What is Posterior Polar Cataract?
A Posterior polar cataract (PPC) is a special type of cataract you’re born with that is difficult for eye doctors to operate on. One of the reasons for this challenge is because there’s a high chance of complications during surgery, such as tearing of the back part of the lens called the posterior capsule, and loss of lens (aphakia). People with PPC have a pre-existing thin posterior capsule, and the cataract adheres strongly to it, making the capsule weak.
PPC can be inherited from your parents; however, it can also appear randomly without any family history. Researchers have found a connection between five genes and PPC. A PPC looks like a round disc-shaped onion ring that is formed from abnormal lens fibers. It can also appear at the end of a remnant of the hyaloid artery, which is a vessel in the eye, or as a benign form of Mittendorf dot, which is a small dot on the front of the lens.
During a PPC surgery, the main goal is to safely remove the cataract without tearing the capsule. This often requires taking the stress off the posterior capsule during the operation. While there are many surgical procedures suggested to handle this unique condition, finding a method that is successful without causing any complications continues to be a challenge for many surgeons.
What Causes Posterior Polar Cataract?
Experts believe that PPC, or posterior polar cataract, comes from either the hyaloid artery not disappearing as it usually does during development, or invasive embryonic tissue working its way into the lens of the eye. PPC develops early in the process of becoming an embryo and can result in issues like sensitivity to light, difficulty handling bright light, and vision problems later on in adulthood (between the ages of 30 and 50). It’s been observed that PPC usually gets passed down in families in what’s considered an autosomal dominant pattern, but sometimes it happens out of the blue without any family history.
Speaking of family history, about 40 to 50% of people with PPC have a positive family history, meaning the condition runs in their families. Multiple studies looking at genetic pathways have shown that this autosomal dominant PPC can actually vary quite a bit between different people. The exact reason why the fibre like structures inside the lens get disrupted during development isn’t fully understood yet.
Research has shown that PPC is linked to five specific genes (called CTTP1 to CTTP5), which are located on different chromosomes. The CRYAB gene, 450delA, and Pro20Ser are also associated with CTTP2, the CHMP4B gene is linked to CTTP3, and the PITX3 gene, among others, is linked to CTTP4.
Risk Factors and Frequency for Posterior Polar Cataract
PPC, or posterior polar cataract, occurs in approximately 3 to 5 people out of every 1,000. It is often found in both eyes in 65 to 80% of these cases and appears equally in men and women. Among all congenital cataracts, PPC makes up around 7% and therefore represents the same percentage of eyes needing cataract surgery. In one piece of research, 111 PPC cases were identified alongside 37,000 people without eye defects. Different studies have reported varying incidences of PPC, ranging from as low as 4% to as high as 36%.
There are also various conditions that have been associated with PPC. These include:
- Retinitis pigmentosa
- Wilms tumor and aniridia
- Anterior polar cataract
- Microcornea
- Microphthalmia
- Skin conditions such as scleroderma, ectodermal dysplasia, Rothmund syndrome, and dyskeratosis congenita
Signs and Symptoms of Posterior Polar Cataract
Posterior polar cataracts (PPC) usually cause issues with vision both up close and at a distance. Symptoms include experiencing glare, seeing halos, reading difficulties, night-time driving problems, sensitivity to light, and decreased ability to discern contrasts. The severity of these symptoms increases with age due to age-related narrowing of the pupil and thickening of the PPC. In early childhood, PPC can lead to poor vision, lazy eye, and eye misalignment, specifically outward turning of the eye. Over time, expectations for visual and anatomical improvements with intraocular lenses increase.
Diagnosis of PPC is done through detailed eye examination, specifically with a slit-lamp machine. This test reveals a thick, white, disc-like opacity in the back of the eye, which often resembles a bull’s eye. The size and thickness of this opacity can help gauge the level of impacted vision, with larger opacities causing more vision loss. Coincident conditions, such as other types of cataracts or white spots on the PPC (known as Daljit Singh Sign), can also be seen during PPC examination. These coincident cataracts include posterior subcapsular cataracts, cortical cataracts, and nuclear sclerotic cataracts.
Different classification systems are used to better describe PPCs:
- Duke-Elder’s stationary PPC: This is seen in 65% of cases and is a localized, circular opacity with an onion ring or bull’s eye appearance. It may have small lesions around it. It could be covered by nuclear sclerotic cataracts sometimes.
- Duke-Elder’s progressive PPC: The change appears as a white opacity in the back of the lens. It often affects vision between the ages of 30 and 50 years.
- Daljit Singh’s classification: Divided into four types based on appearance and impact on vision.
- Schroeder’s classification: Grades pediatric PPC from 1 to 4 based on how much it impacts the red reflex through the pupil (indicator of eye health). It also guides the management of PPC.
- Vasavada’s classification: Categorizes into three types based on its relation to the back of the eye.
Regardless of the classification system used, the recommendation is always to treat PPC promptly to prevent severe vision loss or complications.
Testing for Posterior Polar Cataract
If your doctor suspects you might have an issue with the back part of the lens in your eye (the posterior polar cataract), they’ll perform several tests and evaluations to have a clear understanding of your eye health and to direct the best treatment plan for you. Here’s what you might expect:
First, your ability to see from a distance and up-close will be assessed using the Snellen visual acuity test. This test measures how well you can see letters or symbols from a certain distance. This helps your doctor measure the size and severity of your eye issue.
Next, your doctor will examine the back of your eye (fundus), both with your pupils in their natural state and after they’ve been widened (dilated). This is done to check for any eye problems. If you later have surgery it’s useful to rule out any further complications such as small pieces of the lens dropping down or the retina detaching at the back of the eye.
After this, your doctor might do an A-Scan ultrasound. This test measures the length of your eye from front to back, readings from keratometry (a test to measure the curve of your cornea – the clear front surface of your eye) and checks the appropriate lens power for inserting a replacement lens, if necessary.
In cases where the eye is cloudy and the doctor cannot get a clear view to the back of the eye, a B-Scan ultrasound might be done. This test can help detect any other problems in the eye, such as retinal issues or problems with the optic nerve which connects your eye to your brain. This scan can inform potential future treatments and provide useful information to discuss with you about your visual future.
Another useful test is the Anterior Segment Optical Coherence Tomography (ASOCT). This is a type of imaging test that offers clear view of the eye’s interior, and it can assess the condition of the back surface of the lens. It helps your doctor to prepare for surgery and discuss with you the eventual outcomes of the surgery.
Intraoperative ASOCT can be used during surgery to guide the necessary steps. This advanced technology has improved the diagnosis and management of eye conditions. It can also help to identify specific signs that indicate the status of your eye health and guide the possible intra-operative management.
The doctor might also apply Modified Posterior Optical Coherence Tomography (m-OCT). This is another type of imaging technology useful in identifying certain signs that predict the condition of the lens and the potential for issues during and after surgery.
Additional tests like a complete blood count, kidney function tests, lung function tests, and an electrocardiogram (ECG) which checks your heart rhythm, might also be needed before surgery. Your doctor will also ensure you are generally healthy to go through surgery. This comprehensive evaluation ensures comprehensive care for your visual health.
Treatment Options for Posterior Polar Cataract
Medical treatment has a limited role in managing PPC, a condition that affects the eyes. This treatment is typically only needed for patients with rare systemic disorders. Doctors will commonly evaluate children diagnosed with PPC for these disorders. Some patients with particular skin or neurological conditions are known to develop PPC.
Surgery is the primary treatment method for those dealing with PPC. Indications for surgery include glare and light sensitivity, trouble reading small print, and trouble with everyday tasks. Early detection of PPC is also an indicator for possible surgery, as the risk for complications is lower. Surgery for children with PPC should be carried out as soon as possible to prevent blindness.
The choice of surgical technique depends on affordability, skill of the surgeon, and the need for surgery. Previously, a method called extracapsular cataract extraction (ECCE) was used to manage PPC. This is now being replaced by manual small incision cataract surgery (MSICS) due to better outcomes. Phacoemulsification is often chosen for PPC surgery since it has been shown to have fewer complications than ECCE.
Surgical anesthesia selection relies on several factors including the severity of the PPC, patient age, existing health conditions, and surgeon experience. Sometimes during surgery, if the patient clenches their eyes, this can result in positive vitreous pressure, which is an added risk factor. As such, doctors may suggest a gentle massage after peribulbar or retrobulbar anesthesia to keep pressure in check.
There are a number of detailed steps and techniques used during surgery, including making the main corneal incision and utilizing an ophthalmic viscosurgical device. These techniques, along with selecting the right phacoemulsification parameters and nucleotomy techniques, can help ensure excellent surgical outcomes.
In some cases, despite the best efforts, posterior capsular tear (PCR) can happen during surgery. This can be managed by injecting viscoelastic to maintain the form of the anterior chamber and prevent further complications. The surgeon can also perform anterior vitrectomy to carefully remove the front of the vitreous gel inside the eye.
To finish the surgery, the surgeon will place an intraocular lens implant within the eye. If a PCR happens and it is small enough, it can be converted into a circular capsulorhexis to allow easier placement of a single piece of an intraocular lens in the lens capsule. The anterior chamber is then carefully formed and the incision is hydrated.
Understanding all of this can feel overwhelming, but rest assured, your specialist will ensure the best course of action is taken to manage your eye condition, and will explain all surgical steps in detail.
What else can Posterior Polar Cataract be?
There are different types of eye conditions, which include but are not limited to:
- Posterior subcapsular cataract
- Posterior lenticonus
- Focal traumatic cataract
- Congenital cataract
- Lens abscess
- Lenticular intraocular foreign body
What to expect with Posterior Polar Cataract
The outcome of PPC, or posterior polar cataract, can depend on a lot of factors. These include the stage of the cataract, the surgeon’s expertise, decision-making, and timing, as well as careful review of the patient’s medical history and current condition.
For complex PPC cases, like stage 3 and stage 4 or cases where the back of the eye’s capsule is already thin or has an opening, the outlook might be uncertain. This is due to potential complications such as the rear side of the capsule getting breached, vitreous (the clear gel that fills the space between the lens and retina) spilling into the front chamber of the eye, or falling of the nucleus (the central part of the eye) into the lower parts of the eye. It can also get complicated if the artificial lens (IOL) can’t be placed due to the lack of support from the capsule.
Similarly, cases where the posterior capsule (the back part of the eye’s lens) spontaneously ruptures can also have an uncertain outcome. However, if the surgery is conducted by a skilled and experienced surgeon, the result is usually excellent, leading to a significant improvement in vision.
Possible Complications When Diagnosed with Posterior Polar Cataract
Before Surgery:
- Lazy eye
- Posterior capsular dehiscence (opening in the back layer of the lens of the eye)
During Surgery:
- Posterior capsular rupture (tear in the back layer of the lens)
- Zonular dialysis (separation of the fibers that support the lens)
- Nucleus drop (dropping of the central part of the lens into the back of the eye)
- Aphakia (absence of the lens in the eye)
- Vitreous prolapse (slipping of the gel-like substance in the eye)
- Cortex drop (dropping of the outer part of the lens into the back of the eye)
- Corneal edema (swelling of the cornea)
- Iridodialysis (separation of the iris from its attachment to the eye)
- Hyphema (bleeding into the front of the eye)
- Descemet membrane detachment (separation of the inner layer of the cornea)
- Fish mouthing of the main incision
- Corneal burn
After Surgery:
- IOL decentration (dislocation of inserted artificial lens)
- IOL drop (fall of artificial lens)
- Retained cortex (remaining outer part of the lens in the eye)
- Fibrinous uveitis (inflammation in the eye)
- Hyphema (bleeding into the front of the eye)
- Secondary glaucoma (increase of eye pressure due to other eye diseases)
- Vitreous touch syndrome
- Vitreous wick syndrome
- Wound leak
- Descemet membrane detachment (separation of the inner layer of the cornea)
- Macular edema (swelling in the central part of the retina)
Recovery from Posterior Polar Cataract
After a standard cataract surgery and if there are no complications with the eye, patients should use topical medicines which include steroids and antibiotics. Examples include prednisolone 1% or dexamethasone 0.1%, or a mixture of steroids and antibiotics like 0.3% moxifloxacin with 1% prednisolone or 0.3% gatifloxacin with 0.1% dexamethasone. These medications should be applied to the eye starting from a week after the surgery, and the doses should reduce gradually each week.
If a patient is prescribed just a steroid medicine, a separate antibiotic must also be taken. This can be either 0.3% ofloxacin, 0.3% moxifloxacin, or 0.3% gatifloxacin, and it should be used four times a day for 20 days. This will protect the patient from other possible bacterial infections. Some eye doctors might also recommend using 5% homatropine two times per day for 15 days. This can help decrease inflammation in the eye after surgery.
However, in situations where a patient experiences a tear in the back of their eye lens (posterior capsular rent) and a bulging of the jelly-like substance in their eye (vitreous prolapse) during surgery, further medication would be needed. Aside from the ones already mentioned, they will also need to take an oral antibiotic called ciprofloxacin 750 mg, an anti-inflammatory tablet with 50 mg diclofenac and 10 mg serratiopeptidase, and a medicine for stomach acid called pantoprazole 40 mg, twice each day for five days. This is to prevent a severe infection in the eye called endophthalmitis.
If the patient has complications such as an issue where the lens or its surrounding cortex drops into the back of the eye during surgery, they should be checked by a vitreoretinal surgeon. This is an eye specialist that deals with disorders at the back of the eye. They can help to decide whether more surgical procedures are needed or if conservative management is better. If a patient has lost their lens during surgery (intraoperative aphakia), plans should be made to implant a new lens within 1 to 2 months after inflammation has been controlled. It is crucial that these patients are closely monitored and well-informed for a successful recovery after the operation.
Preventing Posterior Polar Cataract
It’s important for the patient to understand the specific type of inherited cataract they have and any possible complications associated with it. They should also be informed about what to expect in terms of outcomes when handled by a expert medical professional, as well as what treatment options are available to them.
Furthermore, they should be provided with clear instructions on how to take their medication after surgery, along with why it’s important to follow the treatment plan and plan regular check-ups. In addition to this, the patient should be made aware of the need for their family members to be tested for “PPC” a type of inherited cataract.
