FULL THICKNESS corneal transplants are necessary when a patient has significant central corneal scarring from trauma or keratoconus. High astigmatism or corneal irregularity postoperatively often needs to be corrected successfully with specialty contact lenses.

Post-penetrating keratoplasty (PK) corneal ectasia is thought to occur secondary to thinning and steepening of the tissue at the graft-host junction (Moramarco et al, 2022). The peripheral steepening causes the whole graft to bulge like keratoglobus and creates a corneal surface with extreme sagittal height, which can make fitting challenging.

CASE #1

A 58-year-old male has a previous history of keratoconus and PK of his right eye 30 years prior. His left eye has light perception vision post retinal detachment. Systemically, he has a pertinent history of Graves’ disease that was successfully managed. Slit lamp exam OD is remarkable for extreme corneal ectasia with a clear full thickness corneal graft (Figure 1). The patient’s right eye was successfully fit with a 20mm diameter (hexafocon B, Dk 141) scleral lens, power –17.25D, sagittal depth 7,859 microns, and a spherical landing zone. Visual acuity was 20/25 with the scleral lens.

Cases like this will be best fit with a scleral lens for successful stability. Larger-than-average diameters are necessary to create the extreme amount of sagittal depth needed to properly vault the cornea from limbus to limbus without creating compression of the landing zone.

CASE #2

A 78-year-old male patient with a history of keratoglobus had previous PK of his right and left eyes 35 and 10 years ago, respectively. He previously had a poorly fit corneal GP lens OD (Figure 2). Slit lamp exam is remarkable for recurrent corneal ectasia and scarring in both eyes.

Scleral lenses are the best option to fit his extreme sagittal height changes secondary to post-PK ectasia. Scleral lens parameters are: OD 16.5mm diameter (hexafocon A, Dk 100), power –14.37D, sagittal depth 6,267 microns, and a 300-micron toric landing zone (Figure 3); OS 16.5mm diameter (hexafocon A, Dk 100), power –2.00D, sagittal depth 5,193 microns and a 100-micron toric landing zone. The patient is able to successfully wear his scleral lenses without complications and has improved stability compared to his previous corneal GP lenses, with visual acuities of 20/40 OD and 20/25 OS.

IN CONCLUSION

These case examples exemplify the extreme sagittal height changes that sometimes need to be addressed when fitting an eye that exhibit post-PK ectasia, especially for patients who have a previous diagnosis of keratoconus (Miura et al, 2023). Scleral lenses often are the only successful option in these cases.

For sagittal heights greater than 7,000 microns, increasing lens diameter (as was done in the first case example) is necessary to achieve an acceptable fit. Utilize hyper-Dk materials to minimize neovascularization and always be mindful of potential graft rejection, which can initially present with injection and corneal edema. CLS

References

1. Moramarco A, Gardini L, Iannetta D, Versura P, Fontana L. Post Penetrating Keratoplasty Ectasia: Incidence, Risk Factors, Clinical Features, and Treatment Options. J Clin Med. 2022 May 10;11:2678.
2. Miura M, Leon P, Nahum Y, et al. Recurrent Keratoconus: Corneal Transplants for Keratoconus Develop Tomographic Ectatic Changes. Cornea. 2023 Jun 1;42:708-713.