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Corneal curvature, astigmatism progress up to 30 years after PK for keratoconus
Am J Ophthalmol. 2009;147(2):227-233.
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Keratometric instability advanced up to 30 years after penetrating keratoplasty for keratoconus but remained stable up to 20 years after the same procedure for Fuchs’ dystrophy.
The retrospective, comparative study included 85 eyes of 63 patients who underwent PK for keratoconus and 83 eyes of 60 patients who underwent PK for Fuchs’ dystrophy. The keratoconus group had a mean age of 36 years and the Fuchs dystrophy group had a mean age of 69 years at the time of surgery. The same suturing technique was used in all cases.
Follow-up examinations were performed at 13 months (1 month after final suture removal) and 5, 10, 15, 20, 25 and 30 years.
Study data showed mean corneal curvature and astigmatism increasing throughout the study period (both P < .001) in the keratoconus group. Corneal curvature and astigmatism did not change for up to 20 years in the Fuchs’ dystrophy group. Recurrent ectasia was identified in five keratoconic eyes; thinning of the recipient rim at the graft-host junction was seen in four of those eyes.
“Our data suggest that keratometric instability after PK for keratoconus is attributable to delayed, progressive ectasia in the host corneal rim,” the study said.
This study shows that patients with keratoconus often have progressive steepening with astigmatism after keratoplasty due to ectasia at the graft host interface. These cases were performed in the late 1970s and early 1980s when there was the tendency to do what we would today consider relatively small grafts for keratoconus (mean of 7.9 mm in the study), and there was the tendency to still oversize the grafts (mean recipient bed 7.6 mm in this study). With today’s philosophy of trying to remove the already ectatic cornea (my average diameter of graft is 8.5 mm for keratoconus) without oversizing the graft, this should be less frequent than in years past, but still may end up requiring repeat larger transplant in some patients.
– David R. Hardten, MD
OSN Cornea/External Disease Board Member