Purpose <p>To study the peculiarities of a morphologic pattern of tear ducts depending on their biometric characteristics in primary acquired nasolacrimal duct obstruction (PANDO).</p> Methods <p>Lacrimal sac wall samples were obtained from 21 patients with PANDO. The mean slice area of the vertical part of the tear ducts was calculated, and two groups were defined: with stenotic (<i>n</i> = 11) and ectatic changes (<i>n</i> = 10). A histologic, histochemical, and immunohistochemical studies were performed. Statistical analysis was performed, comparing the mean values in the two groups, as well as correlation analysis. Differences were considered reliable at <i>p</i> &lt; 0.05.</p> Results <p>The stroma of the lacrimal sac wall exhibited evidence of an inflammatory reaction, regions of fibrous component proliferation, and an increased area of collagen fibers with a predominance of type I collagen. Quantitative analysis confirmed the number of α-SMA-positive cells, which were counted to assess their distribution and correlation with severity of fibrotic changes. The area of the vertical section of the tear duct correlated with the area of the fibrous component and the α-SMA-positive cells. Type I collagen density was in correlation with the age of the patients. The area of collagen and α-SMA-positive cells in patients with stenotic and ectatic changes was statistically significantly different.</p> Conclusion <p>The degree of ectasia showed a significant correlation with the severity of fibrotic changes, including the area of the fibrous component and the number of α-SMA-positive cells. These findings highlight the close relationship between morphological and biometric characteristics in tear duct pathology.</p>