PostLASIK Intraocular Lens Power Adjustment Nomogram Joseph Diehl

Post-LASIK Intraocular Lens Power Adjustment Nomogram Joseph Diehl jdiehl@ucla. edu 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… n LASIK surgery on the rise n Changes to corneal power from LASIK are not adequately detected by corneal topography n With inaccurate corneal power measurements, IOL calculations are inaccurate as well n …and cataract patients have an unsatisfactory refractive result n

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) n Retrospective, chart-based study of consecutive patients having cataract surgery after LASIK n Requires pre- and post-LASIK surgical records n

Methods n n 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 32 suitable eyes from 23 patients n Average 59 years (range: 45 -74) n 60% female, 40% male n 25 myopic LASIK, 7 hyperopic LASIK n MSRE (D) mean: std dev: (range) n Pre-LASIK -5. 9 +/- 4. 9 (-14. 8 to 3. 4) n n Post-LASIK -1. 0 +/- 1. 5 (-4. 8 to 1. 6)

RESULTS n post-cataract MSRE (D): Mean +/- Std Dev: (Range) n Predicted error: Actual error: 0. 8) n Absolute error: n -2. 0 +/- 1. 8 (-6. 3 to 0. 7) -0. 3 +/- 0. 7 (-1. 8 to 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.

Outcomes: Deviation from equation 56% 41 % 3% Less than 0. 5 D 0. 5 to 1. 0 D More than 1. 0 D

Statistically Speaking: n 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) n

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 n n n n 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