Abstract
PurposeTo measure retinal nerve fiber layer (RNFL) thickness in a population-based setting.MethodsIn the population-based Beijing Eye Study 2011 with 3468 individuals, RNFL thickness was measured in a subgroup of 1654 (47.7%) study participants by spectral domain optical coherence tomography (iVue SD-OCT).ResultsMean RNFL thickness was significantly (P<0.001) higher in the inferior sector (131.4±20.6 µm) than the superior sector (126.1±19.1 µm), where it was higher than in the temporal sector (79.8±12.2 µm;P<0.001), where it was higher than in the nasal sector (75.1±12.6 µm;P<0.001). In multivariate analysis, mean global RNFL thickness (103.2±12.6 µm) increased significantly with younger age (standardized correlation coefficient beta:−0.30;P<0.001), larger neuroretinal rim area (beta:0.26;P<0.001), shorter axial length (beta:−0.21;P<0.001), thicker subfoveal choroidal thickness (beta:0.15;P<0.001), larger optic disc area (beta:0.10;P<0.001), less refractive lens power (beta:0.10;P<0.001), flatter anterior cornea (beta:0.07;P = 0.01) and female gender (beta:0.05;P = 0.03). In this population with an age of 50+ years, the age-related decline in RNFL thickness was 0.5 µm per year of life or 0.36% of an original RNFL thickness of 137 µm at baseline of the study at 50 years of age. Mean global RNFL thickness decreased by 2.4 µm for each mm enlargement of axial length.ConclusionsThe RNFL profile shows a double hump configuration with the thickest part in the inferior sector, followed by the superior sector, temporal sector and nasal sector. Factors influencing global RNFL thickness were younger age, larger neuroretinal rim, shorter axial length, thicker subfoveal choroid, larger optic disc, less refractive lens power, flatter anterior cornea and female gender. Beyond an age of 50+ years, RNFL decreased by about 0.3% per year of life at an age of 50+ years and by 2.4 µm per mm of axial elongation. These findings may be of interest for the knowledge of the normal anatomy of the eye and may be of help to diagnose diseases affecting the RNFL.
Highlights
The retinal nerve fiber layer (RNFL) is located between the inner retinal limiting membrane as basal lamina of the Muller cells and the retinal ganglion cell layer
The examination of the RNFL is of high importance for the diagnosis of optic nerve anomalies and diseases, since the retinal ganglion cell axons continue into the optic nerve fibers behind the optic nerve head
The RNFL can be assessed by conventional ophthalmoscopy [1], on wide-angle fundus photographs [2], by confocal scanner laser tomography [3], scanning laser polarimetry [4], and optical coherence tomography (OCT) [5,6]
Summary
The retinal nerve fiber layer (RNFL) is located between the inner retinal limiting membrane as basal lamina of the Muller cells and the retinal ganglion cell layer. The RNFL consists of the retinal ganglion cell axons, which are covered by astrocytes and bundled by processes of Muller glial cells. The examination of the RNFL is of high importance for the diagnosis of optic nerve anomalies and diseases, since the retinal ganglion cell axons continue into the optic nerve fibers behind the optic nerve head. With the clinical introduction of the new generation of spectral domain OCTs, the OCT based examination of the RNFL has become one of the most important tools to assess the status of the optic nerve. Since normative data of the RNFL thickness measured by the new generation of OCTs in population-based studies have been scarcely available so far [7], we conducted this study to measure the RNFL thickness by spectral domain OCT in the population-based Beijing Eye Study. A population-based study in contrast to a hospital-based investigation has the advantage to be free of a potential selection bias by the referring ophthalmologists
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