BLOOD VESSELS AND MACULAR EDEMA
• In conditions like Retinal microaneurysms and Coats’ disease, direct focal treatment of
the vessels may lead to resolution of the condition. Leaking vessels may lead to
macular edema. The treatment of such vessels with a focal laser may help manage the
associated macular edema.
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29. THERMAL LASER PHOTOCOAGULATION
• Before the era of intravitreal injections, thermal photocoagulation with the argon blue-
green laser or krypton red was the first-line of treatment for exudative age-related
macular degeneration (AMD) in cases of extrafoveal CNVM. However, treatment of
subfoveal and juxtafoveal lesions usually yielded a dense scotoma with a high
recurrence rates for the CNVM.
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30. TRANSPUPILLARY THERMOTHERAPY (TTT)
• A more intense, destructive modality, this is occasionally used for the treatment of
choroidal melanomas, retinoblastoma, subfoveal choroidal neovascular membranes
(CNVM) and other ocular tumors. TTT involves long exposures (~60 s) of a large spot
(1.2–3 mm) at low irradiance (~10 W/cm2), using a near-infrared Diode (810 nm) laser
that is thought to induce intralesional hyperthermia and subsequent vascular occlusion
and lesion shrinkage.
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31. THANK YOU
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