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S.L.T
Selective Laser Trabeculoplasty as
Primary Treatment for Open-angle
Glaucoma
Outline
• Open-Angle Glaucoma
▫ What’s open-angle glaucoma?
▫ Diagnosing open-angle glaucoma
▫ Treatments for open-angle glaucoma
• What is SLT?
▫ Preface
▫ Historical Perspective
▫ How Does it treat
• Why SLT?
▫ Benefits
▫ Risks
▫ SLT vs. ALT
• How it’s Performed
What’s Open-Angle Glaucoma?
•Fluid circulating inside eye
•The eye receives its nourishment from a clear
fluid that circulates inside the eye.
•This fluid must be constantly returned to the
blood stream through the eye's drainage canal,
called the trabecular meshwork.
•Excess fluid builds pressure
•In the case of open-angle glaucoma, something has
gone wrong with the drainage canal.
•When the fluid cannot drain fast enough, pressure
inside the eye begins to build.
•Pressure pushes against the
optic nerve
•This excess fluid pressure pushes against the
delicate optic nerve that connects the eye to the
brain.
•If the pressure remains too high for too long,
irreversible vision loss can occur.
Diagnosing Open-angle Glaucoma
• Glaucoma is a “silent killer” or like “slow poison”
In most cases it begins un-noticeably and damages the eyes without any sign or symptom till it
is very late and the patient is almost at the verge of blindness. This is the reason that
awareness about glaucoma and its treatment is important to prevent this blinding disease.
Everyone should be checked for glaucoma at around age 35 and again at age 40. Those
considered to be at higher risk, including those over the age of 60 should have their
pressure checked every year or two.
•Tonometer:
Your doctor will use tonometry to check your eye pressure. After
applying numbing drops, the tonometer is gently pressed against
the eye and its resistance is measured and recorded.
•Ophthalmoscope
An ophthalmoscope can be used to examine the shape and color of
your optic nerve. The ophthalmoscope magnifies and lights up the
inside of the eye. If the optic nerve appears to be cupped or is not
a healthy pink color, additional tests will be run.
•Perimetry
Perimetry is a test that maps the field of vision. Looking straight
ahead into a white, bowl-shaped area, you'll indicate when you're
able to detect lights as they are brought into your field of vision.
This map allows your doctor to see any pattern of visual changes
caused by the early stages of glaucoma.
Treatments for Open-Angle Glaucoma
To control glaucoma, your doctor will use one of three basic types of treatment:
medicines ,laser surgery, or filtration surgery . The goal of treatment is to lower
the pressure in the eye.
•Medicines
• They work by either slowing the production of
fluid within the eye or by improving the flow
through the drainage meshwork.
•Laser Surgery
•Argon Laser Trabeculoplasty and Selective Laser
Trabeculoplasty surgery treat the drainage canal. the
laser beam is applied to the trabecular meshwork
resulting in an improved rate of drainage.
•ECP is another type of laser procedure. it treats the
ciliary body. reduces the amount of fluid production
thereby reducing the intra ocular pressure.
•Filtration surgery
•Filtration surgery is performed when medicines and/or laser surgery are
unsuccessful in controlling eye pressure. During this microscopic procedure, a
new drainage channel is created to allow fluid to drain from the eye.
Selective Laser
Trabeculoplasty
Preface
• Selective laser trabeculoplasty (SLT) is one of
greatest advances in the surgical treatment of
intraocular pressure (IOP) in patients with
open-angle glaucoma. Prior to its introduction,
medications and argon laser trabeculoplasty
(ALT) were the ophthalmologist's primary tools.
Historical Perspective
• ALT has been available for more than 20 years for treating patients
whose open-angle glaucoma was not controlled by medication.
• Results showed that ALT could be more effective than the topical
agents available at the time.
• However, ALT is not without complications: Studies have shown
that the effect of ALT significantly diminished over time;
• Furthermore ALT:
▫ Damages the microstructure of the trabecular meshwork.
▫ Produces heat which cause damage to the surrounding structural
collagen fibers
▫ Causes endothelial cells to migrate.
Historical Perspective
• SLT may be an improvement over ALT; SLT Lowers Pressure
With Minimal Damage
• SLT was further developed by Coherent Medical (now Lumenis)
with work done by Dr. Latina. In 1995 SLT was introduced
worldwide, and it was cleared by the FDA in March 2001.
• The key concept in the design of this laser system was to direct the
energy towards only pigment-containing cells in the trabecular
meshwork.
• SLT requires a specially designed laser:
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A short pulse to allow for thermal relaxation
Precise wavelength for optimal melanin absorption
Sufficient energy to heat melanin to the point that it releases cytokines
Sufficient spot size to ensure full coverage at the trabecular meshwork
• Lumenis has specifically developed the “Selecta II Glaucoma Laser
System” to these specifications, meeting all of the clinical conditions
necessary to perform successful SLT procedures again and again.
Historical Perspective
• Mark Latina, M.D. inventor of SLT did cell culture and animal
experiments to determine the specific energy range for selective cell
damage.
• Through his investigation parameters were determined which would
activate certain pigment containing meshwork cells while sparing
immediately adjacent non-pigmented cells.
• Further human studies showed the pressure lowering effects of
Selective Laser Trabeculoplasty without observable damage to the
trabecular meshwork cells.
How does SLT achieve lower pressure
with minimal damage ?
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The underlying mechanism is selective
photothermalysis
▫ Which enables the laser to precisely target
intracellular melanin granules to activate
individual cells while not disturbing adjacent
non-pigmented cells.
▫ The activated cells release cytokines that trigger
a targeted macrophage response to the
trabecular meshwork cells.
▫ The macrophages reactivate the meshwork
reducing fluid outflow resistance and lowering
intraocular pressure.
SLT Uses Frequency Doubled, Q-Switched
YAG Laser
▫ For SLT the light energy is provided by a
specially designed Q-switched, frequency
doubled Nd:YAG laser operating at 532nm green
with an output of from 0.3 to 1.5 mill joules.
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The target tissue is melanin granules within
individual trabecular meshwork cells.
Based on the size of the pigment granules, it is
necessary to deliver the light energy within 1
microsecond. The Q switched laser pulse width
is 3 nanoseconds, well within the required time
interval to contain the energy and temperature
rise to the pigment granules.
Experimental Results :
Methods :
• 45 eyes of 31 patients with open-angle glaucoma or ocular hypertension
(intraocular pressure [IOP] 23 mm Hg on 2 consecutive measurements) underwent
selective laser trabeculoplasty as primary treatment.
• All patients underwent complete ophthalmic evaluation before and at intervals after
treatment.
• This evaluation included
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visual acuity
slit lamp examination
Ophthalmoscopy
Gonioscopy
visual field analysis.
• The IOP was measured 1 hour, 1 day, 1 week, and 1, 3, 6, 12, 15, and 18 months
postoperatively.
• During the follow-up period, patients were treated with topical antiglaucoma
medications as required.
Experimental Results :
Results :
• Mean ± SD decreased by 7.7 ± 3.5 mm Hg (30%), from 25.5 ± 2.5 mm Hg to 17.9 ±
2.8 mm Hg (P<.001).
• Only 2 eyes (4%) did not respond to selective laser trabeculoplasty, and 3 eyes (7%)
required topical medications to control their IOP at the end of the follow-up period.
• Forty eyes (89%) had a decrease of 5 mm Hg or more.
• Visual acuity, visual fields, and gonioscopic findings remained unchanged.
• Complications included conjunctival redness and injection within 1 day
postoperatively in 30 eyes (67%).
• One hour after selective laser trabeculoplasty, an increase in IOP of more than 5 mm
Hg was detected in 5 eyes (11%), while an increase in IOP between 2 and 5 mm Hg
was measured in 3 eyes (7%).
Conclusion :
• Selective laser trabeculoplasty is effective and safe as a primary treatment for patients
with ocular hypertension and open-angle glaucoma.
SLT; Benefits and Risks
• Advantages:
▫ safest glaucoma laser surgery available
▫ effectively treats glaucoma and prevents future vision loss in the vast majority of
patients
▫ reduces or eliminates the need for glaucoma medication in many patients
▫ extremely fast and precise treatment option
▫ minimal or no discomfort experienced during the procedure
▫ repeatable with minimal risk
▫ SLT stimulates the body’s natural mechanisms to enhance outflow of the fluid in
your eye.
• Disadvantages:
As with any surgery, complications can occur during SLT glaucoma laser surgery, but
are not common. The most common side effect of SLT is:
▫ an increase in intraocular pressure for a few hours following the treatment.
Some possible complications include :
▫ Irritation
▫ Inflammation
▫ worsening of the glaucoma
SLT vs. ALT
• SLT incorporates "cold laser" technology Which Results less thermal
damage to the trabecular meshwork architecture than that caused by the
argon laser.
• SLT achieves isolated destruction of the pigmented trabecular meshwork
cells. There is minimal or no thermal or collateral damage to the
surrounding non-pigmented cells because the energy output during SLT is
100 times less than that of ALT, and the pulse duration is much shorter.
• Endothelial membrane formation on the trabecular meshwork,
found in eyes treated with ALT, is not typically observed after SLT.
usually
SLT vs. ALT
• ALT produces crater formation, coagulative damage, fibrin deposition and
disruption of trabecular beams and endothelial cells. Eyes treated with SLT
do not show these findings, and the general structure of the trabecular
meshwork is preserved. The lack of thermal and structural damage to the
trabecular meshwork makes SLT potentially repeatable.
• Precise Targeting Not Required for SLT.Since Selective Laser
Trabeculoplasty depends on the laser parameters for targeting the
pigmented cells, it is not necessary to have a small spot size or to precisely
target a site in the trabecular meshwork as compared to traditional Argon
Laser Trabeculoplasty.
How SLT performed
• Pre-Op
pulse. In cases with significant
variation in trabecular pigmentation,
the pulse energy is decreased if
bubble formation occurred as
described above.
▫ Preoperatively, careful goinoscopy
should be done to visualize the
trabecular meshwork and plan the
treatment area. The procedure is
done with the Lumenis Selecta laser • Post-Op
system.
▫ After laser treatment, prednisolone
▫ Preoperative medications consists of
acetate 1% is administered and
a drop each of lopidine or Alphagan
continued n the treated eye four
and topical anesthesia. A Goldman,
times daily for four to seven days.
three-mirror goniolens is placed on
the eye with methylcellulose. The
aiming beam is focused onto the
pigmented trabecular meshwork.
• During
▫ Treatment is done in single-burst
mode, placing 50 ± 5 contiguous, but
not overlapping, 400-micrometer
laser spots along 180 degrees. Bubble
formation is monitored with each
References:
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http://www.ophthalmic.lumenis.com/
http://www.eyeworld.org
http://www.eyecentrerivercity.com.au/
http://archopht.ama-assn.org/
http://www.revophth.com/
http://www.revoptom.com/
http://www.mpomg.com/
http://sdhawan.com/
http://wikipedia.org/
http://www.glaucomaslt.com/
http://www.drjindra.com/
Thanks For Your Attention !