• 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.

    8 External Disease and Cornea

    Chapter 7: Corneal Dystrophies and Ectasias

    Ectatic Disorders

    Keratoconus

    Keratoconus is a common disorder (incidence of about 1 per 2000) in which the central or paracentral cornea undergoes progressive thinning and protrusion, resulting in a coneshaped cornea (Fig 7-24; see also Fig 7-35). A hereditary pattern is not prominent or predictable, but positive family histories have been reported in 6%–8% of cases. Multiple chromosomal loci for keratoconus have been reported, but the identification of specific genes remains elusive. Clinically unaffected first-degree relatives have a higher chance of showing subclinical topographic abnormalities associated with keratoconus than does the general population. The prevalence of keratoconus in first-degree relatives has been shown to be 3.34%. There is a slight female preponderance, and the incidence is higher in South Asia and the Middle East. Genetic predisposition and environmental risk factors such as eye rubbing, inflammation, atopy, hard contact lens wear, and oxidative stress all play a role in the onset and progression of keratoconus.

    Onset occurs during puberty, and the progression rate is greatest in young people. Progression typically slows in the fourth decade of life and is unusual after age 40 years but can occur. The presence of hyperelastic joints may be as high as 50% in these patients. Keratoconus can be associated with ocular diseases such as vernal keratoconjunctivitis, Leber tapetoretinal degeneration, retinitis pigmentosa, and floppy eyelids. It can also be associated with systemic diseases, including atopic disease, Down syndrome, Ehlers-Danlos syndrome, osteogenesis imperfecta, sleep apnea, and mitral valve prolapse.

    Figure 7-24 Keratoconus. Note the marked corneal protrusion, a hallmark of keratoconus.

    Feder RS, Neems LC. Noninflammatory ectatic disorders. In: Mannis MJ, Holland EJ, eds. Cornea. Vol 1. 4th ed. Philadelphia: Elsevier; 2017:820–843.

    Kiliç A, Colin J. Advances in the surgical treatment of keratoconus. Focal Points: Clinical Modules for Ophthalmologists. San Francisco: American Academy of Ophthalmology; 2012, module 2.

    McMonnies CW. Abnormal rubbing and keratectasia. Eye Contact Lens. 2007;33(6 Pt 1): 265–271.

    Saidel MA, Paik JY, Garcia C, Russo P, Cao D, Bouchard C. Prevalence of sleep apnea syndrome and high-risk characteristics among keratoconus patients. Cornea. 2012;31(6): 600–603.

    Wang Y, Rabinowitz YS, Rotter JI, Yang H. Genetic epidemiological study of keratoconus: evidence for major gene determination. Am J Med Genet. 2000;93(5):403–409.

    PATHOLOGY

    Histologically, keratoconus shows the following:

    • iron deposition in the basal epithelium at the base of the cone

    • fragmentation or breaks of the Bowman layer

    • thinning of the corneal stroma and overlying epithelium

    • folds or breaks in the Descemet membrane

    • variable amounts of apical scarring

    CLINICAL PRESENTATION

    Nearly all cases are bilateral, but asymmetry is common. Early biomicroscopic and histologic findings include breaks in the Bowman layer followed by fibrous growth through the break, leading to reticular scarring (Fig 7-25). As progression occurs, the apical thinning of the central cornea worsens, as does the degree of irregular astigmatism. There is generally no associated keratitis or corneal neovascularization.

    Figure 7-25 Broad, oblique slit-lamp image (high magnification). Breaks at the level of the Bowman layer (white arrow) are apparent. The black arrow indicates where collagen has presumably filled in a previous break. Vogt striae are also seen. This is the mechanism of the superficial reticular scarring seen in keratoconus.

    (Reprinted from Shapiro MB, Rodrigues MM, Mandel MR, Krachmer JH. Anterior clear spaces in keratoconus. Ophthalmology. 1986;93(10):1316–1319.)

    Scissoring of the red reflex on retinoscopy is commonly associated with irregular astigmatism and is an early sign of keratoconus. Rizzutti sign, a focusing of the light within the nasal limbus when a penlight is shone from the temporal side, is another early but nonspecific finding. Munson sign, an inferior deviation of the lower eyelid contour on downgaze (Fig 7-26), is also nonspecific and is a late sign. Iron deposition within the basal epithelium at the base of the cone forms a Fleischer ring (Fig 7-27), best seen with the slit lamp using a broad, oblique beam and the cobalt-blue filter. The line becomes narrower and increasingly well defined as the disease progresses. Fine, parallel stress lines, Vogt striae, can be observed in the posterior stroma at the apex of the cone and may disappear with application of external pressure (Fig 7-28).

    Spontaneous perforation in keratoconus is extremely rare. However, a tear can occur in the Descemet membrane, usually late in the disease course, resulting in the sudden development of corneal edema, or acute hydrops (Fig 7-29). Allergy and eye rubbing are risk factors for the development of hydrops, which is more common in patients with Down syndrome. The break in the posterior cornea usually heals spontaneously within 3 months; the corneal edema then disappears, but posterior stromal scarring occurs. Some patients experience improved vision following the resolution of hydrops because of apical flattening. The improved vision will depend on the extent and location of the scar. Occasionally, stromal clefts can be seen in association with hydrops. Even large clefts usually close, but corneal neovascularization can develop.

    Figure 7-26 Munson sign. Note the angulation of the lower eyelid with the eye in downgaze.

    (Courtesy of Woodford S. Van Meter, MD.)

    Figure 7-27 Fleischer ring (arrow), demonstrated using diffuse illumination with a cobalt-blue filter.

    (Courtesy of James J. Reidy, MD.)

    Figure 7-28 Vogt striae are fine folds in the posterior stroma at the cone apex. Striae become less apparent when external pressure is applied.

    (Courtesy of Robert S. Feder, MD.)

    Figure 7-29 Corneal edema in keratoconus due to a sudden rupture of the Descemet membrane (acute hydrops).

    (Courtesy of Robert S. Feder, MD.)

    EVALUATION

    Keratometry can be used to detect keratoconus even at an early stage. Irregular astigmatism, indicated by the inability to superimpose the circular mires, is commonly seen. Inferior steepening, an early finding in keratoconus, can be detected by comparing measurements obtained with the patient in primary gaze to those in upgaze. Corneal topography and corneal tomography (Fig 7-30) have become indispensable in the management of keratoconus and are used by clinicians in several ways, such as detecting early keratoconus, following its progression, fitting contact lenses, and managing the postoperative patient. Important power map findings include superior flattening, inferior steepening, increase in I–S ratio (inferior to superior power), and significant skewing of the radial axes of the bow tie, in contrast to the normal symmetric bow-tie pattern of regular astigmatism. Findings obtained via slit-scanning devices, Scheimpflug imaging, or anterior segment OCT include decentered islands of elevation anteriorly and/or posteriorly. The elevation map is developed in reference to a computer-generated best-fit sphere.

    These devices can also identify abnormal corneal thinning and/or decentration of the thinnest cornea, which is particularly significant when it is coincident with an island of elevation. Scheimpflug imaging and OCT have largely supplanted ultrasonic pachymetry. Accurate measurement of corneal thickness and elevation has been the cornerstone of recent advances in keratoconus detection programs. Examples of other advances are the various indices and graphic representations of both the change in thickness from thinnest cornea to limbus (more dramatic in keratoconus) and the impact of calculations of the best-fit sphere when the thinnest cornea is included or eliminated from the calculation. Serial evaluations over time are necessary to determine whether the changes noted are unlikely to progress (forme fruste keratoconus) or whether subclinical or suspected keratoconus is progressing and likely to become symptomatic. Corneal ectasia can also occur in association with ablative keratorefractive surgery (eg, LASIK or PRK). Risk factors for ectasia after LASIK or PRK are young age, high myopia, thin residual stromal bed, thin preoperative cornea, and abnormal preoperative contour. A young patient with a suspicious corneal contour who is considering refractive surgery should be observed over time to determine whether keratoconus will develop.

    Figure 7-30 Corneal contour map. Upper left: Scheimpflug-based imaging illustrates a power map with inferior steepening and superior flattening. Upper right: An isolated island of anterior elevation above a best-fit sphere coincident with the maximum steepness. Lower right: An isolated island of posterior elevation. Lower left: Marked thinning in an area coincident with steepening and elevation.

    (Courtesy of Robert S. Feder, MD.)

    Feder RS. Corneal topography. In: Feder RS, ed. The LASIK Handbook: A Case-based Approach. 2nd ed. Philadelphia: Wolters Kluwer; 2013:32–39.

    Gomes JA, Tan D, Rapuano CJ, et al. Global consensus on keratoconus and ectatic diseases. Cornea. 2015;34(4):359–369.

    Rao SN, Raviv T, Majmudar PA, Epstein RJ. Role of Orbscan II in screening keratoconus suspects before refractive corneal surgery. Ophthalmology. 2002;109(9): 1642–1646.

    Weisenthal R. Optical coherence tomography. In: Feder RS, ed. The LASIK Handbook: A Case-based Approach. 2nd ed. Philadelphia: Wolters Kluwer; 2013:40–46.

    Yeu E, Belin MW, Khachikian SS. Topographic analysis in keratorefractive surgery. In: Mannis MJ, Holland EJ, eds. Cornea. Vol 1. 4th ed. Philadelphia: Elsevier; 2017: 1728–1735.

    MANAGEMENT

    Some cases of mild keratoconus can be successfully managed with glasses. Patients should be counseled about the risk of progression with continued eye rubbing. Contact lenses can mask the associated irregular corneal astigmatism (Fig 7-31), and their use results in a dramatic improvement in vision in most cases. Although most patients will require hard or rigid gas-permeable lenses, some patients, particularly those with mild disease, may achieve improved vision and comfortable wear with soft lenses. Hybrid (rigid gas-permeable center with a soft lens “skirt”) or scleral lenses (standard or custom-made) may be helpful in more advanced disease. A central subepithelial scar can, on occasion, be removed (superficial keratectomy), allowing continued comfortable wear of contact lenses. Intrastromal corneal ring segments can be implanted to center the cone and facilitate successful contact lens wear. The procedure does not prevent progression, however, and is not intended to reduce dependence on glasses or contact lenses. Corneal crosslinking is used in patients with progressive disease. The risk of progression is greater in adolescents, who may benefit the most from this treatment. The greatest efficacy is achieved in mild to moderate cases. Corneal crosslinking may not work as well in cases of post-LASIK ectasia or in patients with more severe disease. Crosslinking may be performed in concert with intrastromal ring insertion. See also BCSC Section 13, Refractive Surgery.

    Figure 7-31 Hard contact lens effect on the keratoconus power map; with lens (right side) and without lens (left side). Upper left: Apical scarring has resulted in flattening, as noted in the power map. Lower left: The corresponding videokeratoscopic image is irregular, and the rings are widely spaced. Upper right: The power map appears much more normal when acquired with the patient wearing a contact lens. Lower right: The videokeratoscopic image is also much more regular, with narrower spacing.

    (Courtesy of Robert S. Feder, MD.)

    Keratoplasty becomes an important option under the following circumstances:

    • poor vision even with a comfortable contact lens fit (usually due to scarring)

    • contact lens intolerance even with good vision

    • unstable contact lens fit (even with good vision and tolerance)

    • progressive thinning to the corneal periphery approaching the limbus, requiring a very large graft (with increased risk)

    • corneal hydrops that fails to clear after several months

    PK is still the most widely performed surgical procedure for the treatment of keratoconus, and the prognosis is excellent. Some surgeons prefer DALK for keratoconus, especially when tissue suitable for PK is in short supply. Endothelial cell counts are significantly higher at 6 months following DALK compared with PK. Endothelial rejection does not occur after DALK, but stromal rejection is still possible. Postostoperative wound integrity in the case of postoperative trauma is better with DALK than with PK. (See Chapter 15 for further discussion of PK and DALK.)

    Hydrops is treated conservatively with topical hypertonic agents and/or a soft contact lens for several months. A cycloplegic agent may help with pain relief. Aqueous suppressants may decrease the flow of fluid into the cornea. Intracameral injection of air or gas (SF6 or C3F8) may help in speeding the resolution of hydrops. Pupil dilation and/or inferior peripheral iridectomy may reduce the risk of pupillary block. Hydrops is not an indication for emergency keratoplasty.

    Feder RS, Neems LC. Noninflammatory ectatic disorders. In: Mannis MJ, Holland EJ, eds. Cornea. Vol 1. 4th ed. Philadelphia: Elsevier; 2017:820–843.

    Kiliç A, Colin J. Advances in the surgical treatment of keratoconus. Focal Points: Clinical Modules for Ophthalmologists. San Francisco: American Academy of Ophthalmology; 2012, module 2.

    Panda A, Aggarwal A, Madhavi P, et al. Management of acute corneal hydrops secondary to keratoconus with intracameral injection of sulfur hexafluoride (SF6). Cornea. 2007;26(9): 1067–1069.

    Raiskup-Wolf F, Hoyer A, Spoerl E, Pillunat L. Collagen crosslinking with riboflavin and ultraviolet-A light in keratoconus: long-term results. J Cataract Refract Surg. 2008;34: 796–801.

    Terry M, Ousley P. Deep lamellar endothelial keratoplasty visual acuity, astigmatism, and endothelial survival in a large prospective series. Ophthalmology. 2005;112(9):1541–1548.

    Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. 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