Transcript p75 Nerve Growth Factor Receptors May Mediate Apoptosis in

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
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?”
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
Failed PKP
Keratoconus
K scar
K ectasia
Fuchs
Others
Total
23
11
5
4
2
2
5
52
44.23
21.15
9.62
7.69
3.85
3.85
9.62
100.00
Results

Paired Student’s t-test comparisons

Comparisons to the 2-4 month point (baseline, D±SE)
2-4 vs 5-7
N=41
Mean Difference
-0.420±0.314
-0.419±0.302
0.104
0.192
0.182
Comparisons of each measurement to its previous time
point
2-4 vs 5-7
5-7 vs 8-10
8-10 vs 11-13
N=41
Mean Difference
P value

2-4 vs 11-13
N= 21
-0.270 ±0.162
P value

2-4 vs 8-10
N= 29
N=29
N= 20
-0.270±0.162
-0.162±0.262
-0.213±0.338
0.104
0.543
0.538
Overall, no statistical difference in K change over time
Results

Repeated measures ANOVA

SSR – at ANY time point after 2 to 4 mo., N=36
Descriptive Statistics
K 2 to 4
Mean difference Std. Deviation
0
43.77
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
visual outcomes than Combined procedure2
 Sequential procedure also safe3
 Better


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
 Avg.
study:
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