contact lens case reports

Managing PMD with a Semi-scleral Contact Lens
BY PATRICK J. CAROLINE, FAAO, & MARK P. ANDRé, FAAO

In past columns we've discussed a wide range of contact lens modalities for managing pellucid marginal degeneration (PMD), including aspheric GPs, piggyback lenses, toric soft lenses and bitoric GP designs. This month we'll review the use of the Jupiter Lens (Medlens Innovations, Inc., also distributed by Essilor) in managing one of these complex corneas.

Recognizing PMD

PMD is often a bilateral disorder hallmarked by a thinning of the inferior, peripheral cornea. The corneal thinning begins approximately 1mm to 2mm above the inferior limbus, separated by a region of uninvolved cornea that lies between the thinned zone and the limbus. The condition commonly manifests itself between the ages of 20 and 40 with equal gender distribution and no apparent hereditary transmission. Subjective symptoms are strictly visual secondary to a dramatic increase in against-the-rule corneal astigmatism.

PMD can manifest many of the same features as keratoconus, but in PMD the central and paracentral cornea retains a normal thickness. In PMD, the corneal mapping demonstrates inferior midperipheral zones of corneal steepening at 4 o'clock and 8 o'clock that produce a butterfly wing-like or kissing pigeons pattern that's diagnostic of PMD.

Fitting the Jupiter Lens

Patient JM is a 40-year-old male with a 15-year history of PMD. His more-involved right eye with Ks of 36.75 @ 86/ 47.12 @176 had become uncomfortable in his current lens due to excessive lens rocking at 4 o'clock and 8 o'clock secondary to the high degree of against-the-rule corneal astigmatism (Figure 1). We suggested that JM might benefit from the stability of a Jupiter mini-scleral lens design.

We selected a 15.0mm diagnostic lens with a base curve radius equal to the steepest K read-
ing. We placed two drops of fluorescein into the bowl of the lens prior to lens application and adjusted the base curve (steeper or flatter) until we achieved slight apical clearance and feather inferior touch across the inferior ectasia. The scleral skirt should align with an edge that rises just above the scleral epithelium (Figure 2).

We determined the lens power by a spherical over-refraction. JM ultimately achieved a visual acuity of 20/25 and is able to wear the lens comfortably throughout all his waking hours.

Patrick Caroline is an associate professor of optometry at Pacific University and is an assistant professor of ophthalmology at the Oregon Health Sciences 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 Alcon Labs, CooperVision and SynergEyes, Inc.