Glaucoma Evaluation, Management & Surgery
Glaucoma is a disease that damages the nerve in the back of your eye called the optic nerve. The optic nerve is responsible for sending the signals to your brain that enable you to see. If left untreated, glaucoma will cause a slow but steady loss of vision.
Glaucoma is typically caused by an increase in pressure inside your eye. This increased pressure
happens because of a decrease in the outflow of the fluid of the eye, called aqueous, through its normal pathway. This blockage results in an increase in pressure, which damages the optic nerve.
Glaucoma has no early warning signs. Most patients do not know they have it until they visit their eye doctor. Untreated glaucoma can cause a gradual, sometimes undetectable, loss of vision starting in your peripheral vision.
While glaucoma is not curable, there are several treatments that will help control the disease, including medication and/or surgery.
This laser is used to stimulate the trabecular meshwork in order to increase aqueous outflow. The trabecular meshwork is the first part of the outflow system and looks like a filter under a microscope. The lase stimulates the tissue to “open up” in order to allow more outflow. It has about an 80% success rate of varying degree. Many times, even if the laser is successful, the patient will still need to be on an eye drop in order to control the eye pressure fully.
EX–PRESS ® Glaucoma Filtration Device
The Express shunt is a device that is used during a traditional trabeculectomy surgery. It is utilized in order to increase the safety and decrease the risk of complications with this procedure. During a traditional trabeculectomy and alternate outflow system is created. The conjunctiva, which is the thin loose tissue that covers the eye, is incised and dissected in order to create a reservoir for the fluid to flow. A flap is then created in the underlying sclera. Underneath this flap either a hole can be created or the Express shunt can be implanted.
Express shunt has a standard 50 micron diameter opening which limits the amount of fluid that can pass through the shunt. This offers far better control of fluid flow when compared to the hole that is created during a trabeculectomy, which on the low side is 250 microns and usually larger. The trabeculectomy also necessitates creating a hole in the iris so that it doesn’t plug the hole. The Express shunt does not require this. The flap is then closed over the shunt and the conjunctiva is sutured back to its original location. The aqueous will then flow through the
shunt and out from under the scleral flap into the subconjunctival space creating a blister like structure called a “bleb”. The conjunctiva then absorbs the fluid decreasing the eye’s pressure.
For more information on the EX–PRESS ® Glaucoma Filtration Device you may visit the manufacturer’s website.
Baerveldt Glaucoma Implant
The Baerveldt Glaucoma Implant is commonly referred to as a non-valved tube shunt. It is a silicone device that is used to shunt the aqueous from the inside of the eye to the outside. It has two parts. The first part is the “plate”. It is a broad, flat, smooth and flexible piece of silicone contoured to follow the curve of the eye. It is placed under the conjunctiva and in between two extraocular muscles. The plate provides the surface area and scaffolding for the overlying conjunctival tissue to form a capsule. This capsule is the reservoir into which the tube will shunt the aqueous. The tube is placed into the front part of the eye, either in front or behind the iris. This allows the fluid to escape to the reservoir which absorbs the fluid and lower the eye’s pressure.
The Baerveldt tube does not have a valve to restrict flow. Therefore, an absorbable suture is tied around the tube in order to inhibit flow. This will give the eye time to build a capsule around the plate, which will then be able to limit flow and keep the eye pressure from going too low. This will take approximately 6-8 weeks. The patient will continue using glaucoma eye drops until the tube begins working.
To learn more about the Baerveldt Glaucoma Implant you can visit the manufacturer’s website.
Ahmed Valved Glaucoma Implant
As the name implies the Ahmed Glaucoma Implant has a valve, which differentiates this device from the Baerveldt Glaucoma Implant. By using a valve the tube can begin working immediately without having to wait for the capsule to form around the plate. The other parts of the surgery and the premise of the implant are the same. These are good implants to use on patients when the eye pressure is extremely high and glaucoma eye drops are not lowering the eye pressure enough to prevent damage while waiting for a Baerveldt tube to open and begin working.
To learn more about the Ahmed Valved Glaucoma Implant you can visit the manufacturer’s website.
Cycolphotocoagulation (CPC) is the destruction of part of the ciliary process tissue using a diode laser. The ciliary processes produce aqueous in the eye. Therefore, by reducing the number of functioning ciliary processes the aqueous, and subsequently the eye pressure are also reduced. There is a regular form and a micropulsed form of CPC. The micropulsed form is used earlier in patients who have minimal damage, but whose eye pressure isn’t controlled well with eyedrops or who may have already failed laser trabeculoplasty. The micropulsed form causes less ciliary process damage and less inflammation, which can lead to fewer side effects. The regular form of CPC is typically used after the patient has already had prior glaucoma surgeries, but the pressure is still not as low as needed and eye drops aren’t working. There is risk for more side effects, but this form of CPC typically lowers the eye pressure more than the micropulsed form.
To learn more about Cyclophotocoagulation you can visit the manufacturer’s website.
Minimally Invasive Glaucoma Sugeries (MIGS)
There are many types of MIGS for glaucoma control. They all work by trying to increase the flow of aqueous through the trabecular meshwork into the canal of Schlemm thereby lowering eye pressure. They are typically performed in conjunction with cataract surgery. The two MIGS procedures Dr. Overlease most frequently performs is the iStent Inject and Goniotomy.
The iStent Inject is a small device that penetrates through the trabecular meshwork into the Canal of Schlemm. Thus, providing a direct conduit for the aqueous to bypass the trabecular meshwork and flow directly into the canal lowering eye pressure.
To learn more about the iStent Inject you can visit the manufacturer’s website.
Goniotomy uses a specially designed instrument to strip away a section of trabecular meshwork. This provides direct communication between the anterior chamber and Schlemm’s canal, as well as the local collector channels. By removing the trabecular meshwork, its resistance to outflow is removed and eye pressure is lowered.
To learn more about goniotomy you can visit the manufacturer’s website.