Mean%20Keratometry%20Measurement%20Post%20Penetrating%20Keratoplasty

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Mean Keratometry Measurement Post Penetrating
Keratoplasty

• Jacky Yeung MSc MD,
• Stephanie Baxter MD FRCS(C)
• Department of Ophthalmology,
  Hotel Dieu Hospital,
  Queens University, Kingston
• Authors have no financial interest

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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

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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?
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Study Objective

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

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Experimental Methods

• Design - Retrospective case series
• Approval by Queens 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

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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

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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 44.23
Failed PKP 11 21.15
Keratoconus 5 9.62
K scar 4 7.69
K ectasia 2 3.85
Fuchs 2 3.85
Others 5 9.62
 Total 52 100.00
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Results

• Paired Students t-test comparisons
• Comparisons to the 2-4 month point (baseline,
  DSE)
• Comparisons of each measurement to its previous
  time point
• Overall, no statistical difference in K change
  over time

2-4 vs 5-7 N41 2-4 vs 8-10 N 29 2-4 vs 11-13 N 21
Mean Difference -0.270 0.162 -0.4200.314 -0.4190.302
P value 0.104 0.192 0.182
2-4 vs 5-7 N41 5-7 vs 8-10 N29 8-10 vs 11-13 N 20
Mean Difference -0.2700.162 -0.1620.262 -0.2130.338
P value 0.104 0.543 0.538
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Results

• Repeated measures ANOVA
• SSR at ANY time point after 2 to 4 mo., N36

Descriptive Statistics Descriptive Statistics Descriptive Statistics Descriptive Statistics
  Mean difference Std. Deviation
K 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 Tests of Within-Subjects Effects
P value 0.022
Overall, the difference in average K post PKP w/
SSR is lt 0.4 to 0.8 D, with an average standard
deviation of 2D. This suggest
statistical, but minimal clinical significance.
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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

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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)

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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