New Threshold for Large Optic Discs in Children Using Bruch's Membrane Opening Area

To compare the peripapillary retinal nerve fiber layer (pRNFL) thickness of large optic discs in children (LOD-C) with normal sized optic discs in children (NOD-C) and large optic discs in adults (LOD-A).

We included 127 eyes per group (n = 381). Optic discs were considered large if the Bruch's membrane opening (BMO) area was ≥2.5 mm2. pRNFL thickness and minimal rim width (BMO-MRW) were compared between the pediatric groups and the large optic disc groups.

The mean global pRNFL thickness (3.5-mm circle) was 100.2 ± 12.1 µm for LOD-C, 95.9 ± 11.7 µm for NOD-C, and 97.7 ± 10.5 µm for LOD-A. It was significantly thicker in LOD-C compared with NOD-C; the difference decreased toward the periphery. The mean global BMO-MRW was 280.0 ± 41.1 µm for LOD-C, 320.7 ± 10.5 µm for NOD-C, and 252.9 ± 45.8 µm for LOD-A. It was significantly thinner in LOD-C compared with NOD-C, and significantly thicker in LOD-C compared with LOD-A. pRNFL and BMO area showed a positive correlation which was higher if BMO area was >2.8 mm2, BMO-MRW and BMO are showed a negative correlation which was higher if BMO area was <1.9 mm2.

RNFL and BMO-MRW of pediatric optic discs with BMO area <1.9 mm2 and >2.8 mm2 should be interpreted with caution, because they seem to be strongly influenced by optic disc size.

The novel thresholds for small and LOD-C will help to account for the effects of disc status on RNFL and MRW. They will furthermore help clinicians to better diagnose children with suspicious discs for glaucoma.