Submit Receive an email when new articles are posted on this topic. Never before have we had so many options available for our patients who desire freedom from spectacles. This is true for all refractive error conditions including astigmatism and presbyopia. However, providing new alternatives to our habitual long-term contact lens wearers poses new challenges. Long-term contact lens wear can alter corneal physiology and corneal topography and can cause transient but substantial refractive error changes. The ultimate goal of rehabilitation is to prevent unnecessary lens re-orders, time and, more importantly, over- or under-corrections after refractive surgery.
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Is It Keratoconus or Corneal Warpage? Topographically, one of the most common characteristics shared by these two conditions is superior corneal flattening with inferior corneal steepening. Defining Characteristics Fitting rigid gas permeable RGP or PMMA lenses flatter than the central keratometer reading so that they ride superiorly, under the upper lid, results in molding of the corneal curvature. Before the advent of corneal topography, corneal warpage was generally described as a condition that included distorted keratometer mires with or without irregular astigmatism and reduced vision on post-lens wear refraction.
With the increased use of topography, corneal warpage has been re-defined to include central irregular astigmatism with a loss of radial asymmetry superior flattening and inferior steepening , and a reversal of the normal flattening corneal contour. These changes are associated primarily with lens decentration. Corneal shape is the most important criteria used to differentiate normal and abnormal corneal flattening.
Typically, a normal cornea demonstrates a prolate shape, meaning that the curvature is steeper centrally and flattens toward the periphery. The shape factor is a positive value, generally between 0 and 0. Since RGPs are firmer than the cornea, the corneal curvature loses its elliptical shape and often assumes a less prolate shape or more oblate shape when they are worn. This means that the peripheral curvature is steeper than the central curvature.
From my experience, normal RGP fitting often reduces the shape factor to approximately 0 to 0. This does not necessarily represent corneal warpage, but rather a sphericalization of the cornea due to the spherical base curve of the rigid lens.
However, as the shape factor becomes negative, it implies that the corneal surface has assumed an oblate shape and most likely, has become warped. Patient Diagnosis The central cornea in Figure 1 is flatter than the peripheral curvature i.
This patient has significant corneal warpage, not keratoconus, despite the obvious pattern of superior flattening and inferior steepening. References are available upon request.
To receive them via fax, call and request document He is in private practice in Virginia Beach, Virg.
Managing Corneal Warpage
Annulo-aortic ectasia for example refers to a proximal dilatation of the aortic root and its diagnosis is based on the increase in aortic wall diameter. It occurs in Marfan syndrome, in which the cornea also thins and flattens read: Keratoconus and the Marfan paradox. This is supported by the inspection and proper interpretation of curvature and elevation maps of keratoconic eyes. A mild inferior steepening is often found as a topographic sign in early forms of keratoconus: The curvature map left shows a mild inferior steepening. One should not interpret this as an area of local protrusion. On the contrary, this area of the cornea is located in a more posterior plane than its superior counterpart, as shown on the vertical crossectional image taken by the Scheimplfug camera red arrow , and also demonstrated on the elevation map, which reveals a more negative elevation relative to the best fit sphere. This change in corneal curvature occurred in a patient after a number of years of vigorous eye rubbing.
Corneal Warpage (Moldeamiento Corneal)
LEBOW, OD The goal of refitting corneal warpage is to return normal radial symmetry to the cornea by distributing lens mass evenly over the corneal surface. Patients with corneal warpage are rarely aware of their problem, and typically overwear their lenses without the benefit of spectacles to use when lenses are off the eye. Visualizing the changes topographically not only helps to define the problem, but also enables the patient to participate in its resolution. Patient History Patient C. She presents with a history of being refit two years ago with RGP lenses that were never comfortable.