Intraocular Lens Power Calculation for Cataract Surgery after LASIK in the Absence of Pre-LASIK Data

PURPOSE: To evaluate the correlation between the conventional method and the clinical history method those determine intraocular lens (IOL) power for cataract surgery in eyes with prior laser in situ keratomileusis (LASIK) in the absence of pre-LASIK data. METHODS: The medical records of 200 eyes in 100 patients who had been treated with LASIK for myopia and were followed up for more than 6 months were reviewed. The IOL powers by conventional method using post-LASIK keratometric value and by clinical history method were compared. RESULTS: The mean values of IOL powers by conventional method, and by clinical history method were +20.00+/-1.48D (+13.74~+23.23D) and +20.79+/-1.28D (+17.27~+24.32D), respectively. The following equation describes the regular relationship between the two METHODS: IOL(CHM) (clinical history method)=0.708*IOL(CM) (conventional method) +6.624 (r=0.816, p<.01). CONCLUSIONS: This equation may offer more accurate IOL power for cataract surgery in eyes with prior LASIK surgery in the absence of pre-LASIK data.

Relationship between Clinical History Method and Orbscan II for Measuring Corneal Power after LASIK

PURPOSE: To evaluate the relation between clinical history method and Orbscan II for corneal power measurement after laser in situ keratomileusis (LASIK). METHODS: A total of 77 consecutive eyes of 43 patients who were treated with LASIK for myopia were followed up for at least 6 months. Corneal power by clinical history methods (CK) was compared with 3.0 mm zones of simulated keratometry (Sim-K), with 0.5, 1.0, 1.5, 2.0 and 3.0 mm zones of axial power maps (AP) and with 2.0, 3.0, 3.5, 4.0 and 5.0 mm zones of total optical power maps (TOP). RESULTS: Sim-K and all AP-map zones using Orbscan II were significantly higher (P<.001) than the CK value, while all TOP-map zones were significantly lower (P<.001) than the CK value. Among them, 3.0 and 4.0 mm TOP-map zones showed the highest correlation with the corneal power by CK (r2=0.889, P<.001; r2=0.889, P<.001). The correlation was higher with 3.0 mm TOP-map zone (r2=0.800, P<.001) than with 4.0 mm TOP-map zone (r2=0.793, P<.001) in high myopia patients. CONCLUSIONS: Although 3.0 and 4.0 mm TOP-map zones of Orbscan II were correlated highly with the CK value, these correlations were relatively low in high myopia patients and 3.0 mm TOP-map zone was better correlated than 4.0 mm TOP-map zone in these patients.

Intraocular Lens Power Calculation in the Absence of Pre-PRK Data in Moderate Myopic Eyes

PURPOSE: To evaluate the correlation between the conventional method and the clinical history method for intraocular lens power calculation for cataract surgery in eyes with previous photorefractive keratectomy in the absence of pre-PRK data. METHODS: The medical records of 38 eyes in 23 patients who had been treated with PRK for myopia and were followed up for more than 1 year were reviewed. The IOL powers by conventional method using post-PRK keratometric value and by clinical history method were compared. RESULTS: The mean values of IOL powers by conventional method, and by clinical history method were +20.58 +/- 1.10D (range, +16.37~+22.80D) and +21.06 +/- 0.85D (range, +18.85~+22.8D), respectively. The following equation describes the regular relationship between the two METHODS: IOLCHM (clinical history method)= 0.683*IOLCM (conventional method) +7.005 (r=0.878, p<.01). When the IOL powers by conventional method were applied to this equation, the mean difference of value between the IOL powers calculated from this equation and those of the clinical history method was?0.01 +/- 0.41D (range, -0.99~+0.76D). CONCLUSIONS: This equation will be helpful to calculate the IOL power for cataract surgery in eyes with previous PRK in the absence of pre-PRK data.

Intraocular Lens Power Calculation for Cataract Surgery in Patients who had Previous Refractive Surgery (RK 1 Case, PRK 3 Cases, LASIK 1 Case)

The purpose of this study is to assess the accuracy of IOL power calculations using clinical history method in patients who undergo cataract surgery after previous PRK, RK, or LASIK.Five eyes of 3 patients who had previous PRK, RK, or LASIK underwent phacoemulsifications with IOL implantation.We calculated IOL power for target refractive error using clinical history method.We compared postoperative refractive error to target refractive error at 3 months after cataract surgery.In the first case (RK (od)& PRK (os)), there was 3.50 diopter undercorrection on the right eye and IOL was exchanged.And target refractive error was achieved on the left eye.In the second case (LASIK patient)there was 1.00 diopter undercorrection.In the third case (PRK (ou)), right eye achieved 0.75 diopter undercorrection and left eye achieved 0.50 diopter overcorrection.The types of cataract were nuclear sclerotic in 3 cases and anterior subcapsular in 2 cases.To determine the exact IOL power after refractive surgery, using clinical history method would be good alternative in these patients.