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Sara Bierwerth, OD
Cornea/Contact Lens Resident, SCCO
ABSTRACT
Pellucid marginal degeneration (PMD) is a condition exhibiting inferior corneal steepening. This case
serves to inform of scleral lens designs best suited for PMD patients and discuss whether corneal
“touch” is acceptable within these designs.
CASE HISTORY
A 56 year-old white male was recently seen for a comprehensive eye exam and annual contact lens
follow-up. He reported his eyes feeling dry throughout the day, and difficulty with blurring of his vision
at all distances intermittently each day. He also reported discomfort with his current contact lenses in
each eye, and occasional spontaneous lens ejection. His ocular history is remarkable for Pellucid
Marginal Degeneration and medical history significant for hypertension and hypercholesterolemia.
Current medications included Lipitor, aspirin, fish oil, saw palmetto, and a multivitamin. The patient’s
only ocular medication was artificial tears as needed in each eye.
PERTINENT FINDINGS
Upon examination best visual acuity through habitual contact lenses showed 20/50- in each eye. The
patient’s current lens design was a large diameter (11.2mm) corneal gas permeable lens for each eye.
Slit lamp examination revealed inferiorly displaced RGPs, with harsh bearing over the inferior area of
ectatic cornea and excessive inferior edge lift. Corneal health was compromised, with a grade 2+
moderate, diffuse, superficial punctate keratitis over the inferior cornea OU. Additionally, there was
three and nine-o’clock corneal staining present in both eyes, and encroachment of limbal blood vessels.
Nasally, along the limbus, one to two millimeters of corneal pannus was also noted in each eye. No
other corneal scarring or Vogt’s striae were seen in either eye. A moderate amount of conjunctival
hyperemia also existed in both eyes.
DIFFERENTIAL DIAGNOSIS
Prior to making a definitive diagnosis, it is important to consider other corneal ectatic conditions,
including keratoconus and post-surgical thinning seen after procedures such as radial keratectomy and
Laser-Assisted In-Situ Keratomileusis. Topography and keratometry were performed, confirming the
corneal steepening and “kissing doves” pattern indicative of PMD. The left eye exhibited a much
steeper corneal measurement, with the steep K-reading being 60.00 D, as opposed to the right eye of
51.88 D.
DIAGNOSIS AND DISCUSSION
Pellucid marginal degeneration is often described as a rare variant of keratoconus, though it is not yet
clear whether each is a separate disease or rather a phenotypic variation of the same disorder. Though
no statistical data exists indicating its exact prevalence, it is commonly thought to be much less common
than keratoconus, but more prevalent than keratoglobus.
Sara Bierwerth, OD
Cornea/Contact Lens Resident, SCCO
Clinical features of this condition include inferior corneal changes: a clear area of corneal thinning,
usually severe, in an arcuate shape including the entire inferior corneal quadrant. Between this area
and the limbus usually exists cornea of normal thickness. Upon performing corneal topography one will
find irregular corneal astigmatism, showing a flattening of the cornea along the vertical meridian just
superior to the thinned zone. In advanced cases, such as this patient discussed, one is able to view an
inferior protrusion of the cornea upon profile view. See the images below of the patient.
Less advanced PMD in right eye
Advanced/severe PMD corneal changes
in left eye.
TREATMENT AND MANAGEMENT
With this patient’s corneal condition of PMD being confirmed in each eye, the next step in the treatment
included a re-fitting of gas-permeable contact lenses. Due to inability of the corneal lenses to center
well, and the periodic ejection, scleral lenses were decided upon. An initial scleral lens fitting was
performed in office, with a vault reduction method used for assessing appropriate base curvature. Due
to the advanced appearance of the left eye a larger diameter (18.2 mm) Jupiter scleral lens with a
reverse geometry design was chosen, with the right eye’s initial lens being a standard 15.6 mm diameter
lens.
Upon follow-up, the lenses were assessed on each eye after an initial settling period of 30 minutes.
Visual acuity improved to 20/30 in the right eye and 20/25- in the left. While there was light inferior
corneal touch (in the area of steepening), each eye showed adequate limbal clearance and scleral
alignment. Lenses were dispensed that day, and the patient was taught application and removal
techniques. A new order was placed to gain more inferior corneal and limbal clearance for both eyes.
At the patient’s next follow-up, corneal integrity was carefully examined. Below are photos showing
each eye’s fluorescein pattern with the newly ordered lens, the tear meniscus (indicating thinning
inferiorly of the tear layer), and the positive sodium fluorescein staining seen. While the right eye
showed a more “feathery” touch, both eyes exhibited a moderate amount of corneal staining.
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Sara Bierwerth, OD
Cornea/Contact Lens Resident, SCCO
OD area of light touch and resultant corneal staining.
Minimal tear layer over inf. cornea.
OS area of greater touch and resultant corneal staining.
No tear layer over inf. cornea.
The newly ordered lenses, while exhibiting more inferior clearance and less corneal touch, still did not
entirely vault the cornea (especially left eye). A new pair was ordered to further vault the cornea by
steepening the secondary peripheral curve, or increasing the lens’ reverse geometry design.
This last lens order offered full corneal clearance and complete vaulting over the entire cornea. The
patient’s final vision was measured to be 20/20- in the right eye and 20/30+ in the left. It is expected to
further improve after dispensing these optimally fitting lenses, and will be assessed in two weeks.
Finalized scleral lenses: a profile view.
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Sara Bierwerth, OD
Cornea/Contact Lens Resident, SCCO
Finalized scleral lenses: fluorescein patterns.
It’s important to take into consideration the corneal appearance post-lens wear in making fit-changes of
each lens. While occasional light, feathery corneal touch is acceptable in some cases, in others (such as
this patient) it is not—resulting in superficial punctate keratitis or other corneal changes. Careful
monitoring is needed to ensure that the patient is not developing corneal irritation from the fit.
CONCLUSION
PMD is a condition which causes irregular corneal astigmatism and resultant poor vision through
spectacles. Rigid gas permeable lens designs offer an improvement in vision, with scleral lenses being
ideal for lens centration. When fitting a patient with PMD, a reverse geometry design is often needed to
completely vault the inferior peripheral cornea. This case report shows that even light, feathery corneal
touch produced complications and keratitis. It is important to examine carefully the cornea on all
follow-up visits to ensure that there is adequate lens vaulting.
RESOURCES
Belin M., Asota I., Ambrosio R., Khachikian S. Perspectives: What’s in a Name: Keratoconus, Pellucid
Marginal Degeneration, and Related Thinning Disorders. American Journal of Ophthalmology.
Vol: 152 (2011) 157-161.
DeNaeyer G., Breece R. Fitting Techniques for a Scleral Lens Design. Contact Lens Spectrum. (2009)
http://www.clspectrum.com/articleviewer.aspx?articleid=102474
Jinabhai A., Radhakrishnan H., O’Donnell C. Review: Pellucid corneal marginal degeneration: A review.
Contact Lens and Anterior Eye. Vol: 34 (2011) 56-63.
Messer B., Part II: Trouble-shooting astigmatism. Review of Cornea and Contact Lenses. (2012)
http://www.reviewofcontactlenses.com/content/d/gas-permeable_strategies/i/1832/c/33090/
Van der Worp, Eef, “Scleral Lens Case Report Series: Beyond the Corneal Borders” (2012). Books and
Monographs. Book 5. http://commons.pacificu.edu/mono/5
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