• Oct 2014
    AAO Cornea/External Disease PPP Panel, Hoskins Center for Quality Eye Care
    Cornea/External Disease


    These are summary benchmarks for the Academy’s Preferred Practice Patterns® (PPP) guidelines. The Preferred Practice Patterns series of guidelines has been written on the basis of three principles.

    • Each Preferred Practice Pattern should be clinically relevant and specific enough to provide useful information to practitioners.
    • Each recommendation that is made should be given an explicit rating that shows its importance to the care process.
    • Each recommendation should also be given an explicit rating that shows the strength of evidence that supports the recommendation and reflects the best evidence available.

    Preferred Practice Patterns provide guidance for the pattern of practice, not for the care of a particular individual. While they should generally meet the needs of most patients, they cannot possibly best meet the needs of all patients. Adherence to these Preferred Practice Patterns will not ensure a successful outcome in every situation. These practice patterns should not be deemed inclusive of all proper methods of care or exclusive of other methods of care reasonably directed at obtaining the best results. It may be necessary to approach different patients' needs in different ways. They physician must make the ultimate judgment about the propriety of the care of a particular patient in light of all of the circumstances presented by that patient. The American Academy of Ophthalmology is available to assist members in resolving ethical dilemmas that arise in the course of ophthalmic practice.

    The Preferred Practice Pattern® guidelines are not medical standards to be adhered to in all individual situations. The Academy specifically disclaims any and all liability for injury or other damages of any kind, from negligence or otherwise, for any and all claims that may arise out of the use of any recommendations or other information contained herein.

    For each major disease condition, recommendations for the process of care, including the history, physical exam and ancillary tests, are summarized, along with major recommendations for the care management, follow-up, and education of the patient. For each PPP, a detailed literature search of PubMed and the Cochrane Library for articles in the English language is conducted. The results are reviewed by an expert panel and used to prepare the recommendations, which they rated in two ways.

    The panel first rated each recommendation according to its importance to the care process. This “importance to the care process” rating represents care that the panel thought would improve the quality of the patient’s care in a meaningful way. The ratings of importance are divided into three levels.

    • Level A, defined as most important
    • Level B, defined as moderately important
    • Level C, defined as relevant but not critical

    The panel also rated each recommendation on the strength of evidence in the available literature to support the recommendation made. The “ratings of strength of evidence” also are divided into three levels.

    • Level I includes evidence obtained from at least one properly conducted, well-designed randomized controlled trial. It could include meta-analyses of randomized controlled trials.
    • Level II includes evidence obtained from the following:
      • Well-designed controlled trials without randomization
      • Well-designed cohort or case-control analytic studies, preferably from more than one center
      • Multiple-time series with or without the intervention
    • Level III includes evidence obtained from one of the following:
      • Descriptive studies
      • Case reports
      • Reports of expert committees/organizations (e.g., PPP panel consensus with external peer review) 

    PPPs are intended to serve as guides in patient care, with greatest emphasis on technical aspects. In applying this knowledge, it is essential to recognize that true medical excellence is achieved only when skills are applied in a such a manner that the patients’ needs are the foremost consideration. The AAO is available to assist members in resolving ethical dilemmas that arise in the course of practice. (AAO Code of Ethics)

    Initial and Follow-up Evaluation

    Initial Exam History

    • Disease onset and course
    • Vision impairment
    • Ocular, medical, and family history

    Initial Physical Exam

    • Visual function assessment
    • External examination
      • Corneal protrusion
      • Eyelids and periorbital skin
    • Slit-lamp biomicroscopy
      • Presence, extent, and location of the corneal thinning or protrusion
      • Indication of previous ocular surgery
      • Presence of Vogt striae, prominent corneal nerves, Fleischer ring, or other iron deposition
      • Evidence of corneal scarring or previous hydrops, and presence of prominent corneal nerves
    • IOP measurement
    • Fundus examination: assessment of red reflex for dark area, and retina for tapetoretinal degenerations

    Diagnostic Tests

    • Keratometry
    • Corneal topography
    • Topographic power map
    • Topographic elevation map
    • Corneal pachymetry

    Care Management

    • Therapy is tailored to the individual patient, depending on the visual impairment and treatment option(s).
    • Vision can be corrected with eyeglasses, but contact lenses may be required as keratoconus progresses.
    • Rigid corneal gas permeable contact lenses can mask corneal irregularities. New hybrid contact lenses provide higher oxygen permeability and greater RGP/hydrogel junction strength. Piggyback contact lenses may be employed in cases of corneal scaring or decentered cones. Scleral lenses may be indicated when RGP and/or hybrid contact lenses fail.
    • Intrastromal corneal ring segment implantation can improve contact lens tolerance and BCVA for patients with corneal ectasia, a clear cornea, and contact lens intolerance.
    • Collagen crosslinking can improve corneal rigidity by increasing bonds between fibers.
    • Lamellar keratoplasty using DALK techniques can be considered for progressive keratoconus without significant scarring or hydrops. Crescentic lamellar keratoplasty is an option when maximal thinning is in the cornea’s periphery.
    • Peripheral thinning and ectasia can be managed by a standard decentered lamellar procedure for tectonic support, followed by a central penetrating keratoplasty later.
    • Penetrating keratoplasty is indicated when a patient can no longer achieve functional vision with eyeglasses or contact lenses, or when persistent corneal edema occurs following hydrops. Descemet stripping endothelial keratoplasty cannot correct ectatic disorder.
    • Penetrating keratoplasty is preferred over DALK in cases of deep stromal scarring.
    • A lamellar graft can be performed for tectonic support when ectasia occurs in the far periphery of the cornea.

    Follow-Up Evaluation

    • Follow-up evaluation and visit intervals are dictated by treatment and disease progression.
    • Annual follow up is recommended for cases of ectasia unless the patient has significant changes in visual function.
    • Patients should be made aware of the warning signs of rejection and should seek medical attention promptly if symptoms occur. The practitioner should be aware of the slit-lamp biomicroscopic findings of epithelial, stromal, and endothelial rejection.

    Counseling and Referral

    • When medical therapy with eyeglasses and/or contact lenses cannot improve visual function, a referral to an ophthalmologist trained in surgical treatments for corneal ectasia is indicated
    • Patients with a history of allergy and atopy may require a referral to a dermatologist or allergist
    • Patients with floppy eyelid disease may be best managed by an oculoplastics specialist and referrals to other medical specialists may also be needed