PURPOSE. To establish a normative range of intraocular pressure (IOP) in preterm infants and to identify important perinatal factors that could affect the IOP during the early weeks of neonatal life. METHODS. The IOP of 104 preterm infants, with a median (interquartile range) gestational age of 29.8 (28.7-30.9) weeks and birth weight of 1208 (1049 -1370) g, were assessed in a university-affiliated tertiary neonatal center. These infants had IOP measured by a handheld tonometer at 1, 4, 6, 8,

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... 10 weeks of postnatal age. The mixed-effects models were used to evaluate the longitudinal IOP measurements and to identify critical perinatal factors that would significantly affect the ocular pressure. RESULTS. A percentile chart of IOP in preterm infants was constructed, and the median (10th-90th percentile) IOP ranged from 16.9 (12.3-21.5) to 14.6 (10.1-19.2) mm Hg at 26.1 and 46.4 weeks of postconceptional age, respectively. The IOP was significantly and negatively associated with postconceptional age (P Ͻ 0.001), mean blood pressure (P ϭ 0.01), Apgar score at 1 minute (P ϭ 0.04), and use of inhaled corticosteroids (P ϭ 0.03), but was positively correlated with the commencement of high-frequency oscillatory ventilation (P ϭ 0.01). CONCLUSIONS. A quantitative statistical model has been developed and a percentile chart of IOP constructed for preterm infants that could be used for future reference. Pediatric ophthalmologists and neonatal clinicians can compare the IOP of preterm infants against this chart and make relevant quantitative adjustments for critical perinatal factors so that the IOP may be properly evaluated, both in healthy and ill infants.