contact lens case reports

Managing Corneal Irregularity of Unknown Etiology

BY PATRICK J. CAROLINE, FAAO, & MARK P. ANDRE, FAAO

Patients sometimes present with a history of decreased best-corrected visual acuity in one eye only. Occasionally, this decreased acuity is of unknown and unexplainable etiology. In these individuals the ocular examination reveals no corneal, crystalline lens or posterior segment anomalies, but corneal mapping often reveals an irregular topography.

Their topography doesn't exhibit any of the hallmark patterns common in keratoconus or pellucid marginal degeneration. This might indicate that the abnormal corneal shape is related to a previous corneal trauma or infection. However, the lack of any corneal opacity and/or scarring makes that diagnosis less likely. Therefore, we simply refer to these unexplained topographic findings as FLCs (funny looking corneas).

Figure 1. Corneal mapping of DL's normal right eye and abnormal left eye.

Managing Irregular Cornea

One such individual is patient DL, whom we first examined 10 years ago. At that time his best corrected spectacle acuity was 20/20 in the right eye and 20/30 in the left eye. Corneal mapping showed a normal with-the-rule astigmatism OD and an irregular cornea OS. The patient and his mother denied any knowledge of a previous corneal injury or infection to the left eye.

We proceeded to fit DL with GP lenses that corrected the irregular astigmatism OS and provided him with 20/20 vision in both eyes.

At that time we informed DL that if the irregular astigmatism was secondary to an ectatic condition (keratoconus or PMD), then time and progression of the condition would most likely provide clarity to the diagnosis. We've now followed the patient for 10 years and his corneal topographies are identical to those we captured more than a decade ago (Figure 1). In fact, he continues to wear the exact base curve lenses we originally fit in 1996 (Figure 2).

Still a Mystery

Today, the exact cause of DL's irregular astigmatism (and that of many others like him) remains a mystery. We continue to believe that it might be related to a forgotten childhood trauma or infection, yet in such patients amblyopia doesn't appear to be present.

If this is an acquired, non-progressive anomaly, we might best refer to it as keratoconus fruste. In 1937 Amsler described a mild, non-progressive form of keratoconus that can occur anytime throughout life. The condition was hallmarked by ill-defined, irregular topographical findings with no related corneal thinning or scarring.

Whether you refer to this as keratoconus fruste or simply as irregular cornea, the treatment remains the same: GP lenses. CLS

Figure 2. DL's GP correction.

For references, please visit www.clspectrum.com/references.asp and click on document #140.

Patrick Caroline is an associate professor of optometry at Pacific University. He is also a consultant to Paragon Vision Sciences and SynergEyes, Inc. Mark André is an associate professor of optometry at Pacific University. He is also a consultant for CooperVision and SynergEyes, Inc.