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Model of Hyperopic Shift After DSEK Dana Wallace MD, Richard Hwang BS, and Natalie Afshari MD Duke University Eye Center The authors have no financial interests to disclose. DSEK: A refractive neutral procedure? lPartial posterior lamellar transplant indicated in patients with endothelial dysfunction lSutureless nNo astigmatic effect lNow known to induce a hyperopic shift nImplications on “triple” procedures (CE/IOL/DSEK) Covert DJ and Koenig SB. Ophthalmology 2007; 114:1272-1277. Koenig SB and Covert DJ. Ophthalmology 2007;114:221-226. Jun et al. Cornea 2009; 28: 19-23. Purpose lChanges in posterior curvature are responsible for the hyperopic shift that occurs in DSEK. lThe magnitude of this shift remains unpredictable. lTo derive a mathematical model that can be used preoperatively to predict the observed hyperopic shift after DSEK. Gorovoy MS. Cornea 2006; 25:886-889. Koenig SB, et al. Cornea 2007; 26: 670-674. Price FW Jr, Price MO. J Refract Surg 2005; 21:339-345. Methods Based on the assumptions of the thick lens equation and the Gullstrand model eye, we developed a mathematical model to predict the hyperopic shift that occurs after DSEK based on preoperative pachymetry and endothelial graft thickness. Formula Dcornea = Dant + Dpost - (d/n)(Dant)(Dpost) lDant = refractive power of anterior surface = (1/r1)(nant-nair) nr1 = radius of curvature of anterior surface lDpost= refractive power of posterior surface = (1/r2)(nant-naq) nr2 = radius of curvature of posterior surface ld = corneal thickness ln = refractive index As applied to DSEK lPreoperative corneal power nDetermined by preoperative pachymetry lPostoperative corneal power nGraft thickness of the graft was added to the corneal pachymetry nGraft thickness of the graft was subtracted from the posterior radius of curvature lThe difference in these calculations reveals a hyperopic shift. As applied to patients PatientPreop MrxPreop Pachymetry (m) Graft Thickness (m) Predicted Hyperopic Shift Observed Hyperopic Shift 10.00-0.50x092643103+0.07+1.25 2+0.25-1.25x105640100+0.06+0.96 30.00-0.25x165640142+0.09+0.375 Calculations were only performed in pseudophakic eyes. PatientPreop MrxPreop Pachymetry (m) Graft Thickness (m) Predicted Hyperopic Shift Observed Hyperopic Shift 10.00-0.50x092643103+0.58+1.25 2+0.25-1.25x105640100+0.56+0.96 30.00-0.25x165640142+0.80+0.375 Interestingly, if we use the eye as only one refractive surface, the model is more accurate. Dcornea = (naq-nair)/radius of curvature Other Factors to Consider lEndothelial graft is thicker peripherally than centrally lIn the first few postoperative months, the graft edges thin faster than the vertex A more accurate “r2” lCan current imaging modalities facilitate these measurements? nPentacam nAnterior Segment OCT lCan we use a model of an ellipse to more accurately predict r2? Conclusions lThe hyperopic shift induced by DSEK is the result of changes in corneal thickness and posterior radius of curvature lPrediction of the hyperopic shift induce