Post-LASIK Intraocular Lens Power Adjustment Nomogram Joseph Diehl Kevin Miller, MD Jules Stein Eye Institute, David Geffen School of Medicine at UCLA --No Disclosures--

What’s the problem? Cataract surgery normally gives a good refractive result, BUT… Cataract surgery normally gives a good refractive result, BUT… LASIK surgery on the rise LASIK surgery on the rise Changes to corneal power from LASIK are not adequately detected by corneal topography Changes to corneal power from LASIK are not adequately detected by corneal topography With inaccurate corneal power measurements, IOL calculations are inaccurate as well With inaccurate corneal power measurements, IOL calculations are inaccurate as well …and cataract patients have an unsatisfactory refractive result …and cataract patients have an unsatisfactory refractive result

How do we solve it? Investigate the relationship between the LASIK- induced correction in manifest spherical refraction equivalent (MSRE) and post-cataract MSRE (the post-operative error) Investigate the relationship between the LASIK- induced 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 Retrospective, chart-based study of consecutive patients having cataract surgery after LASIK Requires pre- and post-LASIK surgical records Requires pre- and post-LASIK surgical records

Methods Plot LASIK correction in MSRE (in Diopters) vs predicted (based on K values from corneal topography) post-cataract MSRE (D) 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 On same graph, plot the actual post-cataract MSRE The difference between the predicted and actual post- cataract MSRE is the post-operative error the surgeon should target to achieve emmetropia for the given LASIK correction in MSRE The difference between the predicted and actual post- cataract 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 Graph the LASIK correction against this difference to determine if a relationship exists

Patient Demographics 32 suitable eyes from 23 patients 32 suitable eyes from 23 patients Average age 59 years (range: 45-74) Average age 59 years (range: 45-74) 60% female, 40% male 60% female, 40% male 25 myopic LASIK, 7 hyperopic LASIK 25 myopic LASIK, 7 hyperopic LASIK MSRE (D) mean: std dev: (range) MSRE (D) mean: std dev: (range) Pre-LASIK /- 4.9 (-14.8 to 3.4) Pre-LASIK /- 4.9 (-14.8 to 3.4) Post-LASIK /- 1.5 (-4.8 to 1.6) Post-LASIK /- 1.5 (-4.8 to 1.6)

RESULTS post-cataract MSRE (D): Mean +/- Std Dev: (Range) post-cataract MSRE (D): Mean +/- Std Dev: (Range) Predicted error: /- 1.8 (-6.3 to 0.7) Predicted error: /- 1.8 (-6.3 to 0.7) Actual error: /- 0.7 (-1.8 to 0.8) Actual error: /- 0.7 (-1.8 to 0.8) Absolute error: 0.5 +/- 0.5 (0.0 to 1.8) Absolute error: 0.5 +/- 0.5 (0.0 to 1.8)

} -2 Arrows 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.

41 % 56% 3% Less than 0.5 D0.5 to 1.0 DMore than 1.0 D Outcomes: Deviation from equation

Statistically Speaking: Deviation from trendline (D): Deviation from trendline (D): Mean +/- Std Dev (Range) Mean +/- Std Dev (Range) /- 0.6 (-1.1 to 0.8) /- 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: Mean of 0.65 D (0.64 to 0.71)

Post-LASIK IOL Power Adjustment Nomogram LASIK correction (D) target MSRE (D) Target error (D) for emmetropia= (L)^ (L) L=LASIK correction (D)

Discussion Mathematical relationship clearly evident between LASIK correction and post-cataract refractive error 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 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 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) Inconsistencies in measurement of MSRE (measured by technician, physician, or machine) No method yet that consistently produces results equal to eyes without refractive surgery No method yet that consistently produces results equal to eyes without refractive surgery Necessary to have complete LASIK records Necessary to have complete LASIK records Imperative that patients return for all scheduled LASIK post-operative examinations to get accurate and stable MSRE 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 Prospective use of nomogram necessary to further refine graph and determine predictive value