Mean Keratometry Measurement Post Penetrating Keratoplasty Jacky Yeung MSc MD, Stephanie Baxter MD...
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Transcript of Mean Keratometry Measurement Post Penetrating Keratoplasty Jacky Yeung MSc MD, Stephanie Baxter MD...
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
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
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?”
Achieving Surgical Success Post PKP
Study Objective
To determine the extent that Selective Suture Removal (SSR) has on the mean corneal curvature (average K) post PKP
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
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
Results - Demographics Mean age = 64.5 ± 18.8 yrs, M = 25, F = 27 Patient excluded - if no suture removal
N = 52 (2-4 mo), 41 (5-7 mo), 29 (8-10 mo), 21 (11-13 mo)
Reasons for PKP # %
PBK 23 44.23Failed PKP 11 21.15Keratoconus 5 9.62K scar 4 7.69K ectasia 2 3.85Fuchs 2 3.85Others 5 9.62 Total 52 100.00
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
Results
2-4 vs 5-7N=41
2-4 vs 8-10N= 29
2-4 vs 11-13N= 21
Mean Difference -0.270 ±0.162 -0.420±0.314 -0.419±0.302
P value 0.104 0.192 0.182
2-4 vs 5-7N=41
5-7 vs 8-10N=29
8-10 vs 11-13N= 20
Mean Difference -0.270±0.162 -0.162±0.262 -0.213±0.338
P value 0.104 0.543 0.538
Results Repeated measures ANOVA
SSR – at ANY time point after 2 to 4 mo., N=36
Descriptive Statistics
Mean difference Std. DeviationK 2 to 4 43.77 0 2.13
K 5 to 7 44.16 -0.39 2.21
K 8 to 10 44.07 -0.30 1.85
K 11 to 13 44.61 -0.84 2.31
Tests of Within-Subjects Effects
P value 0.022
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.
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
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)
Conclusion
1. The average K post PKP does not seem to vary significantly with SSR
2. The average Ks can be used at any point 3 months post PKP for IOL power calculation in patients needing cataract surgery
3. If necessary, further SSR post cataract surgery should have little effect on the refractive outcome
4. Consider earlier cataract surgery for earlier visual recovery in post