Tear osmolarity in premature infants.

Purpose: To measure and report tear osmolarity in premature infants and to assess the change, if any, that occurs with increasing maturity.

Methods: In a prospective study of consecutive infants born at less than 37 weeks gestational age undergoing screening for retinopathy of prematurity, serial measurements of tear osmolarity were obtained at preterm, term, and 3 months post-term. Mean ± standard deviation tear osmolarity and percentage of infants with tear osmolarity value greater than 308 and greater than 316 mOsm/L were calculated at each stage of maturity.

Results: Twenty-five premature infants of mean post-conceptional age 33.5 weeks and mean birth weight 1,159 ± 259 g were tested. Mean tear osmolarity was 296 ± 19.1, 302.8 ± 18, and 301.1 ± 20.9 mOsm/L at pre-term, term, and post-term, respectively. There was no significant effect for time on tear osmolarity values (P = .59). Tear osmolarity was greater than 308 mOsm/L in 32% and greater than 316 mOsm/L in 16%.

Conclusion: Mean tear osmolarity in premature infants is within the expected normal range for adults and shows no significant change at term or post-term. More than two-thirds of premature infants have tear osmolarity values below the suggested diagnostic cut-offs for dry eye disease in adults. Most preterm infants do not have a dry eye based on assessment of tear osmolarity.