Recent Papers: The Ocular Surface
THE OCULAR SURFACE
The Ocular Surface, a quarterly, a peer-reviewed journal, is an authoritative resource that integrates and interprets major findings in diverse fields related to the ocular surface, including ophthalmology, optometry, genetics, molecular biology, pharmacology, immunology, infectious disease, and epidemiology. Its critical review articles cover the most current knowledge on medical and surgical management of ocular surface pathology, new understandings of ocular surface physiology, the meaning of recent discoveries on how the ocular surface responds to injury and disease, and updates on drug and device development. The journal also publishes select original research reports and articles describing cutting-edge techniques and technology in the field.
Maximal tear secretion evoked by controlled stimulation of corneal sensory nerves in healthy individuals and dry eye subjects
María L. MerinoJavier BelmonteJose RosasM. Carmen Acosta. Juana Gallar. Carlos Belmonte
ABSTRACT
Purpose: To measure, the tear flow changes evoked in healthy subjects and dry eye disease (DED) patients by controlled sensory stimulation of the eye surface with i-Onion™, a new stimulation device.
Methods: Sensory corneal nerves were stimulated with an instrument (i-Onion™) that ejects puffs of CO2 gas (99.9%) at 200 ml⋅min 1 for 3s, delivered 5 mm from the cornea. Using Schirmer test strips, tear volumes were measured over 3 min in the cornea of one eye before (basal tear volume -BTV) and in the other eye after stimulation of the sensory nerves with CO2 (stimulated tear volume -STV). These measurements were obtained from a control group of adults of either sex (17 students aged 20–30 and 29 subjects without signs of dry eye aged 25–61), a cohort of DED patients (aged 34–75) that included 12 asymptomatic, suspected DED subjects (Schirmer <7 mm and/or TBUT <10s), and 30 Sj¨ogren’s syndrome (SS) patients.
Results: CO2 stimulation significantly increased the tear volume (BTV = 14.6 ± 1.0 mm, STV = 19.0 ± 1.1 mm: n= 46) in 78% of control subjects, reflecting a mean tear reserve volume (TRV = STV-BTV) of 4.4 ± 0.8 mm. Individual differences were wide, and while no increase in reflex tearing was evoked in 30% of subjects with a BTV >10 mm, the remaining 70% responded vigorously to stimulation, even those with a BTV >18 mm. Asymptomatic DED subjects displayed weaker responses to CO2 stimulation, with lower STVs. Both the BTV and STV of SS patients were low, significantly below those of the healthy controls.
Conclusions: Measuring the rise in reflex tearing volume evoked by controlled corneal stimulation provides objective information about the tear glands’ secretory capacity in health and disease.