Hypoplasia of the optic nerve

Area of Science:

• Ophthalmology
• Neurology
• Developmental Biology

Background:

• This study correlates premorbid ophthalmoscopic and histopathologic findings in an infant with bilateral optic nerve hypoplasia and hydranencephaly.
• Optic nerve hypoplasia (ONH) is a congenital condition resulting from the underdevelopment of the optic nerve.
• Hydranencephaly is a severe congenital brain malformation where the cerebral hemispheres are absent and replaced by cerebrospinal fluid.

Observation:

• A distinctive "double-ring sign" was observed during ophthalmoscopic examination.
• This sign was characterized by two concentric rings visible on the optic nerve head.
• The infant presented with bilateral hydranencephaly, a severe brain malformation.

Findings:

• Histopathology revealed the double-ring sign was caused by an extension of the retina and retinal pigment epithelium (RPE) over the lamina cribrosa.
• The outer ring represented the sclera-lamina cribrosa junction, while the inner ring marked the RPE termination.
• The hypoplastic optic nerve head appeared whitish due to fibroglial tissue surrounding the central retinal vessels.

Implications:

• The findings suggest a potential in utero vascular insult after the third gestational month as the cause.
• This insult may have led to cystic cavitation in the cerebral hemispheres and retrograde degeneration of retinal ganglion cells.
• Understanding the pathogenesis of ONH in complex neurological conditions like hydranencephaly is crucial for diagnosis and management.