Impact of melanin on choroidal measurements.

The thickness of the choroid is measured on the optical coherence tomography (OCT) as the distance between the hyperreflective retinal pigment epithelium and the hyperreflective chorio-scleral junction, contributed by the choroidal vessels and choroidal melanocytes. Our hypothesis is that the amount of absorption and reflectance of the infrared wavelength OCT light by the melanin present in the choroidal melanocytes contribute to the visibility of the choroidal structures and choroidal thickness on OCT. We explain this hypothesis via two representative cases with choroidal pigmentary abnormalities. In conclusion, we believe that the optical properties of the melanin in choroid influences choroidal measurements and may lead to inaccurate assessment. Therefore, further understanding about choroidal pigmentation is necessary before we further adapt choroidal biomarkers in our clinical practice.