Abstract: Objective To put forward the medical identification theory for pilot candidates with primary iridociliary cysts by studying its onset features. Methods A total of 2 107 students graduated from senior middle schools in 2012 underwent slit-lamp examination.Those with confined peripheral iris bulging underwent routine ultrasound biomicroscopy (UBM). The number and sites of iridociliary cysts, changes of eye chamber and depth of anterior eye chamber axis were recorded. Results Slit-lamp examination showed local peripheral iris bulging in 16 candidates (16 eyes), accounting for 0.76% of the total candidates. The diagnosis of primary iridociliary cysts was established in 11 candidates (22 eyes) by UBM. The anterior eye chamber depth of the right and left eyes was 3.193 4 mm(range 2.614 -3.791 7 mm) and 3.189 8 mm (range 2.554 6 -3.781 8 mm), respectively. The incidence of anterior eye chamber change secondary to primary iridociliary cyst was 36.36% with angle closure and narrow angle of eye chamber accounted for 13.64%and 22.72%, respectively. Both huge iridociliary cyst and more than 2 iridociliary cysts were commonly observed in the candidates. Conclusion The onset features of primary iridociliary cysts are similar in pilot candidates and normal subjects. Those with poly- or huge iridociliary cysts accompaning shallow anterior eye chamber or marked change of anterior eye chamber angle are medically identified as disqualified pilot candidates. An overall medical identification should be made for those with single or small iridociliary cysts but not accompanying marked anterior eye chamber depth or angle change.