Glaucoma (cont.)
Laser or surgery
There are several forms of laser therapy for glaucoma. Laser iridotomy (see the section above on closed-angle glaucoma) involves making a hole in the colored part of the eye (iris) to allow fluid to drain normally in eyes with narrow or closed angles.
Laser trabeculoplasty is a laser procedure performed only in eyes with open angles. Laser trabeculoplasty does not cure glaucoma, but is often done instead of increasing the number of different eye drops. In some cases, it is used as the initial or primary therapy for open-angle glaucoma. This procedure is a quick, painless, and relatively safe method of lowering the intraocular pressure. With the eye numbed by anesthetic drops, the laser treatment is applied through a mirrored contact lens to the angle of the eye. Microscopic laser burns to the angle allow fluid to better exit the drainage channels.
Laser trabeculoplasty is often done in two sessions, weeks or months apart. Unfortunately, the improved drainage as a result of the treatment may last only about two years, by which time the drainage channels tend to clog again. There two types of laser trabeculoplasty: argon laser trabeculoplasty (ALT) and selective laser trabeculoplasty (SLT). ALT is generally not repeated after the second session due to the formation of scar tissue in the angle. SLT is less likely to produce scarring in the angle, so, theoretically, it can be repeated multiple times. However, the likelihood of success with additional treatments is still very poor. Thus, the options for the patient at that time are to resume the eye drops or proceed to surgery.
Laser cilioablation (also known ciliary body destruction or cyclophotocoagulation) is another form of laser treatment generally reserved for patients with severe forms of glaucoma with poor visual potential. This procedure involves applying laser burns to the part of the eye that makes the aqueous fluid (ciliary body). These laser burns destroy the cells that make the fluid, thereby reducing the eye pressure. This type of laser is typically performed after other more traditional therapies have failed.
Glaucoma surgery
Trabeculectomy is a delicate microsurgical procedure used to treat glaucoma. In this operation, a small piece of the clogged trabecular meshwork is removed to create an opening and a new filtering pathway is made for the fluid to exit the eye. For the new pathway, a small filtering bleb is created from conjunctival tissue. (The conjunctiva is the clear covering over the white of the eye.) The filtering bleb is a cyst-like raised area that is placed at the top part of the eye under the upper lid. The new drainage system allows fluid to leave the eye, enter the bleb, and then pass into the capillary blood circulation (thereby lowering the eye pressure). Trabeculectomy is the most commonly performed glaucoma surgery. If successful, it is the most effective means of lowering the eye pressure.
Aqueus shunt devices (Glaucoma implants or tubes) are artificial drainage devices used to lower the eye pressure. They are essentially microscopic tubes attached to a reservoir. The reservoir (or plate) is placed beneath the conjunctival tissue. The actual tube (which extends from the reservoir) is placed inside the eye to create a new pathway for fluid to exit the eye. This fluid collects above the reservoir beneath the conjunctiva creating a filtering bleb. This procedure may be performed as an alternative to trabeculectomy in patients with certain types of glaucoma.
Viscocanalostomy is an alternative surgical procedure used to lower eye pressure. It involves removing a piece of the sclera (eye wall) to leave only a thin membrane of tissue through which aqueous fluid can more easily drain. While it is less invasive than trabeculectomy and aqueous shunt surgery, it also tends to be less effective.
The surgeon sometimes creates other types of drainage systems. While glaucoma surgery is often effective, complications, such as infection or bleeding, are possible. Accordingly, surgery is usually reserved for cases that cannot otherwise be controlled.
Next: What is in the future for glaucoma? »
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