SLT Laser vs YAG Laser: When a Clinic Needs One, the Other or Both

What the two lasers have in common

Both devices use a Q-switched neodymium-doped YAG crystal to produce nanosecond pulses, both are delivered through a slit lamp with a coaxial aiming beam, and both are applied through a contact lens. Both work by short, localised interaction rather than long thermal heating, which is why exposure to surrounding tissue is limited.

The difference is mainly in wavelength and target. An SLT laser frequency-doubles the 1064 nm output to 532 nm and uses it to stimulate pigmented trabecular cells. A YAG laser uses 1064 nm for photodisruption of non-pigmented tissue such as the posterior capsule or iris stroma.

Because they look alike on a slit lamp, staff sometimes assume that the settings are interchangeable. They are not: an SLT energy in the YAG range could cause damage, and a YAG energy applied by an SLT protocol would have no useful effect. Clear labelling of the room and training of technicians prevents confusion, particularly in combined workstations.

SLT laser: wavelength, energy and indication

SLT stands for selective laser trabeculoplasty. The 532 nm light is absorbed by melanin in trabecular meshwork cells, which is thought to improve aqueous outflow and lower intraocular pressure in open-angle glaucoma and ocular hypertension. Energies are low, in the sub-millijoule to low-millijoule range, and the spot is large.

The CITO 532 has a pulse energy of 0.2–2.0 mJ, a 400 µm spot, diode-pumped µ-Chip technology, Quick-Repetition at about 10 Hz and a laser class of 3B. See SLT laser settings for how energy is titrated.

YAG laser: wavelength, energy and indication

The Nd:YAG laser at 1064 nm is used for posterior capsulotomy when the capsule clouds after cataract surgery, and for peripheral iridotomy in angle-closure. Energies are higher than in SLT, delivering a plasma micro-explosion that cuts tissue. Some clinics also use it for vitreolysis in selected cases.

The Q-Las offers 0.5–10 mJ, a 4 ns pulse, burst of 1, 2 or 3 pulses, up to 10 Hz Quick-Repetition and focus shift of 0, 150 or 300 µm posterior. For details see YAG laser capsulotomy and YAG laser iridotomy.

Side-by-side: what to compare

The clinical decision about which laser to use is always the ophthalmologist's. For the buyer, the table above shows why these are complementary rather than competing devices.

• Wavelength: SLT 532 nm; YAG 1064 nm.
• Target: SLT pigmented trabecular meshwork; YAG capsule, iris and vitreous opacities.
• Effect: SLT is a biological stimulus with low energy; YAG is mechanical photodisruption.
• Typical energy: SLT sub-millijoule to low millijoule; YAG a few millijoules, device range up to 10 mJ.
• Disease: SLT open-angle glaucoma and ocular hypertension; YAG posterior capsule opacification and angle closure.

One, the other or a combined workstation

A clinic attached to cataract surgery will use YAG first; a glaucoma service will want SLT. When both are needed, the COBRA combines the CITO 532 and the Q-Las as two fully independent lasers on a wheelchair-accessible table with height adjustment up to 920 mm, so one slit lamp and one footprint serve both.

Budget-wise, two lasers on one table usually cost less in space and installation than two stations, but you depend on a single base for both services. Ask about the service plan and the availability of spare parts, and about the training offered for each laser.

For a wider view read our ophthalmic laser buying guide. To discuss the right configuration, contact Beckfinity.