Corneal warpage is an unintentional corneal shape change associated with contact lens wear (Michaud, 2008). For low-Dk materials (polymethyl methacrylate [PMMA] and some hydrogels), the corneal reshaping is likely due to hypoxia and edema (Lebow, 2000; Michaud, 2008). For higher-Dk materials (GP and some hydrogels), it is a result of mechanical manipulation of the cornea from a poor fit and/or chronic metabolic insult (Lebow, 2000; Schornack, 2003). GP lenses that are not well fit, typically too flat or decentered, can warp the cornea (Lebow, 2000). No matter the etiology of the warpage, the end result is the same: inadvertent corneal molding causing irregular astigmatism and visual symptoms (Lebow, 2000).

Warpage Versus Keratoconus

Both warpage and keratoconus can present with decreased acuity, changes in refraction, distortion, and asthenopia with glasses secondary to the irregular astigmatism (Schornack, 2003; Michaud, 2008). In warpage, the corneal shape regresses back to normal, and “spectacle blur” improves within a range of weeks to months depending on the lens type used (Michaud, 2008). In keratoconus, the spectacle blur will not diminish. Keratoconus can also present with an array of specific corneal findings, including paracentral steepening, corneal thinning, stromal scarring, Vogt’s striae, and a Fleischer’s ring (Lebow, 2000; Tang et al, 2016). Keep in mind that these findings may be absent or difficult to visualize in forme fruste keratoconus, which makes proper evaluation of tomography and pachymetry crucially important.

Case in Point

A long-term GP wearer reported new symptoms of spectacle blur in the right eye. Best-corrected visual acuity OD was 20/30. No clinical signs of keratoconus were present on slit lamp exam. Corneal tomography indicated an irregular, asymmetric, with-the-rule bow tie on the tangential map (Figure 1), with mild inferior steepening that is suspicious for early keratoconus. However, the Belin/Ambrosio display of corneal elevation and corneal pachymetry (Figure 2) indicates no abnormalities in either, which is inconsistent with keratoconus. These findings steered the diagnosis toward warpage rather than keratoconus. The patient was refit into a better-aligned GP lens, and the warpage resolved over a few weeks.

Summary

Careful corneal examination and interpretation of multiple tomography features are required to differentiate between corneal warpage and early keratoconus. Of course, corneal warpage can typically be avoided in the first place by optimizing the contact lens fit and/or material. CLS

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