Skip to main content
  • AAO PPP Cornea/External Disease Committee, Hoskins Center for Quality Eye Care
    Cornea/External Disease
    Compendium Type: I

    By the American Academy of Ophthalmology Preferred Practice Pattern Corneal/External Disease Committee: Francisco J. Garcia-Ferrer,1 Esen K. Akpek, MD,2 Guillermo Amescua, MD,3 Marjan Farid, MD,4 Amy Lin, MD,5 Michelle K. Rhee, MD,6 Divya Varu, MD7 David C. Musch, PhD, MPH,8 Francis S. Mah, MD,9 Steven P. Dunn, MD10

    As of November 2015, the PPPs are initially published online-only in the Ophthalmology journal and may be freely downloaded in their entirety by all visitors. Open the PDF for this entire PPP or click here to access the PPP on the journal's site. Click here to access the journal's PPP collection page.

    1 Mercy Clinic Eye Specialists, St. Louis, Missouri
    2 The Wilmer Eye Institute, Johns Hopkins University, Baltimore, Maryland
    3 Department of Ophthalmology, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami Florida
    4 Gavin Herbert Eye Institute, Department of Ophthalmology, University of California, Irvine, California
    5 John A. Moran Eye Center, University of Utah, Salt Lake City, Utah
    6 Department of Ophthalmology, Icahn School of Medicine at Mount Sinai, New York, New York
    Dell Laser Consultants, Austin Texas
    Department of Ophthalmology and Visual Sciences, University of Michigan, Ann Arbor, Michigan
    Departments of Cornea and External Diseases, Scripps Clinic Torrey Pines, La Jolla, California
    10 Michigan Cornea Consultants, P.C., Southfield, Michigan


    Patients with unstable refractions should be evaluated for evidence of corneal ectasia. .

    The ophthalmologist needs to measure many aspects of visual function, since best-corrected visual acuity (BCVA) may not completely characterize visual function in these patients.      

    Signs of corneal ectasia can include, but are not limited to: inferior steepening, superior flattening, skewing of radial axes on power topographic maps, abnormal islands of elevation anteriorly and/or posteriorly on tomography and decentered or abnormal corneal thinning or rate of change of corneal thickening from the center to the periphery.

    Prior to refractive surgery, corneal topography and tomography performed following a period of contact lens abstinence should be reviewed for evidence of irregular astigmatism or abnormalities suggestive of keratoconus or other forms of corneal ectasia.

    When corneal ectasia occurs following keratorefractive surgery, it is usually determined that the residual stromal bed following surgery was thinner than expected, that the flap was thicker than expected, or that the patient had preoperative signs of subclinical ectasia by tomography.

    It is impossible preoperatively to identify all patients at risk for postkeratorefractive corneal ectasia. Those with risk factors for ectasia may not develop the condition following laser vision correction surgery and some without obvious risk factors may develop ectasia following laser vision correction.

     Corneal cross-linking (CXL) reduces the risk of progressive ectasia in patients with keratoconus (particularly in its early stages) and stabilizes the corneal. It also stabilizes cases of corneal ectasia occurring after keratorefractive surgery.            

     Deep anterior lamellar keratoplasty (DALK) may be used to treat ectatic disease.  Its advantages include no risk for endothelial rejection and a low risk of stromal rejection.  Progressive endothelial cell loss following DALK may also be less than following penetrating keratoplasty.

    Literature Search

     Corneal Ectasia PPP - 2018 - Literature Search.pdf