Contact Lens Case Reports

Correcting High Astigmatism Post-Penetrating Keratoplasty

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

Our 24-year-old female patient had a Herpes simplex virus infection OD at age 16 that left her with a dense corneal scar. She underwent penetrating keratoplasty (PKP) surgery OD at age 22. Two years postoperatively, she was referred to us for contact lens fitting.

Examination Findings

Slit lamp exam showed a clear graft with 16 interrupted sutures still in place; all of the knots were buried within the stroma. Simulated keratometry revealed 18.00D of with-the-rule corneal astigmatism with Ks of 28.00 (12.05mm) @ 173/46.00 (7.35mm) @ 83 (Figure 1).

Figure 1. Corneal mapping of the patient’s right eye showing 18.00D of with-the-rule corneal astigmatism.

Anterior segment optical coherence tomography (OCT) OD revealed a lower-than-normal sagittal height of the anterior eye (3,480 microns); the peripheral corneal angles were significantly higher than normal at 43.8º and 45º (normal is 38º), resulting in a plateau shape to the anterior cornea (Figure 2).

Figure 2. Anterior segment OCT of the patient’s right eye showing a “plateau” postoperative shape.

Fitting a Scleral Lens

We placed a diagnostic scleral lens with a sagittal height of 4,200 microns onto the patient’s right eye. The fluorescein pattern and OCT imaging showed excellent apical clearance, but significant lens bearing in the peripheral cornea (Figure 3). We therefore increased the peripheral corneal clearance zone of the lens. Because this increased the sagittal height of the lens, we also flattened the base curve radius to 38.00D (8.88mm). Figure 4 shows this lens dispensed to the patient. She reported excellent comfort with the lens and 20/25 visual acuity.

Figure 3. The initial diagnostic lens with a sagittal height of 4,200 microns.

Figure 4. The lens dispensed to the patient with the increased peripheral corneal clearance zone.

This case outlines two important features of modern scleral lenses: 1) the lacrimal lens created by a scleral lens design is capable of correcting almost any amount of corneal toricity, and 2) one of the more common lens design changes required when fitting scleral lenses is increasing the depth of the peripheral corneal clearance zone. CLS

Patrick Caroline is an associate professor of optometry at Pacific University. He is also a consultant to Contamac. Mark André is an associate professor of optometry at Pacific University. He is also a consultant for CooperVision.