Selective Laser Trabeculoplasty (SLT)
Selective Laser Trabeculoplasty (SLT) uses a very focused beam of light to treat the drainage angle of the eye. This surgery makes it easier for fluid to flow out of the front part of the eye, decreasing pressure in the eye. Laser trabeculoplasty may be helpful in treating people with open angle glaucoma that continues to get worse in spite of medication treatment. It may also be helpful in treating older adults with open-angle glaucoma who are not able to use medicines to treat the condition.
The procedure is done as an outpatient. Eye drops are put in the person’s eye before or after the procedure to decrease the amount of fluid in the eyes and prevent elevation in eye pressure immediately after laser treatment. A special microscope (slit lamp) and lens (goniolens) are used to guide the laser beam to the canals (trabecular meshwork) where fluid drains from the eye. The surgeon then applies several tiny laser spots to the drainage area of the eye.
During trabeculectomy – sometimes also called filtration surgery – a piece of tissue in the drainage angle of the eye is removed, creating an opening. The opening is partially covered with a flap of tissue from the sclera, the white part of the eye, and the conjunctiva, the clear thin covering over the sclera. This new opening allows fluid (aqueous humor) to drain out of the eye, bypassing the clogged drainage channels of the trabecular meshwork.
As the fluid flows through the new drainage opening, the tissue over the opening rises to form a little blister or bubble, called a bleb. The bleb is located where the sclera, or white of the eye, joins the iris, the colored part of the eye. During office visits after surgery, the doctor looks at the bleb to make sure that fluid is still draining out of the new opening. Not all blebs have to be easily seen to work.
Trabeculectomy is used to treat open-angle glaucoma and chronic closed-angle glaucoma. Trabeculectomy is usually done when medicine treatment and laser treatment for glaucoma has failed to reduce the pressure in the eyes enough to prevent damage to a person’s eyesight.
Tube-shunt surgery involves placing a flexible plastic tube with an attached silicone drainage pouch in the eye to help drain fluid (aqueous humor) from the eye. This type of surgery is usually done after a trabeculectomy that failed. If a person already has or is likely to form scar tissue in the eye, this type of surgery may be done at the start. Tube-shunt surgery is most often used for people who have had previous trabeculectomy surgery that was not successful, usually due to scarring.
Tube-shunt surgery is also frequently used to treat glaucoma when a person has a:
- Difficult case of glaucoma and the doctor thinks that other surgical methods may fail.
- Form of glaucoma in which new blood vessels grow on the colored part of the eye, or iris. This is called neovascular glaucoma and occurs primarily in people with diabetes or who have vascular diseases in the eye. It is difficult to control.
In this procedure, the surgeon applies a probe to the surface of the eye in the operating room. The probe serves to deliver laser pulses to the ciliary body which partially destroys the tissue of the ciliary body. The ciliary body produces the fluid that fills the front of the eye. When the ciliary body tissue is destroyed, less fluid is produced, thus lowering the eye pressure.
Cyclophotocoagulation is typically reserved for very difficult glaucoma cases when all other means of lowering eye pressure have been tried and failed.