• My Dashboard My Education Find an Ophthalmologist
  • Home
  • Coronavirus
  • For Ophthalmologists
    • Meetings
      • AAO 2022
        • Meeting Information
          • Past and Future Meetings
          • Mobile Meeting Guide
          • Contact Information
          • Annual Meeting News
          • Health and Safety
          • Policies and Disclaimers
        • Program
          • Program Highlights
          • Subspecialty Day
          • Virtual Meeting
          • Program Committees
          • CME
          • Meeting Archives
        • Expo
        • Registration
        • Hotels & Travel
          • Hotel Reservation Information
          • Chicago
          • International Attendees
          • Hotel Meeting Space
        • Presenter Central
          • Presenter Central
          • Abstract Selection Process
          • Submission Policies
          • Subject Classification/Topics
          • Instruction Courses and Skills Transfer Labs
          • Papers and Posters
          • Videos
          • Grand Rounds Symposium
          • Program Participant and Faculty Guidelines
          • Faculty Development Program
        • Exhibitors
          • Exhibitor Central
          • Exhibitor Portal Information
          • Exhibitor Prospectus
          • New Exhibiting Companies
          • Exhibitor Resources
          • International Exhibitors
          • Promotional Opportunities
          • Exhibitor Hotel Reservations
      • Mid-Year Forum
        • Registration and Travel
        • Congressional Advocacy Day
        • Advocacy Ambassador Program
        • Program
        • Schedule
        • Sponsored Attendees
        • News
      • Codequest
        • Codequest Instructors
        • Claim Codequest CME or CEU Credit
      • Eyecelerator
    • Clinical Education
      • COVID-19
      • Education
        • Browse All Education
        • Courses
        • Cases
        • Learning Plans
        • Interactive
        • Focal Points
        • Wills Eye Manual
        • Disease Reviews
        • Clinical Webinars
        • Diagnose This
        • Self-Assessments
        • Educational Centers
          • Glaucoma Education Center
          • Pediatric Ophthalmology Education Center
          • Laser Surgery Education Center
          • Myopia Resources
          • Oculofacial Plastic Surgery Center
          • Redmond Ethics Center
      • Journals
      • Guidelines
        • Browse All Practice Guidelines
        • Preferred Practice Patterns
        • Clinical Statements
        • Compendium Guidelines
        • Complementary Therapy Assessments
        • Medical Information Technology
        • Ophthalmic Technology Assessments
        • Patient Safety Statements
        • Choosing Wisely
        • Low Vision
        • Eye Care for Older Adults
        • Eye Disease Statistics
        • About the Hoskins Center
      • Video and Image Library
        • Browse All Videos
        • Clinical and Surgical Videos
        • Presentations and Lectures
        • 1-Minute Videos
        • Master Class Videos
        • Basic Skills Videos
        • Interviews
        • Images
        • Submit an Image
        • Submit a Video
      • Podcasts
        • Browse All Audio and Podcasts
        • Experts InSight
        • Ophthalmology Journal
      • News
        • Browse All Clinical News
        • Editors' Choice
        • Headlines
        • Current Insight
      • CME Central
        • Browse All CME Activities
        • Claim CME Credit and View Transcript
        • CME Planning Resources
        • Complete Your Financial Disclosure
        • Joint Sponsorship Portal
        • LEO Continuing Education Recognition Award
        • Safe ER/LA Opioid Prescribing
        • Check Your Industry Payment Records
      • MOC
      • Resident Education
        • Resident Education Home
        • Browse All Resident Content
          • Courses
          • Flashcards
          • Interactive Cases and Simulations
          • Videos
          • Webinars
        • OKAP and Board Exam Resources
          • OKAP Exam
          • Board Prep Resources
          • OKAP and Board Review Presentations
          • Study Flashcards
        • Cataract Master
        • Diversity and Inclusion Education
        • News and Advice from YO Info
        • Pediatric Ophthalmology Education Center
        • PGY-1 and PGY-2 Resources
        • Simulation in Resident Education
    • Membership
      • Join
      • Renew
      • Current Member
      • Volunteer
      • Physician Wellness
      • Member Directory
      • Member Obituaries
      • AAOE Membership
    • Advocacy
      • Advocacy News
      • Get Involved
        • Ways to Give
        • How to Get Involved
        • Congressional Advocacy
        • Support the Academy's Agenda
        • Research Legislation
        • Find Your Legislators
        • I Am an Advocate
        • Advocacy at Home
        • Advocate Tools
        • Best Practices for Advocating at Home
        • Social Media Toolkit
        • Letter to Editor
        • Town Hall Guide
        • Guide to Engaging With New Lawmakers
        • Resources
        • Attending a Political Fundraiser
      • OPHTHPAC
        • About Us
        • Join OPHTHPAC
        • OPHTHPAC Blog
      • Surgical Scope Fund
        • Support Surgery By Surgeons
        • Surgery By Surgeons Blog
    • Publications
      • EyeNet Magazine
        • Latest Issue
        • Archive
        • Subscribe
        • Advertise
        • Write For Us
        • Corporate Lunches
        • Contact
        • MIPS 2022
      • Focal Points
      • Ophthalmology
      • Ophthalmology Glaucoma
      • Ophthalmology Retina
      • YO Info
      • Scope
    • Subspecialties
      • Cataract/Anterior Segment
      • Comprehensive Ophthalmology
      • Cornea/External Disease
      • Glaucoma
      • Neuro-Ophthalmology/Orbit
      • Ocular Pathology/Oncology
      • Oculoplastics/Orbit
      • Pediatric Ophthalmology/Strabismus
      • Refractive Management/Intervention
      • Retina/Vitreous
      • Uveitis
    • IRIS Registry
      • About
      • Using the Registry
        • User Guide
        • Medicare Reporting
        • Maintenance of Certification
        • Non-EHR Reporting
      • Sign Up
        • Application Process
        • Why Participate
        • Once You've Applied: Getting Started
        • What Practices Are Saying About the Registry
      • Requirements
        • EHR Systems
        • Data & Technical Needs
      • Research
      • Registry Dashboard
      • News
      • Medicare & MIPS
    • Medicare Information
    • Diversity, Equity, and Inclusion
  • For Practice Management
    • Managing Your Practice
      • Managing Your Practice Topics
      • Coronavirus Resources
      • Reopening & Recovery
      • Practice Forms Library
      • Practice Management News and Advice
      • AAOE-Talk
      • Video Library
      • Ophthalmology Job Center
      • Benchmarking and Salary Tools
      • Academy Consultations
      • Consultant Directory
    • Coding
      • Coding Topics
      • Codequest Events
      • Ask the Coding Experts
      • Coding Updates and Resources
      • Coding for Injectable Drugs
      • EM Documentation
      • ICD-10-CM
      • Ophthalmic Coding Specialist (OCS) Exam
      • Retina
      • Savvy Coder
    • Webinars and Events
      • Annual Meeting
      • Codequest Courses
      • Mid-Year Forum
      • Webinar Recordings
    • IRIS Registry
      • Merit-Based Incentive Payment
    • Medicare and MIPS
      • MIPS
        • Quality
        • Promoting Interoperability
        • Improvement Activities
        • Cost
        • Avoid a Penalty
      • Resources
      • Medicare Participation Options
      • Medicare Advantage Plans
      • New Medicare Card
      • Provider Enrollment, Chain and Ownership System (PECOS)
    • Regulatory Compliance
      • HIPPA Resources
      • Office of Inspector General
      • Audits
      • OSHA
    • AAOE Membership
      • Join AAOE
      • Membership Benefits
      • Renew/Pay Dues
    • About AAOE
      • AAOE Board of Directors
      • AAOE Content Committee
      • Volunteer Opportunities
  • For Public & Patients
    • Eye Health A-Z
    • Symptoms
    • Glasses & Contacts
    • Tips & Prevention
    • News
    • Ask an Ophthalmologist
    • Patient Stories
    • No Cost Eye Exams
    • Español
      • A - Z de Salud Ocular
      • Síntomas
      • Anteojos y Lentes de Contacto
      • Consejos y Prevención
      • Noticias
      • Relatos de Pacientes
      • Exámenes de la vista sin costo
      • English
  • AAO 2022
    • Meeting Information
      • Past and Future Meetings
      • Mobile Meeting Guide
      • Contact Information
      • Annual Meeting News
      • Health and Safety
      • Policies and Disclaimers
    • Program
      • Program Highlights
      • Subspecialty Day
      • Virtual Meeting
      • Program Committees
      • CME
      • Meeting Archives
    • Expo
    • Registration
    • Hotels & Travel
      • Hotel Reservation Information
      • Chicago
      • International Attendees
      • Hotel Meeting Space
    • Presenter Central
      • Presenter Central
      • Abstract Selection Process
      • Submission Policies
      • Subject Classification/Topics
      • Instruction Courses and Skills Transfer Labs
      • Papers and Posters
      • Videos
      • Grand Rounds Symposium
      • Program Participant and Faculty Guidelines
      • Faculty Development Program
    • Exhibitors
      • Exhibitor Central
      • Exhibitor Portal Information
      • Exhibitor Prospectus
      • New Exhibiting Companies
      • Exhibitor Resources
      • International Exhibitors
      • Promotional Opportunities
      • Exhibitor Hotel Reservations
  • About
    • Who We Are
      • What We Do
      • About Ophthalmology
      • The Eye Care Team
      • Ethics and the Academy
      • History
      • Museum of Vision
      • Values
    • Governance
      • Council
      • Board of Trustees
      • Committees
      • Academy Past Presidents
      • Secretariats
      • Elections
      • Academy Blog
      • Academy Staff Leadership
    • Leadership Development
    • Awards
      • Laureate Recognition Award
      • Outstanding Advocate Award
      • Outstanding Humanitarian Service Award
      • International Blindness Prevention Award
      • Distinguished Service Award
      • Guests of Honor
      • Secretariat Award
      • Straatsma Award
      • Achievement Award Program
      • Artemis Award
      • EnergEYES Award
      • International Education Award
      • International Scholar Award
      • Commitment to Advocacy Award
      • Visionary Society Award
    • Financial Relationships
    • Policy Statements
    • Related Organizations
      • Subspecialty/Specialized Interest Society Directory
      • State Society Directory
      • Subspecialty/Specialized Interest Society Meetings
      • State Society Meetings
      • Resources for Societies
    • Year in Review
      • 2020 Year in Review
  • Foundation
    • About
      • 2020-2021 Annual Report
      • Annual Report Archives
      • News From the Chair
      • Foundation Staff
    • Our Impact
      • Partners for Sight
      • Donor Spotlights
      • Global Ophthalmic Community
      • Sponsorships
      • Patients and the Public
    • Giving Options
      • Our Supporters
      • Estate and Planned Giving
      • Ophthalmic Business Council
      • Parke Center Campaign
      • Minority Ophthalmology Mentoring Campaign
      • Museum of the Eye Campaign
    • Orbital Gala
      • Why Attend
      • Photo Recap
      • Corporate Support Opportunities
      • Tribute Gifts
      • Silent Auction
      • Corporate Sponsors
    • Donate
    • Museum of the Eye Campaign
      • Museum Supporters
  • Museum of the Eye
    • Visit
    • What's On
      • Museum Galleries
      • Special Exhibitions
      • Current Events
      • Past Events
    • Explore
      • Research and Resources
      • Collection Search
      • Previous Exhibits
      • Oral Histories
      • Biographies
    • Volunteer
    • Mailing List
    • Donate
    • About the Museum
      • Museum Blog
  • Young Ophthalmologists
    • YO Info
    • Learn to Bill
    • Engage with the Academy
  • Senior Ophthalmologists
    • Scope
    • Practice Transitions
  • International Ophthalmologists
    • Global Programs and Resources for National Societies
    • Awards
    • Global Outreach
  • Residents
  • Medical Students
×
Shop
Log In Create an Account
  • For Ophthalmologists
  • For Practice Management
  • For Public & Patients
  • Coronavirus
  • About
  • Foundation
  • Museum of the Eye
  • COVID-19
  • Journals
  • Education
    • Education
    • Courses
    • Cases
    • Learning Plans
    • Interactive
    • Focal Points
    • Wills Eye Manual
    • Disease Reviews
    • Clinical Webinars
    • Diagnose This
    • Self-Assessments
    • Education Centers
      • Glaucoma Education Center
      • Pediatric Ophthalmology Education Center
      • Laser Surgery Education Center
      • Oculofacial Plastic Surgery Center
      • Redmond Ethics Center
      • Myopia Resources
      • Thyroid Eye Disease Resources
  • Guidelines
    • Practice Guidelines
    • Preferred Practice Patterns
    • Clinical Statements
    • Ophthalmic Technology Assessments
    • Patient Safety Statements
    • Complementary Therapy Assessments
    • Compendium Guidelines
    • Medical Information Technology
    • Low Vision
    • Choosing Wisely
    • Eye Care for Older Adults
    • Eye Disease Statistics
    • About the Hoskins Center
    • Artificial Intelligence
    • Premium IOLs
    • Patient-Reported Outcomes with LASIK Symptoms and Satisfaction
  • Multimedia
    • Multimedia Library
    • Video
      • 1-Minute Videos
      • Presentations and Lectures
      • Master Class Videos
      • Basic Skills Videos
      • Clinical and Surgical Videos
      • Interviews
      • Resident Lectures
      • Submit a Video
      • YO Video Contest
    • Podcasts
      • Browse Podcast Archive
      • Experts InSight Podcast
      • Ophthalmology Journal Podcast
    • Images
      • Submit an Image
  • News
    • Clinical News
    • Editors' Choice
    • Headlines
    • Current Insight
  • CME
    • CME Central
    • Claim CME Credit and View Transcript
    • CME Planning Resources
    • Complete Your Financial Disclosure
    • Joint Sponsorship Portal
    • LEO Continuing Education Recognition Award
    • Safe ER/LA Opioid Prescribing
    • Check Your Industry Payment Records
  • MOC
  • Residents
    • Resident Education Home
    • Browse All Resident Content
      • Courses
      • Flashcards and Study Presentations
      • Interactive Cases and Simulations
      • Videos
      • Webinars
    • Cataract Master
    • Diversity and Inclusion Education
    • News and Advice from YO Info
    • OKAP and Board Exam Resources
      • OKAP Exam
      • Board Prep Resources
      • OKAP and Board Review Presentations
      • Study Flashcards
    • Pediatric Ophthalmology Education Center
    • PGY-1 and PGY-2 Resources
    • Resident Knowledge Exchange
    • Simulation in Resident Education
    • Clinical Education /
    • Book Excerpts /
    • Basic and Clinical Science Course - Excerpt
  • 2020–2021 BCSC Basic and Clinical Science Course™

    Go to Academy Store Learn more and Purchase.

    2 Fundamentals and Principles of Ophthalmology

    Part IV: Biochemistry and Metabolism

    Chapter 7: Tear Film

    Tear Secretion

    Contrary to earlier belief—which ascribed basic secretion to the accessory lacrimal glands of Krause and Wolfring and reflex secretion to the main lacrimal gland—it is now thought that all lacrimal glands function as a unit in conjunction with the ocular surface and the brain. In addition, the cornea and conjunctiva can respond by secreting electrolytes, water, and mucins.

    Although the meibomian glands are innervated, it is not known whether nerves mediate lipid secretion from these glands. Reflex tear secretion is neurally mediated and induced in response to physical irritation (ie, superficial corneal and conjunctival sensory stimulation by mechanical, thermal, or chemical means), psychogenic factors, and bright light. Induction of sensory nerves by a local neural reflex activates the parasympathetic and sympathetic nerves that innervate the tear glands and epithelia, causing secretion (Fig 7-4). Tear turnover rate has been demonstrated to be significantly lower in a symptomatic patient with dry eye (5%) than in an asymptomatic dry eye patient (12%).

    A neural feedback mechanism for tear secretion has been widely accepted. The cornea and lacrimal gland are not directly connected; however, corneal damage profoundly affects the lacrimal gland, which, in turn, downregulates tear production. In the vicious circle theory of DES, this downregulation is due to the secretion of inflammatory cytokines that block neural signals for tear secretion (Fig 7-5). The feedback loop, initiated by inflammation on the surface of the eye, further suppresses or downgrades lacrimal gland function, creating a vicious circle that worsens DES (Fig 7-6).

    Peptide and steroid hormones constitute another mechanism for stimulating tear secretion (in addition to nerves), as follows:

    • Peptide hormones, including α-melanocyte-stimulating hormone (α-MSH) and adrenocorticotropic hormone (ACTH), stimulate protein secretion from the main lacrimal gland.

    • Steroid hormones, specifically the androgens, stimulate secretion of sIgA from the main lacrimal gland and lipid from the meibomian glands.

    Figure 7-4 Sensory and motor nerves connecting the components of the lacrimal functional unit. Sensation (afferent) from the ocular surface is provided by branches of the long ciliary nerve of the ophthalmic division of cranial nerve V (CN V1). Efferent fibers from both members of the autonomic nervous system stimulate lacrimal secretion at the main and accessory lacrimal glands.

    (Modified with permission from Pflugfelder SC, Beuerman RW, Stern ME, eds. Dry Eye and Ocular Surface Disorders. New York: Marcel Dekker; 2004.)

    Figure 7-5 Disruption of the neural feedback loop in dry eye syndrome (DES). The white lines represent the normal pathway of the lacrimal functional unit. The red lines demonstrate disruption of the pathway.

    (Illustration by Cyndie C.H. Wooley.)

    Eyelid movement is important in tear film renewal, distribution, turnover, and drainage. As the eyelids close in a complete blink, the superior and inferior fornices are compressed by the force of the preseptal muscles, and the eyelids move toward each other, with the upper eyelid moving over the longer distance and exerting force on the globe. This force clears the anterior surface of debris and any insoluble mucin and expresses secretions from meibomian glands. The lower eyelid moves horizontally in a nasal direction and pushes tear fluid and debris toward the superior and inferior puncta. When the eyelids are opened, the tear film is redistributed. The upper eyelid pulls the mucoaqueous phase of the tear film by capillary action. The lipid layer spreads as fast as the eyelids move, so that no area of the tear film is left uncovered by lipid.

    See BCSC Section 7, Oculofacial Plastic and Orbital Surgery, which discusses the lacrimal system in depth, with numerous illustrations.

    • Stern ME, Gao J, Siemasko KF, Beuerman RW, Pflugfelder SC. The role of the lacrimal functional unit in the pathophysiology of dry eye. Exp Eye Res. 2004;78(3):409–416.

    Figure 7-6 The vicious circle theory of DES. LASIK = laser in situ keratomileusis; MGD = meibomian gland dysfunction; MMP = matrix metalloproteinase.

    (Modified with permission from Baudouin C, Aragona P, Messmer EM, et al. Role of hyperosmolarity in the pathogenesis and management of dry eye disease: proceedings of the OCEAN group meeting. Ocul Surf. 2013;11(4):Fig 1.)

    Excerpted from BCSC 2020-2021 series: Section 2 - Fundamentals and Principles of Ophthalmology. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.

  • Most Commented
    Loading, please wait...
    There are no comments available.
    Most Viewed
    Loading, please wait...
    Most Viewed content is not available.
  • The Academy Store
    2022-2023 Basic and Clinical Science Course, Complete Print Set
    2022-2023 Basic and Clinical Science Course, Complete eBook Set
    2022-2023 Basic and Clinical Science Course, Complete Print and eBook Set
    2022-2023 Basic and Clinical Science Course, Residency Print Set
    2022-2023 Basic and Clinical Science Course, Residency eBook Set
    2022-2023 Basic and Clinical Science Course Complete Set
    2022-2023 Basic and Clinical Science Course Residency Set
    2022-2023 Basic and Clinical Science Course, Section 01: Update on General Medicine
    2022-2023 Basic and Clinical Science Course, Section 02: Fundamentals and Principles of Ophthalmology
    2022-2023 Basic and Clinical Science Course, Section 03: Clinical Optics and Vision Rehabilitation
    2022-2023 Basic and Clinical Science Course, Section 04: Ophthalmic Pathology and Intraocular Tumors
    2022-2023 Basic and Clinical Science Course, Section 05: Neuro-Ophthalmology
    2022-2023 Basic and Clinical Science Course, Section 06: Pediatric Ophthalmology and Strabismus
    2022-2023 Basic and Clinical Science Course, Section 07: Oculofacial Plastic and Orbital Surgery
    2022-2023 Basic and Clinical Science Course, Section 08: External Disease and Cornea
    2022-2023 Basic and Clinical Science Course, Section 09: Uveitis and Ocular Inflammation
    2022-2023 Basic and Clinical Science Course, Section 10: Glaucoma
    2022-2023 Basic and Clinical Science Course, Section 11: Lens and Cataract
    2022-2023 Basic and Clinical Science Course, Section 12: Retina and Vitreous
    2022-2023 Basic and Clinical Science Course, Section 13: Refractive Surgery
    The Technician Point System: How to Improve Practice Accountability and Bottom Line (Free Member Webinar)
    Transitioning Your Practice: Retiring, Selling or Buying a Practice (Free Member Webinar)
    How to Build a Patient-First Culture (Free Member Webinar)
    2022 IRIS Registry (Intelligent Research in Sight) Preparation Kit
    Advances in Medical and Surgical Management: The 2022 Update on Glaucoma
    Presbyopia-Correcting IOLs
    2022 Codequest - Multistate (Recorded March 29)
    2022 Codequest Virtual (Multistate)
    Retina Patient Education Video Collection
    Cataract and Refractive Surgery Patient Education Video Collection
 
  • Contact Us
  • About the Academy
  • Jobs at the Academy
  • Financial Relationships with Industry
  • Medical Disclaimer
  • Privacy Policy
  • Terms of Service
  • Help
  • For Advertisers
  • For Media
  • Ophthalmology Job Center

OUR SITES

  • EyeWiki
  • International Society of Refractive Surgery

FOLLOW THE ACADEMY

Medical Professionals

  • Facebook
  • Twitter
  • LinkedIn
  • YouTube

Public & Patients

  • Facebook
  • Twitter
  • Instagram
  • YouTube

Museum of the Eye

  • Facebook
  • Twitter
  • Instagram
  • YouTube
  • Trip Advisor
  • Yelp
© American Academy of Ophthalmology 2022