Coloboma of the Optic Nerve

Clinical Characteristics
Ocular Features: 

Isolated colobomas of the optic nerve in the absence of other malformations may occur unilaterally or bilaterally.  The optic nerve cups are often huge and may have residual glial tissue in them.  Serous detachments of the macula are frequently observed and the risk for extensive retinal detachments is high. Microphthalmos with a cyst (6% of eyes), simple microphthalmos (39% of eyes), and microcornea (84% of eyes) are frequently associated.  The visual prognosis is poor when these occur in combination with an optic nerve coloboma (less than 20/400 acuity in 67% of eyes).  Isolated optic nerve colobomas without other malformations have the best vision (only 7% have acuity of less than 20/400).  Retinal vessels are anomalous as well.  They are often increased in number and have a generally straight course in the peripapillary region.

It has been argued that the morning glory disc anomaly may be an expression of this syndrome but this remains to be established.

Systemic Features: 

No systemic disease is present.

Genetics

This malformation frequently follows an autosomal dominant pattern of transmission secondary to a mutation in the PAX6 gene.

The PAX6 gene impacts DNA transcription and mutations are therefore often associated with a variety of ocular malformations, including uveal colobomas and various forms of anterior chamber dysgenesis.

Optic nerve dysplasia resembling optic pits or the morning glory disc anomaly is a feature of the papillorenal syndrome (120330) but this condition is caused by mutations in the PAX2 gene.

Treatment
Treatment Options: 

None.  Low vision aids may be helpful in some patients.

References
Article Title: 

References

Jeng-Miller KW, Cestari DM, Gaier ED. Congenital anomalies of the optic disc: insights from optical coherence tomography imaging. Curr Opin Ophthalmol. 2017 Aug 16. doi: 10.1097/ICU.0000000000000425. [Epub ahead of print].

PubMedID: 288817389

Azuma N, Yamaguchi Y, Handa H, Tadokoro K, Asaka A, Kawase E, Yamada M. Mutations of the PAX6 gene detected in patients with a variety of optic-nerve malformations. Am J Hum Genet. 2003 Jun;72(6):1565-70.

PubMedID: 12721955

Hornby SJ, Adolph S, Gilbert CE, Dandona L, Foster A. Visual acuity in children with coloboma: clinical features and a new phenotypic classification system. Ophthalmology. 2000 Mar;107(3):511-20.

PubMedID: 10711890