GP Lens Case Grand Rounds Troubleshooting Guide – 43

Post-Penetrating Keratoplasty: Jeffrey Sonsino, OD, FAAO

Background

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.

Medications:

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):

OD: 20/30+
OS: LP

Biomicroscopic Evaluation:

OD: Trichiasis

  • 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
  • Aphakia

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

Follow-up:

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:

Final Outcome:

Visual Acuity:
OD: 20/30+2

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.

Supplemental Reading:

  1. Gruenauer-Kloevekorn C,Kloevekorn-Fischer U,Duncker GI. Contact lenses and special back surface design after penetrating keratoplasty Br J Ophthalmol 2005; 89:1601-1608.
  2. Javadi MA, Motlagh BF, Jafarinasab MR, Rabbanikhah Z, Anissian A, Souri H, Yazdani S. Outcomes of penetrating keratoplasty in keratoconus. Cornea 2005 Nov;24(8):941-6.
  3. Lagnado R, Rubinstein MP, Maharajan S, Dua. Management options for the flat corneal graft. Cont Lens Anterior Eye. 2004 Mar;27(1):27-31.
  4. Martin R, Rodriguez G. Reverse geometry contact lens fitting after corneal refractive surgery. J Refract Surg 2005, Vol 21(6); 753-6.
  5. Rubinstein MP, Sud S. The use of hybrid lenses in management of the irregular cornea. Cont Lens Anterior Eye 1999 Vol 22(3); 87-90.
  6. Touzeau O, Borderie VM, Allouch C, Laroche L, Late changes in refraction, pachymetry, visual acuity, and corneal topography. Cornea 2006; Vol 25(2):146-52.

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