Retinal nerve fibre layer thickness measured with SD-OCT in a population-based study of French elderly subjects: the Alienor study

Abstract

Purpose: To establish normative data of retinal nerve fibre layer (RNFL) thickness in the elderly and to determine the factors influencing its thickness.

Methods: Peripapillary RNFL thickness was measured with spectral domain OCT (SD-OCT) in 210 elderly participants from the Alienor population-based study who were aged 75 years or older. The measure was assessed in six segments (the superotemporal, temporal, inferotemporal, inferonasal, nasal and superonasal segments). RNFL data were analysed across age and sex strata in non-glaucoma participants. Mixed linear models were used to evaluate the associations of RNFL thickness with age, sex, ocular parameters and vascular risk factors.

Results: The mean global RNFL thickness was 91.4 μm (SD: 12.6), ranging from 55 to 122; the highest values were found in the inferotemporal and superotemporal segments. After adjustment for sex and ocular parameters, including axial length, increasing age was significantly associated with lower thickness globally (mean thinning per decade = 5.6 μm, p = 0.003), in the superotemporal (-12.7 μm per decade, p < 0.0001) and inferotemporal (-8.1 μm per decade, p = 0.022) segments. RNFL thickness tended to be higher in women than in men, but this trend was significant only in the inferotemporal segment (+6.6 μm for women, p = 0.012). The axial length was associated with RNFL thickness globally and in most segments. RNFL thickness did not differ according to cataract extraction. There were no associations between vascular factors and RNFL thickness.

Conclusion: Retinal nerve fibre layer thickness decreased with age globally and in the supero- and inferotemporal segments, even after 75 years; it also tended to be higher in women, particularly in the inferotemporal segment. Normative data on RNFL thickness should consider these characteristics as well as ocular parameters, particularly axial length.

Keywords: RNFL thickness; SD-OCT; elderly; population-based study.