Injections in which medication is injected directly into the eye are called “Intravitreal injections”. This refers to the fact that the medication is injected into the vitreous cavity of the eye. The vitreous cavity is the central cavity of the eye which is filled with clear vitreous gel. Medication is injected into this compartment of the eye , because it is the most effective way to get the highest concentration of medication to the retina.
There are many conditions that are treated with intravitreal injections including wet macular degeneration, diabetic retinopathy, retinal vein occlusions and others. Please refer to the videos on this web site and the information on specific diseases to see how these injections are used for specific retinal conditions.
Everyone is intimidated, and sometimes terrified, when they hear that they have to have an injection of medication into the eye. It's hard to imagine a worse place to have an injection, but the fact is that these injections are usually tolerated very well by most patients. Most patients after receiving their first injection come back saying that they don't know why they lost so much sleep before the 1st injection.
It is important for patients requiring these injections to understand that we make every effort to use the best anesthetic possible to keep the eye comfortable and numb during the injection. Also, many patients are afraid that they will move during the injection, but this is very rare since the eye is usually very numb for the injection. If there is any feeling at all during the injection it is usually just a slight pressure sensation. Another concern patients have is that they will see the needle coming at their eye during the injection. This is not the case. The injection is given in the sclera, which is the white coating over the eye a few millimeters back from the iris and the pupil.
How is the Injection Performed?
The first step in giving an intravitreal injection is to sterilize and numb the eye. The eye is usually sterilized, after the eye has been numbed with topical anesthetic, using a dilute iodine solution. This has been shown to be the most effective way to eliminate any bacteria from the eye, and it is safer than using antibiotics which can select for resistant bacteria should an infection develop following the injection.
There are several ways to anaesthetize the eye. This can be achieved using topical anaesthetic drops or gel. Sometimes the anesthetic is soaked into a Q-tip applicator which is placed under the eyelid for 20 or 30 minutes. Another method is to perform a subconjunctival injection with anaesthetic to numb the eye prior to the intravitreal injection. All of these methods can result in excellent anesthesia. Your doctor will select the method that he feels is best for you.
After the eye has been sufficiently numbed, an eyelid speculum is placed between the eyelids to hold the eye open. There is usually minimal discomfort with this after the eye has been anaesthetize. The purpose is to keep the eyelids away from the needle during the injection. The eyelids are the most likely structure to carry bacteria which can contaminate the needle and cause an infection in the eye following the injection. Also, patients don't have to worry about reflexively closing the eye during the injection or keeping it open with the speculum in place.
The injection itself is very quick and usually only takes a second. Again, many patients feel nothing at all, but some patients can feel a quick stinging or pressure sensation which quickly goes away.
When the injection has been completed, some patients can see the medication as it swirls around and mixes in the fluid of the eye. On occasion, there may be an air bubble in the solution and patients can see a small dark bubble in the bottom of their vision for a few hours.
After an injection it is not uncommon for the eye to be slightly red and irritated for several hours. This can be relieved by using artificial tears every hour. Also, a cold compress for a few minutes every hour can also relieve these symptoms.
The two main things to avoid following an injection are getting contaminated material in the eye, such as blowing debris or unsterile water, and rubbing the eye. There is no problem with washing, either bathing or taking a shower, but we recommend keeping the eyes closed while washing.
It is important to understand that the eye should be much more comfortable within 24 hours after the injection. If there is increasing pain and/or decreasing vision more than 24 hours after the injection, it is important to call our office so that we can determine whether the patient should be seen urgently.
What are the possible side effects of an intravitreal injection?
The risk of side effects must always be weighed against the risk of not performing an injection. No one wants an injection in their eye, but the consequences of not receiving the injection are usually severe vision loss or blindness.
Minor Side Effects
1. Redness, tearing and irritation. These symptoms are common following in injection but tend to be worse in patients suffering from dry eyes. We recommend using artificial tears frequently after an injection, but in patients with dry eyes it may also help to use artificial tears frequently before an injection. If patients are experiencing severe irritation following each injection, we usually recommend that they use their artificial tears several times on the day of the injection prior to coming in for their appointment. A cold compress, such as a bag of frozen peas wrapped up in a hand towel, can be applied to the eye for a few minutes every hour. Some patients also find it helpful to take a sleep aid, such as Tylenol PM, and take a nap following the injection . Keeping the eyes closed can help to alleviate the symptoms.
2. Floaters and bubbles. It's common to see the medication mixing in the vitreous fluid for a while following the injection. This can result in temporary blurred vision and occasionally longer lasting floaters. These do not cause any permanent damage to the vision, but can be annoying. On occasion, there can be an air bubble in the medication solution and this shows up as a dark circle in the bottom of the vision for a few hours.
3. Subconjunctival hemorrhage. There are many small blood vessels in the conjunctiva, which is the white layer over the eye. It is impossible to identify all of these blood vessels when an injection is given, so it is not uncommon for a small amount of bleeding to occur under the conjunctival layer. This is very much like a bruise on the skin. These hemorrhages are almost always harmless, but can look serious, and oftentimes frighten patients by their appearance. Some or all of the white part of the eye can become red and filled with blood. This is something most people pick up by looking in a mirror or by a friend or family member noticing it. This is rarely associated with significant discomfort. These hemorrhages can be much worse if patients are taking anticoagulants such as aspirin, Coumadin, Plavix or many of the new anticoagulant medications. Like a bruise, these hemorrhages generally clear over a period of several days without treatment . A cold compress can sometimes limit the hemorrhaging.
4. Corneal abrasions. Because the eye is numb following the injection for several minutes to a half an hour, patients can sometimes rub the eye excessively without being aware that they are damaging the cornea. This can result in a corneal abrasion which can be very painful. It is extremely important not to rub the eye following the injection. The eye can be gently dabbed if tearing occurs but rubbing should be avoided until the following day.
This is generally considered the most serious complication that can occur. Fortunately, this only occurs one in every 3000 to 5000 injections. This condition is an infection of the inside cavity of the eye. It occurs when the needle used for the injection is contaminated by bacteria, usually on the eyelids or on the outside of the eye. This can also occur as a result of contamination of the medication during its preparation at the pharmacy, but this is even more rare. The two main symptoms of endophthalmitis are increasing pain and decreasing vision 24 hours or more following the injection. If these symptoms occur, we instruct our patients to call the office immediately. The outcome of treating these infections are dependent primarily on the type of bacteria that infects the eye and the speed with which it is diagnosed and treated. Unfortunately, with very virulent bacterial infections or significant delays in treatment, the outcome can be very poor and some eyes can remain totally blind.
Serious side effects
As with any medical treatment, serious side effects are possible, but rare with intravitreal injections.
This complication is even more rare, occurring in one in every several thousand patients. The primary symptom of a retinal detachment is flashing lights, increasing floaters, and a relatively rapid loss of vision. Again, these are symptoms that we recommend should be reported immediately if they occur following an injection. Fortunately, most retinal detachments can be surgically repaired.
Increased risk of strokes or heart attacks
This is somewhat controversial and is only of concern with the class of medications known as VEGF inhibitors or anti-VEGF drugs. When some of these drugs have been used in much higher doses to treat cancer, there has been a documented increase in the risk of blood clots resulting in strokes and heart attacks. However, the risk involved with the very small doses injected into the eye has not been definitively confirmed. Many doctors feel that these injections are safe even in patients that have had a stroke or heart attack.
1. How many injections will I have to have?
The number of injections depends on the response of the eye to the injections and the condition being treated. There is no predetermined number of injections when they are started. Your doctor may be able to give you an idea of how long treatment might last after he has been able to evaluate your response to the first few injections.
2. Do I need a driver when I come in for my injections?
Many patients that have good vision in the other eye are able to drive themselves in for the injection, but it is probably wise to have someone drive you in for your first injection. We recommend that patients arrange a driver when they require injections in both eyes at the same time.
3. Can I return to work the following day?
Yes, most patients have no problems returning to work on the following day.
4. Will I see the needle coming at my eye during the injection?
No. When the injection is performed, the patient is asked to look in the direction away from the area in which the injection is placed.
5. Do I have to put medicated eye drops in my eye or keep the eye covered following the injection?
No. We recommend that patients use artificial tears as needed, and whatever prescribed eye drops they have been previously prescribed as directed.