Glaucoma affects around one in every 50 people aged over 40 in the UK, causing irreversible vision loss if not picked up early and treated. It occurs when fluid builds up in the front part of your eye due to a clogged drainage mechanism. This increases the pressure inside your eye (intraocular pressure), which damages your optic nerve — the nerve that carries visual information from your eyes to your brain so that you can see.
Glaucoma is a silent condition. By the time vision loss is noticeable to an individual, the condition is already quite advanced. This is why it is important to have regular eye exams with your optometrist where your intraocular pressure is checked. This is especially important if you have a family history of the disease as you will have a one-in-five chance of developing glaucoma yourself.
Without treatment, glaucoma leads to blind spots in your vision, which grow until you become permanently blind. With treatment, in most cases, blindness can be avoided and further vision loss prevented.
The main treatment for glaucoma is special eyedrops applied once or twice a day to reduce the pressure in your eyes. However, if you can’t tolerate eyedrops due to side effects, your eyedrops stop working or aren’t able to lower your intraocular pressure enough, your doctor may recommend laser treatment.
Laser treatment uses a high-energy beam of light to target specific tissue in your eye in order to prevent fluid from building up. If laser treatment isn’t successful or you have previously had laser treatment and your intraocular pressure is on the rise again, your doctor may recommend a surgical procedure called a trabeculectomy.
This surgery creates a flap valve in your eye, which allows fluid to gradually leave your eye thereby reducing the pressure. It is important that the fluid is allowed to leave the eye in a controlled way to stop it from leaking out too quickly.
A trabeculectomy takes around one hour to complete and is performed under local anaesthesia so you will be awake but won’t feel any pain. First, the white part of your eye (conjunctiva) is lifted up. A flap valve is made using the underlying tissue (sclera), and underneath this valve, a channel is made that connects to the front part of your eye where fluid builds up.
Stitches are used to hold the flap valve in place so that fluid can leave the front part of your eye in a controlled manner. Finally, your conjunctiva is sewn back in place. Fluid can now pass out of the front part of your eye and into an area created under your conjunctiva called a bleb. The bleb appears as a small lump/blister on the upper half of your eyeball, which is hidden by your upper eyelid. The fluid that collects in the bleb is subsequently absorbed into your blood vessels.
If there is a lot of scarring around the bleb, this can stop fluid from flowing out. To help prevent this, an anti-scarring substance is applied during your trabeculectomy, and after your procedure, you will be given steroid eye drops. In some cases, this isn’t enough and further surgery is needed.
Risks of trabeculectomy
In around 95% of cases, a trabeculectomy is successful. However, in a minority of cases, complications occur, such as infection, bleeding, scarring and the eyeball becoming too soft. All of these complications can be sight-threatening.
A trabeculectomy isn’t always suitable for every case of glaucoma. It depends on the type of glaucoma you have and your intraocular pressure. The normal range of intraocular pressure is 15–21 mmHg.
If you have high-pressure glaucoma, where your intraocular pressure is above 30 mmHg, a trabeculectomy is usually successful at bringing the pressure down to within the normal range.
However, if you have normal-pressure glaucoma, where your intraocular pressure is already within the normal range, but your optic nerve is still being damaged, a trabeculectomy may be less successful. This is because the procedure needs to lower your intraocular pressure closer to around 10 mmHg. This is more challenging as if too much fluid passes through the flap valve, your eye can become too soft, which can also cause vision problems.
Depending on the type of glaucoma you have, your ophthalmologist will discuss the risks and benefits of a trabeculectomy to determine whether it is suitable for you.
You will have lots of follow-up appointments after your trabeculectomy to monitor the progress of your recovery as it is not always straightforward. For example, you may need further surgery if the stitches that hold your flap valve in place are too firm or too loose. You may also find that your central vision is blurry in the early stages of your recovery.
It usually takes several months before the final results of your trabeculectomy become clear ie the extent of the reduction in your intraocular pressure and your clarity of vision.
In around 50–60% of cases, scarring around the bleb occurs in the early stages of recovery and this needs subsequent interventions to restore the function of the trabeculectomy. This may involve scraping away scar tissue or removing the stitches that hold the flap valve in place.
In around 5% of cases, scarring around the bleb occurs much later and you may need further glaucoma surgery to reduce your intraocular pressure. This may involve a second trabeculectomy or the placement of a tube called an aqueous shunt.
In around 80% of cases, after several months of recovering from a trabeculectomy, glaucoma eye drops are no longer needed to maintain a healthy intraocular pressure.
New techniques are being developed to perform minimally invasive glaucoma surgery. These techniques reduce scarring to the eye and can, therefore, further improve long-term success rates.
There is also a move towards glaucoma treatment that doesn’t involve the use of eye drops, which can cause side effects and can also be an inconvenience for patients. The UK’s National Institute of Care Excellence now recommends a procedure called selective laser trabeculoplasty where appropriate, instead of eye drops.
This procedure applies lasers to tissue in the eye called the trabecular meshwork — this is the drainage mechanism through which fluid flows out of your eyes. When the trabecular meshwork becomes clogged, your intraocular pressure increases, causing glaucoma. Selective laser trabeculoplasty helps unclog this drainage mechanism. It is less invasive than a trabeculectomy and has a 75–85% success rate in keeping the intraocular pressure down in the long term.
Advances in both the treatment of glaucoma, combined with improved screening for the condition, mean that most individuals with glaucoma in the UK do not go blind and can preserve their vision for longer.
Mr Amar Alwitry is a Consultant Ophthalmologist at Spire Nottingham Hospital specialising in cataract and refractive surgery and glaucoma. He performs over 1,600 cataract procedures every year, has published over 35 research articles and has undertaken specialist training in premium intraocular lens use. He is also a Speciality Advisor to the CQC for Ophthalmology.
If you're concerned about symptoms you're experiencing or require further information on the subject, talk to a GP or see an expert consultant at your local Spire hospital.