Abstract
Purpose: :
To investigate the dependence of the central retinal and the parapapillary nerve fiber layer thickness (PNFL), measured with Spectralis-OCT (Heidelberg Engineering, dual SD-OCT and cSLO system), on the refraction and the axial length of the globe (ALG).
Methods: :
Central volume scan (49 single scans) through the macula and circular scan around the optic nerve were performed with Spectralis OCT in 107 randomly selected eyes of healthy subjects. Refraction was measured in the undilated pupil using an autorefractometer (Topcon). ALG was measured with an IOL-Master (Zeiss, Meditec). Minimal foveal thickness and 9 ETDRS-zones, macular volume and PNFL were evaluated for a possible dependence on refraction and ALG using multiple regression analysis.
Results: :
One hundred two eyes were included in the study (age of subjects 19 to 30, mean 26.2 years). The spherical equivalent (SE) ranged between -7.5 and +4.125 dpt (mean -1.11), and ALG between 21.63 and 26.45 mm (mean 23.96). There was no detectable dependence of the minimal foveal retinal thickness, of the inner zones, of the inner and outer zone volumes or the total volume of the macula on both parameters. Although there was no dependence of the outer zones on SE, the measured retinal thickness of the outer temporal, superior and nasal zones decreased with increasing ALG (p<0.05). Central retinal thickness increased with increasing ALG (p=0.03). A clear correlation was found between the nasal and inferior PNFL and SE and t ALG (p<0.01; r>0.4). On the contrary, there was no dependence of the thickness of the temporal PNFL on both parameters (p>0.8), and nasal PNFL on ALG.
Conclusions: :
Because of the high speed measuring with Spectralis OCT and adjustment of eye movements (Eye tracker) with cSLO it is now possible to perform measurements with a high degree of accuracy. Whereas in healthy eyes the parafovea is thinner with increasing ALG, foveolar thickness, total volume of the macula and the physiologically thinner areas of the PNFL are not affected by this parameter.
Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • retina • refraction