Post-LASIK Post-LASIK Intraocular Lens Intraocular Lens

Power Adjustment Power Adjustment NomogramNomogram

Joseph DiehlJoseph Diehljdiehl@ucla.edujdiehl@ucla.edu

Kevin Miller, MDKevin Miller, MD

Jules Stein Eye Institute, Jules Stein Eye Institute, David Geffen School of Medicine at UCLADavid Geffen School of Medicine at UCLA

--No Disclosures----No Disclosures--

What’s the problem?What’s the problem? Cataract surgery normally gives a good Cataract surgery normally gives a good

refractive result, BUT…refractive result, BUT… LASIK surgery on the riseLASIK surgery on the rise Changes to corneal power from LASIK are Changes to corneal power from LASIK are

not adequately detected by corneal not adequately detected by corneal topographytopography

With inaccurate corneal power With inaccurate corneal power measurements, IOL calculations are measurements, IOL calculations are inaccurate as wellinaccurate as well

……and cataract patients have an and cataract patients have an unsatisfactory refractive resultunsatisfactory refractive result

How do we solve it?How do we solve it? Investigate the relationship between the Investigate the relationship between the

LASIK-induced correction in manifest LASIK-induced correction in manifest spherical refraction equivalent (MSRE) spherical refraction equivalent (MSRE) and post-cataract MSRE (the post-and post-cataract MSRE (the post-operative error)operative error)

Retrospective, chart-based study of Retrospective, chart-based study of consecutive patients having cataract consecutive patients having cataract surgery after LASIKsurgery after LASIK

Requires pre- and post-LASIK surgical Requires pre- and post-LASIK surgical recordsrecords

MethodsMethods Plot LASIK correction in MSRE (in Diopters) vs Plot LASIK correction in MSRE (in Diopters) vs

predictedpredicted (based on K values from corneal (based on K values from corneal topography) post-cataract MSRE (D)topography) post-cataract MSRE (D)

On same graph, plot the On same graph, plot the actualactual post-cataract post-cataract MSREMSRE

The difference between the predicted and The difference between the predicted and actual post-cataract MSRE is the post-actual post-cataract MSRE is the post-operative error the surgeon should target to operative error the surgeon should target to achieve emmetropia for the given LASIK achieve emmetropia for the given LASIK correction in MSREcorrection in MSRE

Graph the LASIK correction against this Graph the LASIK correction against this difference to determine if a relationship existsdifference to determine if a relationship exists

Patient DemographicsPatient Demographics 32 suitable eyes from 23 patients32 suitable eyes from 23 patients Average age 59 years (range: 45-74) Average age 59 years (range: 45-74) 60% female, 40% male60% female, 40% male 25 myopic LASIK, 7 hyperopic LASIK25 myopic LASIK, 7 hyperopic LASIK MSRE (D) mean: std dev: (range)MSRE (D) mean: std dev: (range) Pre-LASIK -5.9 +/- 4.9 (-14.8 to Pre-LASIK -5.9 +/- 4.9 (-14.8 to

3.4)3.4)

Post-LASIK -1.0 +/- 1.5 (-4.8 to 1.6)Post-LASIK -1.0 +/- 1.5 (-4.8 to 1.6)

RESULTSRESULTS post-cataract MSRE (D): Mean +/- Std Dev: post-cataract MSRE (D): Mean +/- Std Dev:

(Range) (Range)

Predicted error: -2.0 +/- 1.8 (-6.3 to Predicted error: -2.0 +/- 1.8 (-6.3 to 0.7)0.7)

Actual error: -0.3 +/- 0.7 (-1.8 to Actual error: -0.3 +/- 0.7 (-1.8 to 0.8)0.8)

Absolute error: 0.5 +/- 0.5 (0.0 to Absolute error: 0.5 +/- 0.5 (0.0 to 1.8) 1.8)

ACTUAL post-cataract MSRE (D)PREDICTED post-cataract MSRE (D)

-7

-6

-5

-4

-3

-2

-1

0

1

2

-13 -12 -11 -10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4

LASIK correction (D)

ACTU

AL

pos

t-ca

tara

ct M

SRE

(D)

} -2Arrows demonstrate a single patient with a LASIK correction of -5 D. Implanted IOL had a predicted post-op MSRE of -3 diopters, but an actual post-op MSRE of only -1. Difference of -2, so this patient will be -5, -2 on following graph.

LASIK correction (x) vs target MSRE (y)y = -0.0177x2 + 0.192x - 0.0624

-7

-6

-5

-4

-3

-2

-1

0

1

2

-13 -12 -11 -10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4

LASIK correction (D)

Targ

et M

SRE

(D)

0

2

4

6

8

10

12

14

16

18

# patients41 %

56%

3%

Less than 0.5 D 0.5 to 1.0 DMore than 1.0 D

Outcomes: Deviation from equation

Statistically Speaking:Statistically Speaking: Deviation from trendline (D):Deviation from trendline (D): Mean +/- Std Dev (Range)Mean +/- Std Dev (Range) -0.1 +/- 0.6 (-1.1 to 0.8)-0.1 +/- 0.6 (-1.1 to 0.8)

ABSOLUTE deviation from trendline (D): ABSOLUTE deviation from trendline (D): Mean +/- Std Dev (Range) Mean +/- Std Dev (Range) 0.5 +/- 0.3 (0.0 to 1.1)0.5 +/- 0.3 (0.0 to 1.1)STANDARD (statistically predicted) ERROR:STANDARD (statistically predicted) ERROR:

Mean of 0.65 D (0.64 to 0.71)Mean of 0.65 D (0.64 to 0.71)

Post-LASIK IOL Power Post-LASIK IOL Power Adjustment NomogramAdjustment Nomogram

LASIK correction (D) target MSRE (D) LASIK correction (D) target MSRE (D) -12-12 -4.9-4.9-11-11 -4.3-4.3-10-10 -3.8-3.8-9-9 -3.2-3.2-8-8 -2.7-2.7-7-7 -2.3-2.3-6-6 -1.9-1.9-5-5 -1.5-1.5-4-4 -1.1-1.1-3-3 -0.8-0.8-2-2 -0.5-0.5-1-1 -0.3-0.3 11 0.1 0.1 22 0.3 0.3 33 0.4 0.4 44 0.5 0.5

Target error (D) for emmetropia=

-0.0177(L)^2+0.192(L)-0.0624

L=LASIK correction (D)

DiscussionDiscussion Mathematical relationship clearly evident between LASIK Mathematical relationship clearly evident between LASIK

correction and post-cataract refractive errorcorrection and post-cataract refractive error Cataract surgeon selects IOL with predicted post-operative Cataract surgeon selects IOL with predicted post-operative

MSRE that correlates in nomogram with LASIK correctionMSRE that correlates in nomogram with LASIK correction Post-LASIK and post-cataract MSRE measurements done Post-LASIK and post-cataract MSRE measurements done

at inconsistent intervals, because patients didn’t return for at inconsistent intervals, because patients didn’t return for follow-up, however, cornea can take months to stabilizefollow-up, however, cornea can take months to stabilize

Inconsistencies in measurement of MSRE (measured by Inconsistencies in measurement of MSRE (measured by technician, physician, or machine)technician, physician, or machine)

No method yet that consistently produces results equal to No method yet that consistently produces results equal to eyes without refractive surgeryeyes without refractive surgery

Necessary to have complete LASIK recordsNecessary to have complete LASIK records Imperative that patients return for all scheduled LASIK Imperative that patients return for all scheduled LASIK

post-operative examinations to get accurate and stable post-operative examinations to get accurate and stable MSREMSRE

Prospective use of nomogram necessary to further refine Prospective use of nomogram necessary to further refine graph and determine predictive valuegraph and determine predictive value