Glaucoma Laser procedures are commonly used in glaucoma management. Two of the most frequently performed procedures are Laser Peripheral Iridotomy (LPI) and Selective Laser Trabeculoplasty (SLT).
Although both use laser energy, they treat very different types of glaucoma and eye pressure problems.
Understanding the difference helps patients make informed decisions about their treatment.
Why is Glaucoma Laser Treatment Performed
Glaucoma damages the optic nerve when pressure inside the eye becomes too high for that eye to tolerate.
Doctors aim to reduce intraocular pressure (IOP) to slow or prevent optic nerve damage.
Laser procedures can help by either:
• Improving the drainage of fluid from the eye
• Opening blocked pathways inside the eye
Unlike traditional surgery, glaucoma lasers are usually quick outpatient procedures performed in the clinic.
Laser Peripheral Iridotomy (LPI)
What Is LPI?
Laser Peripheral Iridotomy (LPI) is a glaucoma laser procedure used to treat or prevent angle-closure glaucoma.
In some eyes, the drainage angle between the iris and cornea becomes too narrow, blocking fluid flow. When this happens, pressure inside the eye can rise suddenly.
During LPI, a small opening is created in the peripheral iris using a laser.
This tiny opening allows fluid inside the eye to move freely and helps prevent dangerous pressure spikes.
When Is LPI Recommended?
LPI is commonly advised for:
• Primary angle closure
• Angle-closure glaucoma
• Narrow drainage angles detected during eye examination
• Preventing acute angle-closure attacks
In many patients, the procedure is preventive, performed before permanent optic nerve damage occurs.
What Happens During the Procedure?
The procedure usually takes 5–10 minutes per eye.
Steps typically include:
- Eye drops are used to numb the eye.
- A special contact lens is placed on the eye.
- The laser creates a tiny opening in the iris.
Most patients experience minimal discomfort.
Benefits of LPI
• Prevents acute angle-closure attacks
• Helps normalize fluid flow inside the eye
• Quick outpatient procedure
• Usually permanent
However, some patients may still require glaucoma drops or additional treatment depending on the condition of the drainage angle.
Selective Laser Trabeculoplasty (SLT)
SLT is done when eye pressure needs better control than eye drops alone can provide. Or, also when eye drops are to be avoided.
What Is SLT?
Selective Laser Trabeculoplasty (SLT) is a glaucoma laser treatment used primarily for open-angle glaucoma, the most common type of glaucoma worldwide.
In open-angle glaucoma, the drainage system (trabecular meshwork) becomes less efficient at removing fluid from the eye.
SLT uses gentle laser energy to stimulate the drainage system and improve fluid outflow, which helps lower eye pressure.
When Is SLT Used?
SLT may be recommended when:
• Eye drops are not controlling pressure adequately
• Patients experience side effects from medications
• Patients prefer reducing long-term drop use
• Early glaucoma where laser may be used as first-line treatment
Recent clinical studies have shown SLT can be an effective initial treatment option for many patients with open-angle glaucoma.
What Happens During SLT?
The procedure usually takes 10–15 minutes.
Typical steps include:
- Numbing drops are placed in the eye.
- A special lens is used to focus the laser on the drainage system.
- Laser pulses stimulate the trabecular meshwork.
Patients typically resume normal activities shortly afterward.
Benefits of SLT
• Lowers intraocular pressure without daily drops
• Non-invasive outpatient procedure
• Minimal recovery time
• Can sometimes be repeated if necessary
However, SLT does not work for every patient, and some people still require medications or additional treatment.
LPI vs SLT: Key Differences
| Feature | LPI | SLT |
|---|---|---|
| Main purpose | Prevent or treat angle closure | Improve drainage in open-angle glaucoma |
| Target area | Iris | Trabecular meshwork |
| Type of glaucoma | Angle-closure glaucoma | Open-angle glaucoma |
| Mechanism | Creates small opening in iris | Stimulates drainage system |
| Duration | Usually permanent | Effect may reduce over time |
Is Laser Treatment Enough for Glaucoma?
Laser treatment can be very effective, but glaucoma management usually involves long-term monitoring.
Depending on the patient, treatment may include:
• Eye drops
• Laser procedures
• Minimally invasive glaucoma surgery (MIGS)
• Traditional glaucoma surgery
The goal is always the same: protect the optic nerve and preserve vision over time.
The Importance of Early Evaluation
Many patients with glaucoma do not notice symptoms in the early stages.
Laser procedures like LPI and SLT are most effective when glaucoma or narrow angles are detected before significant optic nerve damage occurs.
Regular eye examinations that include:
• Eye pressure measurement
• Optic nerve evaluation
• OCT imaging
• Visual field testing
are critical for early diagnosis.
Frequently Asked Questions
1. Is glaucoma laser treatment painful?
Most glaucoma laser procedures such as Laser Peripheral Iridotomy (LPI) and Selective Laser Trabeculoplasty (SLT) are not painful. Numbing eye drops are used before the procedure, and patients may only feel mild pressure or brief discomfort. The treatment typically takes 10–15 minutes and is performed as an outpatient procedure.
2. Can SLT laser replace glaucoma eye drops?
In some patients with open-angle glaucoma, Selective Laser Trabeculoplasty (SLT) can reduce or delay the need for glaucoma medications. However, not everyone responds the same way. Some patients may still need eye drops after the laser treatment to maintain safe eye pressure levels.
3. Is Laser Peripheral Iridotomy (LPI) a permanent treatment?
Laser Peripheral Iridotomy (LPI) usually creates a permanent opening in the iris that helps fluid flow normally inside the eye. This can prevent dangerous pressure spikes in angle-closure glaucoma. However, patients still need regular eye examinations to monitor eye pressure and optic nerve health.
4. When should someone consider glaucoma laser treatment?
Laser treatment may be recommended when:
• Eye pressure remains high despite medications
• The drainage angle of the eye is narrow or blocked
• Patients cannot tolerate glaucoma eye drops
• Doctors want to prevent an angle-closure attack
An eye specialist determines the most appropriate treatment after examining the optic nerve, drainage angle, and eye pressure.
5. What is the success rate of SLT laser for glaucoma?
Selective Laser Trabeculoplasty (SLT) lowers eye pressure in about 60–80% of patients with open-angle glaucoma. The pressure reduction usually appears within a few weeks. In some patients the effect may gradually reduce over several years, and the procedure can sometimes be repeated.
6. How long does glaucoma laser treatment take?
Both Laser Peripheral Iridotomy (LPI) and Selective Laser Trabeculoplasty (SLT) are quick procedures that usually take 5–15 minutes per eye. Patients typically go home the same day and can resume normal activities soon after the treatment.
7. Do all glaucoma patients need laser treatment?
No. Many patients with glaucoma are treated successfully with eye drops and regular monitoring. Laser treatment is recommended when medications are not enough, when the drainage angle is narrow, or when doctors want to reduce long-term dependence on eye drops.
When Should You Consider a Second Opinion?
Patients often seek a second opinion when:
• Multiple glaucoma medications are being prescribed
• Laser treatment has been suggested
• Eye pressure remains uncontrolled
• Surgery is being discussed
A structured glaucoma evaluation helps determine the best long-term strategy for protecting vision.
Dr Shibal Bhartiya
Glaucoma • Second Opinion • Advanced Care
🌐 www.drshibalbhartiya.com
📞 +91 88826 38735
Read the research articles
This article has been written by Dr Shibal Bhartiya, a glaucoma specialist in Gurgaon known for ethical, patient-centred glaucoma care and independent glaucoma second opinions.
She has published peer-reviewed research on glaucoma laser and surgeries, examining how treatment decisions should balance medical evidence, patient preferences, and long-term vision outcomes.
These peer-reviewed article discussing glaucoma treatment are benchmarks for glaucoma surgeons globally, and can be accessed on PubMed here, here, here, here, here, here, here, and here
