Posterior Polar Cataract

Key Points at a Glance

Key Points of This Disease

• Posterior polar cataract (PPC) is a subtype of congenital cataract that produces a dense, white, disc-shaped opacity at the posterior pole of the lens.
• Shows autosomal dominant inheritance, and 65–80% of cases are bilateral.
• The posterior capsule is fragile with a high risk of rupture, making it one of the most caution-requiring types in cataract surgery.
• Hydrodissection is contraindicated; hydrodelineation is recommended.
• In adults, photophobia, halos, and reduced contrast are the main complaints, worsening in bright environments or with miosis.
• In recent years, several new surgical techniques that minimize intraoperative manipulation of the posterior capsule have been proposed to reduce complications.

1. What is posterior polar cataract?

Posterior polar cataract (PPC) is a subtype of congenital cataract characterized by a well-defined, dense white discoid opacity located just beneath the posterior capsule at the posterior pole (near the center of the pupillary area, slightly nasal).

The inheritance pattern is primarily autosomal dominant, and multiple genetic loci have been identified. Sporadic cases have also been reported. The opacity often occurs at the terminal end of remnants of the hyaloid artery, presenting a wide range of severity from benign Mittendorf dot to severe cataract that impairs visual function.

The incidence is lower compared to other cataract subtypes. 65–80% of cases are bilateral; in unilateral cases, attention must be paid to the risk of amblyopia. The opacity forms in early life, but its clinical significance may increase with age.

The diameter of the opacity is reported to be 1.8–3.0 mm. The posterior capsule is often fragile and thin, making it difficult to accurately assess its condition preoperatively with slit-lamp examination.

Q Is posterior polar cataract hereditary?

A

It is mainly inherited in an autosomal dominant pattern. If one parent is affected, the probability of transmission to a child is about 50%. Sporadic cases also occur, so it can develop even without a family history.

2. Main Symptoms and Clinical Findings

Subjective Symptoms

The characteristic of posterior polar cataract is that even a small opacity significantly affects visual function because it is located at the center of the pupil.

• Photophobia (glare) and halos: Worsens markedly in bright environments or under miosis. One of the most common complaints.
• Visual acuity loss: Varies depending on the size and density of the opacity and the degree of associated nuclear sclerosis. Patients may experience visual dysfunction even when Snellen visual acuity is “normal.”
• Reduced contrast sensitivity: Visual acuity is preserved in high-contrast environments but decreases significantly in low-contrast or glare conditions.
• Amblyopia (pediatric cases): In unilateral cases with early onset, amblyopia that hinders visual development may occur.

Clinical Findings

Slit-lamp examination reveals a disc-shaped white opacity at the posterior pole beneath the posterior lens capsule. The opacity has clear borders and is classified into the following four types according to the Daljit Singh classification.

Types 1 and 2

Type 1: Posterior polar cataract with posterior subcapsular cataract (PSC). The mildest form.

Type 2: Round to oval disc-shaped opacity with an onion-like ring structure. May be accompanied by gray-white spots at the edge.

Types 3 and 4

Type 3: Disc-shaped opacity with dense white spots at the edge. Often accompanied by a fragile, thinned, or deficient posterior capsule. Used as the “Daljit Singh sign” to predict posterior capsule rupture.

Type 4: A combined type where nuclear sclerotic cataract is superimposed on types 1–3. This has the highest surgical difficulty.

Additionally, based on the temporal progression of the condition, there is also a classification into Stationary type, which shows central opacity and a target-like ring, and Progressive type, where radial opacities expand over time.

Anterior segment OCT (AS-OCT) allows morphological evaluation of the posterior capsule, and three categories of posterior capsule defect have been described: “conical,” “moth-eaten,” and “ectatic.” Irregular contours of the posterior capsule or localized anterior protrusion (conical sign) suggest an existing posterior capsule tear.

3. Causes and Risk Factors

The main cause of posterior polar cataract is genetic predisposition. Genetic loci associated with global ocular diseases such as anterior segment mesenchymal dysgenesis and persistent hyperplastic primary vitreous (PHPV) have also been reported to be involved in posterior polar cataract.

Opacification often occurs at the terminal end of remnants of the hyaloid artery. This is thought to be due to scar-like changes remaining at the posterior pole of the lens when the hyaloid artery regresses near the posterior capsule during the embryonic period.

Environmental risk factors have not been clearly identified at present. Opacification may progress with age or be complicated by nuclear sclerosis (type 4).

Points to note in daily life

• Since posterior polar cataract is a hereditary disease, your family members (especially children) should also undergo regular eye examinations.
• If your child has unilateral involvement, early consultation with an ophthalmologist is important for early detection and treatment of amblyopia.
• If you have symptoms of photophobia and halos, wearing sunglasses or avoiding bright environments can help alleviate symptoms.

4. Diagnosis and Examination Methods

Diagnosis is made by comprehensively evaluating the location and shape of the opacity, whether it is bilateral, family history, age, and other factors.

Diagnostic Item	Characteristics
Location of opacity	Subcapsular, near the center of the pupil, or nasal side
Shape of opacity	Disc-shaped, well-defined, dense white
Diameter of opacity	1.8–3.0 mm
Affected eye	Bilateral (65–80%) or unilateral
Inheritance pattern	Autosomal dominant inheritance

Preoperative evaluation

It is important to assess the condition of the posterior capsule before surgery.

• Slit-lamp examination: Although it is difficult to directly evaluate the fragility or adhesion of the posterior capsule, basic confirmation is performed.
• Anterior segment OCT (AS-OCT) and ultrasound biomicroscopy (UBM): These are useful for evaluating adhesion of opacities to the posterior capsule and posterior capsule defects ²⁾. Irregularities in the contour of the posterior capsule or a conical sign suggest a preexisting posterior capsule tear.
• Scheimpflug imaging: Allows three-dimensional evaluation of cataract morphology.
• Brightness acuity test (BAT): Used to assess visual function under glare conditions.
• Macular OCT: Performed to evaluate concurrent retinal disease when visual impairment is disproportionate to cataract severity.
• B-mode ultrasound: Performed when dense cataract makes posterior segment observation difficult.

Q Can the risk of posterior capsule rupture be predicted preoperatively?

A

It is difficult to accurately assess posterior capsule fragility with slit-lamp examination alone. If anterior segment OCT reveals irregular posterior capsule contour or localized protrusion (cone sign), it suggests a pre-existing posterior capsule tear and requires caution. Detailed informed consent before surgery is important.

5. Standard Treatment

Surgery is selected when there is an impact on visual function such as decreased vision, photophobia, or halos. Due to the fragility of the posterior capsule, the risk of intraoperative complications is high, and it is important to choose the appropriate surgical technique and master the procedure.

Preoperative Preparation and Anesthesia

This often takes longer than standard cataract surgery. Topical anesthesia is the basis, but if the surgery time is prolonged, sub-Tenon’s or retrobulbar anesthesia may be necessary.

Intraoperative Basic Principles

The most important thing is to minimize manipulation of the posterior capsule, keep the anterior chamber stable at all times, and perform surgery calmly and carefully without rushing.

• Hydrodissection is absolutely contraindicated: Due to adhesions to the posterior capsule, hydrodissection carries a high risk of posterior capsule rupture.
• Perform hydrodelineation: Separate the nucleus from the epinucleus to preserve a protective epinuclear layer between the nucleus and posterior capsule.
• Set low aspiration pressure and flow: During nucleus fragmentation and aspiration, aim for bottle height 60 cm, aspiration pressure 100 mmHg, and aspiration flow 20 mL/min. Do not rotate the nucleus.
• Use viscoelastic appropriately: Choose a dispersive viscoelastic as first choice for posterior capsule protection, endothelial protection, and coverage in case of posterior capsule rupture.

Capsulotomy (CCC)

Perform continuous curvilinear capsulorhexis (CCC). The size should be approximately 5 mm, but adjust according to nucleus size and intraoperative needs ¹⁾. A larger continuous curvilinear capsulorhexis facilitates nucleus division and removal, and is advantageous for nucleus delivery in case of posterior capsule rupture.

Nucleus fragmentation and emulsification technique

Various techniques have been reported to avoid damaging the posterior capsule.

• Standard PEA (phacoemulsification): Can be selected for nuclear hardness grade 2–3 or when the opacity is small.
• Layer-by-layer method, bimanual method, inside-out delineation method, etc.: Each technique emulsifies the nucleus in stages while preserving the epinucleus.

Two-Y Crushing Technique (new technique)¹⁾: For posterior polar cataracts with moderate to hard nuclear hardness, after sufficiently separating the nucleus and epinucleus by hydrodelineation, the nucleus is dislocated into the anterior chamber using two Y-shaped rotators, manually crushed into four or more pieces, and then phacoemulsified. This method requires no rotation of the nucleus and minimizes cumulative dissipated energy (CDE) (achieving low values of 1.80 for the right eye and 1.66 for the left eye)¹⁾. It provides high anterior chamber stability and reduces the risk of posterior capsule rupture.

Precautions when removing the ultrasound probe and I/A tip

When removing the tip, the anterior chamber pressure may drop, causing the posterior capsule to bulge forward and rupture. To prevent this, replace the anterior chamber with OVD (viscoelastic material) before withdrawing the tip.

Cortical aspiration and posterior capsule management

Carefully aspirate and remove the epinucleus and cortex from the periphery. The central white opacity should be handled last with maximum caution. Posterior capsule polishing is generally not performed due to the risk of rupture.

IOL (intraocular lens) insertion

• If the posterior capsule is intact: Insert a one-piece hydrophobic acrylic IOL in the bag¹⁾.
• If there is a small posterior capsule rupture: Attempt careful in-the-bag fixation.
• If there is a large posterior capsule rupture: choose ciliary sulcus fixation with a 3-piece IOL.
• If capsular support is completely lost: an anterior chamber IOL (ACIOL) or sutured/scleral-fixated IOL is required.

Treatment Precautions

• Hydrodissection must never be performed as it can cause posterior capsule rupture.
• Rotating the nucleus sharply increases the risk of posterior capsule rupture. Minimize nuclear manipulation.
• If posterior capsule rupture occurs, it may lead to serious complications such as vitreous prolapse, nucleus drop, and IOL dislocation.
• The complication rate has decreased from about 30% in the 1990s to about 15% after the 2000s, but it remains high.

Q How frequent are surgical complications of posterior polar cataract?

A

Posterior capsule rupture is the most important intraoperative complication, with some literature reporting an incidence of up to 36% of cases. Due to improvements in surgical devices and techniques, it has decreased to around 15% after the 2000s. Other complications include nucleus drop, vitreous prolapse, high intraocular pressure, posterior capsule opacification, retinal detachment, and cystoid macular edema.

6. Pathophysiology and Detailed Mechanism

Embryological Background

The formation of posterior polar cataract is closely related to the regression process of the hyaloid artery during the embryonic period. The hyaloid artery normally regresses completely before birth, but its terminal remnants near the posterior capsule can cause scar-like changes in the posterior pole. Therefore, minor remnants may only be observed as a Mittendorf dot, while more prominent remnants form clinical posterior polar cataract.

Posterior Capsule Fragility

In posterior polar cataracts, the posterior capsule is often fragile and thinned in and around the opacity. Adhesion between the opacity and the posterior capsule may occur, but it is difficult to accurately assess the degree of adhesion preoperatively with slit-lamp examination. In some cases, spontaneous rupture of the posterior capsule occurs before surgery.

In cases with a posterior capsule defect, the following morphologies are observed on anterior segment OCT:

• Conical type: The posterior capsule is disrupted at the posterior pole, and the opacity extends into the anterior vitreous.
• Moth-eaten type: The capsule is preserved up to the edge of the opacity, but there is a defect directly beneath the opacity.
• Dilated type: The capsule appears with attached opacity but has an irregular appearance.

Genetic Background

Genes associated with posterior polar cataract overlap with loci involved in anterior segment mesenchymal dysgenesis and PHPV. It shows high penetrance with autosomal dominant inheritance, but there is phenotypic variability even within the same family.

Why Nuclear Rotation Is Dangerous During Surgery

In posterior polar cataract, the posterior capsule is adherent to the opacity, so rotating the nucleus causes traction on the posterior capsule, directly triggering posterior capsule rupture ¹⁾. Additionally, ultrasonic energy vibrations and surge (sudden aspiration pressure fluctuations) can also act on the posterior capsule and induce rupture. This is the pathophysiological basis for the surgical strategy of “no rotation, low aspiration pressure, low flow rate.”

7. Latest Research and Future Perspectives (Research Stage Reports)

For Patients: Please Read Carefully

The following content is currently at the research stage or in clinical trials and is not standard treatment available at general hospitals. It is reference information for professionals regarding future medical developments.

Potential and Challenges of the Two-Y Crushing Technique

The novel “Two-Y Crushing Technique” reported by Ramatchandirane et al. (2024) is noteworthy for its ability to completely avoid nuclear rotation and reduce cumulative ultrasound energy in phacoemulsification for PPC ¹⁾.

In one case where this technique was performed, low cumulative ultrasound energy values of 1.80 in the right eye and 1.66 in the left eye were achieved, and best-corrected visual acuity of 6/6 (with good IOL placement) was confirmed in both eyes on postoperative day 1 ¹⁾. This technique is considered safe only in cases where hydrodelineation is performed well and the boundary between the nucleus and epinucleus is clearly visible.

However, this report is a case report with only one case (both eyes), and the level of evidence is low. Further validation with a larger number of cases is needed.

Advances in Posterior Capsulotomy Techniques

Combining primary posterior capsulorrhexis is also being studied as a planned approach to manage posterior capsule rupture. Additionally, IOL fixation strategies combined with anterior vitrectomy using a vitrector after posterior capsule rupture are being investigated at multiple institutions.

---

8. References

1. Ramatchandirane B, Pathuri DS, Devalla MD, et al. Two-Y Crushing Technique: A Simple Technique to Crack the Nucleus in a Posterior Polar Cataract Using Two-Y Rotators. Cureus. 2024;16(6):e63416. DOI: 10.7759/cureus.63416.
2. American Academy of Ophthalmology. Cataract in the Adult Eye Preferred Practice Pattern. Ophthalmology. 2022;129(1):1-126.