What is Glaucoma?
Glaucoma is a multifactorial disease of the eye. In simple terms, the intraocular pressure is higher than normal and this intraocular pressure slowly damages the optic nerve. The optic nerve carries the vision impulses from the eye to the occipital lobe of the brain which is the vision center. There are cases when the intraocular pressure is normal but still the person has glaucoma damage to the eye. The normal intraocular pressure ranges from 10 to 21 mmHg.
There are three basic types of treatment for glaucoma:
There are several topically applied eye medications that lower the eye pressure.
There are three different types of laser treatments for glaucoma which are SLT, ALT, and MLT.
There are several different glaucoma surgical procedures for glaucoma and some of those are Trabeculectomy, Canaloplasty, Trabectome, Ahmed Shunt, Molteno Shunt, Baerveldt Shunt, and Solx Deep Light Gold Micro-Shunt.
Normal Fluid Flow and Intraocular Pressure
The ciliary body located behind the iris (colored portion of the eye) produces the fluid that fills up the front portion of the eye (anterior chamber) called the aqueous humor. The fluid flows through the pupil and fills up the anterior chamber. The aqueous humor is drained from the anterior chamber through the trabecular meshwork which is located inside the anterior chamber where the sclera (white portion of the eye), cornea (clear portion of the eye), and iris. The fluid flows through Schlemm’s canal and into a vein in the conjunctiva. The eye pressure is the relationship of the amount of aqueous humor production and the drainage of the aqueous humor from the eye. Most intraocular pressure elevation is due to obstruction of outflow of fluid through trabecular meshwork.
Selective Laser Trabeculoplasty or SLT Mechanism of Action
Selective Laser Trabeculoplasty or commonly known as SLT is often used to lower the intraocular pressure to treat open angle glaucoma. The Selective Laser Trabeculoplasty machine is made by Lumenis. It uses a Q-switched frequency-doubled Nd: YAG: 532 nm wavelength green laser. A laser is a device that emits a focused beam of light at one particular wavelength. Different wavelengths of light have different properties from cutting and burning (heat) to cold lasers that cut or remove tissue without heat.
The SLT laser beam is applied to the trabecular meshwork and the melanin pigment cells absorb the light without causing thermal or coagulative damage to adjacent tissue. This causes microscopic openings in the trabecular meshwork. It also causes an increase in biological cytokines and cellular mediator activities following laser radiation. It stimulates macrophages to enter the trabecular meshwork. The macrophages remove obstructive proteins and remodel the trabecular meshwork improving fluid outflow from the eye and lowering the intraocular pressure.
Benefits of SLT
SLT treatment can lower the intraocular pressure to the same level as the strongest topical glaucoma medication.
The intraocular pressure can be controlled in many cases without the use of medications.
There are no side effects related to the use of glaucoma medications.
Patients don’t have to remember to use their glaucoma medications.
Side Effects of SLT
The treatment can cause inflammation inside the eye but it is almost always temporary.
The SLT treatment may not lower the intraocular pressure.
Selective Laser Trabeculoplasty or SLT Procedure
Topical anesthesia drops are instilled onto the eye to numb the eye. A contact lens is place on the cornea to help aim the laser onto the trabecular meshwork. The laser beam treatment is then applied to the trabecular meshwork. The treatment is usually applied half way around the eye per treatment session. The procedure lasts approximately two or three minutes and most people do not have any pain during the treatment. Topical prednisone eye drops are usually prescribed to be used four times a day for four days. There are no restrictions after the treatment. The intraocular pressure lowers to its final level in four to six weeks after the treatment is completed.