We appreciate Dr Baum's letter about our study of tearing in newborns1 and understand the reason for his comment about our use of the term basal tear secretion. We are aware of Jordan and Baum's 1980 article in which they contended that the Schirmer test using topical anesthesia (Schirmer tear test #2, Alcon Laboratories, Fort Worth, Tex) does not totally suppress reflex tearing because of residual eyelid and cilia stimulation by the paper strip.2 Theoretically, these authors indeed may be correct. This effect, however, was not evident in 5 of our preterm infants in whom reflex secretion amounted to only 0- to 2-mm wetting of the strips. Jordan and Baum measured a notable decrease in tear volume from approximately 7 to 2.4 µL and a decreased tear meniscus following the use of a topical anesthetic; the 2.4-µL figure may or may not represent basal secretion. Their findings that stimulation of the lower eyelid margin increased the turnover by 300% was determined by fluorophotometry after a Schirmer test strip filter paper (Whatman 41, Whatman, Alcon Laboratories) was lightly rubbed on the lower eyelid margin and cilia for 15 seconds. One may question how closely this maneuver emulates the effect of a Schirmer test strip, as it rests in one position on the lower eyelid during the clinical test.
Isenberg SJ, Apt L. Basal vs Reflex Lacrimation. Arch Ophthalmol. 1999;117(1):140-141. doi: