What is Siderosis Bulbi?
Siderosis bulbi is a condition where iron gets stuck in the eye, leading to changes in the eye’s structure and color over time. This can happen because of an iron-containing object that’s been in the eye for a long time, or from iron in the blood. This condition was first described by Bunge in 1890 and it has a tendency to affect parts of the eye like the cornea, iris, lens, and retina, which all originate from epithelial cells. The iron buildup in these areas can change the shape and structure of the tissues. Therefore, getting a detailed eye examination is crucial to spot this condition early. This way, people with ocular siderosis can get prompt treatment and avoid any delays that might worsen their situation.
What Causes Siderosis Bulbi?
Siderosis bulbi is a condition that happens when a foreign body containing iron is stuck inside the eye. The most common way this can occur is from an injury with a hammer and chisel, which accounts for about 41.7% to 59% of cases. Other, less noticeable incidents can also cause siderosis bulbi, such as gunshots, electric welding, nail gun accidents, explosions, and car crashes.
Risk Factors and Frequency for Siderosis Bulbi
When something foreign enters the eye, it’s often something metallic, making up 78 to 86% of all eye foreign body cases. The most common types of these metallic foreign bodies are iron and lead. This mostly happens to middle-aged men. The foreign body usually enters through the cornea (the clear front part of the eye), but sometimes, it can enter through the sclera (the white part of the eye) or the limbus (border between the cornea and sclera).
- 78% to 86% of all cases of foreign bodies in the eye are metallic, with iron being the most common, followed by lead.
- Mostly middle-aged men are affected by this.
- Usually, the foreign body enters the eye through the cornea (82.9% of cases), but it can also enter through the sclera (11.4% of cases) or the limbus (5.7% of cases).
- Once inside the eye, the foreign body is most likely to end up in the vitreous (the clear gel-like substance inside the eye) at a rate of 61%. It can also lodge in the retina (innermost, light-sensitive layer of the eye) at a rate of 14% or under the retina at a rate of 5%.
Signs and Symptoms of Siderosis Bulbi
Ocular siderosis, a condition caused by a foreign body in the eye, can be tricky to diagnose. It usually starts with a gradual decrease in vision and difficulty seeing at night. Other symptoms can include colored vision disturbances or blind spots. Several tests and symptoms can help identify this condition.
- Seidel’s test can locate an entry wound in cases of alleged open-globe injuries.
- Other signs can be swelling in the cornea, bleeding under the conjunctiva, or a hole in the iris.
- An examination with a device called a slit-lamp may show rust-colored or yellowish deposits in the cornea.
- Iron deposits in the iris may cause it to change color, which can be reversed once the foreign body is removed.
- The pupils might not react to light as expected, or they may restrict excessively when exposed to a low dose of a drug called pilocarpine. These signs can also be reversed.
- Glaucoma, a type of eye pressure, can occur due to iron deposit in the eye’s drainage system, though it’s quite rare.
- Lens damage or discoloration can occur due to the foreign body or due to iron deposits. This can also lead to a type of clouding in the eye known as a cataract.
- The retina, located at the back of the eye, can degrade due to the presence of the foreign body, and in some cases can also lead to swelling of the optic nerve. Removing the foreign body may resolve this symptom.
- Other severe complications can also occur, such as bleeding in the vitreous, retinal detachment, the formation of scar-like tissue on the retina, and swelling of the macula. An eye inflammation condition, known as uveitis can also occur.
Testing for Siderosis Bulbi
If there’s a concern that a foreign body might have entered your eye (also known as an intraocular foreign body, or IOFB), there are several methods doctors can use to confirm this and assess the damage. These methods include X-ray, CT scan, MRI, ultrasound, ultrasound biomicroscopy (UBM), and Optical Coherence Tomography (OCT). There are also specific tests like Electroretinography (ERG) that can help doctors understand how your retina has been affected.
Now, metallic or non-metallic IOFBs can appear on an X-ray, but this test alone can’t really pinpoint the exact location or nature of a foreign body. Most times, doctors prefer to use an ultrasound, which is able to detect both metallic and non-metallic IOFBs. While useful, ultrasound has its limitations too. It may not give an accurate size of the foreign body, it might miss foreign bodies located deep within your eye area, and it requires an experienced operator to perform.
The go-to test for metallic foreign bodies, however, is a non-contrast CT (NCCT) scan. This test can accurately identify what the foreign body is, where exactly it’s located in the eye, and how big it is. For non-metallic foreign bodies, MRI scans are more effective, they also provide a detailed look at the optic nerve and the soft tissue around your eye without exposing you to radiation. However, MRI scans are avoided if there’s a chance the foreign body is a ferromagnetic object— an object that’s attracted to magnets— as this could cause further damage to the eye.
Other imaging tools include ultrasound biomicroscopy (UBM) and Optical Coherence Tomography (OCT). UBM is typically used for foreign bodies in the front of the eye, while OCT is used for those in the back. But if there’s an open-globe injury – a full-thickness wound of the eye wall—UBM is avoided due to the risk of infection, whereas OCT is preferable because it’s non-invasive and more comfortable for patients.
An Electroretinography (ERG) test is central to the identification of siderosis bulbi, a condition that leads to progress vision loss due to an iron foreign body in the eye. Fluorescein angiography (FA), a type of medical imaging used to visualize the retina, can further show the damage in ocular siderosis, especially damage done to retinal circulation. Progressive visual field constriction, a symptom where you lose the periphery of your vision, is reported in advanced cases of ocular siderosis, sometimes in association with glaucomatous damage.
Treatment Options for Siderosis Bulbi
If you get injured and a small metallic object becomes lodged in your body, the doctors will first check your vaccine status and give you a tetanus booster shot if needed. They’ll also provide antibiotics to guard against common germs. It’s important to remove this foreign object as soon as possible to avoid complications like siderosis bulbi, a condition that can affect your eyes due to an iron foreign body, and endophthalmitis, an inflammation of the inner parts of your eye.
It’s usually better to do this in one surgery instead of multiple ones. Certain conditions call for instant removal, like if the foreign body is located in the front part of your eye or not contained within the retina, which is the back part of your inner eye. If surgery is delayed more than 14 days, there’s a higher risk of retinal detachment and other changes to your retina. If the foreign body is made of iron and is located in your eye lens, it may be removed at the same time as cataract surgery because the iron particles may leak out over time.
In cases of open injuries to the eye globe, immediate wound closure is essential. But sometimes, the removal of the foreign body may be postponed if the necessary equipment isn’t available or swelling of the cornea hinders surgery. The decision to delay surgery has to consider the risks and benefits of doing so.
If surgery is delayed, regular checks, including Electroretinography (ERG) testing every 2-3 months, can monitor the eyes condition. If test results remain stable, doctors might increase the gap between follow-ups. However, if the patient can’t comply with the follow-up schedule or the ERG results show decline, immediate removal of the foreign body is necessary.
In surgery, traditional methods might involve removing a metallic foreign body from the back of your eye via an external approach using an external electromagnet. However, this method comes with a higher risk of damages to your eye and is now usually saved for removing remnant foreign bodies. Nowadays, a preferred method is using an internal approach with a forceps or intra-ocular magnet, which is less traumatic. Before lifting the foreign body, perfluorocarbon liquid is used to protect the macula, the central part of the retina.
If the foreign body is in the front part of your eye, it can be removed via the limbal or scleral approach. Using a balanced salt solution or specific devices, it can be dislodged from its location. Smaller foreign bodies might need gonioscopy assistance for removal, which involves using a special contact lens to examine the part where the cornea meets the iris.
Finally, deferoxamine is a special drug that can help prevent siderosis, but it can’t repair cells that have already been damaged. Use of this drug is limited because it can cause side effects like bone issues, hearing loss, night blindness, color vision problems, and changes to the eye’s retina.
What else can Siderosis Bulbi be?
Ocular siderosis, a condition which affects the eye, can sometimes be confused with other serious eye conditions because it presents very similar symptoms. For example, retinal arteriolar narrowing and pigmentary retinal degeneration – changes to the small blood vessels in the eye and damage to the light-sensitive layer at the back of the eye – are typical signs of both siderosis bulbi and retinitis pigmentosa, a group of rare genetic eye disorders. It’s particularly tricky in rare cases when there’s suspicion of retinitis pigmentosa in just one eye. In such cases, a history of trauma involving an iron foreign body can steer a diagnosis towards ocular siderosis.
Another eye condition, Adie’s tonic pupil, can also mimic ocular siderosis. This is due to a common symptom – mydriasis, which is an abnormal dilation of the pupil. Plus, in cases of ocular siderosis, there’s an exaggerated reaction to the drug pilocarpine. Both conditions harm the eye’s nervous system, but the damage occurs in different areas. In Adie’s tonic pupil, the problem is with the ciliary ganglion, a part of the nervous system in the mid-brain, whereas in siderosis bulbi, it’s local parasympathetic neuropathy, a type of nerve damage that occurs in the eye itself.
What to expect with Siderosis Bulbi
There are a number of factors that might lead to a worse outcome after an eye injury. These include being younger, having a large foreign body in the eye (average length= 5.7mm) with high energy, having vision weaker than 20/200 at the time of injury, retaining the foreign body for a long period, having the foreign body located in the back of the eye, and presenting with other symptoms such as a blood-filled front part of the eye (hyphema), bleeding in the jelly-like substance that fills the eye (vitreous hemorrhage), retinal detachment or infection within the eye (endophthalmitis).
Having multiple surgeries can also lead to increased health problems. There’s a tool known as the Ocular Trauma Score (OTS), developed by Kuhn and his team. This tool can be used to predict the outcome and the likely vision quality for penetrating eye injuries.
The length of the wound where the object entered the eye also plays a role in determining the risk of damage to the retina. Shorter wounds result in less energy dissipation, which allows for deeper penetration into the eye, leading to significant damage to the retina. Blunt foreign bodies cause more damage to the eye compared to sharp foreign bodies of the same size, due to the greater transfer of energy at the time of impact.
Possible Complications When Diagnosed with Siderosis Bulbi
Intraocular foreign bodies (IOFB) can lead to various complications often associated with an open-globe injury—a kind of eye injury where the outer layer of the eye gets wounded. The most harmful complication following eye trauma is endophthalmitis, which is an inflammation within the eyeball. In the absence of IOFB, around 2.1% to 11.9% of people with an open-globe injury develop post-traumatic endophthalmitis. However, if an IOFB is present, it accounts for about 3.8% to 48.1% of endophthalmitis cases. Factors that contribute to a poor prognosis include increase in harmful organisms, associated tissue damage, and delay in treatment.
Another complication that can threaten sight from an open-globe injury is Sympathetic Ophthalmia (SO). It is a bilateral, or both eyes, inflammation inside the eye that usually follows an eye trauma or surgery that has caused a penetrating wound. The incidence of SO is reported between 0.28-1.9% in penetrating ocular trauma.
IOFB can also lead to several complications in the front part of the eye, such as hyphema (blood in the front part of the eye), traumatic cataract, rupture of the lens capsule, dislocation of the lens, and secondary open-angle glaucoma (a condition that damages the optic nerve).
There are also chances of Siderosis Bulbi, a condition related to the presence of iron foreign body in the eye, that can also lead to optic nerve damage and cystoid macular edema (swelling in the central part of the retina). There’s also a higher risk of epiretinal membrane (a thin layer of fibrous tissue that can develop on the surface of the retina) formation leading to a condition where the retina folds, causing Proliferative Vitreoretinopathy (PVR) and retinal detachment.
Common complications:
- Endophthalmitis
- Sympathetic Ophthalmia (SO)
- Hyphema
- Traumatic cataract
- Rupture of the lens capsule
- Dislocation of the lens
- Secondary open-angle glaucoma
- Siderosis Bulbi
- Optic nerve damage
- Cystoid macular edema
- Epiretinal membrane formation
- Retinal folds (Macular Puckering)
- Proliferative Vitreoretinopathy (PVR)
- Retinal detachment
Preventing Siderosis Bulbi
We need to increase public awareness about eye injuries that can happen at the workplace, as prevention is critical to avoid dangerous complications. There are two main medical concerns we want to avoid: penetrating ocular injuries, which means a serious injury that enters the eye, and siderosis bulbi, a condition where iron particles get into the eye and causes damage.
If people understand the serious consequences of siderosis bulbi, they might be more motivated to protect their eyes at work. This can include safety measures like wearing protective glasses, eye goggles, or face shields.
Patients also need to be aware of the possible complications if they have trauma to the eye that results in an open-globe injury (which means the outer shell of the eye gets damaged) or siderosis bulbi. They should understand that the long-term outcome or prognosis can be affected by these conditions and how important it is to have regular check-ups with their eye doctor.
