TY - JOUR
T1 - Intraocular Lens Calculations after Hyperopic Refractive Surgery
AU - Chokshi, Amit R.
AU - Latkany, Robert A.
AU - Speaker, Mark G.
AU - Yu, Guopei
PY - 2007/11
Y1 - 2007/11
N2 - Purpose: To evaluate the effect of hyperopic refractive surgery on intraocular lens (IOL) power calculation, compare published methods of IOL power calculation after refractive surgery, evaluate the effect of prerefractive surgery refractive error on IOL deviation, and introduce a new alternative formula for IOL calculation in patients who have had refractive surgery for hyperopia. Design: Retrospective noncomparative case series. Participants: Twenty eyes from 13 patients who had undergone cataract surgery after previous hyperopic refractive surgery. Methods: Seven different methods of IOL calculation were performed retrospectively: clinical history (IOLhisK), clinical history method at spectacle plane (IOLhisKs), vertex (IOLvertex), back calculated (IOLBC), calculation based on average keratometry (IOLavgK), calculation based on steepest keratometry (IOLsteepK), and calculation based on the double K formula (IOLdoubleK). Each method's result was compared with an exact IOL (IOLexact), which would have resulted in emmetropia. Each method was then compared with change in spherical equivalent induced by refractive surgery (SEh). A paired t test was used to determine statistical significance. Main Outcome Measure: Mean error in IOL power prediction for each method when compared to IOLexact. Results: When evaluating different methods of IOL calculations, IOLvertex was the most accurate, with a mean deviation from emmetropia of 0.42±1.75 diopters (D), followed by IOLBC (+0.54±1.86 D), IOLhisK (+1.56±2.35 D), IOLhisKs (+1.57±2.35 D), IOLsteepK (+1.59±2.25 D), IOLdoubleK (+1.65±2.56 D), and IOLavgK (+2.24±2.46 D). There was no statistical difference between IOLvertex, IOLBC, and IOLexact. The power of IOLavgK would be inaccurate by 0.27x+1.53, where x = SEh. Thus, most patients without the adjustment to IOLavgK would be left myopic. However, when IOLavgK is adjusted with this formula, there is no statistical difference to IOLexact. Conclusions: For IOL power selection in previously hyperopic patients, a predictive formula based only on SEh and current average keratometry readings was not found to statistically differ from IOLexact. The IOLvertex and IOLBC, which also did not statistically differ from IOLexact, require prerefractive surgery keratometry readings that are often not available to the cataract surgeon.
AB - Purpose: To evaluate the effect of hyperopic refractive surgery on intraocular lens (IOL) power calculation, compare published methods of IOL power calculation after refractive surgery, evaluate the effect of prerefractive surgery refractive error on IOL deviation, and introduce a new alternative formula for IOL calculation in patients who have had refractive surgery for hyperopia. Design: Retrospective noncomparative case series. Participants: Twenty eyes from 13 patients who had undergone cataract surgery after previous hyperopic refractive surgery. Methods: Seven different methods of IOL calculation were performed retrospectively: clinical history (IOLhisK), clinical history method at spectacle plane (IOLhisKs), vertex (IOLvertex), back calculated (IOLBC), calculation based on average keratometry (IOLavgK), calculation based on steepest keratometry (IOLsteepK), and calculation based on the double K formula (IOLdoubleK). Each method's result was compared with an exact IOL (IOLexact), which would have resulted in emmetropia. Each method was then compared with change in spherical equivalent induced by refractive surgery (SEh). A paired t test was used to determine statistical significance. Main Outcome Measure: Mean error in IOL power prediction for each method when compared to IOLexact. Results: When evaluating different methods of IOL calculations, IOLvertex was the most accurate, with a mean deviation from emmetropia of 0.42±1.75 diopters (D), followed by IOLBC (+0.54±1.86 D), IOLhisK (+1.56±2.35 D), IOLhisKs (+1.57±2.35 D), IOLsteepK (+1.59±2.25 D), IOLdoubleK (+1.65±2.56 D), and IOLavgK (+2.24±2.46 D). There was no statistical difference between IOLvertex, IOLBC, and IOLexact. The power of IOLavgK would be inaccurate by 0.27x+1.53, where x = SEh. Thus, most patients without the adjustment to IOLavgK would be left myopic. However, when IOLavgK is adjusted with this formula, there is no statistical difference to IOLexact. Conclusions: For IOL power selection in previously hyperopic patients, a predictive formula based only on SEh and current average keratometry readings was not found to statistically differ from IOLexact. The IOLvertex and IOLBC, which also did not statistically differ from IOLexact, require prerefractive surgery keratometry readings that are often not available to the cataract surgeon.
UR - http://www.scopus.com/inward/record.url?scp=35648993554&partnerID=8YFLogxK
U2 - 10.1016/j.ophtha.2007.01.019
DO - 10.1016/j.ophtha.2007.01.019
M3 - Article
C2 - 17459483
AN - SCOPUS:35648993554
SN - 0161-6420
VL - 114
SP - 2044-2049.e1
JO - Ophthalmology
JF - Ophthalmology
IS - 11
ER -