Thickness differences in specific sections of the retinal nerve fiber layer (RNFL) as seen on OCT-angiography (OCT-A) may help clinicians distinguish between superior segmental optic hypoplasia (SSOH) and normal-tension glaucoma (NTG), a study in the Journal of Glaucoma suggests.

While a differential diagnosis between the two conditions has often posed a challenge for clinicians and several modalities have been developed to solve this issue, no standard method has yet been established, the researchers noted in their paper.

The retrospective study included 26 patients with SSOH with definite visual field (VF) defects and 40 patients with NTG who had inferior VF defects.

The study compared age, sex, intraocular pressure, refractive error, RNFL thickness and VF defects between the groups. In addition, the researchers compared the peripapillary vessel density measured on OCT-A between the groups.

On OCT RNFL imaging, the researchers observed thinner superonasal segments and thicker superotemporal areas in SSOH patients. In the OCT-A analysis, the peripapillary vessel density of the superonasal segment was significantly lower in the SSOH group than in the NTG patients. Additionally, the perpipalpillary vessel density was significantly higher in the superotemporal segment in participants with SSOH than in the NTG group.

The optimal superonasal-to-superotemporal ratio cutoff was 0.8828, with a sensitivity of 95% and specificity of 92.3% for the diagnosis of SSOH.

Further large-scale studies are required to verify the study’s findings, the researchers noted.

Lee SY, In JH, Kim CH. Usefulness of optical coherence tomography angiography in the differential diagnosis between superior segmental optic hypoplasia and normal-tension glaucoma. Journal of Glaucoma. May 8, 2020. [Epub ahead of print].