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Related Experiment Videos

Basic tear flow. Does it exist?

A Jordan, J Baum

    Ophthalmology
    |September 1, 1980
    PubMed
    Summary
    This summary is machine-generated.

    Physiologic tear flow is maintained with age, but topical anesthetics significantly reduce tear volume and reflex tearing in both young and old individuals. Lid stimulation can still increase tear turnover despite anesthesia.

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    Area of Science:

    • Ophthalmology
    • Physiology

    Background:

    • Tear film dynamics are crucial for ocular surface health.
    • Age-related changes in tear production and sensation are not fully understood.
    • Topical anesthetics are commonly used in ophthalmology but can affect tear function.

    Purpose of the Study:

    • To compare tear flow and volume in young and old adults.
    • To evaluate the effects of topical anesthetics on tear secretion.
    • To investigate the role of reflex tearing in response to stimulation.

    Main Methods:

    • Fluorophotometry and Schirmer testing were used to measure tear flow and volume.
    • 15 healthy volunteers (young and old) participated.
    • Corneal and conjunctival sensitivity were assessed with and without topical anesthesia (proparacaine 0.5% vs. cocaine 4%).

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    Main Results:

    • Proparacaine 0.5% provided better anesthesia with fewer complications than cocaine 4%.
    • Older subjects showed less reflex tearing but similar physiologic tear flow and sensitivity compared to younger subjects.
    • Topical anesthetics significantly reduced tear flow and volume in both age groups.
    • Lid margin and cilia stimulation increased tear turnover by over 300%, even with anesthesia.
    • Schirmer testing with anesthesia yielded higher flow rates than fluorophotometry measurements of physiologic or post-anesthetic tear flow.

    Conclusions:

    • Physiologic tear secretion is age-independent in healthy individuals.
    • Topical anesthetics significantly impair reflex tearing and reduce overall tear volume.
    • Tear secretion is highly dependent on sensory input, with reflex tearing playing a major role.