Overview of Intravitreal Implants

Intravitreal implants are a treatment method for diseases impacting the back part of the eye. These implants are designed to release medication gradually and for a longer period of time. The advantage of this method is that it directly delivers the drug to the eye’s inner part, bypassing the body’s system and concentrating the drug where needed.

There are two types of intravitreal implants – non-biodegradable and biodegradable. Non-biodegradable implants can release their medication more evenly and last longer. However, as they do not break down, they need to be surgically removed or replaced. They are also larger, requiring a bigger incision for insertion. Materials used for these include ethylene vinyl acetate, polyvinyl alcohol, or polysulfone capillary fiber. Vitrasert and Retisert are popular non-biodegradable implants.

On the other hand, biodegradable implants have the advantage of not needing surgical removal or replacement. They break down over time and leave the body completely. Materials like polylactic acid or polyglycolic acid are used to make these implants. An example of a biodegradable implant is a steroid implant containing dexamethasone called DEX Implant (Ozurdex).

Anatomy and Physiology of Intravitreal Implants

The barrier between your blood and your eye, simply known as the blood-ocular barrier, is made up of two parts: the blood-aqueous barrier and the blood-retinal barrier. The blood-retinal barrier has two sections – an inner and an outer barrier. The inner section involves a network of tight junctions between tiny blood vessels known as endothelial cells in the retina. The outer now involves something known as retinal pigment epithelium, which is a layer of cells in your retina.

These barriers can limit how much of a medicine actually reaches the deeper part of the eye. One way to bypass these barriers is to inject the medicine directly into the vitreous, the jelly-like substance in the eyeball. This can provide a high concentration of medicine exactly where it’s needed, with less risk of side effects elsewhere in the body. The drawback is that these injections don’t last very long, so they have to be done frequently.

To tackle this problem, doctors can turn to something called intravitreal implants. These are small devices that are implanted into the eye, where they can steadily release medicine over a longer period. This means the eye keeps receiving the medicine it needs, without the constant need for injections.

Why do People Need Intravitreal Implants

Different types of implants can be put inside the eye to treat various eye conditions. Some of these implants are non-biodegradable and some are biodegradable. Non-biodegradable means they don’t break down naturally in the body, while biodegradable ones do.

Non-biodegradable implants:

1. Ganciclovir (Vitrasert) is an implant that has been approved by the FDA for treating a type of eye infection affecting people with AIDS, called retinitis by the cytomegalovirus (CMV). The implant allows a slow release of the medicine in the eye for about 5 to 8 months.

2. Fluocinolone Acetonide is used in implants like Retisert, which is used to treat chronic non-infectious inflammation in the back of the eye, also known as uveitis. It is also used in Iluvein and Yutiq, which are being studied for other eye inflammation conditions and diabetic macular edema, swelling in the center of the retina caused by diabetes.

3. Triamcinolone Acetonide (I-vation) is a implant used to treat diabetic macular edema.

4. Ranibizumab Port Delivery System (PDS) is a unique implant that releases medication to treat a condition called neovascular AMD, in which new blood vessels grow and leak fluid, causing vision loss. This implant can be refilled with medication.

Biodegradable implants:

1. Dexamethasone (DEX implant) is used to treat swelling in the retina caused by retinal veins being blocked, non-infectious uveitis, and diabetic macular edema.

2. Verisome delivers different treatments such as anti-inflammatory drugs or steroids for up to a year. It treats chronic fluid build-up in the center of the retina due to blocked retinal veins and neovascular AMD.

The FDA has approved the DEX Implant for dealing with diabetic macular edema in several situations including eyes undergoing cataract surgery, pseudophakic (artificial lens) patients, people who recently had a stroke or heart attack, and others.

When a Person Should Avoid Intravitreal Implants

There are certain circumstances when specific treatments for eye conditions should not be used, because they could cause harm. This is known as a contraindication. For instance, Vitrasert shouldn’t be used if the patient has an eye infection, a torn or detached retina, or is allergic to medications called acyclovir or ganciclovir. This treatment also shouldn’t be used alongside a particular medication given through a vein called cidofovir.

Similarly, treatments involving tiny devices placed into the eye that slowly release steroids, also known as intravitreal implants, should not be used in patients with allergies or infections around or in the eye, which could include viral, bacterial, or fungal infections. They should also not be used in glaucoma patients who have a significantly enlarged ‘cup’ (a particular part of the eye) compared to the ‘disk’ (another part of the eye). A specific type of this treatment, called a DEX implant, should also not be used in patients with certain eye conditions, such as a torn posterior capsule, lack of a certain part of the eye, or eyes where the lens is fixed in place by a surgeon. This is because the implant could possibly move into a part of the eye called the anterior chamber.

Ranibizumab PDS is another treatment that has a list of situations where it shouldn’t be used. These include in patients with infections around or in the eye, cases of eye inflammation, allergic reactions to the medication itself, or a recent history of heart attack or stroke. It should not be given to pregnant individuals and should be used with caution in those with severe kidney disease or those who are on dialysis for kidney failure.

Equipment used for Intravitreal Implants

Before any procedure is done, doctors must ask for your permission, which is also referred to as informed consent. The procedure might be carried out in the doctor’s office under strict cleanliness rules, but a more complicated and lengthy procedure may need to be done in an operating room.

In both cases, it’s crucial that everything is done in a clean, germ-free manner. This involves steps like cleaning hands properly, putting on sterile gloves, using a clean device called an eyelid speculum that helps keep your eye open, and applying a solution which kills germs, to your eye.

The tools used may change depending on the specific type of procedure being performed inside your eye, technically known as an intravitreal implantation. Items that may be needed include a clean cloth that covers the area around the eye, scissors for cutting this cloth, the eyelid speculum as mentioned above, measuring instruments known as calipers, a type of tweezer called toothed forceps, clean cotton buds, sterile syringes and needles, tubes for making incisions in the white portion of the eye, a blade for cutting into the white part of the eye, and materials used for stitching up any incisions made.

How is Intravitreal Implants performed

Before starting a certain kind of eye procedure, the medical team does a ‘time out’ to make certain they have the correct eye and the right implant for the surgery, and that the implant has not expired.

The patient is then prepared for the procedure. They’ll lie on their back in a comfortable position, with their head kept steady. The type of anesthesia or numbing medicine used will depend on the size of the implant; larger implants might require local or general anesthesia, which means you might be asleep or partly asleep for the procedure. For smaller implants, anesthesia is usually applied directly to the surface of the eye. Some doctors also prefer to inject anesthesia into the space underneath the white of the eye.

The doctors will then sterilize the eye area using a solution called povidone iodine. They’ll put anesthetic drops on your eye to numb it, along with povidone-iodine drops in the lower part of the eye to clean it. After that, a sterile device called a speculum is placed in the eye to keep it open during the procedure.

The next step is to mark the injection site, the exact location depends on the status of your eye lens: If you still have your own lens (phakic), an artificial lens (pseudophakic), or no lens (aphakic), different distances from the center of the eye are recommended for the injection site.

Once everything is ready, the eye implant is inserted. The method of insertion depends on the kind of implant. Some implants are inserted into a cavity within the eye after making a small cut in the outer layer of the eye. Other smaller implants are injected through a thin needle into the same cavity. Yet another type of implant is surgically secured at a certain part of the eye. Some implants require creating a small incision or hole in the eye through which the implant is inserted. It varies depending on the specifics of the implant.

After the implant is inserted, the doctors will check to ensure it is correctly positioned inside the eye using a special instrument called an indirect ophthalmoscope. At the end of the procedure, the eye speculum is removed, more povidone-iodine drops are applied and the eye is gently covered with a patch for about an hour.

Possible Complications of Intravitreal Implants

If you get an implant placed inside your eye, you might experience some complications afterwards. These can include issues such as increased redness of the white part of your eye, blood clots in the eye, loss of the clear gel inside the eye, low eye pressure, or detaching of layers in the eye. You might also unintentionally touch the lens inside your eye during surgery, have inflammation inside your eye, or have your wound reopen.

A specific type of eye implant, called NBI, might require several surgeries for insertion, replacement, or removal and can lead to higher chances of post-surgery complications. This could include swelling and infection inside the eye, clouding of the eye, bleeding, cataracts, and detachment of the retina, the light-sensitive tissue at the back of your eye.

Other specific implants such as Vitrasert can cause a layer of scar tissue to form over your retina, while Retisert can have its main components come apart causing vision problems. A type of implant called BI might also release its drug too quickly during the final stage of the implant. This could lead to complications due to drug toxicity. BI can also obscure vision, and their movement in front of the retina or anterior chamber is a possible complication.

Steroid eye implants might increase eye pressure which can lead to glaucoma (a serious eye condition that can cause vision loss) or speed up cataract development. These implants can also move into the front part of your eye and cause damage to the corneal endothelium, the thin tissue covering the front of your eye.

An implant called Ranibizumab PDS may lead to complications such as inflammation or retinal detachment, the relocating of the implant, septum displacement, bleeding, wear and tear of the tissue, and bubble formation.

Once implants are inserted, it’s crucial to have regular check-ups to monitor how well the treatment is going and to spot any complications early on. Usually, these visits are every 4 to 6 weeks. At each appointment, eye doctors make sure to check your vision, measure your eye pressure, look for reactions in the front part of your eye and check for cataract progression. They also utilize tools like optical coherence tomography (OCT) – which provides an image to check your eyes, OCT angiography – which looks at the blood flow in your eye, and fundus fluorescein angiography – which uses a special dye to look at blood circulation in the eye – to assist in monitoring your condition and treatment response.

What Else Should I Know About Intravitreal Implants?

Eye implants come with several benefits. Here are some notable ones:

First, they enable medication to bypass a certain barrier in the eye, allowing for more drug to directly reach the inner part of the eye compared to when the drug is given through the entire body.

Second, since the drug is delivered closer to the specific part of your eye that needs it (the retina and vitreous), it helps to reduce side effects on other body parts.

Third, these implants provide a longer-lasting way to get the needed drugs into your eye.

Fourth, they can deliver drugs that can’t be given by other methods or in circumstances where it’s hard for patients to stick to their medication schedule.

Fifth, if there are any negative side effects, the drug can be quickly removed from the eye. This is different from drugs given through an injection into the eye.

Finally, these implants protect drugs that don’t last long in the body and typically require frequent doses.

Because the drug is delivered straight to the eye, a smaller dosage is needed, which means you no longer have to take a drug for the entire body, or the dose of such a drug can be reduced significantly. This makes treatment safer due to fewer side effects and can last longer.

Frequently asked questions

1. What type of intravitreal implant will be used for my treatment? 2. How long will the implant release medication in my eye? 3. Are there any contraindications or situations where the implant should not be used? 4. What are the potential complications or side effects associated with the implant? 5. How often will I need to come in for check-ups to monitor the implant's effectiveness and any potential complications?

Intravitreal implants can provide a steady release of medicine into the eye over a longer period of time. This means that you will not need frequent injections and the medicine will be continuously delivered to the eye, ensuring that it receives the necessary treatment without the risk of side effects in other parts of the body.

You may need intravitreal implants if you have certain eye conditions that can be treated with this method. However, there are certain contraindications and situations where intravitreal implants should not be used. These include allergies or infections around or in the eye, glaucoma with a significantly enlarged cup, certain eye conditions such as a torn posterior capsule or lack of a certain part of the eye, and eyes where the lens is fixed in place by a surgeon. It is important to consult with your healthcare provider to determine if intravitreal implants are appropriate for your specific situation.

Intravitreal implants should not be used in patients with allergies or infections around or in the eye, including viral, bacterial, or fungal infections. They should also not be used in glaucoma patients who have a significantly enlarged 'cup' compared to the 'disk'.

To prepare for Intravitreal Implants, the patient should lie on their back in a comfortable position, with their head kept steady. The type of anesthesia or numbing medicine used will depend on the size of the implant. The doctors will then sterilize the eye area using a solution called povidone iodine and put anesthetic drops on the eye to numb it.

The complications of Intravitreal Implants include increased redness of the white part of the eye, blood clots in the eye, loss of the clear gel inside the eye, low eye pressure, detaching of layers in the eye, unintentional touching of the lens inside the eye during surgery, inflammation inside the eye, reopening of the wound, swelling and infection inside the eye, clouding of the eye, bleeding, cataracts, detachment of the retina, formation of scar tissue over the retina, components of the implant coming apart causing vision problems, release of the drug too quickly leading to drug toxicity, obscuring of vision, movement of the implant in front of the retina or anterior chamber, increased eye pressure leading to glaucoma or cataract development, damage to the corneal endothelium, inflammation or retinal detachment, relocating of the implant, septum displacement, wear and tear of the tissue, and bubble formation. Regular check-ups are crucial to monitor the treatment and spot any complications early on.

The symptoms that require Intravitreal Implants include chronic non-infectious inflammation in the back of the eye (uveitis), diabetic macular edema (swelling in the center of the retina caused by diabetes), retinal swelling caused by blocked retinal veins, and neovascular AMD (new blood vessels growing and leaking fluid, causing vision loss). These symptoms can be treated with different types of implants, both non-biodegradable and biodegradable, that release medication slowly into the eye.

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