ObjectiveTo analyze the ultrasonographic features of adenoma of the nonpigmented ciliary epithelium (ANPCE). MethodsA retrospective series of case studies. From January 2014 to October 2021, 31 patients (31 eyes) with ANPCE (ANPCE group) were diagnosed in the eye center of Beijing Tongren Eye Center of Beijing Tongren Hospital, Capital Medical University, and 17 patients (17 eyes) with ciliary body melanoma (control group) diagnosed at the same time were selected as the control group. There was no significant difference in age (t=－0.564) and sex composition ratio (χ2=0.182) between the two groups (P=0.576, 0.670). All patients underwent ultrasound biomicroscopy to obtain the measurement parameters: tumor height, maximum basal diameter, maximum diameter, ratio of maximum diameter to basal diameter and ratio of maximum diameter to height; tumor location, shape, internal echogenicity intensity, echogenicity uniformity, degree of sound attenuation, invasion of iris, anterior displacement of the iris, lens subluxation were observed. The measurement parameters and observation indexes of the two groups were compared by independent sample t-test and χ2 test. Receiver operating characteristic (ROC) curve was drawn, area under the ROC curve (AUC) was determined, and parameter indicators with differential diagnosis value were screened. ResultsThe maximum diameter, height, maximum basal diameter, ratio of the maximum diameter to the maximum basal diameter, and the ratio of the maximum diameter to the height of the tumors in the ANPCE group and the control group were 5.64±0.98 mm, 4.24±0.59 mm, 3.66±0.71 mm, 1.58±0.34, 1.34±0.19 and 7.82±2.03 mm, 4.47±2.44 mm, 7.02±1.96 mm, 1.13±0.16, 2.09±1.06. The maximum diameter, the maximum basal diameter, and the ratio of the maximum diameter to the height of the tumor in the ANPCE group were all smaller than those of the control group, and the ratio of the maximum diameter to the maximum basal diameter was greater than that of the control group, and the differences were statistically significant (t=－4.159, －6.808,－2.924, 6.257; P<0.05). The tumors in the ANPCE group were mainly spherical (87.1%, 27/31), with no significant acoustic attenuation (77.4%, 24/31), less invading the root iris (77.4%, 24/31), and the tumors were mostly located in the ciliary body coronal (74.2%, 23/31); tumors in the control group were mainly hemispherical (47.1%, 8/17) or spherical (47.1%, 8/17), with significant sound attenuation (76.5%, 13/17), most of the tumors invaded the iris (70.6%, 12/17), and the tumors were mostly located from the pars plana to the coronal (76.5%, 13/17). There were statistically significant differences in the position, shape, sound attenuation degree, and whether it invaded the iris between the two groups of eyes (χ2=15.132, 19.767, 13.118, 10.581; P<0.05). The results of ROC curve analysis showed that the ratio of the largest diameter to the largest base diameter, the degree of sound attenuation and the AUC of whether the iris was violated were higher, which were 0.881, 0.769, and 0.740, respectively. ConclusionsUltrasound biomicroscopy is helpful in the diagnosis and differential diagnosis of ANPCE and ciliary body melanoma. The ratio of maximum diameter to maximum basal diameter, the degree of sound attenuation and whether it invades the root iris are important parameters to distinguish the two tumors.