Evaluation of optic nerve head morphology of small optic discs in healthy eyes with different optical coherence tomography parameters.

BACKGROUND/ AIM

To compare Bruch's Membrane Opening- Minimum Rim Width (BMO-MRW), peripapillary retinal nerve fibre layer (pRNFL) thickness at different peripapillary diameters, and ganglion cell layer- inner plexiform layer (GCL-IPL) thickness between in eyes with small optic discs and normal discs.

METHOD

In this cross-sectional study, we selected healthy eyes. The patients were divided into two groups: the first group consisted of those with a disc area smaller than 1.60 mm² (Small disc group, 92 patients), and the second group included those with a disc area between 1.60 mm² and 2.50 mm² (Normal disc group, 71 patients). Spectralis OCT (Heidelberg Engineering, Inc., Heidelberg, Germany) was used to measure BMO-MRW and pRNFL thickness at three different diameters (3.5 mm, 4.1 mm, and 4.7 mm) using the Glaucoma Module Premium Edition (GMPE) software version 6.0. The thickness of GCL-IPL and pRNFL at a diameter of 3.4 mm were measured using Cirrus OCT (Carl Zeiss Meditec, Dublin, CA, USA).

RESULTS

In the small disc group, the disc area, rim area, and cup/disc ratio were smaller compared to the normal disc group (p < 0.05 for each). In the small disc and normal disc groups, pRNFL thickness at each three diameters (3.5 mm, 4.1 mm, and 4.7 mm) measured by Spectralis OCT were similar in all quadrants (superior temporal, superior nasal, nasal, inferonasal, inferotemporal, and temporal) and GCL-IPL (average, minimum) and pRNFL thickness measured with Cirrus OCT were similar in all quadrants (superior, nasal, inferior, and temporal). However, BMO-MRW measurements in all quadrants were larger in the small disc group (p < 0.05 for all).

CONCLUSION

RNFL and GCL-IPL measurements were similar in all quadrants in both group. However, BMO-MRW measurements were higher in all quadrants in the small disc groups.