Copyright 1999 American Medical Association. All Rights Reserved. Applicable FARS/DFARS Restrictions Apply to Government Use.1999
In the article, "Development of Tearing in Preterm and Term Neonates," Isenberg et al1 extend their investigations in newborn tearing and clearly demonstrate that preterm infants have less tearing as measured by Schirmer tear test strip results, both with and without topical anesthesia. After acknowledging that "some think that nearly all tearing is reflex,"2 however, they define Schirmer tear test results with and without topical anesthesia as basal and reflex lacrimation, respectively. Since the filter paper strip used for Schirmer testing evokes reflex lacrimation due to stimulation of eyelid cilia even after the ocular surface is anaesthetized,2 they are inaccurate in terming the results of Schirmer testing after topical anesthesia as "basal secretion." They also believe "It is helpful . . . to consider total tear production as the relative sum of basal and reflex secretion."1(p775) I do not know of any published evidence that demonstrates anything other than reflex lacrimation. In support of their definitions, Isenberg et al1 cite an article by Keith and Boldt3 and conclude that "congenital absence of the lacrimal gland . . . affects reflex more than basal secretion," a conclusion never reached by Keith and Boldt. In that single case report, minimal tearing was evoked but no discernible lacrimal gland was seen on computed tomographic scan or direct visual observation. Hypoplasia of the gland may be sufficient to escape detection by these techniques.
Baum JL. Basal vs Reflex Lacrimation. Arch Ophthalmol. 1999;117(1):140-141. doi: