Once Glaucoma has been diagnosed, the most important aim is to lower the pressure in the eye which is caused by the build-up of aqueous humor. This will prevent further damage to the optic nerve with the resulting blindness.
Surgery is the last resort in relieving pressure in the eye. Normally eye drops or other medications will treat the causes of glaucoma and surgery will not be necessary. You can read the full details in the article on Glaucoma Treatment. However in some cases, surgery is unavoidable.
All surgical procedures, whether by laser or incision, aim to increase the drainage of the fluid, thereby reducing pressure in the eye and preventing a further loss of vision.
All glaucoma surgery is done as an outpatient procedure and patients need to be accompanied home as they will not be able to drive at that time. Numbing eye drops are applied to the eye before surgery. Most laser surgery takes just 10-15 minutes, whilst incisional surgery takes about an hour and must be performed in an operating room. Normal activities may generally be resumed the following day and check-ups will monitor the success of the surgery.
The following descriptions outline common surgical procedures for Glaucoma.
Selective Laser Trabeculoplasty
This procedure is generally used for patients who are unable to maintain the strict regular input of eye drops, which would otherwise be used to reduce the build up of aqueous humor. This surgical procedure is done using a laser. The aim of the surgery is to create tiny holes in the filtration angle of the eye. This is where the cornea and the iris meet, and normally fluids drain away naturally through this angle.
Selective Laser Trabeculoplasty is the very latest procedure which has been developed. It creates minimal heat damage to the surrounding delicate tissue of the eye and is much safer than previous techniques. Eye drops may still be necessary even after the procedure, but Selective Laser Trabeculoplasty is being considered as a more practical option in treating open-angle glaucoma even before eye drops are used.
Trabeculectomy, Trabeculotomy and Goniotomy
Sometimes the eye doctor may decide that a surgical incision needs to be made into the tiny drainage system in the eye to create new channels for draining the eye.
A trabeculectomy would involve removing part of the drainage system inside the eye. This procedure is common when eye drops and medications have failed to control the intraocular pressure. A trabeculectomy aims to create a controlled drainage of the aqueous humor in the eye.
A trabeculotomy varies in that the same surgery is performed and incisions are made to drain the fluid, but no tissue is removed from the drainage system.
A goniotomy is used on children and infants. This involves a special lens being used to view the inner eye structure in order to make incisions in the trabecular meshwork. Once again the aim is simply to allow the aqueous fluid to drain and avoid a build-up of the fluid which causes damage to the ocular nerve.
Iridotomy and Iridectomy
During an iridotomy the surgeon will create a hole in the iris by laser to drain the passages which may be blocked by the iris of the eye.
Similarly an iridectomy involves the surgeon removing a tiny part of the iris to drain the fluid. This is common with narrow-angle glaucoma.
Shunts and Implants
Shunts are small plastic devices that are attached during surgery to the surface of the eye. Shunts or implants have a tiny tube which is inserted into a hole created during a trabeculectomy, allowing the aqueous humor to drain from the eye. A shunt operation diverts the fluid past the damaged or blocked filtration channels.
Shunts may be made of silicone or polypropylene. Some shunts are hollow in design, but others are more complex and have valves to control the drainage. Complications may occur if the pressure is too low to allow the eye to function, or if the implant is badly positioned and causes decomposition of the cornea. Further problems may also occur if the tubes begin to erode the surrounding eye tissue.
Shunts currently in clinical trials include the Ex-PRESS Mini Glaucoma Shunt which aims to drain the aqueous humor from the eye to a specific drainage area. It is about the size of a grain of rice and is implanted during surgery beneath the conjunctiva, between the area where fluid collects and the sclera, or white part of the eye.
DeepLight Glaucoma Treatment System will also combine titanium sapphire laser energy to insert a hollow gold shunt into the filtration angle of the eye, creating a new channel through which the fluid can drain. This SOLX laser only targets pigmented cells, minimizing damage to the rest of the eye. The DeepLight Gold Micro Shunt is unique as it confines drainage to the interior of the eye. Hopefully this will reduce complications in future surgical procedures.
Nonpenetrating Glaucoma Surgery
All the above procedures involve incisions to the eye. More superficial incisions have fewer complications than a deeper trabeculectomy. A Deep Sclerectomy involves a minimally invasive incision to the white of the eye whilst still creating drainage.
A Viscocanalostomy allows the insertion of a viscoelastic gel-like material which may provide space for drainage of the aqueous humor, thus preventing intra ocular pressure and possible glaucoma.
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