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M. N. Jones, S. B. Kaye, W. Ayliffe, W. J. Armitage, D. F. P. Larkin, On behalf of the UK Transplant Ocular Tissue Advisory Group; Comparison of Graft Outcomes of Deep Anterior Lamellar Keratoplasty versus Penetrating Keratoplasty for Keratoconus. Invest. Ophthalmol. Vis. Sci. 2008;49(13):1151.
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There has been a significant increase in the proportion of deep anterior lamellar keratoplasty (DALK) performed for Keratoconus in the United Kingdom, in that it has risen from 8.5% to 33% between 1999-00 and 2006-07. However, univariate survival estimates showed that the survival of first grafts was consistently lower (p=0.06) for DALK compared with Penetrating Keratoplasty (PK). At 3 years, the graft survival rates were 93% (95% CI: 92-95) for PK and 89% (95% CI: 81-93) for DALK. The purpose of this study is to compare the graft outcomes of the two procedures after taking account of other pre-operative factors.
There were 2831 first grafts for Keratoconus reported to UK Transplant between April 1999 and March 2006, of which PK were performed on 2246 patients (79%) and DALK on 585 patients (21%). Of these 2831, follow-up has been reported in 2533 instances (89%). A Cox regression model was fitted to identify the donor and recipient factors affecting graft survival. A variable identifying the type of graft (PK or DALK) was then added to the model to determine whether DALK still had a higher risk of graft failure after allowing for other risk factors. Further information specific to DALK was obtained from a supplementary questionnaire for all failed grafts.
There is significant evidence that type of graft affects graft survival, after taking account of other relevant risk factors (p=0.007). A patient receiving a DALK is twice as likely to experience graft failure compared to a patient who receives a PK. Failure to achieve satisfactory vision and opacification of the graft were the main reasons for graft failure reported on the supplementary questionnaire for failed DALK. 10 out of 26 DALK failures occurred within the first 75 days and graft survival rates were similar between the two groups (p=0.8) when all early failures (those in first 75 days) were excluded.
Overall graft survival was significantly poorer for DALK patients compared with PK patients and this significant difference remained after taking account of other risk factors. However, there was no difference in graft survival when short-term failures were excluded.
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