What is Aniridic Fibrosis Syndrome?
Aniridic fibrosis syndrome, first discovered by Tsai and his colleagues in 2005, is a rare condition that can occur in people who are born with aniridia – a condition where the iris is either partially or fully absent. This syndrome usually happens as a side effect of certain eye surgeries, particularly when a lens is implanted in the eye during cataract surgery. It’s characterized by a growing membrane inside the front part of the eye after surgery, which can mess up the placement of the implanted lens and lead to other issues in the retina. It usually affects patients who’ve undergone multiple eye surgeries due to complications from their congenital aniridia. So far, it’s been reported in a total of seventeen cases ranging in age from 8 months to 71 years.
When someone has aniridia, they lack an iris, which is the part of the eye that regulates the amount of light that gets in. This condition can either be inherited or occur spontaneously and is often linked to other eye problems, such as foveal hypoplasia and nystagmus, which may require surgical treatment. Other common eye issues associated with aniridia include glaucoma, cataracts, keratopathy, and optic nerve coloboma with possible hypoplasia. Because of these additional complications, individuals with aniridia often have poor vision, usually between 20/100 to 20/200, with foveal hypoplasia being the biggest factor limiting their visual acuity. Aniridia is usually caused by various mutations in the PAX6 gene, and the specific mutation can significantly affect the physical characteristics observed and resulting conditions. These PAX6 gene mutations are frequently part of well-known clinical syndromes, such as WAGR or WAGRO, but other genetic mutations and sporadic cases can also cause aniridia.
What Causes Aniridic Fibrosis Syndrome?
The exact cause of a disease called aniridic fibrosis syndrome is not known yet. This disease, which causes gradual tissue thickening, seems to only happen in people who were born with a condition called aniridia and have had eye surgery, especially when an artificial device is implanted in the eye. However, it’s not always the case that they’ve had this kind of surgery.
The tissue thickening seems to start from the part of the eye where the iris – the colored part of the eye – should be. It often first shows up around the intraocular lens, a kind of implant in the eye. This thickening gradually moves forward to cover the entire front part of the eye. If no surgical intervention is done, it may also move backward to cover the ciliary body – a part of the eye that produces the transparent fluid in the front of the eye – and the front part of the retina – the layer at the back of the eye that senses light.
Scientists are still unsure about what factors increase the risk of getting aniridic fibrosis syndrome. This is largely due to the limited number of cases reported. But interestingly, out of the seventeen cases that have been reported, 88% were female. In an initial study, all patients had undergone cataract surgery; most of them had acrylic intraocular lens implanted, and several had implants for draining fluid to treat glaucoma. Additionally, several patients had a history of cornea transplant combined with limbal stem cell transplantation. Similar potential risk factors were also found in other reports. So, the use of implantable devices, multiple surgeries, and being female may increase the risk of getting the disease.
Scientists might identify additional contributing risk factors as more cases are reported. These might be linked to specific surgical techniques, other types of implantable devices, or any unknown genetic mutations that make a person more susceptible to the disease.
Risk Factors and Frequency for Aniridic Fibrosis Syndrome
Congenital aniridia, a rare eye condition, is estimated to occur between 1 in 64,000 and 1 in 100,000 people. Currently, we don’t have much data on how often congenital aniridia leads to a condition known as “aniridic fibrosis syndrome.” In one study, it was observed in roughly 4.5% of the cases, which equated to seven out of 155 aniridia-affected eyes.
Signs and Symptoms of Aniridic Fibrosis Syndrome
Aniridic fibrosis syndrome is a condition that typically leads to a baseline reduction in a person’s best-corrected vision. This means that even with eyeglasses or contact lenses, individuals with this syndrome may have poorer vision than normal. Often, people with this syndrome might only seek medical help when they notice a further decrease in their visual ability. On examining the eye, the doctor might find a fibrous membrane growing from the iris residue. Since people with this syndrome are generally used to having poor vision, they might put off seeing a doctor.
As time passes, the membrane can continue to grow and may begin to affect parts of the eye like the Intraocular Lens (IOL), the ciliary body (a part of the eye that produces the transparent liquid inside the eye), and the retina (the part at the back of the eye that receives light). These changes can make the membrane more visible during an eye examination. Another potential symptom of aniridic fibrosis syndrome is endothelial decompensation, which is a degradation or weakening of the inner layer of cells in the cornea.
Testing for Aniridic Fibrosis Syndrome
If a patient is diagnosed with Aniridic Fibrosis Syndrome, it means they already have a condition known as aniridia and have likely undergone several eye procedures. Despite improvements in genetic testing that can help identify different causes of aniridia, there is currently no test or clinical study that shows whether a patient might develop complications from surgery related to scarring.
The diagnosis of this disease is made based on a doctor’s examination and observing certain key signs or symptoms in a patient. Regular eye checks, particularly of the front part of the eye and eye pressure, are critical for early detection of any related health problems. Several different types of eye exams, including slit lamp exams, gonioscopy, and indirect ophthalmoscopy, can help evaluate how much scarring has occurred. As this fibrous tissue continues to develop, a patient’s vision often deteriorates over time.
Treatment Options for Aniridic Fibrosis Syndrome
Aniridia, a condition characterized by a lack of an iris in the eye, is usually managed with medication at first. But over time, surgery becomes a necessity for preserving or improving vision, and for cosmetic reasons. Unfortunately, this surgical intervention can sometimes lead to a condition known as aniridic fibrosis syndrome.
Experts recommend routine checks and early surgery when aniridic fibrosis syndrome arises. Early surgical interventions are crucial to maintain vision, as a fibrous membrane within the eye could continue to grow, and exacerbate other eye problems. This recommended surgery includes penetrating keratoplasty (which replaces part of the cornea) and membranectomy with PCIOL explantation or exchange (to remove a fiber-like tissue in the eye).
After surgery, it’s crucial that patients have their condition closely monitored because fibrosis (or a buildup of fibrous tissue) may come back. It has been reported that this happened in 40% of aniridic fibrosis syndrome patients who had a membranectomy with PCIOL exchange procedure. However, no recurrence was seen when the intraocular lens (IOL) was removed.
Before surgery, it may be beneficial to consider reducing the number of devices inside the eye. For example, the Boston KPro type 1, a specific kind of artificial cornea, has been found to improve vision without any recurrence of the fibrous membrane in patients with aniridic fibrosis syndrome. The success of the device is thought to be due to its placement away from the root of the iris, which is believed to be the area causing the fibrosis.
Finally, certain issues related to fibrous overgrowths, like retinal detachment, can be addressed with additional surgical procedures if needed.
What else can Aniridic Fibrosis Syndrome be?
When doctors suspect a patient may have a condition called aniridic fibrosis syndrome, they need to consider some other conditions that could appear similar. These include:
- Diseases caused by the same (PAX6) genetic mutation
- Diseases related to aniridia, a condition where the iris (the colored part of the eye) is completely or partially absent
- Other conditions that lead to the formation of unwanted or unnatural tissues behind the cornea or inside the eye
One such condition is Peter anomaly, which is also linked to mutations in the PAX6 gene and can cause similar fibrous growth in the eye, especially after surgery.
Another condition to consider is Iridocorneal Endothelial Syndrome (ICE), which can also cause strange tissue growths inside the eye. However, ICE can often be differentiated from aniridia-based conditions using a technique called specular microscopy, which allows the doctor to see the cells of the cornea clearly.
Doctors should also consider other, unidentified causes of strange tissue growth around artificial lenses placed in the eye, which have been reported in the medical literature.
Finally, an inflammatory response caused by chronic uveitis (a form of eye inflammation) following cataract surgery could create a membrane-like structure around the artificial lens in the eye, similar to aniridic fibrosis syndrome.
What to expect with Aniridic Fibrosis Syndrome
The outlook for patients with a condition called aniridia, which affects vision, is often not good and may result in reduced eyesight. However, it’s important to note that the outlook can improve significantly for patients who have aniridia-related fibrosis syndrome if it’s identified early and treated promptly. In such cases, their eyesight can improve to match what it was before developing aniridia, as long as there are no other complicating factors.
Possible Complications When Diagnosed with Aniridic Fibrosis Syndrome
As mentioned earlier, there’s a chance that the fibrous growth may come back after the surgical removal of membrane. However, no such recurrence has been observed in patients who underwent surgery for intraocular lens (IOL) extraction or had Boston KPro type 1 implants. Aniridia, the underlying condition, often comes with many associated health issues, including systemic symptoms. These can have a significant impact on a person’s quality of life.
Preventing Aniridic Fibrosis Syndrome
People who have aniridia, a condition that affects the eyes, will likely need to have eye surgery to restore or enhance their vision. Following surgery, some may experience the growth of fibrotic membranes, a type of scar tissue, which can harm the inside of the eye and reduce sharpness of sight. Therefore, those with aniridia should be advised to keep in regular contact with their eye doctor and schedule frequent checkups.
