Measuring RNFL thickness

Operator-dependent centring and automatic centring retinal nerve fibre layer (RNFL) thickness measurement patterns (RNFL3.45 and NHM4) have been shown to be in good agreement, according to a study published in Clinical and Experimental Ophthalmology.

Dr Shuning Li et al., Beijing Ophthalmology and Visual Science Laboratory, Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, China, conducted a cross-sectional observational study on 153 eyes of 149 patients. RNFL3.45 and NHM4 were used to measure retinal nerve fibre layer thickness three times daily. The outcome measures were Student's paired t-test, intra-class correlation coefficient, and coefficient of variation, test–retest viability, Pearson's correlation coefficient and Bland–Altman analysis of RNFL thickness measurements.

Paired t-testing demonstrated that the difference between RNFL3.45 and NHM4 measurements were statistically significant in the severe glaucoma group. The Pearson's correlation test revealed a strong correlation of the mean RNFL.

Bland–Altman plots revealed that the differences between RNFL3.45 and NHM4 were larger at thinner RNFL values, but smaller at thicker RNFL values. The intra-class correlation coefficient for RNFL3.45 in control patients and glaucoma patients was 0.990 and 0.997, respectively. For NHM4 the intra-class correlation coefficient was 0.989 and 0.995 for the control patients and glaucoma patients, respectively.

RNFL3.45 and NHM4 are both sufficient methods for RNFL thickness.