Purpose. The aim of this study is to characterise the changes in choroidal thickness during and after a prolonged accom modation period using optical coherence tomography (OCT). Subjects and Methods. This study used 24 test subjects (age 28.2 ± 2.6 years), with n = 18 assigned to the moderate myopic group (MSE: 2.6 ± 1.76 D) and n = 6 to the emmetropic group (MSE: 0.07 ± 0.24 D). The test subjects underwent an accommodation relaxation phase (ten minutes), an accom modation phase (twenty minutes of continuous accommoda tion), and another relaxation phase (ten minutes). Seven OCT scans (Topcon Corporation, Tokyo, Japan) were taken along a horizontal axis on each eye at fiveminute intervals. For each tomogram, the subfoveal, temporal and nasal choroidal thick ness was determined manually at three measurement points (2 mm apart) using a measurement tool. To trigger the process of accommodation, a mobile phone was attached to the side of the OCT device and the display was projected into the measurement beam path of the OCT via a semitransparent mirror (demand of accommodation = 5.0 D). Results. During accommodation, the choroidal thickness decreased significantly by an average of 8.06 ± 7.33 µm in the subfoveal region, 4.00 ± 11.00 µm in the nasal region, and 5.29 ± 12.52 µm in the temporal region (each with p < 0.01). Furthermore, emmetropic eyes showed a significantly strong er decrease in the subfoveal region (13.08 ± 8.58 µm) than myopic eyes (6.39 ± 6.06 µm). In the ten minutes following the accommodation phase, the choroid returned to its initial thickness, showing no significant difference (p = 0.80) in the degree of recovery between myopic and emmetropic eyes. Conclusion. The study shows that the process of accommo dation is associated with a decrease in choroidal thickness. The results further suggest that accommodation in myopic eyes entails a smaller decrease in choroidal thickness than in emmetropic eyes. The apparatus design developed spe cifically for this study to project a smartphone display into the measurement beam path of the OCT device is suitable for stimulating accommodation over a longer period while performing repeated OCT scans. Keywords myopia, accommodation, choroidal thickness