In 1958, Leydhecker et al. measured IOP in 10,000 normal subjects with a Schiotz ophthalmometer and concluded that the distribution of IOP in the normal population was not normal and that the right side of the distribution curve was skewed upward. For convenience, the normal IOP range was found to be 11-21 mmHg (Goldmann’s pressure flattening IOP) based on statistical rules. In functional terms, “normal IOP” is defined as a value that does not lead to glaucomatous retinal optic nerve morphology and visual impairment. However, the range of this normal population is limited and does not include data for minors. Recent studies have differed as to whether the normal IOP values for adolescents and children can be extended to the normal population statistics described above. Kageyama et al [9] performed NCT in 180 healthy children aged 6 months-15 years with a success rate of 72.2% (130/180), and the youngest child who completed the examination was 2 years old with a result of 10-28 mmHg (15.1± 2.6 mm Hg). These studies suggest that the upper limit of the normal range of IOP in adolescents is likely to be higher than 21 mmHg. When the body mass index (BMI) is ≥30 kg/m2, the IOP measurement is high and the IOP pressure difference is increased. In addition, it has been suggested that IOP values tend to decrease with age. Therefore, a combination of factors should be considered when determining whether IOP is normal or not.