Presentation on role of lasers in glaucoma

1. Gokul Krishnan
JSS Medical College
Role of lasers in glaucoma.

2. Glaucoma
• A chronic, progressive optic neuropathy caused by a group of ocular conditions,
which lead to damage of the optic nerve with loss of visual function.
• The most common risk factor is increased IOP.
• Classification :

3. Laser
• Laser induced tissue interactions:
1. Thermal Effects :
A. Photocoagulation : Laser light is absorbed by the target tissue or by
neighboring tissue, generating heat that denatures proteins (i.e.,coagulation)
B. Photovaporization : Vapourises intracellular fluids creating incisions
in tissue. Eg: CO2 lasers
Light Amplification by Stimulated Emission of Radiation

4. 2. Ionization Effects:
A. Photodisruption: Power density is so great that molecules are broken
apart into their component ions, creating a rapidly expanding ion ‘plasma’. This
ionization and expanding plasma create subsequent shockwave effects which
causes explosive disruption resulting in excision.
3. Photochemical Effects :
A. Photoradiation : Releases cytotoxic free radicals – used in tumors

5. Laser applications in glaucoma
1. Diagnostic : Heidelberg Retinal Tomography (HRT), GDx, Optical Coherence
Tomography (OCT)
2. Therapeutic : - Laser Iridotomy (Argon, Nd:YAG)
- Selective Laser Trabeculoplasty (Nd:YAG lasers)
- Suturolysis (Argon lasers)
- Cyclophotocoagulation (Nd:YAG, diode, Argon)
- Iridoplasty
- Treatment of ciliary processes on aqueous misdirection

6. Laser Iridotomy
• Accumulation of aqueous behind the iris occurs due to pupillary block which
further shallows the anterior chamber causing narrowing of angles.
• Laser treatment is done to connect anterior and posterior chamber for relieving
pupillary block.
• Relatively non-invasive
• Preferable to surgical iridotomy

7. Indications
• Acute angle closure glaucoma
• Chronic angle closure glaucoma
• Aphakic or pseudophakic pupillary block
• Malignant glaucoma
• Prophylactic Peripheral Iridotomy

8. Contraindications
• Corneal oedema
• Corneal opacity
• Flat anterior chamber
Types of lasers
• Photodisruptive Nd:YAG laser
• Photothermal Argon lasers

9. Procedure :
• Pilocarpine 2% or 4% reduces thickness and unfolds the iris.
• Pre-laser IOP must be controlled so that the cornea will be clear during the
procedure.
• Oral Acetozolamide and 1% Topical Apraclonidine is given one hour prior to
procedure – it helps to avoid further damage to nerve by IOP spike
• Laser beam is focused in the stroma rather than on the surface with pulse per
burst 1-3 so that laser would be utilised better.

10. Complications:
• Microhaemorrhage during the procedure
• Temporary blurring of vision
• Corneal burns
• Increased IOP
• Endothelial and lens damage
• Sterile hypopyon due to iritis
• Laser induced inflammation

11. Laser Trabeculoplasty
• Improves eye’s drainage system and reduces the IOP
• Laser burns are placed between anterior and posterior trabecular meshwork
• Two types :
• Argon Laser Trabeculoplasty (ALT)
• Selective Laser Trabeculoplasty (SLT)

12. Mechanism of action:
Argon Laser Trabeculoplasty
• Causes shrinkage of inner trabecular ring
↓
• Opening of Aqueous drainage channels
↓
• Increases the outflow
Selective Laser Trabeculoplasty
• SLT targets pigmented trabecular meshwork cells without causing thermal damage to non-pigmented cells or
structure.

13. Indications
• Open angle glaucoma
• Failed medical therapy to control IOP
• When surgery is contraindicated
• Poor compliance of the patient
Contraindications
• Total angle closure
• Hazy media
• Inflammatory Glaucoma

14. Procedure
• Topical Apraclonidine 1% drops given to prevent IOP spikes
• Oral Acetozolamide given 1 hour prior and immediately
• Transient decrease in vision due to gonioscopy contact fluid
• Inflammation
• Significant IOP elevation
• Transient iritis
Complications

15. Advantages of SLT over ALT
• Utilises selective photothermolysis to target specific pigmented cells leaving
trabecular meshwork intact
• Stimulates body’s natural mechanism to enhance aqueous outflow
• Simple and fast outpatient procedure
• Repeatable
• No burning or scarring in the trabecular meshwork
• Non limiting treatment for future procedures

16. Laser Peripheral Iridoplasty
• It is an effective means of opening an appositionally closed angle.
• Procedure consists of placing contraction burns in the extreme periphery to
contract the iris stroma between the site of burn and angle so it physically
opens an angle.
• Argon lasers are used with lowest power setting that creates contraction of iris.

17. Indications
• Plateau iris syndrome
• Angle closure in nanophthalmos
• Widening of angles before ALT & SLT
• Acute attack of angle closure glaucoma with no response to medications
• Severe corneal edema
• Flat anterior chamber
• Synechial angle closure
Contraindications

18. Complications
• Iritis
• Corneal endothelial burns
• Permanent pupil dilations
• Transient IOP rise

19. Argon Laser Suturolysis
Indications
• Release tight sutures after trabeculectomy to lower IOP further down
• Can be done after 3 days to 3 weeks from surgery
• Lyse one suture at a time
Complications
• Conjunctival perforation
• Flat anterior chamber

20. Cyclophotocoagulation
• Reduces aqueous production by destruction of ciliary epithelium
• Semiconductor diode laser is used for this procedure
• Techniques :
1. Trans scleral
2. Trans pupillary
3. Endoscopic laser

21. Indications
• Failure of multiple filtering surgeries
• Primary procedure to alleviate pain in neovascular glaucoma with poor visual
potential
• Painful blind eye
• When surgery is not feasible
• As an alternative to drainage devices
• In case of intractable pediatric glaucoma

22. Complications
• Moderately severe iritis
• IOP spike, pain
• Loss of vision

23. Recent advances
Micro pulse laser therapy
• A continuous wave laser beam is delivered into short, repetitive low energy
pulses seperated by a rest period which allows tissue to cool down between
each pulse
• It is tissue sparing, causes less damage while providing high efficacy

24. Summary
• Lasers are an important part in the management and treatment of glaucoma
• Several situations exist when laser therapy may prove beneficial to the control
of IOP, in association with medical therapy & may enhance quality of life by
preserving visual function.

25. Thank you.