Mean Keratometry Measurement Post Penetrating Keratoplasty

1. Mean Keratometry Measurement Post Penetrating Keratoplasty Jacky Yeung MSc MD, Stephanie Baxter MD FRCS(C) Department of Ophthalmology, Hotel Dieu Hospital, Queen’s University, Kingston Authors have no financial interest

2. Achieving Surgical Success Post PKP • Goals of Penetrating Keratoplasty: Anatomical Success and Visual Success • Factors affecting visual success: 1) Irregular Astigmatism - Treated with Selective Suture Removal (SSR) - guided by visual acuity (VA), refraction, manual keratometry, topography 2) Lens opacity post PKP - Cataract formation, 1 in 4 PKP pts in 1 yr post-op1 1) Rathi et al. J Cataract Refract Surg. 1997 May;23(4):562-4

3. Achieving Surgical Success Post PKP • Dilemma: Post PKP Pt with Cataract • No longer able to use VA as a useful end-point to assist in SSR because of the cataract • Keratometry may not be stable enough for accurate IOL calculations to do cataract surgery “What to do first: cataract surgery or SSR?”

4. Study Objective • To determine the extent that Selective Suture Removal (SSR) has on the mean corneal curvature (average K) post PKP

5. Experimental Methods • Design - Retrospective case series • Approval by Queen’s Univ. Research Ethics Board • Patients • PKP patients from 2004 to 2007 • Inclusion : ≥18 yo, central round pk, 16 Interrupted suture technique , ≥1 yr FU • Exclusion : graft rejection, subsequent ocular sx, no suture removal, incomplete data

6. Experimental Methods • Main outcome measure: • Average manual keratometry readings at 4 time points – 2-4, 5-7, 8-10 and 11-13 mo after SSR • Statistical analysis • Paired samples t-test for comparing keratometry (K) between time points • Repeated measures ANOVA

7. Results - Demographics • Mean age = 64.5 ± 18.8 yrs, M = 25, F = 27 • Patient excluded - if nosuture removal N = 52 (2-4 mo), 41 (5-7 mo), 29 (8-10 mo), 21 (11-13 mo)

8. Results • Paired Student’s t-test comparisons • Comparisons to the 2-4 month point (baseline, D±SE) • Comparisons of each measurement to its previous time point • Overall, no statistical difference in K change over time

9. Results • Repeated measures ANOVA • SSR – at ANY time point after 2 to 4 mo., N=36 Overall, the difference in average K post PKP w/ SSR is < 0.4 to 0.8 D, with an average standard deviation of ~2D. This suggest statistical, but minimal clinical significance.

10. Discussion CE/PCIOL post-PKP Sequential / Staged procedure has Better visual outcomes than Combined procedure2 Sequential procedure also safe3 Traditionally - approx. 1 year after PKP Early cataract surgery post-PKP Potentially reduce visual rehab time Corneal wounds stability – stable by 3 mo5 Spherical equivalent – stable by 6 mo6 2) Shimmura et al. Cornea. 2003 22(3):234-8 3) Nagra et al. Cornea. 2004 23(4):377-9 4) Geggel H. Refract Corneal Surg. 1990 6(1):55-8 5) Hayashi et al. Am J Ophthalmol. 2006 141(2):241-247

11. Discussion Early cataract surgery post PKP Current study: Avg. Ks measured at early time points post PKP 1) Appear to be stable 2) This may facilitate IOL power calculations that are clinically acceptable during early post-op PKP period • Study limitations: • Retrospective design, small sample size, applicability to other suture techniques, manual keratometry measurements used vs. automated (IOL master, topographic)

12. Conclusion • The average K post PKP does not seem to vary significantly with SSR • The average Ks can be used at any point 3 months post PKP for IOL power calculation in patients needing cataract surgery • If necessary, further SSR post cataract surgery should have little effect on the refractive outcome • Consider earlier cataract surgery for earlier visual recovery in post