MRI scans that measure the optic nerve may be a moderately reliable alternative in diagnosing optic nerve hypoplasia and predicting visual outcomes, a study in the British Journal of Ophthalmology suggests. However, fundus photography to measure optic nerve size should be the main point of reference for an accurate confirmation of the condition, the study’s team added.

In patients with optic nerve hypoplasia, the optic disc can be challenging to see without fundus photography. And since the use of MRI in previous research showed conflicting results, the current investigation used a disease registry to determine the reliability of orbital MRI measurements of the optic nerve diameter to diagnose ONH and the correlation with vision outcomes.

The study included 140 patients with optic nerve hypoplasia (13% unilateral) who were approximately five years old. Of these, the researchers identified 43 subjects who had both orbital MRI and fundus photography prior to two years of age.  The investigators compared measurements of the optic nerve diameter from orbital MRI scans with the standard relative optic disc size taken with fundus photography.

All patients had visual acuity tests when they were five. Relative disc size (disc diameter/disc-macula distance) <0.35 showed 100% sensitivity and specificity for the diagnostic confirmation of optic nerve hypoplasia.

The optic nerve diameter measurements by orbital MRI showed a moderate correlation with disc diameter/disc-macula distance and moderate sensitivity for the diagnosis of optic nerve hypoplasia. Final visual acuity correlated well with disc size measurements with fundus photography but only moderately with optic nerve diameter assessed with orbital MRI.

These results further support the prognostic value of fundus photography for eventual vision outcomes in this population, the researchers noted.