Abstract
Purpose: :
The aim of this study was to evaluate the correlation between axial length (AL) and the thickness of intraretinal layers in the macula.
Methods: :
Forty eyes of 40 healthy subjects (15 male and 25 female) were recruited for this study. The median age of the participants was 26 years (range: 8 to 67 years). The inclusion criteria were best-corrected Snellen visual acuity of 20/20 and no history of any eye diseases. If both eyes were eligible, the study eye was selected randomly. AL was measured for each eye using a Lenstar LS 900 (Haag-Streit AG, Koeniz, Switzerland) device. Optical coherence tomography (OCT) imaging of the macula was also performed by Stratus OCT (Carl Zeiss Meditec, Dublin, CA, USA). OCTRIMA software was used to process the raw data of the OCT scans and to determine the weighted mean thickness of 6 intraretinal layers and the total retina. The correlation between the AL and the thickness values were examined using linear correlation.
Results: :
The mean AL of the eyes was 22.99±1.04mm (range: 20.95 to 25.17mm). There was no significant difference in the thickness of any of the inraretinal layers between males and females. There was no correlation between the thickness of the retinal nerve fiber layer (RNFL), retinal pigment epithelium (RPE) and AL (p=0.13 and p=0.97, respectively). A slight negative correlation was observed between the thickness of the ganglion cell layer and inner plexiform layer complex, inner nuclear layer, outer plexiform layer and AL (p=0.048, r=-0.32; p=0.019, r=-0.37 and p=0.022, r=-0.37, respectively). The correlation was the strongest between the thickness of the outer nuclear layer and the total retina (p=0.003, r=-0.46 and p=0.002, r=-0.49, respectively). The RPE showed a positive correlation with age (p<0.001, r=0.53), while no correlation was obtained between age and any of the remaining intraretinal layers.
Conclusions: :
Our results have shown that in the macular area the thickness of the retina and all intraretinal layers except for the RNFL and the RPE correlate with AL with an increasing trend towards the outer layers. The sex and age of the subjects was shown to have no effect on the results, except for the RPE which was thicker with age. Although further research is warranted, it seems that the effect of AL on retinal layers should be taken into account in future studies.
Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • image processing • retina