Abstract

P 253

Heidelberg Spectralis OCT: Dependence of the central retinal thickness and the parapapillary nerve fiber layer thickness on axial length of the eye and refraction in healthy persons

Ann-Christin Stiller, Yaroslava Chopovska, Melanie Jäger, Birgit Lorenz
Klinik und Poliklinik für Augenheilkunde, Standort Gießen, Universitätsklinikum Gießen und Marburg GmbH, Gießen

Objective
The purpose of the study was to investigate a dependence of the central retinal thickness and the parapapillary nerve fiber layer thickness, measured with Spectralis-OCT (Heidelberg Engineering, dual SD-OCT and cSLO system), on the refraction and the axial length of the globe.
Methods
Measurements were performed on 53 right eyes of healthy subjects, aged 23 to 30 years. Central volume scan consisting of 25 single scans was performed through the macula with Spectralis OCT. A circular scan around the optic nerve was performed to measure the thickness of the parapapillary nerve fiber layer. The refraction was measured in miosis using an autorefractometer (Topcon). The axial length of the eye was measured with an IOL-Master (Zeiss, Meditec). Minimal foveal and central retinal thickness, inner and outer EDTRS- zones, macular volume and parapapillary nerve fiber layer thickness were evaluated for a possible dependence on refraction and axial length of the globe using Pearson-regression.
Results
The spherical equivalent ranged between –6.75 dpt and +2.5 dpt (mean -0.95 dpt), the axial length between 22.23 and 27.12 mm (mean 23.81 mm). There was no detectable dependence of the minimal foveal and the central retinal thickness, of the outer macular zones, of the central and outer or the total volume of the macula on both parameters. Although there was no dependence of the inner macular zones on the spherical equivalent, the measured retinal thickness of the inner superior, nasal and inferior zones and the total volume of the inner retinal zones decreased with increasing axial length of the globe (p>0.05). A clear correlation was found between the superior and inferior parapapillary nerve fiber layer thickness and the spherical equivalent and the axial length of the globe (p<0.01; r>0.4). On the contrary there was no dependence of the thickness of the temporal and nasal nerve fibre layer on both parameters (p>0.4).
Conclusions
Because of the high speed measuring with Spectralis OCT and adjustment of the eye movements (Eye tracker) with cSLO it is now possible to measure especially the foveal retinal thickness with a high grade of accuracy. Whereas in healthy eyes the parafovea is thinner with increasing axial length of the globe, the foveal thickness, the total volume of the macula and the physiologically thinner areas of the nerve fiber layer are not affected by the axial length of the globe.

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