Lasers for Glaucoma
Chat Highlights – October 1, 2014 Guest Speaker – Dr. Anand Mantravadi
Lorraine Miller – Editor, Chat Topic Researcher
On Wednesday, October 1, 2014, Dr. Anand Mantravadi, a glaucoma specialist at Wills, and the glaucoma chat group discussed “Lasers for Glaucoma.”
Moderator: Welcome, Dr. Mantravadi. Lasers are used in the treatment of glaucoma. Laser trabeculoplasty (LTP), laser peripheral iridotomy (LPI), and cyclophotocoagulation (CPC) are three procedures that use a laser. Other uses of a laser in glaucoma are laser peripheral iridoplasty and suture lysis after a trabeculectomy.
P: Are there any other uses of lasers in glaucoma?
Dr. Mantravadi: We also use a laser for capsulotomy or opening the capsule following some cataract surgeries. The laser is commonly used for this procedure.
P: What laser options are available and how is the decision made as to which laser should be used in a trabeculoplasty?
Dr. Mantravadi: Trabeculoplasty comes in a few forms as an argon laser trabeculoplasty and a selective laser trabeculoplasty. Both have similar outcomes and intraocular eye pressure (IOP) lowering effects. The thermal changes on a microscopic scale are more with an argon laser. Both modalities are effective. I would say that selective laser trabeculoplasty is more common these days.
P: Does the physician have a variety of laser powers and length of time of each blast at his discretion or is a set of parameters programmed into the machine?
Dr. Mantravadi: Selective laser trabeculoplasty parameters are fairly standard.
P: What indications should be present to justify a trabeculoplasty?
Dr. Mantravadi: Open angle glaucoma is present with a goal of lowering intraocular pressure.
P: What are the contraindications to performing a laser trabeculoplasty?
Dr. Mantravadi: Relative contraindications could include prior laser trabeculoplasty with historically little to no success in lowering the IOP. The absolute contraindications to the procedure are closed angle glaucomas.
P: Are there preoperative and postoperative treatments for a laser trabeculoplasty?
Dr. Mantravadi: Treatments are not really standardized and vary by practitioner. Some give a preoperative or postoperative IOP lowering drop at the time of the laser. After the laser procedure, some practitioners don’t prescribe any additional medications except for continuing prior glaucoma medications if the patient was on them. Some physicians prescribe a topical anti-inflammatory drop like a steroid or a non-steroidal medication for a few days.
P: What is an ocular Goldmann three mirror lens and how is it used in the procedure?
Dr. Mantravadi: It is a prism lens that enables a view into the angle structures. This is a common lens used to apply the laser energy in the appropriate location.
P: Where on the eye are the burns from a laser trabeculoplasty? Are they placed in the same location for either laser used in the procedure?
Dr. Mantravadi: It is the same location used in both selective laser and argon laser trabeculoplasties. The laser in selective laser does not really create any coagulative damage and placement occurs on the pigmented trabecular meshwork in the angle of the eye.
P: What are the possible complications caused by the procedure?
Dr. Mantravadi: The selective laser could cause a pressure spike and post-laser inflammation could occur. The complications from an argon laser could also be a pressure spike, inflammation, and possible scarring in the angle.
P: What is a selective laser trabeculoplasty? What factors make procedures done by this less painful compared to other modalities?
Dr. Mantravadi: Selective laser is a low energy laser that is thought to be taken up by cells in the trabecular meshwork. Perhaps less energy used is the basis for less ocular discomfort during the procedure. Having done this routinely, I would say it is rare that patients feel any discomfort outside of the contact lens during the brief time of laser application.
P: What are the factors that favor a positive response from a trabeculoplasty?
Dr. Mantravadi: There is some evidence that suggests a pre-laser IOP in the mid 20s has a more pressure lowering effect than a lower pre-laser IOP. A 360-degree treatment seems to achieve a better pressure lowering effect than 180-degrees. The decision to treat 180-degrees or 360-degrees rests entirely with your ophthalmologist. There is a slightly greater risk of pressure spike with a 360-degree treatment. Therefore, if someone has very tenuous pressure control and is already on maximal medical therapy, a 180-degree treatment maybe a safer route and more preferable.
P: What is the pathophysiology of a laser trabeculoplasty?
Dr. Mantravadi: With a SLT, uptake by the cells in the meshwork that stimulates some inflammatory or immunomodulatory cascade enables cells to clear potential debris that is affecting trabecular outflow. With ALT, there are many theories some including thermal contraction which enables the mechanical opening of the trabecular beams.
P: What lasers are used with a laser peripheral iridotomy? Are the same settings used as with a trabeculoplasty?
Dr. Mantravadi: The settings for a laser peripheral iridotomy are not the same settings as used with a trabeculoplasty.
P: When is a laser peripheral iridotomy (LPI) performed?
Dr. Mantravadi: A laser peripheral iridotomy is performed in any case that presents an anatomically narrow angle in a Gonioscopy exam. A Gonioscopy is a prismatic view into the angle structures by an ophthalmologist. An indication for a LPI includes acute or chronic angle closure with scarring evident in the angle. LPI may be needed to prevent issues that come up with retinal procedures such as silicone oil instillation or intraocular lens procedures. YAG and Argon are two commonly employed lasers.
P: What would indicate the need for a prophylactic laser iridotomy?
Dr. Mantravadi: Indications for an iridotomy would be an anatomically narrow angle, chronic or acute angle closure, prophylaxis for some other ocular conditions requiring an iridotomy such as silicone oil instillation, an intraocular lens complex or anterior chamber lens.
P: Are the preoperative and postoperative treatments the same for a LPI as for a laser trabeculoplasty?
Dr. Mantravadi: With a laser iridotomy, many more patients use topical steroids for a few days.
P: Is a Goldmann lens also used for this procedure?
Dr. Mantravadi: No, an iridotomy lens is used. It has a few names depending on who designed it.
P: What are the complications with a laser peripheral iridotomy?
Dr. Mantravadi: The risks always are outweighed by the benefits with this procedure. We see and treat the complications of angle closure glaucoma which can be devastating to the eye. In a conversation of risks and benefits with the patient, it is very important to keep that clear. Uncommon risks of an iridotomy might include limited bleeding, a pressure spike immediately after the procedure, and a very rare incidence of optical line or shadows.
P: What lasers are used with a cyclophotocoagulation?
Dr. Mantravadi: Cyclophotocoagulation typically uses a diode laser.
P: Why would a patient need cyclophotocoagulation?
Dr. Mantravadi: This procedure is usually reserved for complicated glaucomas not amenable to other surgical modalities. The laser thermally impacts the ciliary body’s ability to make aqueous humor by “turning down the faucet” if the drains are not working internally in the eye, thereby, lowering eye pressure.
Q: What procedures are done to prep the patient before cyclophotocoagulation? What postoperative procedures are prescribed and need to be followed by the patient?
Dr. Mantravadi: This is usually done because other modalities are not successful so the laser is performed. The procedure is done in an office setting or sometimes in the operating room depending on the surgeon, the facility, and the urgency. Post-operatively, the same glaucoma medications that were used prior to the procedure are used until the desired response is achieved. In addition, cycloplegia (definition: paralysis of the ciliary muscle of the eye), and anti-inflammatory medications are used. We use a probe applicator to the external surface of the eye.
P: What procedures to prep the patient are done before cyclophotocoagulation?
Dr. Mantravadi: Some physicians use a numbing agent administered behind the eye and others do not. The decision depends on the surgeon, setting, and risk factors.
P: What are possible complications of cyclophotocoagulation?
Dr. Mantravadi: Complications include an inflammatory response, pressures that are too low, a lack of response, and bleeding.
P: What are the long-term side effects following a cyclophotocoagulation procedure?
Dr. Mantravadi: Long term side effects are uncommon but can include too low of an intraocular pressure or vision loss. This can be a very effective modality.
P: What postoperative procedures are prescribed and need to be followed by the patient?
Dr. Mantravadi: The same glaucoma medications are prescribed prior to the procedure. Following the instructions of the treating physician is imperative as they are titrated, modified, or changed based on the response to the laser.
P: When are some of the indicators that determine that a SLT would need to be repeated? If so, when is a decision made about a more invasive procedure?
Dr. Mantravadi: Repeating an SLT is a good option if there was a historically positive response the first time around. An invasive procedure is indicated if the likelihood of achieving the goal pressure for the individual is low with a repeat laser.
P: After any of the laser procedures, would other ocular surface disorders such as dry eye, make visual rehabilitation more difficult?
Dr. Mantravadi: If people have severe ocular surface problems, they will be prone to issues when anything irritates the surface of the eye. A contact lens used for lasers is commonly employed, tolerated by most, but a few may have issues if they have underlying ocular surface problems. There are precautions that can be taken before or after the laser to mitigate these issues.
P: Which laser is used in performing a laser peripheral iridoplasty?
Dr. Mantravadi: Typically, an argon laser is used for an LPI.
P: Could a laser iridotomy affect corneal function?
Dr. Mantravadi: Yes, it is possible, but rare.
P: Data from the Argon Laser Trabeculoplasty (ALT) studies show that the probability of a positive response is greater at the age of sixty and above. Has it been proven that it is true for the Selective Laser Trabeculoplasty (SLT) as well?
Dr. Mantravadi: Many of the patients enrolled in the studies involving SLT are from an older population. I don’t believe a direct comparison with two age groups has been performed when controlled for other variables with SLT. SLT can be performed in younger individuals but clearly the younger patients are more likely to see their results dissipate with time.
P: Why aren’t ALTs or SLTs performed after a trabeculectomy as the pressure increases over time in some patients?
Dr. Mantravadi: There is no dogmatic evidence to the contrary if a laser has not been attempted prior to filtering surgery. However, most all laser data originates in patients who have not had filtering surgery.
P: What are some of the latest advances in lasers used in glaucoma?
Dr. Mantravadi: Endoscopic application of energy to the ciliary body is a more recent option. SLT has been a great option and we are learning more about it in terms of efficacy when used earlier in treatment algorithms.
P: How is an LPI different from a peripheral iridectomy?
Dr. Mantravadi: Both procedures achieve the same thing. LPI is with a laser while an iridectomy is an incisional surgery.
P: Could an LPI be performed after complications with cataract and other procedures?
Dr. Mantravadi: Yes, an LPI can be performed after other procedures.
P: Is success from incisional surgery lessened if an ALT or SLT has been performed prior to the surgery?
Dr. Mantravadi: No, ALT or SLT do not affect the success of an incisional surgery.
P: Are there certain races or demographic groups that tend to respond better to an SLT procedure?
Dr. Mantravadi: There is some evidence that SLTs highly successful results are independent of race.
P: Micropulse laser trabeculoplasty (MLT) using a diode laser has been around for almost a decade. Are there benefits to this laser over the others?
Dr. Mantravadi: Evidence thus far seems to suggest that the IOP lowering effect is similar to SLT and ALT.
P: What is a laser goniopuncture?
Dr. Mantravadi: Laser goniopuncture is laser energy used to make an opening. It can be done after a trabeculectomy if the internal opening occluded for some reason. It can also be done after a canaloplasty if the goal is to create an internal opening.
P: How does a titanium sapphire laser trabeculoplasty differ from the SLT?
Dr. Mantravadi: There is greater tissue penetration with the titanium sapphire laser trabeculoplasty. It is comparable to an ALT. It is too early to tell with the available data.
Moderator: Thank you, Dr. Mantravadi, for a very informative chat! We very much appreciate your time.