Abstract
Purpose: :
The advent of high resolution optical coherence tomography (HR-OCT) images of retinal layers requires to validate novel interpretation paradigms. Here, we investigated the interindividual variability of macula layers segmentation in normal subjects.
Methods: :
We quantitatively and qualitatively analysed HR-OCT images of the macula in a cohort of healthy subjects. A custom made software for image segmentation allowed boundary detection and quantitative analysis of 5 retinal layers: outer segments, inner segments, outer nuclear layer (ONL), outer plexiform layer (OPL) and inner retina. We combined this analysis with en face photoreceptor imaging using adaptive optics, and with axial length measurement.
Results: :
Fifty-three subjects (mean age 32 years) were included. Most of the variability of mean central macular thickness was linked to variations of the shape of the foveal pit, itself mostly due to variations in inner retinal morphology. In the perifoveal area, ONL and OPL thickness were inversely correlated. We noted in more than 50% of eyes frank asymmetry of the OPL which was not correlated to total retinal thickness. Cone photoreceptor density was not correlated with these variations suggesting that variations in the OPL/ONL complex were not related to photoreceptor population.
Conclusions: :
Variations in the organization of the fovea, especially of inner layers, largely accounts for the variability of central macular thickness. In the parafoveal area the respective cellular correspondance of the so-called OPL and ONL remains uncertain, thus interpretation of these layers should be made cautiously. Our results may contribute to distinguish physiological and pathological variations of the macula. Further histological study are required to better understand the correspondance between optical imaging and structure in the retina.
Keywords: imaging/image analysis: clinical • macula/fovea