Congenital Cataract

Key points of this disease

• Congenital cataract is strictly defined as lens opacity present at birth, but it is often collectively referred to as congenital cataract including developmental cataract that occurs in infancy without any cause such as trauma.
• Most unilateral cases are idiopathic, while bilateral cases are often hereditary (autosomal dominant is most common) or associated with systemic diseases. Idiopathic cases account for 30-50% of all cases.
• The critical period for form deprivation amblyopia is 6 weeks after birth for unilateral cases and 10-12 weeks for bilateral cases, and early surgery determines visual prognosis.
• The recommended timing for surgery is 1 month after birth for unilateral cases and 2 months for bilateral cases.
• For unilateral cataract within 6 months of age, primary IOL implantation showed no difference in visual acuity at 4.5 years compared to contact lens management in the IATS study, but IOL eyes had more reoperations due to visual axis opacification.
• In children under 6 years, posterior capsulotomy and anterior vitrectomy are performed to prevent posterior capsule opacification.
• Postoperative glaucoma can develop even after 10 years or more, so long-term follow-up is essential.
• The accuracy of IOL power calculation formulas is significantly lower in children, with achievement rates within ±1.00D of only 35-44% ¹⁾.

1. What is Congenital Cataract?

Congenital cataract, in a narrow sense, refers to lens opacity present at birth. On the other hand, opacity that is not present at birth but develops later is called developmental cataract. However, cataracts in infancy without any cause such as trauma are often collectively referred to as congenital cataract. This article deals with congenital cataract in a broad sense, including developmental cataract.

Childhood cataract can be a major cause of form deprivation amblyopia. If lens opacity exists during the critical period for visual function acquisition, amblyopia develops rapidly. The critical period is 6 weeks after birth for unilateral cases and 10-12 weeks for bilateral cases, and whether appropriate surgery is performed during this period greatly affects the prognosis.

Q What is the difference between congenital cataract and developmental cataract?

A

Strictly speaking, congenital cataract is present at birth, while developmental cataract develops after birth. However, lens opacities in infancy without obvious causes such as trauma are often collectively called “congenital cataract.” Clinically, both are not distinguished, and management is based on the critical period for form deprivation amblyopia, timing of surgery, and postoperative care.

2. Causes and Etiology

Most unilateral childhood cataracts are idiopathic. In bilateral cases, the proportion of hereditary or systemic disease-related causes is higher.

Category	Specific Disease/Cause
Idiopathic	30–50% (most common overall)
Hereditary	Autosomal dominant (most common), autosomal recessive, X-linked recessive
Metabolic disorders	Galactosemia, hypocalcemia, hypoglycemia, diabetes mellitus, Fabry disease, Wilson disease, homocystinuria
Chromosomal abnormalities	Down syndrome (trisomy 21), trisomy 13, 15, 18 syndromes
Systemic syndromes	Lowe syndrome, Alport syndrome, myotonic dystrophy, atopic dermatitis, Hallermann-Streiff syndrome, Pierre Robin sequence
Intrauterine infection	Congenital rubella syndrome, cytomegalovirus, toxoplasmosis, herpes
Drug-induced	Steroids (long-term systemic use)
Ocular disease complications	Persistent fetal vasculature (PFV), congenital aniridia, retinitis pigmentosa, coloboma, retinopathy of prematurity, microphthalmos
Trauma	Ocular contusion or penetrating injury

Cataract in congenital rubella syndrome

Cataracts due to congenital rubella syndrome are characterized by nuclear cataracts, and the virus may persist within the lens. Special attention to infection control (e.g., disposal of surgical instruments and irrigation fluid) is required during surgery.

3. Classification of Opacity Morphology

The morphology and location/degree of opacity determine the impact on visual function and surgical indications.

Opacity type	English name	Opacity location	Impact on visual acuity
Capsular cataract	Capsular cataract	Anterior capsule, posterior capsule, subcapsular	Posterior capsule type has significant impact
polar cataract	polar cataract	anterior/posterior pole	posterior type has greater impact
nuclear cataract	nuclear cataract	embryonic nucleus	powdery type has less impact
zonular cataract	zonular cataract	lamellar cortex	asymmetry indicates greater impact
punctate cataract	punctate cataract	punctate	less impact
Sutural (axial) cataract	sutural cataract	Y-shaped suture area	Minimal impact
Total cataract	total cataract	Complete opacity	Significant impact

Punctate cataract, sutural cataract, and anterior capsular cataract do not cause visual impairment. Lamellar cataract with no laterality and powdery nuclear cataract also do not cause form deprivation amblyopia, so early surgery is not necessary.

The degree of impact on visual function is generally greater for “posterior capsule side than anterior capsule side,” “central area than peripheral area,” and “dense opacity than faint opacity.” In unilateral cases, an opacity of 3 mm or more is judged to affect visual function.

4. Relationship with form deprivation amblyopia

Childhood is a period of visual function acquisition, and cataracts during this period carry a risk of form deprivation amblyopia.

Concept of critical period

The critical period is 6 weeks after birth for unilateral cases and 10 to 12 weeks after birth for bilateral cases. If a cataract affecting visual function is present during the critical period, form deprivation amblyopia develops particularly rapidly in unilateral cases.

Findings suggestive of amblyopia formation

The following findings suggest that amblyopia has already developed in an eye with cataract.

• Visual acuity reduction inconsistent with the degree of cataract
• Poor fixation (the affected eye does not fixate when the healthy eye is occluded)
• Strabismus (unilateral)
• Nystagmus
• Axial length difference between eyes (≥0.5 mm)

Be aware of the critical period for form deprivation amblyopia

The critical period is 6 weeks after birth for unilateral cases and 10–12 weeks for bilateral cases. If cataract affecting visual function is left untreated during this period, amblyopia progresses rapidly. Early ophthalmological consultation and appropriate timing of surgery determine the visual prognosis.

5. Diagnosis and Examination

Diagnosis of cataract and assessment of its impact on visual function are performed simultaneously.

• Red reflex test: Checks for leukocoria in newborns and infants. Useful for early detection of cataract, retinoblastoma, PFV, etc.
• Slit-lamp examination: Evaluates the morphology, size, location, and density of the opacity. Opacities that are posterior capsular, central, or dense have a greater impact on visual function.
• Fundus examination: Checks for ocular complications (PFV, coloboma, etc.). If media opacity is severe and fundus view is poor, perform ultrasound (B-mode).
• Axial length measurement: A difference of ≥0.5 mm between eyes suggests amblyopia. Also essential for IOL power calculation.
• Systemic examination: TORCH infection testing, urinary reducing sugars (galactosemia screening), chromosomal testing (for bilateral cases).

Differential diagnosis: The most important differential diagnosis for leukocoria is retinoblastoma, which must always be ruled out.

6. Surgical Indications

Surgical indications are determined by a comprehensive assessment of the child’s age, actual degree of inconvenience, visual acuity, severity of cataract, status of form deprivation amblyopia, presence of ocular or systemic complications, and the parents’ understanding, cooperation, and wishes.

Cases where surgery is strongly indicated

Cataracts with a high likelihood of causing form deprivation amblyopia, when severe amblyopia has not yet developed.

• Dense unilateral cataract: before 6 weeks of age (aim for around 1 month of age)
• Dense bilateral cataract: before 12 weeks of age (aim for around 2 months of age)

Cases where surgery is not urgent

• Punctate cataract, suture cataract, anterior capsular cataract (no visual impairment)
• Lamellar cataract without laterality, powdery nuclear cataract (do not cause form deprivation amblyopia)
• When severe form deprivation amblyopia has already developed (surgery has limited effect)

Q Are there cases where cataract does not require surgery?

A

For cataracts that do not cause visual impairment, such as punctate cataract, suture cataract, or anterior capsular cataract, early surgery is unnecessary and observation is appropriate. Lamellar cataract without laterality and powdery nuclear cataract also do not cause form deprivation amblyopia, so surgery is not urgent. On the other hand, if the opacity is dense and affects visual function, early surgery should be performed considering the critical period for form deprivation amblyopia.

7. Surgical Methods

Basic Surgical Technique

The basic surgical procedure for pediatric cataract varies by age.

Standard procedure for children under 6 years: Lens (phaco) aspiration + posterior capsulotomy + anterior vitrectomy

In children under 6 years, lens epithelial cell activity is high, and posterior capsule opacification occurs in nearly 100% of cases. Additionally, performing Nd:YAG laser under a slit lamp is difficult, so the basic approach is to perform posterior capsulotomy and anterior vitrectomy during the primary surgery to prevent posterior capsule opacification as much as possible.

When IOL implantation is performed: Lens (phaco) aspiration + posterior capsulotomy + anterior vitrectomy + IOL implantation

When the posterior capsule can be preserved in children aged 6 years or older: Lens (phaco) aspiration + IOL implantation

Indications for IOL Implantation (Guidelines from the IATS Study)

The Infant Aphakia Treatment Study (IATS) provides important guidance on the appropriateness of IOL implantation. This randomized prospective trial compared IOL implantation with contact lens management in infants undergoing unilateral cataract surgery within the first 6 months of life. At 4.5 years of age, no difference in visual acuity was found. However, eyes with IOL implantation had significantly more visual axis opacifications requiring reoperation before 1 year of age. The conclusion is that IOL implantation within the first 6 months of life should be reserved for limited cases, such as when contact lens management is difficult.

Target Refraction for IOL Power

IOL power is often selected to achieve mild myopia around age 20. Intentional hyperopic correction is performed in anticipation of myopic shift with growth, with targets of +5 D at 1 year and +4 D at 2 years.

Accuracy of IOL Power Calculation Formulas

In pediatric IOL implantation, the predictive accuracy of current power calculation formulas is significantly lower than in adults. A comparison of formula accuracy in 108 eyes of 83 children undergoing primary IOL implantation showed that SRK/T and Kane formula had the best performance in terms of mean error and median absolute error¹⁾.

• Achievement rate within ±0.50 D: 20.4–26.9%
• Achievement rate within ±1.00 D: 35.2–43.5% (adults: 93.5–100%)

Younger age and shorter axial length were significant predictors of refractive surprise, while surgical technique and IOL type did not significantly affect accuracy¹⁾. Development of pediatric-specific IOL power calculation formulas is needed.

Q Is an IOL implanted in pediatric cataract surgery?

A

For unilateral cataract within 6 months of age, based on the IATS study, there was no difference in visual acuity between contact lens management and IOL, and reoperation for visual axis opacification was more frequent in IOL eyes, so IOL insertion is limited to selected cases. For children aged 2 years and older, primary IOL implantation is common. The target IOL power is hyperopic overcorrection (approximately +5 D at 1 year of age) anticipating myopic shift with growth, but it is necessary to keep in mind that the accuracy of current calculation formulas is significantly inferior to that in adults.

8. Postoperative Management

Refractive Correction

• Unilateral postoperative: Contact lens correction is the standard. Spectacle correction is optically disadvantageous, so contact lenses are preferred.
• Bilateral postoperative: Management with spectacles is possible.
• Because refractive changes (myopic shift) with growth are large, regular refraction examinations and adjustment of correction power are essential.

Amblyopia Treatment

In unilateral postoperative cases, occlusion therapy of the healthy eye is mandatory.

Occlusion Therapy Schedule (Based on IATS)

Up to 8 months of age, occlude the healthy eye for the same number of hours as the age in months (e.g., 4 hours/day for a 4-month-old). After 8 months, target half of waking hours. Thorough guidance and continuous support for parents are important, and regular outpatient checks of occlusion status should be performed.

Q How many hours of occlusion are needed after surgery?

A

Based on the IATS occlusion protocol, up to 8 months of age, occlude for the same number of hours as the age in months (e.g., 4 hours/day for a 4-month-old). After 8 months, aim for half of waking hours. Insufficient occlusion may not achieve amblyopia treatment effect, while excessive occlusion risks inducing amblyopia in the healthy eye. It is important to adjust occlusion time regularly according to the ophthalmologist’s instructions.

9. Postoperative Complications and Long-term Prognosis

Posterior Capsule Opacification (Visual Axis Opacification)

In children, lens epithelial cell activity is high, and since the lens capsule is not completely removed, contraction of the anterior (posterior) capsulotomy margin or Elschnig pearl-type posterior capsule opacification occurs in nearly 100%. Because Nd:YAG laser is difficult to perform in children under 6 years of age, it is standard to perform posterior capsulotomy and anterior vitrectomy at the time of primary surgery to prevent it. The incidence of visual axis opacification with anterior vitrectomy was 18% (95% CI 8–28%), significantly lower than 60% (95% CI 0–84%) without it ²⁾.

Postoperative Glaucoma

Glaucoma occurs at a high rate after pediatric cataract surgery. Most cases are open-angle glaucoma, and risk factors include young age at surgery and ocular complications such as microphthalmia. Since it can develop even 10 years or more after surgery, long-term follow-up of intraocular pressure is essential.

In a report from the PEDIG registry analyzing 5-year outcomes of PFV-related cataracts, the 5-year cumulative incidence of glaucoma-related adverse events in aphakic PFV eyes was 24% (95% CI 9–37%) ²⁾. In pseudophakic PFV eyes, it was lower at 7% (95% CI 0–20%), and there was no significant difference in glaucoma risk between PFV and non-PFV eyes (age-adjusted HR=1.20, P=.66) ²⁾.

Long-term Prognosis of PFV-related Cataract

Five-year outcomes of 64 eyes with PFV-related cataract (48 aphakic eyes, 16 pseudophakic eyes) ²⁾:

Outcome	PFV Aphakic Eyes	PFV Pseudophakic Eyes
Glaucoma-related adverse events (5-year cumulative)	24% (95% CI 9–37%)	7% (95% CI 0–20%)
Visual axis opacification (with anterior vitrectomy)	18% (95% CI 8–28%)	—
Visual axis opacification (without anterior vitrectomy)	60% (95% CI 0–84%)	45% (95% CI 13–66%)
Retinal detachment (5-year cumulative)	4% (95% CI 0–10%)	7% (95% CI 0–19%)

Age-appropriate visual acuity was achieved in only 10% of eyes (4/42 eyes, 95% CI 3–23%). Visual acuity better than 20/200 was achieved in 59% (95% CI 39–76%) of aphakic PFV eyes and 23% (3/13 eyes) of pseudophakic PFV eyes²⁾. Posterior PFV (with vitreous, retinal, or optic nerve abnormalities) tended to have a worse visual prognosis than anterior PFV (median visual acuity 20/800 vs 20/100)²⁾.

Factors Affecting Visual Prognosis

Early Surgery

Timing of surgery: Early surgery before the critical period has the greatest impact on visual prognosis. Once form deprivation amblyopia develops, treatment becomes difficult.

Presence of Ocular Complications

Complications: Ocular complications such as microcornea, microphthalmos, and posterior PFV worsen visual prognosis. In eyes with PFV, achieving age-appropriate visual acuity is often difficult.

Postoperative Correction and Amblyopia Treatment

Ongoing management: Appropriate postoperative refractive correction and continued occlusion therapy greatly influence visual prognosis. Understanding and cooperation from parents are essential.

Long-term Follow-up

Follow-up: Postoperative glaucoma can develop even more than 10 years after surgery. Regular intraocular pressure measurements should be continued into adulthood.

10. References

1. Jin J, Shen Y, Qu Y, et al. Accuracy of new-generation and traditional intraocular lens power calculation formulas in pediatric primary implantation. J Cataract Refract Surg. 2024. doi:10.1097/j.jcrs.0000000000001527.
2. Haider KM, Repka MX, Sutherland DR, et al. Outcomes and complications 5 years after surgery for pediatric cataract associated with persistent fetal vasculature. Am J Ophthalmol. 2024. (Pediatric Eye Disease Investigator Group)
3. Vasavada AR, Nihalani BR. Pediatric cataract surgery. Curr Opin Ophthalmol. 2006;17(1):54-61. PMID: 16436925.