What is Hyperbaric Oxygen Therapy and Associated Cataracts?
Hyperbaric oxygen therapy (HBOT) is a treatment that involves breathing in 100% oxygen in a pressurized environment. It has some rare drawbacks, one of them being that it can lead to the development of cataracts. Cataracts cause a clouding on the lens of the eye, which can significantly impair vision and could even lead to severe blindness. The most common type of cataracts is nuclear cataracts, which affect the center of the lens and are usually found in older people.
While the exact reason behind the development of cataracts is not fully known, recent research suggests that exposure to oxygen throughout one’s life is a primary contributing factor. This is especially important as we age and the glassy substance in our eyes deteriorates, allowing more oxygen to reach the lens.
If a patient undergoes more than the average 20 to 50 sessions of HBOT treatment, it might result in permanent changes to the lens and possibly cataracts. According to expert opinion, this is likely due to oxidative damage to proteins in the lens. In experiments with guinea pigs exposed to hyperbaric oxygen, researchers found that these animals had twice as many protein clusters in the lens compared to control animals. Similar protein clusters have been noted in human cataracts.
Certain symptoms have been associated with oxygen toxicity in the eye, which could result in myopia (nearsightedness) and the development or worsening of cataracts. Symptoms reported include twitching eyelids, blurred vision, and disturbances in the visual field. Researchers propose that oxygen could cause the proteins in the eye to bond together into larger clusters capable of scattering light. This is similar to what happens with human nuclear cataracts, and may be the final stage of the often-reported “myopic shift” seen in a majority of patients after 20-30 sessions of HBOT. Even though nearsightedness usually improves after a few days or months once the treatment is stopped, cataracts are typically permanent and might require lens replacement surgery.
What Causes Hyperbaric Oxygen Therapy and Associated Cataracts?
The exact reasons why cataracts form aren’t entirely known. It’s thought that there are several factors at play. As people get older, their eye lens (the transparent structure behind the pupil that helps focus light onto the retina) undergoes changes, and they might experience more damage to this lens over time due to “oxidative” harm, which is damage from harmful molecules called free radicals.
Some changes that can occur include:
* The lens becoming heavier, thicker, and less flexible (or what doctors call “accommodative”).
* The centre (“nucleus”) of the lens becoming harder and more compressed as new outer layers, or “cortical layers,” are added. This is known as “nuclear sclerosis.”
* The lens becoming less transparent because the density of the cells making it up decreases and there’s abnormal development of the fibers that make up its structure.
* The speed at which water, as well as small water-soluble molecules, can reach the centre of the lens via surrounding cells lowers, leading to less transport of water, nutrients, and antioxidants.
Recent studies hint that exposure to oxygen throughout one’s life, and especially the increased amount of oxygen reaching the lens with age, are significant factors in developing cataracts. For example, patients who go through hyperbaric oxygen therapy (HBOT is a treatment involving breathing pure oxygen in a room or tube under high pressure) often develop a specific type of cataracts and temporary short-sightedness, which implies that oxygen-related damage to proteins in the lens might occur.
Things that can increase the risk of cataracts include getting older, smoking, drinking alcohol, exposure to ultraviolet light, having diabetes, long-term use of steroids, and malnutrition.
Risk Factors and Frequency for Hyperbaric Oxygen Therapy and Associated Cataracts
Many clinical records have reported the development of reversible short-sightedness, or myopia, during hyperbaric oxygen therapy (HBOT). About 75% of patients go through this change. This short-sightedness is more noticeable when a hood system is used instead of a mask that covers the mouth and nose. Permanent changes like cataracts are rarely seen, but when they do occur, it’s usually after more than 100 therapy sessions. One study showed that out of 15 individuals with clear vision at the start of treatment, 7 developed cataracts after 150 or more therapies. However, it’s important to note that all patients experienced temporary myopia.
A study with fewer treatments – just 40, which is closer to the common number – still showed slight changes to the lens. A yet-to-be-published trial study is underway comparing the short-sighted changes in patients who received oxygen through either a hood or mask. This study also anticipates that about 2% of the 120 patients who underwent 20 to 40 treatments will develop cataracts, suggesting that the actual occurrence of cataracts may be underreported. The reason for this could be that the short-sightedness in many patients can last for several weeks, which might overlook the development of cataracts by the HBOT. Hence, cataracts may only be diagnosed long after the treatment. Also, there’s an idea that HBOT might speed up the development of early cataracts that were already present before treatment began.
Signs and Symptoms of Hyperbaric Oxygen Therapy and Associated Cataracts
If you’re going to have hyperbaric oxygen therapy (HBOT), a common procedure is to have your eyes checked. This is especially important if you have a history of cataracts or vision loss. People with cataracts typically see a gradual decline in their sight and have problems seeing at night or up close. Here are a few key symptoms:
- A decrease in visual acuity (sharpness)
- Sensitivity to bright lights
- Near-sightedness as the cataract gets worse
- Double vision in one eye, which can’t be corrected with glasses, prisms, or contact lenses. This is due to changes in the eye’s lens, which can cause a “lens within a lens” effect
Even without any apparent vision problems, medical professionals should check your eyesight before and after you have HBOT. If you notice your vision getting worse or remain nearsighted for 10 to 12 weeks after treatment, you might need added check-ups or a specialist’s opinion. A detailed eye test can identify changes in the opacity of the lens and guide the planning for future treatments. A cataract might look like a cloudy or yellowish lens when checked, but even with HBOT, the lens might still appear normal despite potential hidden changes.
Testing for Hyperbaric Oxygen Therapy and Associated Cataracts
Before starting hyperbaric oxygen therapy (HBOT), your doctor will want to measure how well you can see. While some doctors might refer you to an eye specialist, most commonly, you will undergo a simple vision test using what’s called a Snellen chart, a tool to assess your visual acuity (sharpness). This vision test is repeated after your therapy, or if you report any changes in your vision while undergoing treatment.
If you experience symptoms, your doctor may conduct a non-dilated eye exam. This exam might reveal abnormalities such as dark spots, cloudiness, or disruptions in the glowing reddish-orange reflection seen during an eye exam, known as the red reflex.
Depending on these results, your doctor might then carry out a more thorough eye exam to evaluate the severity and type of lens cloudiness, symptoms typical of cataracts. They may also perform a dilated eye exam to check for any other conditions affecting your vision. This would rule out any concerns that might prevent complete restoration of vision following cataract surgery.
It is rare to diagnose cataracts during or within weeks of completing HBOT. However, doctors will consider the possibility of cataracts if a condition called a myopic shift, where you become more short-sighted, continues beyond 2 to 3 months of your HBOT treatment. It’s important to note that though uncommon, the slow development of cataracts is a recognized, but rare, side effect of HBOT.
Treatment Options for Hyperbaric Oxygen Therapy and Associated Cataracts
If your vision becomes more nearsighted after stopping Hyperbaric Oxygen Therapy (HBOT), a treatment where you breathe in pure oxygen in a pressurized environment, it’s best to wait and see if it improves. You can use temporary glasses to help with everyday tasks while you are waiting for your vision to improve. If the changes to your vision are significant, you should see an eye specialist for further examination.
If your vision doesn’t get better after 10 to 12 weeks, a detailed eye checkup might reveal that you have a cataract, which is a cloudy area in the lens of the eye. In these situations, the cataract might need to be surgically removed, and replaced with an artificial lens.
Before starting HBOT, your doctor should inform you about the possibility of experiencing changes in your nearsightedness and the potential development of cataracts. If you already have early-stage cataracts, be aware that they may likely progress more quickly during and after HBOT.
What else can Hyperbaric Oxygen Therapy and Associated Cataracts be?
If you’re going through Hyperbaric Oxygen Therapy (HBOT) and you notice that your vision is getting worse, it’s important for your healthcare provider to do a thorough check. This is to make sure that the decline in your vision is not due to other, more common reasons. Sudden loss of vision over a very short period—like within a few minutes or hours—is a serious situation that needs immediate attention. An eye specialist should check for the usual causes of sudden sight loss, such as:
- Blockage of the blood vessels in the retina (retinal arterial occlusion or retinal venous occlusion)
- Stroke in the brain (cerebral stroke)
- Separation of the retina from the back of the eye (retinal detachment)
- Bleeding into the jelly-like substance that fills the back of the eye (vitreous hemorrhage)
Possible Complications When Diagnosed with Hyperbaric Oxygen Therapy and Associated Cataracts
The complications that arise from cataract treatment due to Hyperbaric Oxygen Therapy (HBOT) mainly include difficulties during lens replacement surgery. These challenges pose a risk of inflammation of the middle layer of the eye and both infectious and non-infectious inflammation of the inside of the eye following the operation, as well as longer-term complications.
Some problems that may arise during the surgery include:
- A shallow or flat front part of the eye
- Tearing of the lens capsule
- Bleeding or fluid in the layer between the retina and the white outer layer of the eye
- Bleeding that pushes the retina forward
- Leftover lens material
- Disruption of the jelly-like substance that fills the eye
- Tearing of the iris
- Light-induced damage to the retina
Immediately following surgery, patients might experience:
- Painful inflammation of the eye
- Displacement or incorrect positioning of the artificial lens
- Swelling of the cornea and the macula
- A condition that causes inflammation and clouding in the front part of the eye
- Obstructed blood vessels in the retina due to the use of intraocular vancomycin
It’s important to note that using vancomycin as prevention against post-surgical inflammation of the eye during cataract surgery is generally not advised. Other possible issues include a flat or shallow front part of the eye due to a leak in the surgical wound, retina detachment, and a drop in eye pressure, among other complications.
Long-term complications that may occur following surgery can involve:
- Warped or irregular shape of the eye caused by surgical stitches
- Detachment of the retina
- Clouding of the lens capsule
- Deterioration of the macula
- Seizure of the pupil
- Blackening of the iris
- Chronic inflammation of the middle layer of the eye
- Chronic inflammation inside the eye
- Incorrect power of artificial lens
Preventing Hyperbaric Oxygen Therapy and Associated Cataracts
Getting older is the main reason why people develop cataracts. Doctors also think that being in a hyperbaric environment (a place with more oxygen than normal) might speed up the process of these age-related cataracts. It is important to think about this risk if you are considering hyperbaric oxygen therapy (HBOT). Generally speaking, the risk is small if you are only having hyperbaric therapy for a short time, especially if it is fewer than 40 sessions. No evidence shows that a single session of HBOT can affect vision.
If someone is having a lot of HBOT sessions, eye doctors should check their vision and work out what is causing any vision problems, especially if the person reports continuous changes to their vision for more than 2 to 3 months after finishing HBOT.