Lasers in Ophthalmology

Lasers for Glaucoma

Laser treatment is a safe and effective way of treating glaucoma when used in the right circumstance by an experienced surgeon. 

Some types of laser are used instead of eye drops, or they can be used when eye drops by themselves are not enough to control glaucoma. 

Other types are used to prevent at risk people developing glaucoma reducing the likelihood of running into problems in later life.

Less commonly a different type can be combined with cataract surgery and applied at the end of routine cataract surgery.

Selective laser trabeculoplasty (SLT) 

This is a simple outpatient procedure which takes about 5 minutes per eye. The laser is applied through a contact lens held against the eye after instilling anaesthetic eye drops. 

The laser is directed at the drainage apparatus of the eye, the trabecular meshwork, which is sieve like mesh through which the fluid drains. The laser clears out the debris in the sieve to improve the drainage of fluid out of the eye. It can take about 6 weeks to have its full effect. 

The laser is of very low energy and short duration, nano seconds and therefore does not damage tissue. It restores a clean clear meshwork.

In 2019 the LIGHT trial published in the Lancet confirmed that SLT is effective in preventing the need for eye drops in the majority of patients and concluded that it should be offered instead of eye drops in appropriate patients.

In patients who cant use eye drops or prefer not to it is a good first or second line treatment.

YAG laser peripheral iridotomy (YAG PI) 

In cases of angle closure glaucoma or narrow angles, when fluid cannot reach the drainage apparatus, making a tiny hole inside the eye at the edge of the coloured part of the eye the iris, can help. The hole in the iris (iridotomy) acts as a safety valve to allow the fluid to reach the drain if the access becomes blocked. 

This is very effective at preventing or treating angle closure glaucoma in susceptible eyes, 

It takes only a few minutes per eye in the outpatient clinic. Afterwards patients are asked to use eye drops for about 2 weeks to dampen any inflammation.

Cyclodiode laser 

In cases of advanced glaucoma that may need to have surgery to lower the eye pressure, cyclodiode laser can prevent the need to have an operation. Unlike the above laser treatments which work by helping the fluid to leave the eye, cyclodiode laser slows the production of fluid inside the eye and so lowers the eye pressure. 

It is applied on the surface of the eye after an injection of anaesthetic around the eye. A probe delivers diode laser energy through the wall of the eye to the ciliary body, the structure that produces the fluid that causes the pressure to build up. 

The laser can also be applied directly to the ciliary body inside the eye at the end of routine cataract surgery. This is called endoscopic cyclo photocoagulation or ECP.

This can be a powerful way to reduce the eye pressure. The results are less predictable than with eye surgery but also less risky than operations.

Laser after Cataract Surgery

YAG laser capsulotomy 

During cataract surgery the new lens implant sits inside a transparent sac which is made up of a very fine clear membrane. In about 8 % of eyes after routine successful cataract surgery the vision can become more blurry again.

This is because the rear wall of that membrane that holds the lens implant can become opaque. This is called posterior capsule opacity or PCO. 

YAG laser capsulotomy is the term given to laser treatment for posterior capsule opacity. It is very quick and easy to carry out in the outpatient clinic, taking about 5 to 10 minutes. The laser is applied through a contact lens held against the eye after instilling anaesthetic eye drops. 

Afterwards patients may notice more floaters immediately but these gradually settle over the next few days. The vision is quickly restored to its former clarity and sharpness. This is a very effective and satisfying procedure with minimal risk when carried out by an experienced surgeon.

Laser Refractive Surgery

Excimer and femtosecond lasers

Excimer lasers are used to re shape the surface of the eye by destroying corneal tissue to create a new shape. This acts as a lens to enable light to come to a sharp focus on the retina.

They have been used successfully to prevent the need to wear spectacles. However these procedures are not without risk and are essentially cosmetic treatments for most people choosing to have them.

It is important that when people who have undergone this type of laser develop cataracts, the cataract surgeon is aware of the previous laser treatment. The calculation for the lens that is put inside the eye needs to take into account the altered corneal shape, otherwise the wrong lens may be inserted.

Additionally eye pressure measurements in glaucoma patients are less accurate when the cornea has been thinned by this type of laser, so these  are best avoided in patients with glaucoma.

Laser for treating the Retina

Argon laser retinal photocoagulation

Conditions such as diabetes in which the blood supply of the retina is compromised can damage sight. 

Gentle laser is applied to the retina to treat the leaky blood vessels to prevent the build up of fluid (macular oedema) which would otherwise damage the delicate light sensitive structures in the retina. Injections of an agent to seal the leaky blood vessels can also be useful in this situation. 

More substantive laser treatment is also used when the blood supply is compromised so much that the eye tries to grow new blood vessels to compensate for the poor supply. These new vessels are harmful to the eye, they cause bleeding and scarring. In this situation hundreds or thousands of individual laser applications (pan retinal photocoagulation) may be needed to allow the harmful new vessels to regress preventing further damage. This type of laser can take upto 15 minutes per session and multiple sessions may be needed. It is carried out in the outpatient clinic with a contact lens applied to the eye after instilling anaesthetic eye drops.

Argon laser retinopexy

With ageing the structures inside the eye change just as our skin changes and at some point the gel inside the eye (vitreous) can separate from the retina causing symptoms of flashing lights and floaters. We call this a posterior vitreous detachment or pvd. 

When this happens it is important to have a proper detailed look at the retina by an ophthalmologist to look for a retinal tear or break. If found the tear usually needs prompt treatment with laser to prevent a retinal detachment which could cause permanent sight loss otherwise. 

The tear is treated with laser by sealing the retina around the break so that the tear cannot extend. This is usually done as an outpatient with a contact lens applied to the eye after instilling anesthetic eye drop.