Optic nerve aplasia.

A 10-month-old child was referred in view of convergent squint in the right eye. Antenatal period was uneventful, and family history was noncontributory. The child had otherwise normal developmental milestones. The left eye was normal. The child did not follow light with his right eye. The right eye had 60 prism diopters of esotropia on modified Krimsky test, and ocular motility was full. The corneal diameter (measured during sleep) in the right eye was 6 mm compared to 10 mm in the left eye [Fig. 1a]. Iris was hypoplastic in the right eye [Fig. 1b]. Fundus examination of the right eye showed the absence of optic nerve head and retinal vessels [Fig. 1c]. A large area of chorioretinal atrophy was seen at the posterior pole along with posterior staphyloma and scleral show. Axial length was 22.10 and 19.96 mm in the right and the left eye respectively. Visually evoked responses were absent in the right eye. Magnetic resonance imaging of brain and orbit revealed absent optic nerve with no other intracranial anomalies [Fig. 1d]. The patient was diagnosed with right isolated optic nerve aplasia (ONA), and parents were apprised of the situation.

Figure 1

Colour photograph showing micro-cornea and esotropia in the right eye (a). Anterior segment photograph of the right eye showing hypoplastic iris (b). Colour fundus photograph of the right eye with optic nerve aplasia showing absent optic nerve head and retinal blood vessels, chorio-retinal atrophy, scleral show and visible large choroidal vessels (c). Axial scans of magnetic resonance imaging show absent optic nerve on the right side (d, arrow)

Comment

ONA is a rare developmental anomaly characterized by the absence of optic nerve and retinal blood vessels.[1] It affects both the genders and has no race predilection.[2] While unilateral ONA is rarely associated with brain or developmental anomalies, bilateral ONA is frequently associated with intracranial abnormalities.[3] The commonly associated ocular anomalies include microphthalmos, microcornea, iris hypoplasia, irido-fundal colobomata and cataract.[4] The light perception is invariably absent. No optic nerve head is appreciated on fundus examination, and retinal vessels are absent. The pathogenesis of ONA is not clear, and several mechanisms have been proposed. Failure of mesodermal induction, secondary to a third-order neuronal defect in the ganglion cell layer is probably responsible.[5]

Conclusion

This report highlights the striking clinical features of ONA associated with posterior staphyloma, an association not described previously to the best of our knowledge (searched in PubMed and Google by keywords ONA, staphyloma, ocular features). Detailed neuroimaging is warranted in such cases to exclude associated central nervous system anomalies.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.