Purpose Reflectance of retinal nerve fibre layer (RNFL) can contribute to detecting the presence of glaucomatous damage and defining its extent. As a step towards developing a normative database for RNFL reflectance, we assessed within‐eye and between‐subject variability for RNFL reflectance in healthy eyes. Methods Vertical 30° × 15° volume scans at the optic disc were gathered using SD‐OCT (Spectralis OCT) from people free of eye disease. Scans were gathered for both eyes of 30 younger adults (mean ± SD = 27 ± 3 years) and for one eye of 30 older adults (68 ± 8 years). Reflectance was quantified for each voxel as the depth‐resolved attenuation coefficient (AC). Values for AC were extracted for four slabs (0–52, 24–52, 24–36 and 36–60 μm) and at depths from 24 to 60 μm below the inner limiting membrane (ILM) in 4 μm steps. Results Between‐subject and within‐eye standard deviations (SDs) for the logarithm of AC were similar; median differences were 0.02–0.03 log unit across all four slabs and depths from 24 to 48 μm. Means for the logarithm of AC were higher for younger than older eyes by ~0.1 log unit; this age effect was not due to differences in the raw reflectance of the RNFL, but rather to age‐related changes in reflectance of deeper retina affecting the calculation of AC. Conclusions In both groups, within‐eye variability in RNFL reflectance near the optic disc was similar to between‐subject variability. A better understanding of within‐eye variability would be useful for developing normative databases.

Citation information: Cheung H, King BJ, & Gast TJ. Presumed activated retinal astrocytes and m€ uller cells in healthy and glaucomatous eyes detected by spectral domain optical coherence tomography.

PurposePerfluorocarbon liquid (PFCL) can be used to unfold the retina during vitreoretinal surgery. The subretinal migration of PFCL is an undesirable complication of its use in cases with posterior retinal breaks particularly with associated proliferative vitreoretinopathy. The ‘soft shell’ technique, which is the use of hyaluronate (HA) to cover the break, has been described to prevent such migration. Our aim is to assess the scientific basis of this technique.MethodsA porcine retina model with two holes on a transwell was used to mimic the retinal breaks in vivo. HA solution was used to cover one of the holes. Perfluoro‐n‐octane (PFO) was added on top of the retina model incrementally using a syringe pump. The liquid level of PFO required to cause rupture of the PFO/aqueous interface with or without the HA coating at the two holes was measured. The interfacial tensions between the PFO against water and against HA solution with different aqueous concentrations were measured using pendant drop analysis.ResultsThe interfacial tension between PFO and aqueous with HA coating (68.3 ± 1.29 mN/m) is statistically significant higher than the PFO/aqueous interface without hyaluronate (37.4 ± 3.40 mN/m) (p < 0.05). A higher PFCL level is required to cause the rupture of the PFO/aqueous interface at the hole with HA coating.ConclusionsA greater hydrostatic pressure is needed to rupture the PFO/aqueous interface in the presence of HA coating at the break. The increase may due to the increase in interfacial tension at the interface. This study provides the scientific explanation how the soft shell technique may work.