Choroidal thickness in high refractive errors using spectral-domain optical coherence tomography

Aims of Study: 1. To determine the choroidal thickness CT in eyes of subjects with high refractive errors, using SD-OCT.; 2. To correlate the CT with the refractive error and the axial length in these eyes. Materials and Methods: In this cross-sectional observational study 87 subjects with high myopia, i.e., spherical equivalents (SE) >-6.0D and high hypermetropia, i.e., SE> +3.0 D, aged between 5 to 50 years and with a best-corrected visual acuity (BCVA) of 6/9 or better, were included. In each eye, the CT was measured using SD-OCT scanning at seven retinal points, i.e., subfovea and 0.5 mm, 1.0 mm and 1.5 mm nasal as well as temporal to the fovea. Results: The CT in high myopic eyes was significantly less and in high hypermetropic eyes significantly more than in the controls, with the thinnest choroid present 1.5 mm nasal to the fovea in high myopic eyes and the thickest choroid present subfoveally in high hypermetropic eyes. The subfoveal CT in high myopic eyes had the strongest positive correlation with the SE of refractive error. In high hypermetropic eyes, the strongest positive correlation was found 1.5 mm temporal to the fovea, the point that also showed the strongest negative correlation between the axial length (AL) and the CT. Conclusions: High myopic eyes, i.e., with SE>-6D, have significantly thinner choroids than emmetropes. The CT decreases with an increase in the degree of myopia. High hypermetropes (i.e., SE > + 3 D) have significantly thicker choroids than emmetropes. Higher degrees of hypermetropia and shorter eyeballs are associated with thicker choroids. Keywords: Choroidal thickness, High myopia, High hypermetropia, Optical coherence tomography.