Abstract
Purpose: :
To investigate the development of normal neonatal tear volume and protein concentration, with age and weight.
Methods: :
Two experimental groups were recruited: 30 premature infants (14 female, 16 male; post–conception age (PCA) 35.77±1.77 weeks, 1.87±0.54kg) and 40 full–term infants (19 female, 21 male; 39.86±1.27 weeks, 3.42±0.53kg). As a control, 22 adults (10 female, 12 male; age 24.95±3.63 years) were also recruited. One non–stimulated sample was taken from the lower tear meniscus of one eye using a cellulose rod. This tear collection technique is non–invasive and ensures minimum stimulation of the ocular surface. Tear collection was repeated for 12 premature infants (7 female, 5 male; 37.19±1.76 weeks, 1.97±0.43kg ) and 14 full–term infants (8 female, 6 male; 47.76±6.14 weeks, 5.04±1.34kg). Where volume permitted, samples were assayed with the Bradford test for their total protein content.
Results: :
The mean tear volume (µl ±sd) in premature infants was 2.25±1.28 (6/30 samples <0.5µl) and in full–term infants 2.70±2.29 (9/40 no tear sample detected, 9/40 samples <0.5µl). A repeated sample from the premature group was 5.52±4.84 (all >0.5µl) and from repeated full–term infants 4.51±6.09 (all >0.5µl). In adults the tear volume was 8.95±8.54 (1/22 no tear sample detected). No difference was found between the premature and full–term infant groups (Tukey, p>0.05). Tear volume increased significantly for the repeated tear collection and approached adult like levels (Tukey, p>0.05). However, all infant group volumes were still lower than the adult’s tear volume (ANOVA, p<0.001). Mean total tear protein concentrations (g/l ±sd) was 12.43± 4.32 in premature infants and 10.95± 5.51 in the full–term infants. The repeated premature group was 14.84± 4.29 and 12.93± 3.99 in the repeated full–term infants. In adults the total protein was 13.04± 3.46. No significant difference was found in protein concentrations between any of the groups (ANOVA, p>0.05).
Conclusions: :
1) Premature and full–term infants have a lower tear volume than adults; 2) No difference between premature and full–term infant tear volumes; 3) Tear volume increases rapidly after birth; 4) No differences in total tear protein concentration, despite volume differences.
Keywords: cornea: tears/tear film/dry eye