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  • 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 Cornea/External Disease Committee: Marjan Farid, MD,1 Michelle K. Rhee, MD,2 Esen K. Akpek, MD,3 Guillermo Amescua, MD,4 Francisco J. Garcia-Ferrer, MD,5 Amy Lin, 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 Gavin Herbert Eye Institute, Department of Ophthalmology, University of California, Irvine, California
    2 Department of Ophthalmology, Icahn School of Medicine at Mount Sinai, New York, New York
    3 The Wilmer Eye Institute, Johns Hopkins University, Baltimore, Maryland
    4 Department of Ophthalmology, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, Florida
    5 Mercy Clinic Eye Specialists, St. Louis, Missouri
    6 John A. Moran Eye Center, University of Utah, Salt Lake City, Utah
    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


     The impact of corneal edema on activities of daily living―particularly those influenced by ambient light levels at home, work, and during leisure activities―is often underappreciated. Standard measurement of visual acuity does not give a true representation of the patient’s functional vision.

     Reduced vision in cases of corneal opacification is more often related to corneal surface irregularity than to the opacity itself. A refraction over a rigid gas-permeable (RGP) contact lens can be very helpful in determining if visual loss is due to a corneal surface irregularity.

     Endothelial function is best evaluated by slit-lamp biomicroscopy examination and may be supported by changes in corneal thickness noted on serial pachymetric measurements performed at the same time of day. Specular microscopy is not a direct measure of endothelial function or functional reserve. When diffuse endothelial guttae are present on slit-lamp biomicroscopy examination, specular microscopy rarely provides any valuable information because it is difficult to image the endothelial cells.

     Corneal pachymetry, measured in the morning, is a helpful indicator of the ability of the endothelium to regulate corneal hydration appropriately. Corneas that are abnormally thick in the morning hours may be less able to tolerate proposed intraocular surgery.

    If the cataract surgeon or cornea specialist thinks that decompensation, if not imminent, is likely to occur in the near future, a discussion about modifying the intraocular lens (IOL) power calculation is worthwhile to adjust for changes induced by endothelial keratoplasty (specifically a hyperopic shift due to Descemet stripping automated endothelial keratoplasty [DSAEK] and less so with Descemet membrane endothelial keratoplasty [DMEK]). A full discussion of the added risks of subsequent corneal decompensation is very important in this group of patients and helps to shape their expectations with respect to their condition and the surgery.

     Endothelial keratoplasty has supplanted penetrating keratoplasty as the procedure of choice in cases of endothelial failure in the absence of corneal scarring because patients achieve more rapid visual rehabilitation and reduction in rejection of the transplanted tissue.

    Literature Search

     Corneal Edema and Opacification PPP - 2018 - Literature Search.pdf