Transcript Development of post-LASIK IOL Power Adjustment Nomogram

Post-LASIK Intraocular
Lens Power Adjustment
Nomogram
Joseph Diehl
[email protected]
Kevin Miller, MD
Jules Stein Eye Institute,
David Geffen School of Medicine at UCLA
--No Disclosures--
What’s the problem?
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Cataract surgery normally gives a good refractive
result, BUT…
LASIK surgery on the rise
Changes to corneal power from LASIK are not
adequately detected by corneal topography
With inaccurate corneal power measurements,
IOL calculations are inaccurate as well
…and cataract patients have an unsatisfactory
refractive result
How do we solve it?
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Investigate the relationship between the LASIKinduced correction in manifest spherical
refraction equivalent (MSRE) and post-cataract
MSRE (the post-operative error)
Retrospective, chart-based study of consecutive
patients having cataract surgery after LASIK
Requires pre- and post-LASIK surgical records
Methods
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Plot LASIK correction in MSRE (in Diopters) vs
predicted (based on K values from corneal topography)
post-cataract MSRE (D)
On same graph, plot the actual post-cataract MSRE
The difference between the predicted and actual postcataract MSRE is the post-operative error the surgeon
should target to achieve emmetropia for the given
LASIK correction in MSRE
Graph the LASIK correction against this difference to
determine if a relationship exists
Patient Demographics
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32 suitable eyes from 23 patients
Average age 59 years (range: 45-74)
60% female, 40% male
25 myopic LASIK, 7 hyperopic LASIK
MSRE (D) mean: std dev:
(range)
Pre-LASIK -5.9 +/- 4.9 (-14.8 to 3.4)
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Post-LASIK -1.0
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+/- 1.5
(-4.8 to 1.6)
RESULTS
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post-cataract MSRE (D): Mean +/- Std Dev:
(Range)
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Predicted error:
-2.0 +/- 1.8 (-6.3 to 0.7)
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Actual error:
Absolute error:
-0.3 +/- 0.7 (-1.8 to 0.8)
0.5 +/- 0.5 (0.0 to 1.8)
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ACTUAL post-cataract MSRE (D)
PREDICTED post-cataract MSRE (D)
2
ACTUAL post-cataract MSRE (D)
1
0
-13
-12
-11
-10
-9
-8
-7
-6
-5
-4
-3
-2
-1
} -2
0
1
2
3
-1
-2
-3
-4
Arrows demonstrate a single patient with a LASIK
correction of -5 D. Implanted IOL-5had a predicted
post-op MSRE of -3 diopters, but an actual post-op
MSRE of only -1. Difference of -2,-6
so this patient will
be -5, -2 on following graph.
-7
LASIK correction (D)
4
LASIK correction (x) vs target MSRE (y)
y = -0.0177x2 + 0.192x - 0.0624
2
1
0
-12
-11
-10
-9
-8
-7
-6
-5
-4
-3
-2
-1
0
-1
Target MSRE (D)
-13
-2
-3
-4
-5
-6
-7
LASIK correction (D)
1
2
3
4
Outcomes: Deviation from equation
18
16
56%
14
12
10
41 %
# patients
8
6
3%
4
2
0
Less than 0.5 D
0.5 to 1.0 D
More than 1.0 D
Statistically Speaking:
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Deviation from trendline (D):
Mean +/- Std Dev (Range)
-0.1 +/- 0.6 (-1.1 to 0.8)
ABSOLUTE deviation from trendline (D):
Mean +/- Std Dev (Range)
0.5 +/- 0.3
(0.0 to 1.1)
STANDARD (statistically predicted) ERROR:
Mean of 0.65 D (0.64 to 0.71)
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Post-LASIK IOL Power Adjustment
Nomogram
LASIK correction (D)
-12
-11
-10
-9
-8
-7
-6
-5
-4
-3
-2
-1
1
2
3
4
target MSRE (D)
-4.9
-4.3
-3.8
-3.2
-2.7
-2.3
-1.9
-1.5
-1.1
-0.8
-0.5
-0.3
0.1
0.3
0.4
0.5
Target error (D) for emmetropia=
-0.0177(L)^2+0.192(L)-0.0624
L=LASIK correction (D)
Discussion
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Mathematical relationship clearly evident between LASIK correction and
post-cataract refractive error
Cataract surgeon selects IOL with predicted post-operative MSRE that
correlates in nomogram with LASIK correction
Post-LASIK and post-cataract MSRE measurements done at inconsistent
intervals, because patients didn’t return for follow-up, however, cornea can
take months to stabilize
Inconsistencies in measurement of MSRE (measured by technician, physician,
or machine)
No method yet that consistently produces results equal to eyes without
refractive surgery
Necessary to have complete LASIK records
Imperative that patients return for all scheduled LASIK post-operative
examinations to get accurate and stable MSRE
Prospective use of nomogram necessary to further refine graph and
determine predictive value