Keratoconus Clinical Presentation

  • Author: Barry A Weissman, OD, PhD, FAAO; Chief Editor: Hampton Roy Sr, MD   more...
 
Updated: Nov 23, 2011
 

History

Patients with keratoconus (KC) often report decreasing vision (distortions, glare/flare, and monocular diplopia or ghost images), with multiple unsatisfactory attempts in obtaining optimum spectacle correction.

Soft contact lenses (CLs) and spectacles may initially give satisfactory vision, but vision tends to decline over time and requires rigid gas permeable (GP) contact lenses for correction. Other contact lens options include piggyback lens systems (usually a GP lens over a soft, perhaps silicone hydrogel, lens), hybrid lenses (eg, Sofperm TM, Synergeyes TM), and GP scleral lenses.[9, 15, 12, 10, 22]

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Physical

Keratoconus is divided into mild, moderate, and advanced.

  • Mild keratoconus
    • External and corneal signs are often absent or minimal.
    • A history of multiple inadequate spectacle corrections of one or both eyes may be noted and may include oblique astigmatism on refraction as well as moderate-to-high myopia.
    • Irregularly astigmatic keratometry values (egg-shaped), not necessarily on the steep side of normal (approximately 45 diopters [D]), are consistent with diagnosis.
    • Diagnosis can be confirmed with computer-assisted videokeratography, which may reveal corneal inferior steepening (approximately 80% of keratoconus cases), central corneal astigmatic steepening (approximately 15% of keratoconus cases), or even bilateral temporal steepening (extremely rare).
    • Diagnosis may also be aided by applying a diagnostic rigid contact lens with its base curve equal to the flat keratometry value. One observes a typical nipple pattern by use of sodium fluorescein dye in the underlying tear film.
  • Moderate keratoconus[12]
    • One or more corneal signs of keratoconus are often present.
      • Enhanced appearance of the corneal nerves is noted.
      • Approximately 40% of eyes in patients with moderate keratoconus develop Vogt striae (fine-stress lines) in the deep stroma.
      • Approximately 50% develop the deposition of iron in the basal epithelial cells in a (often partial) ring shape at the base of the conical protrusion called the Fleischer ring.
      • Approximately 20% develop corneal scarring.
    • Superficial corneal scarring can be fibular, nebular, or nodular.
    • Deep stromal scarring may occur, perhaps representing resolved mini-hydrops events.
    • Some patients show scarring at the level of the Descemet membrane (posterior limiting lamina), consistent in appearance with posterior polymorphous corneal dystrophy.
    • Paraxial (usually inferior to the pupil) stromal thinning may be appreciated.
    • Keratometry values typically increase to 45-52 D.
    • Distortion of the retinoscopy and direct ophthalmoscope red pupillary reflex may allow observation of "scissoring" or an inferior distortion termed the oil drop sign.
    • The Munson sign is noted when, upon downgaze, a "V" shape is noted in the cornea's profile against the lower lid margin, an accentuation of the conical shape of the modest to advanced keratoconus cornea.
  • Advanced keratoconus
    • This often results in keratometry values greater than 52 D and enhancement of all corneal signs, symptoms, and visual loss/distortion.
    • Vogt striae are seen in approximately 60% of eyes, and Fleischer ring and/or scarring are seen in approximately 70% of eyes.
    • Acute corneal hydrops can occur.
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Causes

Although not definitively identified, genetic inheritance, systemic and ocular associations, eye rubbing, atopy and specifically ocular allergies, and contact lens wear are proposed risk factors.[23, 9, 10, 11]

Several reports suggest, perhaps coincidentally, associations with keratoconus and other corneal dystrophies.

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Contributor Information and Disclosures
Author

Barry A Weissman, OD, PhD, FAAO  Chief of Contact Lens Service, Professor, Department of Ophthalmology, Jules Stein Eye Institute, University of California, Los Angeles, David Geffen School of Medicine; Adjunct Professor of Optometry, Southern California College of Optometry

Barry A Weissman, OD, PhD, FAAO is a member of the following medical societies: American Academy of Optometry, American Optometric Association, California Optometric Society, and International Society for Contact Lens Research

Disclosure: VSP None Speaking and teaching; Alcon None Speaking and teaching; Vistakon/The Vision Care Institute Grant/research funds support of Fellowship program

Coauthor(s)

Karen K Yeung, OD, FAAO  Director of Optometry, Arthur Ashe Student Health and Wellness Center, University of California, Los Angeles, David Geffen School of Medicine

Karen K Yeung, OD, FAAO is a member of the following medical societies: American Academy of Optometry

Disclosure: Nothing to disclose.

Specialty Editor Board

Fernando H Murillo-Lopez, MD  Senior Surgeon, Unidad Privada de Oftalmologia CEMES

Fernando H Murillo-Lopez, MD is a member of the following medical societies: American Academy of Ophthalmology

Disclosure: Nothing to disclose.

Francisco Talavera, PharmD, PhD  Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Medscape Salary Employment

Christopher J Rapuano, MD  Professor, Department of Ophthalmology, Jefferson Medical College of Thomas Jefferson University; Director of the Cornea Service, Co-Director of Refractive Surgery Department, Wills Eye Institute

Christopher J Rapuano, MD is a member of the following medical societies: American Academy of Ophthalmology, American Society of Cataract and Refractive Surgery, Contact Lens Association of Ophthalmologists, Cornea Society, Eye Bank Association of America, International Society of Refractive Surgery, and Pan-American Association of Ophthalmology

Disclosure: Allergan Honoraria Speaking and teaching; Allergan Consulting fee Consulting; Alcon Honoraria Speaking and teaching; RPS Ownership interest Other; EyeGate Pharma Consulting fee Consulting; Bausch & Lomb Honoraria Speaking and teaching; Bausch & Lomb Consulting; Merck Honoraria Speaking and teaching

Lance L Brown, OD, MD  Ophthalmologist, Affiliated With Freeman Hospital and St John's Hospital, Regional Eye Center, Joplin, Missouri

Disclosure: Nothing to disclose.

Chief Editor

Hampton Roy Sr, MD  Associate Clinical Professor, Department of Ophthalmology, University of Arkansas for Medical Sciences

Hampton Roy Sr, MD is a member of the following medical societies: American Academy of Ophthalmology, American College of Surgeons, and Pan-American Association of Ophthalmology

Disclosure: Nothing to disclose.

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An optic section of a keratoconic cornea shows corneal thinning. Vogt striae and some scarring can also be seen centrally; superiorly, a small (brown) section of the Fleischer ring is noted.
The fluorescein pattern of a rather flat-fitted rigid contact lens on an advanced keratoconic cornea.
 
 
 
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