Name

Largeur du canal scléral et drusen de la papille

Optic nerve drusen are acellular deposits located in the optic nerve head of up to 2.4% of the population. Their pathogenesis remains unknown, although it has been theorized that eyes with optic nerve drusen have a smaller scleral canal, which presumably leads to continuous calcium deposition secondary to physical compression, axonal dysregulation/disruption, and extrusion of mitochondria into the extracellular space. The purpose of this study was to determine whether subjects with optic nerve drusen have smaller scleral canals than subjects without optic nerve drusen, using spectral-domain optical coherence tomography.

We conducted a retrospective study involving patients from Hôpital Fondation A. de Rothschild in Paris. Our study included 103 eyes from 55 patients with optic nerve drusen and 102 eyes from 55 healthy age-matched control subjects. Assessment of scleral canal diameter was performed on all subjects using optical coherence tomography scans with enhanced depth imaging scans of the optic disc. Measurement comparison using Student's t-test was performed in the statistical analysis. 

The average diameter of the scleral canal in the optic nerve drusen group was 1585 µm vs. 1556 in the controls group (p = 0.202, two-tailed independent t-test). There was no statistically significant difference between the two groups. Further age-stratified analysis also showed no statistically significant difference between the average diameters of the drusen-containing optic disks of patients and those of the optic discs of the controls. 

We have shown that eyes with optic nerve drusen have scleral canals that are comparable in size with those of control eyes. This result challenges the common assumption that scleral canals are larger in healthy controls than in optic nerve drusen patients. Different studies tried to assess the correlation between optic nerve drusen and scleral canal sizes by OCT measurements, but there is discrepancy in the existing literature. While some found smaller scleral canals in optic nerve drusen patients than in healthy controls ; others found significantly larger scleral canals in patients with optic nerve drusen compared to patients without optic nerve drusen.

Our results prompt us to conclude that scleral canal size is an unlikely aetiological factor contributing to drusen development.