Laser treatment for glaucoma (SLT): what it involves and what to expect

The eye constantly makes a clear fluid and drains it away. When the drainage channel, the trabecular meshwork, does not work well, pressure inside the eye rises and over time can damage the optic nerve. That damage is glaucoma. Lowering pressure is the only proven way to slow it, which is why drops, laser and surgery all aim at the same target.

The Cambridge leaflet describes SLT as a possible choice for open-angle, pseudoexfoliation or pigmentary glaucoma, for people who cannot tolerate glaucoma drops or find them hard to use as prescribed, and for those who want to combine laser with drops. It is not a treatment for every type. Angle-closure glaucoma, where the drainage angle itself is narrow, is usually approached differently.

Drops are the most common first treatment for open-angle glaucoma, according to the Cambridge leaflet, but they must be taken every day and have side effects. If drops and laser fail to control pressure, surgery to create a new drainage channel may be considered, which the leaflet describes as more invasive with a risk of bleeding and infection. Argon laser trabeculoplasty was formerly the most widely used laser treatment, and the same leaflet lists problems with it including permanent scarring.

For angle-closure disease, Moorfields describes laser peripheral iridotomy, which creates a small hole in the iris to help open the drainage angle, and lens extraction as an alternative. Moorfields adds that lens extraction carries a higher risk of permanent vision loss than iridotomy, though it still describes that risk as low.

Preparation is light. The Gloucestershire leaflet says not to drive to the appointment, because vision is blurred for several hours afterwards, to use your usual drops including your glaucoma drops on the day, to bring your glasses and to allow up to an hour afterwards. There is no fasting.

If you take warfarin and are having an iridotomy rather than SLT, Moorfields asks for a recent blood test showing an INR below 3.0.

Your vision is checked, you give consent and you sit at a machine that looks like the microscope used in eye clinics. Numbing drops go in, and the Cambridge leaflet notes the drops may cause a headache. A contact lens is placed on the front of the eye to focus the beam and hold the lids open, so you do not have to worry about blinking.

Gentle pulses of light are applied. You may hear clicking, see bright light or feel pressure; the Gloucestershire leaflet says most people manage well. The laser targets pigment in specific cells of the drainage channel, and the Cambridge leaflet says the body then repairs those cells in a way that improves drainage while leaving surrounding cells undamaged.

SLT is described as very safe by the Cambridge leaflet. The main concerns are a short-lived rise in pressure just after the laser, which is why it is checked before you leave, and some inflammation. The Gloucestershire leaflet says either problem can be treated with drops or tablets and advises contacting the eye triage service if aching or blurred vision appears a few days later.

The main limit is effectiveness: a leaflet figure of 75 to 85% responding still means a minority do not respond, and the effect may fade. Continue your glaucoma drops unless your clinician tells you otherwise.

Your vision may be hazy for a number of hours and you should not drive until it clears, according to the Gloucestershire leaflet. The Cambridge leaflet says the eye may ache a little for a day or two but should not be painful. Make sure before leaving the clinic that you understand which drops to use and how often. A follow-up pressure check is usual.

Worsening vision, severe pain, or an aching, blurred eye that is not settling a few days later should prompt a call to the eye unit that treated you. Where the eye is red, very painful and nauseous, or vision drops suddenly out of hours, use an eye emergency service, A&E or NHS 111.

Useful questions: what target pressure are we aiming for, how long should it take to see the effect, will I need drops as well, and what is the plan if it does not work. Glaucoma care is long-term, so ask about monitoring intervals. In the NHS, laser is generally offered through the glaucoma clinic; privately, the same laser is offered at an outpatient price point set by each provider, and the pressure target and follow-up questions apply equally.