About
The eye produces a nourishing fluid called the aqueous humour. This fluid circulates around the tissues of the eye and drains away through outflow channels. ‘Normal’ Eye pressure is when the amount of fluid produced is balanced by the amount of fluid draining away. If the fluid in the eyes is not ‘balanced’ then the pressure inside the eye rises and this can lead to a glaucoma.
Glaucoma, if left untreated, causes damage to the optic nerve at the back of the eye, ultimately resulting in loss of vision.
Causes
Glaucoma occurs when the drainage tubes (trabecular meshwork) within the eye become slightly blocked, preventing the fluid which is produced by the eye – known as the aqueous humour – from draining normally . It can also occur if there is an obstruction within the eye such as a blood vessel blocking the trabecular meshwork.
When the fluid cannot drain properly, it results in increased pressure inside the eye which can cause damage to the optic nerves, and the nerve fibers from the retina.
There are various other factors that can lead to glaucoma. These are listed below.
- Age – chronic glaucoma becomes more common with age.
- Ethnic origin – people of African, or Afro-Caribbean origin, tend to have a greater chance of developing chronic glaucoma. Also, people of Asian origin are more likely to develop acute glaucoma.
- Short sightedness – short-sighted people are more likely to develop chronic glaucoma.
- Family history – Having a Family history of Glaucoma also have increases the chances developing the condition. Regular eye screening is highly recommended in this case.
- Medical history – Diabetics are more likely to develop glaucoma than those without the condition.
Symptoms
Glaucoma does not present symptoms until late stages, when it can cause damage to your field of vision. This means that the edge of your peripheral vision can start to disappear causing your vision to narrow. It treatment is delayed these defects can severely affect your vision and can cause tunnel vision.
Treatment
Treatment for glaucoma aims to reduce the pressure in the eye either by helping fluid drain away or reduce the amount of fluid being produced.
The usual treatment for glaucoma is eye drops however in cases where it is resistant to drops, treatment through surgery or laser may need to be performed.
Surgery
Aqueous Shunts
Aqueous shunts are devices that are used to reduce the eye pressure in glaucoma by draining the aqueous humour (natural fluid of the eye) from inside the eye to a small blister or bleb behind the eyelid. Draining the aqueous humor, using a shunt, reduces the pressure on the optic nerve that causes loss of vision in glaucoma. The purpose of lowering the eye pressure is to prevent further loss of vision. Control of the eye pressure with an aqueous shunt will not restore vision already lost from glaucoma. Aqueous shunts have various other names such as tube implants, glaucoma tube shunts, glaucoma drainage devices and glaucoma drainage implants. These all refer to the same thing. Although there are many types of shunts available, three main types are in use at Moorfields Eye Hospital Dubai and Abu Dhabi and they function in a similar fashion.
These are called the Ahmed Glaucoma Valve, The PAUL implant and The Baerveldt Glaucoma Implant.
Indication
- For advanced glaucoma patients with other ocular comorbidities
- Patients that have had other conventional glaucoma surgery that is no longer efficacious
- Patients with drops allergy and side effects
Enhanced Trabeculectomy
Trabeculectomy is a surgical operation that creates an alternative drainage channel, to help aqueous fluid (natural fluid of the eye) drain from your eye. This operation creates a bypass for the blocked natural drain (trabecular meshwork) of your eye. Your eye pressure is reduced because fluid can now drain more easily through the newly created drainage channel.
Indication
- Patients with advanced glaucoma that continues to progress despite medication use
- Patients that need a low pressure to stop progression of glaucoma
- Patients with drops allergy and side effects
MIGS
The recent most increased interest in glaucoma surgery has been in Minimally Invasive Glaucoma Surgery (MIGS) with formidable results in mild to moderate glaucoma. These are designed to improve the safety of surgical intervention for glaucoma. Although initially coined minimally invasive, the term micro seems more appropriate because it truly differentiates these microscopic ophthalmic procedures from other minimally invasive surgical procedures (i.e., general surgery). Most MIGS procedures enhance physiologic outflow and are aimed at a different patient population than traditional filtration surgery. As opposed to competing with traditional filtering surgery, MIGS seems to be more of an alternative to medical therapy in an effort to address adherence challenges, adverse events, and qualityof-life (QOL) issues with topical medications.
Istent
The iStent Trabecular Micro-Bypass Stent (Glaukos, Laguna Hills, CA) received FDA approval in 2012. The device is a heparin-coated, non-ferromagnetic titanium stent with a snorkel shape to facilitate implantation. The device is placed using a singleuse, sterile inserter through a 1.5mm corneal incision. The iStent itself is the smallest FDA approved device, measuring at 0.3mm in height and 1mm in length. The iStent is a safe minimally invasive glaucoma surgery (MIGS) procedure that can reduce the need for daily use of glaucoma eye drops. A small (1mm) titanium drainage stent is inserted into the eye’s natural drainage channel to lower intraocular pressure. Most clinical trials concluded that iStent implantation with phacoemulsification resulted in a significantly lower, long-term decrease in IOP and number of medications used compared to phacoemulsification alone. No major complications have been reported.
XEN Implant
The XEN Glaucoma Implant (AqueSys Implant) was created by AqueSys Inc acquired by Allergan. The implant itself is made out of a soft, collagenderived, gelatin that is known to be noninflammatory. The Xen Gel Stent aims to reduce intraocular pressure by inserting a small drainage tube into the eye. The stent allows fluid to drain from the anterior chamber into a reservoir (bleb) under the conjunctiva. The goal of implantation is to create an aqueous humor outflow path from the anterior chamber to the subconjunctival space. The implant is injected through a small corneal incision with the use of an inserter similar to those used for IOLs. Similar to other implants, it can be performed in conjunction with cataract surgery.
All shunts perform approximately the same function of lowering the eye pressure. It’s important to note that no treatment is guaranteed to completely eliminate the need for eye drops, but the strong results seen in the use of either the Istent or XEN Gel Stent give the right patients a very strong choice for eliminating the need for them.
Indication:
- Patients with mild to moderate glaucoma
- To reduce drops dependence
Laser
Peripheral Iridotomy
This laser treatment uses a YAG laser to make a microscopic hole in the peripheral iris to help passage of fluid resulting in a structural improvement in the access to the trabecular meshwork which are the drains of the eye helping the fluid to pass and reducing the risk of angle closure glaucoma. The procedure does not require admission to hospital and is carried out in the outpatients department.
Indication:
- Patients with closed or narrow angle glaucoma
- To prevent angle closure acute glaucoma in patients that have narrow angles and are at risk
Selective Laser Trabeculoplasty
Selective Laser Trabeculoplasty (SLT) is a safe, quick, simple and non-invasive treatment option used to treat glaucoma. It works by reducing the pressure inside the eye. The eye pressure is known as intraocular pressure (IOP). The procedure does not require admission to hospital and is carried out in the outpatients department.
Indication:
- Reduction in eye pressure without the use of drops
Micropulse Cyclodiode Laser Treatment
Indication:
- Patients where conventional glaucoma surgery is risky
- To help reduce drops burden
The diode laser is a highly concentrated beam of light, which can be used to target and treat a selected area. Often, laser treatment is recommended in order to avoid the need for more invasive surgery. The diode laser is used to produce very small burns in the ciliary body, which produces the watery fluid called aqueous humour, and is situated behind the iris (coloured part of your eye).
