Choroidal and photoreceptor layer thickness in myopic population

This study examined the profile of the choroidal thickness and photoreceptor layer thickness (PRLT) in healthy myopia subjects, with an attempt to find the connection between change of the choroidal thickness and retinal thickness changes.

A total of 64 study participants (64 eyes) were divided into 3 groups in terms of their refractive status: normal sight group (+1.0 D~-1.0 D), mild or moderate myopia group (-1.0 D~-6.0 D), high myopia group (>-6.0 D). The fovea and parafoveal region (the region of 6 mm diameter of the fovea as center) of the images were selected by spectral domain optical coherence tomography. A circle of retinal pigment epithelium (RPE) layer simulated by applying the least square curve fitting technique was obtained. Along the vertical direction of the RPE layer, choroidal thickness (choroidal thickness involved the total thickness at the fovea and parafoveal), PRLT, retinal thickness (RT), ganglion layer thickness (GLT), and retinal nerve fiber layer thickness (RNFLT) in the fovea (PRLT-f, RT-f) or in the -parafoveal region (PRLT-pf, RT-pf, GLT and RNFLT) were calculated by Image J software manually.

As compared with group 1, PRLT-pf, RT-pf, and choroidal thickness were significantly reduced (p<0.05) in group while no significant difference was found in PRLT-f, RT-f, GLT, and RNFLT between the 2 groups. Both univariate and forward multivariate linear regression analysis showed that PRLT-pf and choroidal thickness intertwined obviously.

In high myopia subjects, not only choroidal thickness, but also photoreceptor layer thickness in the parafoveal region decreased significantly. On the basis of neuron vascular unit theory, the change in choroidal thickness is significantly related to the alternation in PRLT and vice versa.