Diagnosis: Congenital Cataract
The most likely diagnosis in this 6-week-old infant with unilateral leukocoria and normal development is congenital cataract, which represents the most common cause of leukocoria in children (35% of cases), followed by retinoblastoma (6% of cases). 1
Immediate Clinical Action Required
- This child requires urgent referral to a pediatric ophthalmologist regardless of the suspected diagnosis, as absent red reflex is an absolute indication for specialist evaluation. 2, 3
- Do not delay referral for additional testing or imaging, as conditions like retinoblastoma or dense congenital cataract can result in permanent vision loss or death if treatment is postponed. 2
Differential Diagnosis Analysis
Why Congenital Cataract is Most Likely (Option C):
- Congenital cataract accounts for 35% of all leukocoria cases in children, making it the single most common etiology. 1
- The lens opacity blocks light transmission through the eye, preventing the normal red reflex and creating the white pupillary appearance. 4
- Normal developmental milestones at 6 weeks support a localized ocular problem rather than systemic disease. 5
- Unilateral presentation is common with congenital cataracts and requires time-sensitive surgical intervention to prevent irreversible amblyopia. 5, 6
Why Retinoblastoma Must Be Excluded (Option B):
- Retinoblastoma represents 6% of leukocoria cases and is the most critical diagnosis to rule out due to life-threatening implications. 1
- While less common than cataract, retinoblastoma cannot be excluded without specialist examination including fundoscopy and ocular ultrasound. 4, 3
- The ophthalmologist will perform comprehensive evaluation to definitively exclude this malignancy. 2
Why Toxocariasis is Unlikely (Option A):
- Ocular toxocariasis typically presents in older children (ages 5-10 years) rather than at 6 weeks of age. 7
- This parasitic infection requires exposure to contaminated soil or animal feces, which is uncommon in a 6-week-old infant with limited environmental exposure.
- Toxocariasis represents a much less common cause of leukocoria compared to congenital cataract. 7
Critical Examination Findings
The ophthalmologist will perform:
- Cycloplegic refraction to accurately determine refractive error and assess for media opacities. 2
- Detailed funduscopic examination under dilation to evaluate the posterior segment and rule out retinoblastoma. 2
- Ocular ultrasound performed by the ophthalmologist to characterize intraocular pathology when direct visualization is blocked. 4, 3
Common Pitfall to Avoid
Do not assume the diagnosis is benign simply because the child is developing normally—both congenital cataract and retinoblastoma can present with normal systemic development while causing severe unilateral visual impairment. 2, 5 The critical window for treating congenital cataract to prevent amblyopia is narrow, and delayed intervention results in permanent vision loss even after successful cataract removal. 5, 6