Quantitative assessment of retinal and choroidal changes by enhanced depth imaging OCT in acute optic neuritis patients

Background

Optic neuritis is one of the common clinical neuro-ophthalmic diseases.Spectral-domain OCT (SD-OCT) is a valuable tool in assessing the thickness changes of retina, while enhanced depth imaging (EDI) OCT can further quantitatively and morphologically evaluate the changes of retina and choroid.The pathological mechanism of optic neuritis is unclear now.

Objective

This study was to quantitatively measure the retinal and choroidal thickness in early optic neuritis eyes by SD-OCT and EDI OCT.

Methods

A prospective cohort study was carried out in Tianjin Eye Hospital from July 2015 to May 2016.Twenty eyes of 20 patients with acute optic neuritis were enrolled as optic neuritis group and 22 eyes of 20 healthy subjects with matched age and gender were included in the normal control group.The mean thickness of retinal nerve fiber layer (RNFL) and choriod in superior, inferior, nasal and temporal quadrants at 3.4 mm around optic disc was measured, and the mean thickness of RNFL, ganglion cell layer (GCL), inner plexiform layer (IPL), inner nuclear layer (INL), outer plexiform layer (OPL), outer nuclear layer (ONL) and photoreceptor layer also was measured by EDI OCT.Pattern visual evoked potential (P-VEP) and visual field were examined in all the individuals, the correlations of mean defect (MD) with the thickness of RNFL, choroid and the thickness of RNFL, GCL, IPL, INL, OPL, ONL, photoreceptor layer at macular area were evaluated.

Results

The RNFL thickness values were (424.00±160.30), (428.40±169.83) and (108.15±50.66)μm in superior, inferior, nasal quadrants at 3.4 mm arear around optic disc in the optic neuritis group, which were significantly higher than (265.68±26.25), (283.27±52.81) and (72.68±12.01)μm in the normal control group (t=4.571, 3.814, 3.190, all at P<0.01), and there was no significant difference between the two groups (t=0.849, P=0.401), and no significant differences were found in choroidal thickness of 4 quadrants between the two groups (all at P>0.05). The thickness of RNFL, GCL and IPL at 1 mm area around macula and the thickness of GCL, IPL, INL at 3 mm area around macula were evidently thining in the optic neuritis group compared with the normal control group (all at P<0.05). The latency of P100 wave was (133.15±11.11) seconds in the optic neuritis group and that in the control group was (94.59±4.38) seconds, showing a significnat difference between them(t=15.058, P<0.05). Positive correlations were found between MD and the RNFL thickess in superior, inferior, nasal quadrants at 3.4 mm arear around optic disc (r=0.649, 0.649, 0.635, all at P<0.05), however, no evidently linear correlations were found between MD and choroidal thickness in 4 quadrands (r=-0.120, -0.102, -0.415, 0.120, all at P>0.05), and the thickness of RNFL, GCL, IPL, INL, OPL, ONL, photoreceptor layer at macular area was significantly linear correlated with MD.

Conclusions

EDI OCT can reflect the RNFL edema around optic disc and thining of various layers of retina at macular area in acuter optic neuritis eyes, however, the choroidal thickess is unchanged.EDI OCT is a useful tool in quantitative evaluation of retinal and choroidal thickness of early optic neuritis.