Post-Penetrating Keratoplasty: Jeffrey Sonsino, OD, FAAO
MB was referred for a contact lens fit following multiple, complicated, combined penetrating keratoplasty procedures, most recently 3 years ago. Since then, he had aphakia, chronic iritis, chronic angle closure glaucoma, trabeculectomy and trichiasis OD. The left eye had phthis bulbi and light perception vision. He arrived wearing a poorly fitting GP lens, which his corneal surgeon felt was mechanically abrading his central cornea.
Test Procedures, Fitting/Refitting, Design & Ordering
Chief complaint: none- patient did not have corneal sensation.
Diamox, Lotemax 6x/day OD, Pilocarpine gel qhs OD, 0.5% Timoptic bid OD, Lumigan qhs OD, Restasis qid OD, artificial tears prn OD
Entering visual acuity (with current contact lens):
- 3+ conjunctival injection
- Central corneal staining congruous with flat fitting habitual GP
- Low riding, large diameter GP contact lens
- Trace cells & flare in anterior chamber
OS: Phthis bulbi
Manual Keratometry: 43.25/44.25@ 90, 3+ distorted mires
Patient Consultation and Education
This is a very complicated case where mechanical abrasion of a poorly fitting contact lens has the potential to cause a graft rejection. The patient has no corneal sensation, so is unable to determine if the contact lens is abrading his cornea. Since the patient is functionally monocular, there is no room for error with a contact lens re-fit.
Initial Contact lens fit:
The patient was fit with a posterior surface aspheric GP lens. The initial lens ordered: 8.54/+14.00/9.3 Boston EO
On follow-up, the lens was placed on the cornea. There was a large air bubble at the graft-host interface. A piggy-back silicone hydrogel lens was inserted beneath the GP lens and the air bubble persisted.
The lens was re-ordered in an intralimbal, reverse geometry, back surface aspheric GP design and lower specific gravity material: 8.60/+12.00/11.0 Fluoroperm 151
The NaFl pattern is shown, note central pooling and low edge clearance:
Pertinent Biomicroscopic findings:
OD: no NaFl stain on central cornea
Contact lens fit:
- Central pooling
- 0.5mm lens movement upon blink
- Inferior centration
- Use of a silicone hydrogel piggy-back lens
Discussion/Alternative Management Options
With post-penetrating keratoplasty eyes, one must first establish if the graft is prolate or oblate in shape. This can be determined by the corneal topography and manual keratometry. A prolate graft will have a steep central zone with a flatter periphery. In these cases, a keratoconic design GP lens will typically be fit. Conversely, an oblate graft is flat centrally and steepens toward the host tissue. This case is interesting in that the central keratometry reading had a medium (rather than flat) base curve. When an aspheric GP lens with corresponding base curve was fit, there was significant space between the GP lens and the graft-host junction. The manifestation of this space is a large air pocket. We went to a reverse geometry lens in order to accommodate the peripheral cornea. Reverse geometry lenses were created for application in orthokeratology. They have a steeper secondary (and sometimes teriarty) curve than the base curve, creating a shape which fits an oblate surface.
A piggy-back silicone hydrogel lens was used to provide protection for the corneal epithelium. With high Dk properties of the hydrogel and GP lens, the risk for microbial infection is minimized.
Since this patient also had a trabeculectomy, we were not disappointed with an inferiorly centering lens. We wanted to stay as far away as possible from the wound site to avoid introduction of pathogens into the anterior chamber. Typically, we avoid GP use in a patient with a trabeculectomy. With a GP lens that is lid attached, there may be constant mechanical abrasion at the elevated bleb. However, in the case of a patient who is monocular, aphakic and has irregular astigmatism, there is no other option for vision correction.
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