Overview of Cyclodiode Laser Glaucoma Therapy
Glaucoma refers to a group of eye diseases that can harm the optic nerve which carries information from our eyes to our brains. This can result in a gradual loss of vision. It often occurs due to high pressure inside the eye, also known as intraocular pressure (IOP). This pressure is the main risk factor for glaucoma, and it’s the one thing we can treat in order to slow or stop the disease from getting worse. Treatment usually involves improving the flow of a fluid called aqueous humour or reducing its production inside the eye.
Since the 1930s, medical professionals have been using different methods to destroy a part of the eye that makes this fluid, called the ciliary body, specifically to treat difficult or uncontrolled cases of glaucoma. There are various methods used, from heat therapy and surgery, to cryotherapy (cold therapy), ultrasound, and lasers. Currently, a 810 nm laser, known as a cyclodiode laser, is commonly used for this. There are different versions of this laser treatment, including Trans-scleral cyclophotocoagulation (TCP), Micropulse (MP-TCP) and Endocyclophotocoagulation (ECP).
Anatomy and Physiology of Cyclodiode Laser Glaucoma Therapy
The aqueous humor, which is a clear fluid in your eye, is produced by parts of the eye called the ciliary processes. This fluid primarily drains through a structure called the trabecular meshwork. Remaining fluid drains through another path called the uveal scleral pathway which doesn’t rely on eye pressure.
There are around 80 ciliary processes that originate from a ring of muscle tissue inside the eye named the ciliary body. These projections are like tiny towers which have a double-layered skin that extends into the front chamber of your eye, over a tissue that has small openings for blood vessels known as fenestrated capillaries. If you look at the eye from the outside, these ciliary processes are about 1.5 millimeters behind the edge of the cornea.
A tool called a continuous-wave TCP diode laser, which emits laser light with a specific wavelength, is used to reduce the size of the ciliary processes. When aimed at these, the laser lowers their size and makes them paler. It can cause significant harm to neighboring tissues, which can also help in draining the clear eye fluid.
Now, compared to the continuous-wave TCP, the MP-TCP works differently. Instead of a constant beam, it sends pulses of laser light to the target. These pulses give time in between the laser ‘on-phase’ for the surrounding tissue to cool off, which reduces damage and helps lower eye pressure. Another type, ECP laser, works by directly seeing the ciliary processes and causing them to shrink, which reduces overall damage.
Why do People Need Cyclodiode Laser Glaucoma Therapy
The Cyclodiode laser is a treatment often used for severe, hard-to-treat forms of glaucoma, which is a condition causing damage to the eye’s optic nerve, often due to high pressure. It is commonly used for patients who haven’t responded well to previous surgery or who have certain types of glaucoma, such as neovascular, traumatic, aphakic, inflammatory and congenital glaucoma. This treatment can also be used for eyes that are painful and unable to see, or eyes that have a low chance of regaining vision.
Other good candidates for the Cyclodiode laser are eyes with significant scarring caused by previous surgery, injury, or inflammation. It’s also an option when acute angle-closure glaucoma, a sudden, painful form of glaucoma, doesn’t respond well to regular medications and laser treatments. The Cyclodiode laser treatment can help stabilize the eye pressure and calm inflammation before other, more permanent, surgical solutions are considered.
This treatment can also be a good choice for people who aren’t suitable for surgery or struggle with following a treatment plan. In more recent times, the Cyclodiode treatment is being seen as a main treatment option, even for eyes that still have good vision. This is especially true in developing countries, where it’s considered a viable long-term option.
There’s another treatment called MP-TCP that can be considered for eyes at a higher risk of surgery complications. This is because MP-TCP has a reputation for being safer. ECP is another common treatment that’s often combined with removal of a cataract but can also be used on its own inside the eye.
When a Person Should Avoid Cyclodiode Laser Glaucoma Therapy
A cyclodiode laser treatment is usually avoided for patients with severely damaged or disorganized internal eye structures. It’s also not the preferred method if there are other treatments available that might work better. This is particularly the case if the eye has good vision or there’s a risk of macular edema, a condition where fluid builds up in your eyes and can cause blurry vision.
This treatment is also not recommended for patients with advanced pseudoexfoliation, a condition where flaky dandruff-like material gets dispersed widely over the eye structures and can cause blockages. This hampers the laser energy from being effectively absorbed, thereby making the treatment less effective.
Special caution is needed with patients suffering from eye inflammation (uveitis) or abnormal growth of blood vessels in the eye leading to high pressure (neovascular glaucoma). These patients may be at a higher risk of severe inflammation and low eye pressure (hypotony) after the operation.
Equipment used for Cyclodiode Laser Glaucoma Therapy
The TCP unit is a small, portable device that uses a type of laser called a semiconductor solid-state diode. It emits energy at a wavelength of 810 nm. This device has a handpiece that’s designed like a curved footplate to fit the roundness of the sclera, the white part of your eye. This makes it easier to deliver the laser energy to the eye.[14][15]
This laser energy goes through a quartz fiber inside the handpiece that’s 600 micrometers wide and placed a little over a millimeter behind the limbus, the border between the white and colored parts of your eye. The handpiece has a tip that sticks out a little to press against the surface of your eye, which helps improve how well the laser energy can work. The laser energy is given out in a continuous wave with the handpiece lined up with the direction you’re looking along the conjunctiva, the front surface of your eye, for the entire time the laser burn is needed.[15][16]
Another device called the MP-TCP also uses a handpiece to deliver laser energy while touching the conjunctiva. However, unlike the continuous-wave TCP, the MP-TCP delivers laser energy in short bursts or “micropulses”.[9]
A third device called the ECP probe is put inside your eye using a handpiece that’s 18-20G, a measurement of the size of the handpiece. This device has an 810 nm diode laser, a strong light source, a guiding laser beam, and a camera for taking video images. The camera gives a wide view of 110 to 160 degrees. Unlike the other two devices, this probe can be used to give laser energy in short pulses or a continuous wave. Using the ECP probe requires an operating microscope and setting up an instrument inside your eye.[5][7][8]
Who is needed to perform Cyclodiode Laser Glaucoma Therapy?
This procedure is often done in a special room at the hospital because the laser used in it can be dangerous. The main person doing this procedure is an eye doctor called an ophthalmic surgeon. The surgeon is helped by a scrub nurse or a theatre team. These are specialized nurses who assist during surgery. The ophthalmic surgeon may give you a certain type of anesthesia called a peri/retrobulbar block. This special anesthetic numbs the area around your eye and stops you from feeling anything during the operation. If there’s an anesthetist available, they might be the one to give you the anesthesia instead of the surgeon.
Preparing for Cyclodiode Laser Glaucoma Therapy
Before eye surgery, it’s vital that doctors thoroughly discuss with patients the potential benefits, risks, expected recovery, and possible complications. The goal of this conversation is to help patients make informed decisions about their treatment plan. As is done for certain glaucoma procedures, the doctor will take into account the overall health of the patient, including the health of their other eye.
It’s also important to check how well a patient handles anesthesia. Some may only need local anesthesia, which numbs a small area of the body, via a peribulbar or retrobulbar block. These blocks are injections given around the eye to prevent feeling and movement during the procedure. Others may require general anesthesia, where the patient is completely unconscious.
If a procedure known as ECP (Endoscopic CycloPhotocoagulation), a type of treatment for glaucoma, is being done at the same time as cataract surgery, the patient’s eye will need a complete examination, along with biometry measurements for IOL (Intraocular Lens). This lens is implanted in the eye during cataract surgery.
The doctor will also check for any signs of inflammation in the eye beforehand, and treat it if necessary. Another factor to consider is whether the patient might need eye surgery in the future. If so, the doctor might choose to avoid using the superotemporal quadrant of the conjunctiva. This is a portion of the thin covering of the eye and the inside of the eyelids, to ensure it’s available for future procedures.
How is Cyclodiode Laser Glaucoma Therapy performed
During the laser procedure, everyone in the room needs to wear protective gear to avoid any accidental scattering of the laser.
TCP
This treatment could be carried out under local anesthesia where a numbing medicine is delivered around your eye. Rarely, you might be put completely to sleep with general anesthesia. Typically, a laser is used, set up to predefined energy levels and you’ll lay flat while a small gadget called a speculum might be used to give the doctor a clear view of your eye. Before starting the laser treatment, a physical check of the structures in your eye is usually carried out, especially if you have a rare case of distorted eye anatomy.
The surgeon applies several laser burns around the edge of the colored part of your eye, usually avoiding the 3 and 9 o’clock positions due to important nerves and arteries found there. The laser’s power is adjusted until no loud popping noise is heard, which would mean tissues in the eye are getting damaged. The number of spots the laser is applied to depends on how much pressure reduction is needed in your eye.
Afterwards, you will be given eye drops several times a day to decrease inflammation; usually, you’ll also continue to take your pressure lowering eye drops and they are only stopped based on your progress.
MP-TCP
This procedure is similar to TCP, though it uses a different device, which sends pulses of laser light, rather than a continuous beam. A special gel is applied to your eye so the laser can work properly. The surgeon moves the laser in a back-and-forth motion over the surface of your eye. Like TCP, the 3 and 9 o’clock positions are also avoided. Laser application continues for up to about 6 minutes and you’ll get postoperative eye drops just like in TCP.
ECP
Before this procedure, your eyes are dilated using drops to give better access to the structures of the eye. In rare cases, local anesthesia might be applied around your eye or the procedure might be carried out under general anesthesia like the others. This is usually carried out after you’ve had cataract surgery. The surgeon makes a small incision in your eye and a substance is applied to maintain the shape of the front part of your eye and create space for better visualization.
The surgeon then inserts a tiny camera and laser device into your eye and watches a video monitor to carry out the procedure. The laser is used to treat the structures of your eye seen on the monitor. Up to 6 structures can be viewed at the same time. The starting power of the laser is between 200 to 300mW and this can be adjusted as necessary to avoid damage to the tissues of the eye.
Afterwards, the substance used to maintain the shape of your eye is removed and the wounds are sealed. Antibiotics and steroids are usually given at the end of the procedure to prevent infection and inflammation, followed by topical postoperative steroids and antibiotics.
Possible Complications of Cyclodiode Laser Glaucoma Therapy
After a diode laser treatment for glaucoma (a group of eye conditions that can cause blindness), there could be some possible side effects or complications. These depend on the type of laser used, the kind of glaucoma a person has, and the particular treatment plan the doctor uses.
Some common side effects include mild to moderate discomfort, redness of the eye, burns on the surface of the eye, skin darkening on the eye surface, changes in the shape of the pupil, and short term inflammation inside the eye. More serious side effects can include bleeding inside the eye, blurry vision, cataracts (cloudiness on the lens of the eye), shifting of the lens, a type of glaucoma called “malignant glaucoma”, other types of bleeding, hole in the wall of the eye, extremely low eye pressure, shrunken eye, and a rare severe inflammatory condition called “sympathetic ophthalmia”.
One type of diode laser treatment, called TCP, may result in very low eye pressure if the energy levels are too high or if many laser “shots” are used. Certain conditions, like a specific type of glaucoma that involves the growth of new blood vessels, and a high eye pressure before treatment, can increase the risk of low eye pressure after TCP. The occurrence of the inflammatory condition “sympathetic ophthalmia” after TCP is rare and estimated to range from 0.03 to 0.17%.
There is another type of TCP, called MP-TCP, which is considered safer because it results in fewer cases of extremely low eye pressure and shrunken eye. This is believed to be due to better control of the treatment to prevent damage to surrounding eye tissues. However, longer duration of treatment and higher power settings may increase the risk for complications.
A treatment called ECP carries similar risks as TCP excluding surface burns of the eye. In comparison, ECP generally has fewer severe complications if the power levels used are less than 500mW. But because it’s an internal eye procedure, it carries additional risks such as damage to the lens, the structure holding the lens, the colored part of the eye (iris), retinal detachment, and serious infection inside the eye. No case of “sympathetic ophthalmia” has been reported from ECP so far.
What Else Should I Know About Cyclodiode Laser Glaucoma Therapy?
Various long-term research studies have shown that Transscleral Cyclophotocoagulation (TCP) — a type of laser eye surgery for glaucoma — effectively reduces internal eye pressure (IOP) in 34 to 94% of patients for up to 5 years after the procedure. External eye pressure (hypotony) happens in up to 10% of patients, severe eye shrinkage (phthisical development) in up to 5%, and some level of vision loss in up to 28%.
In a study where TCP was used to treat more difficult cases of glaucoma or those with decent vision, effective IOP reduction occurred in nearly 80% of patients. Importantly, there were no cases of hypotony, but around 30% of patients lost a bit of visual clarity. This was mostly due to progressive glaucoma, not retinal swelling (macular edema). The vision loss rate was similar to that of another type of glaucoma surgery (trabeculectomy).
Adapting the TCP procedure with lower power has been shown to be safer and still effective in reducing the need for glaucoma medication on patients. Remarkably, it often allowed patients to stop taking oral acetazolamide, a common glaucoma drug.
Different studies have shown MicroPulse Transscleral Cyclophotocoagulation (MP-TCP) had a 52% to 74% success rate with IOP reduction. Hypotony occurred in 5 to 18% of cases, vision loss in 9 to 19% of cases. But the risk of these complications increased with long-term treatment. MP-TCP effectively lowered IOP and reduced the need for medication, with fewer significant complications than TCP.
Endoscopic cyclophotocoagulation (ECP) – another treatment for hard-to-treat adult glaucoma – had a success rate between 74 and 90%. Hypotony happened in up to 8% of cases, vision loss in up to 6%, and severe eye shrinkage in 3% of cases. ECP has shown to be promising in treating hard-to-treat glaucoma. Recent studies even proved that ECP was as effective as certain tube surgeries. It can be combined with lens removal surgery (cataract surgery) and other procedures to enhance IOP-lowering effects. Thus, ECP is an innovative procedure, making it an accessible and effective primary treatment for glaucoma worldwide, even for less advanced cases.