Background: The aim of this study was to investigate the diameters of the bony nasolacrimal canal by computed tomography in normal adult Mongolian population and the effect of gender and age on the nasolacrimal canal diameter. Methods: Using standart tomographic images, we measured the diameters, angle between the bony canal and nasal floor and length of the bony nasolacrimal duct in 150 patients without nasolacrimal duct disease. Results: The anterioposterior diameter of the bony nasolacrimal canal was 6.49± 1.06mm, transverse diameter was 4.56±0.9mm, angle between the bony canal and nasal floor was 69.6±8.1o. No significant difference in anterioposterior diameter and transverse diameter in gender. The angle between the bony canal and nasal floor was significantly greater in male. Conclusions This study may contribute to the establishment of a detailed anatomical and morphometric baseline of the bony nasolacrimal canal and provide useful information for the planning of interventions for nasolacrimal duct obstruction

Background: The shapes of the eye and upper eyelid are distinctive facial landmarks. The palpebral fissure is composed of the free edges of upper and lower eyelids the lateral and medial canthus. Many researchers confirmed that the morphometric characteristics of the palpebral fissure, canthal distance and exophthalmometirc value (EV) vary according to race, ethnicity, age and sex and normative values which may serve as a reference in the index population. Knowledge of normal dimensions, the existence of asymmetry of the palpebral fissure is of value in several clinical specialties including ophthalmology, plastic and reconstructive surgery and traumatology, where it plays a part in the patient evaluation, management and outcomes. Methods: This cross-sectional study was conducted in the Ophthalmological Department, Third State Central Hospital between January 2022 and August 2022. We included participants who are above 18 years, no history of congenital or traumatic craniofacial deformities, any orbital fractures, tumors and surgeries. All measured values that represent eyelid shape and EV were calculated by mean and standard deviation for statistical analysis. Results: A total of 103 participants aged 19-86 were included in the study, of which 44 (42.7%) were male and 59 (57.3%) were female. The distance between the lateral and medial canthus ranged from 20 to 35 mm, and the mean of the right and left side was 28.30+3.23 mm and 28.05+2.99 mm, respectively (p=0.561). The palpebral fissure height ranged from 5 to 13 mm, and the mean of the right and left side was 8.85+1.65 mm and 8.80+1.65 mm, respectively (p=0.816). The mean distance between the lateral canthi were 90.39+5.57 (range: 80-105 mm), whereas the mean distance between the medial canthi were 63.75+4.25 (range: 53-73 mm). The orbital height varied between 27-43 mm (33.73+3.72) and 26-44 mm (33.78+3.73) on the right and left sides, while the orbital width varied between 26-47 mm (36.75+4.53) and 27-45 mm (36.72+4.42) on the right and left sides, respectively. When measuring the exophthalmometric value (EV), the axial position of the eyeball, with the Hertel’s exophthalmometer, it ranged from 8 to 20 mm on both sides (mean value 13.68+3.01 and 13.71+3.00 on the right and left sides, respectively), and there was no statistically significant difference in symmetry (p=0.94). Conclusion The results are determined different from the findings of Chinese, Korean, Afro-American and Caucasian population based studies. Thus further evaluation is required to represent the normative value of Mongolian index population, that is highly beneficial for clinical assessment, diagnosis and management.