Intraocular Pressure Values using IcareⓇ Rebound Tonometer and Correlation with Postconceptional Age in Premature Infants.

Purpose: This study aimedto determine a normative range of intraocular pressure (IOP) values measured with Icare rebound tonometer in premature infants and evaluate IOP variation over time and its correlation with the progression of postconceptional age (PCA). By doing so, we also evaluated advantages of this IOP-measuring method in this population when compared to more traditional methods.

Methods: We conducted a single-center prospective study that included premature infants (gestational age $\le$32 weeks) who were admitted to the neonatal intensive care unit (NICU) in Hospital Professor Doutor Fernando Fonseca. The study took place between January and December 2021. IOP was measured using Icare tonometer on the occasion of the first retinopathy of prematurity (ROP) screening requested by the NICU and again after a two-week interval if PCA was still $\le$37 weeks. IOP measurements were stopped at 37 weeks or if the infant was discharged. The evaluated outcomes were mean IOP values and their correlation with PCA.

Results: Thirty-four eyes of 17 preterm infants with a mean gestational age of 29.4 $\pm$ 2.3 weeks and a mean birth weight of 1222.9 $\pm$ 361.9 gr were evaluated. The mean IOP registered was 16.1 $\pm$ 6.4 mmHg, with a median value of 15.3 mmHg. The top 90${}^{th}$ percentile was 22.1 mmHg and the bottom 10${}^{th}$ percentile was 9.0 mmHg. The average IOP reduction was 4.8 $\pm$ 6.7 mmHg (P = 0.0019) within the two-week interval of PCA.

Conclusion: The mean IOP in premature infants was 16.1 $\pm$ 6.4 mmHg and this value significantly decreased by 4.8 $\pm$ 6.7 mmHg every two weeks of PCA.