by Dr. Andrew Rabinowitz
Lasers have become a critical tool in treating and preventing many types of glaucoma. Lasers were first used in treating glaucoma less than 35 years ago. Prior to their introduction, glaucoma could only be treated medicines or surgery. Lasers now serve as an intermediate treatment between medicine and surgery. Patients are often intimidated by the thought of having to undergo laser treatment. However, those patients who have undergone successful laser treatment will most likely tell you that their experience was pleasant, painless, and fast. Most laser treatments used in the management of glaucoma are performed in an office setting. Lasers usually do not involve needles, sutures, cutting, or bleeding.
There are several types of laser procedures used in the treatment of glaucoma. The most important aspect of laser use in the management of glaucoma is understanding who is a candidate. It is also important that the patient have realistic expectations about what lasers can achieve. In general, lasers do not “cure” glaucoma. Rather, they serve as an important “treatment” used to control this lifelong disease.
Historically, the primary treatment for glaucoma has been eye drop medications. When a patients’ glaucoma can no longer be controlled on eye drops alone, or if they cannot tolerate the eye, they are considered candidates for laser therapy.
An important concept to understand in glaucoma is that of a patient who is on a “Maximally tolerated medical regimen (MTMR.) Many different scenarios can be considered MTMR. Here are a few examples.
1. A patient who is on three or four eye drop medications but who still has a pressure that is higher than the target set by their eye doctor.
2. A patient who is on one or two eye drop medications but who is intolerant to all other medications and who is running a pressure above the target set by their eye doctor
3. A patient who has no problem tolerating eye drops, but who has severe arthritis or Parkinson’s disease. This patients may have limited use of her hands and have difficulty putting in eye drops. If this patient lives alone, and has no one to rely on to instill her drops, she would be considered MTMR
Thus, you can see from these examples, that laser treatment may become necessary at different stages for different patients. There is no question that eye drop medications should be tried as initial therapy. If medical therapy is ineffective, the patient becomes a candidate for laser therapy.
Laser therapy is an effective way to lower pressure. Laser therapy is used to complement the effect of eye drop medications. Laser therapy does NOT replace eye drops medications in most instances. Instead, laser is used to augment the effect of the existing medications. It should be carefully explained to patients that they may still need to use glaucoma medications following successful laser therapy.
Laser therapy does not provide permanent pressure reduction. The benefits of laser can last anywhere from 6 months to 6 years. Often the treatments can be repeated at least once. There are a small percentage of patients in whom laser may not lower the eye pressure to a significant degree.
LASER SURGERY FOR GLAUCOMA
WHAT IS THE DOWNSIDE OF LASER THERAPY?
In most instances, the downside is very small. I tell my patients that the worse thing that can happen is that they do not get any benefit from the treatment. Because the procedure is non-invasive, patients are not exposed to the risk of severe bleeding or infection, which are notable risks with surgery. A small percentage of patients may experience a transient rise in their eye pressure over the first 24 hours following the procedure, but this is short-lived.
Thus, I offer laser treatment to my patients as an option to help control their pressure and avoid surgery. I also tell my patients that the benefits of most laser treatments are not forever, and that if they live long enough, they will likely need surgery in the future.
Laser therapy is an excellent bridge between medical and surgical management of glaucoma. There is a limited downside, and a moderate but not permanent upside.
WHAT IS NEW IN LASER THERAPY?
There are at least two new lasers on the horizon for the treatment of glaucoma. One laser called the “diode” laser is now in use in our practice. Within the next 12 to 24 months we will see the incorporation of a new type of laser for the treatment of glaucoma. This new laser is called the Selecta 7000. This laser is a breakthrough because it will allow us to perform laser treatment on patients who have already undergone “complete treatment” with our existing lasers. Prior to the inception of the Selecta 7000, laser treatment was performed only twice. It was felt that additional treatment could do more harm than good. With the Selecta 7000, we are achieving excellent results in treating people how have had “complete treatment” with our standard lasers.
WHAT TYPES OF LASER SURGERY ARE THERE FOR GLAUCOMA?
The most common procedures performed for glaucoma are:
1. Laser trabeculoplasty
2. Laser iridotomy
I will discuss the indications and procedures for both of these treatments. Many patients may require both treatments over the course of their lives. These treatments were introduced into ophthalmology nearly 30 years ago. The main changes since their inception have been related to improved laser technology. The fundamental principles and goals of these treatments remain unchanged. The goals are to improve drainage of the fluid which fills the eye.
LASER SURGERY FOR GLAUCOMA-ARGON LASER TRABECULOPLASTY (ALT) & DIODE LASER TRABECULOPLASTY (DLT)
Argon laser trabeculoplasty is a laser procedure, which is performed in an office setting. The patient is seated in a comfortable position, and the eye numbed with eye drops. The treatment takes less than 5 minutes to perform, and usually causes only mild pain. Most patients tolerate the procedure without difficulty. There is little to no discomfort following the procedure.
Argon laser trabeculoplasty (ALT) is an important adjunct to medical and surgical treatment of open-angle glaucoma. Diode laser trabeculoplasty (DLT) is apparently equally effective. The indications and techniques for performing ALT have become standardized since its introduction in 1979.
The mechanism by which ALT lowers eye pressure is not known, although an immediate “mechanical” effect on the trabecular meshwork (drain of the eye) is widely accepted. Besides the immediate thermal effect of the burns on surrounding tissues, including tightening of the meshwork (circumferential shortening), there may be a long-term metabolic effect.
ALT should be considered for patients with open-angle glaucoma who cannot be controlled by a maximum tolerated medical regimen (MTMR.) Additionally, it should be considered in those patients who are intolerant to or unable to use topical medications. ALT is also appropriate as a method of delaying filtering surgery, especially for the systemically fragile elderly patient. A follow-up of patients enrolled in the Glaucoma Laser Trial (GLT) showed that initial treatment with ALT of newly diagnosed patients with open-angle glaucoma was at least as effective as initial treatment with eye drops.
ALT is relatively successful in patients over 50 years of age with primary open-angle glaucoma, especially in cases associated with pseudoexfoliation and pigmentary dispersion. ALT has poor success in eyes with congenital or juvenile-onset glaucoma, inflammatory glaucoma, and post-traumatic glaucoma with angle recession injury. The effects are relatively unpredictable in patients who have undergone prior cataract surgery.
ALT produces an average decrease in eye pressure of 7 to 10mm Hg. The amount of eye pressure drop obtained increases as baseline pressure increases. Eye pressure tends to drift back toward the baseline following ALT. The average benefit in eye pressure control lasts 2 to 5 years. By 5 years after ALT, about 46% of treated patients remain better controlled. The failure rate is approximately 10% per year and, by 10 years after ALT, one half of treated eyes have undergone filtering surgery.
ALT is a safe, widely performed procedure. The following pages illustrate the treatment process.
LASER SURGERY FOR GLAUCOMA -LASER IRIDOTOMY
Laser iridotomy is indicated in the treatment of acute and chronic angle-closure glaucoma, combined-mechanism glaucoma, pseudophakic and aphakic papillary-block glaucoma, and incomplete surgical iridectomy.
ANGLE CLOSURE GLAUCOMA:
Angle-closure glaucoma must be given a high priority among eye diseases because its effects can be devastating. Bilateral blindness can result in 2 to 3 days from onset. Angle-closure glaucoma, can be prevented with proper recognition and therapy. Few conditions in ocular disease offer such a great opportunity for relief of human suffering. There is a dramatic difference between the devastation of untreated angle-closure glaucoma and its permanent prevention with early recognition and appropriate treatment.
NARROW ANGLE GLAUCOMA:
Narrow angle glaucoma can and should be recognized by all eye care physicians. The condition, if treated promptly with laser iridotomy, can greatly reduce the chances of visual impairment. The INITIAL treatment for narrow angle glaucoma is laser iridotomy. This procedure is done in an office setting, with the patient seated in a comfortable position. The eye is numbed with anesthetic eye drops. A special contact lens is placed on the eye, and the laser used to make a small hole in the colored part of the eye known as the iris. This small hole is usually not detectable with the naked eye. The hole is usually placed superiorly, in an area covered by the upper eyelid. Narrow angle glaucoma can occur in people of ALL ages. It is not uncommon to first diagnose this condition when patients are in their late 30’s or early 40’s. Many patients when initially told that they have this condition become quite alarmed. Their alarm grows when the doctor informs them that the initial treatment for this condition is laser surgery. Patients often want to know if they can use eye drops instead of having laser surgery. Unfortunately, this is one disease where eye drops CANNOT take the place of laser treatment. Equally disappointing to the patient at first pass is the fact that some people will require drops even if laser surgery is successful. Those patients have what is known as combined mechanism glaucoma.
Most important, however, is the fact that this is a treatable disease. The laser treatment usually takes only a few minutes, but its benefits can last a lifetime. .
If a patient has doubts about the diagnosis and the need for treatment, they should seek a qualified second opinion immediately. This often allays their fears, and allows them to proceed with the procedure without hesitation.
GLAUCOMA SURGERY-LASER IRIDOTOMY
The patient is premedicated with a topical anesthetic. Pretreating the patient with a miotic agent such as pilocarpine is advantageous. The miotic pupil provides greater iris surface area for treatment, ensures a thinner iris for easier penetration, and minimizes the chance of errant laser energy causing retinal injury. Pre-treatment with medications which lower eye pressure is recommended, because 30% of patients develop elevated pressure after laser iridotomy. Pretreatment with alpha-adrenergic agents such as apraclonidine (Iopidine,) or Brimonidine (Alphagan,) may prevent a post laser spike in IOP. These topical medications also may limit the amount of iris bleeding when the Nd:YAG laser is used. In addition to these medications being given 1 hour before the laser surgery, a second drop is applied at the completion of the treatment.
The end point of treatment for both laser modalities (Argon, YAG) is a well-defined, clean, hole.
After treatment, the patient should be examined during the subsequent 1 to 3 hours and again within the next week. Patients should be given topical steroids to be used hourly on the day of the procedure, then q.i.d. for 4 more days.
The following page demonstrates the type of iris burn attained with the two types of lasers used to create the iridotomy. The procedure can be performed using either one or two lasers. Some patients are treated using only one laser, while other patients require the use of two lasers. The decision of using one or two lasers is made by the surgeon. This decision is based upon the unique anatomy of each individual’s eye.