Prospective evaluation of intraocular lens calculation after myopic refractive surgery

PURPOSE: To evaluate outcome after refractive surgery in cataract patients for whom intraocular lens (IOL) selection was based on the use of a myopic regression formula. METHODS: This prospective case series included 20 eyes of 14 patients who had previous uncomplicated myopic refractive surgery, followed by uncomplicated cataract extraction with IOL implantation. Calculation of IOL was based on flattest keratometry readings, spherical equivalent refraction before refractive surgery, and an adjustment factor derived from the regression formula: -(0.47x + 0.85). Following cataract extraction, refractive error was compared against refractive aim. The power of IOL obtained by the regression formula (IOL(RF)) was compared to those obtained using the clinical history method at the spectacle plane (IOL(HisKs)) and the Double-K formula (LOL(DoubleK)). The results acquired with each technique were compared with those achieved using an IOL back-calculated for emmetropia (IOL(exact)). RESULTS: Using the regression formula, IOL calculations produced postoperative cataract extraction refractions within 1.00 diopter (D) (range: -1.00 to 0.78 D) of the intended outcome. Mean spherical equivalent refraction after cataract extraction was -0.31 +/- 0.56 D. Twelve of 20 eyes had sufficient data to evaluate the statistical relationships among the three formulas compared with IOL(exact). Paired t test results revealed IOL(RF) (P = .0932) and IOL(HisKs) (P = .9955) were not statistically different from IOL(exact) whereas IOL(DoubleK) was statistically different from IOL(exact) (P = .0008). CONCLUSIONS: The myopic regression formula is recommended for postoperative myopic LASIK IOL selection to provide a simple, accurate, and consistent method of predicting IOL calculation that is not statistically different from IOL(exact).     

Intraoperative optical refractive biometry for intraocular lens power estimation without axial length and keratometry measurements

PURPOSE: To correlate intraoperative aphakic autorefraction to conventional emmetropic intraocular lens (IOL) calculations and derive an empiric predictive model for IOL estimation based on optical refractive biometry without axial length and keratometry measurements. SETTING: Institutional Review Board of the University of Southern California, Los Angeles County General Hospital, Los Angeles, California, USA. METHODS: A pilot group of 22 eyes of 22 patients scheduled for cataract surgery were enrolled in a prospective trial. All patients had a standard preoperative workup with subsequent cataract extraction and IOL implantation according to conventional biometric measurements and IOL calculations. Intraoperative autorefractive retinoscopy was used to obtain aphakic autorefraction and to measure the aphakic spherical equivalent before lens implantation. A linear regression analysis was used to correlate the aphakic spherical equivalent to the final adjusted emmetropic IOL power to empirically derive a refractive formula for IOL calculation (optical refractive biometry method). A second validation series of 16 eyes was used in a head-to-head comparison between the optical refractive biometry and the conventional IOL formulas. A subset of 6 eyes from the validation series were post-refractive cases having subsequent cataract surgery. RESULTS: Intraoperative retinoscopic autorefraction was successfully obtained in all 22 patients in the pilot group and all 16 patients in the validation group. The spherical equivalent of the aphakic autorefraction correlated linearly with the final adjusted emmetropic IOL power (P<.0001, with adjusted r(2)=.9985). The relationship was sustained over an axial length range of 21.43 to 25.25 mm and an IOL power range of 12.0 to 25.5 diopters (D). In a subsequent validation series of 10 standard and 6 post-laser in situ keratomileusis (LASIK) cataract cases, the optical refractive biometry method proved to be a better predictive model for IOL estimation than conventional formulas; 83% of the LASIK eyes and 100% of the normal eyes were within +/-1.0 D of the final IOL power when aphakic autorefraction was used, compared with 67% of LASIK eyes and 100% of the normal eyes, using the conventional methodology. CONCLUSIONS: A new model for IOL power calculation was derived based on an optical refractive methodology that breaks away from the conventional art introduced by Fyodorov in the 1960s. A purely refractive algorithm is used to predict the power of the IOL at the time of surgery without the need for axial length and keratometry measurements. This method bypasses some limitations of conventional biometry and shows promise in the post-refractive cataract cases.     

Intraocular lens power calculations after refractive surgery: consensus-K technique

PURPOSE: To describe a new strategy for intraocular lens (IOL) power calculations after laser in situ keratomileusis (LASIK), determine the accuracy of the method, and compare the results with those of previously described techniques. SETTING: Emory Eye Center, Atlanta, Georgia, USA. METHODS: This retrospective comparative series compared eyes having cataract extraction after laser in situ keratomileusis (LASIK) and eyes having cataract extraction without previous surgery (control group) from January 1997 to December 2005. In the LASIK group, 2 strategies were used to determine the appropriate corneal curvature (K) value for IOL calculation: (1) the nonconsensus method and (2) the consensus-K technique. Postoperative outcomes were compared and included refraction, deviation from target refraction, and deviation from the ideal K or ideal IOL value for several techniques. RESULTS: There were 43 LASIK eyes (14 nonconsensus and 29 consensus K) and 50 control eyes. The mean absolute deviation from target refraction in the nonconsensus group (1.47 diopters [D]) was significantly higher than that in the consensus-K group (0.52 D) (P = .02) or control group (0.44 D) (P = .01); the mean was not statistically different between the consensus-K group and the control group (P = .5). Compared with values with the consensus-K technique, the absolute deviation from back-calculated K values was significantly higher (P<.05) with all other K-generating methods tested except the classic refractive history method (0.56 D versus 0.65 D) (P = .4). When compared with the IOL value generated using the consensus-K technique, the absolute deviation from back-calculated IOL values was significantly higher for all other methods (P<.05). CONCLUSIONS: The consensus-K technique generated refractive outcomes similar to those in the control group and was better than with all other K- or IOL-generating techniques except the classic refractive history method. The consensus method showed less variability and higher predictability than all other methods tested.     

兒童IOL眼與無IOL眼的屈光度增長

目的 探讨儿童IOL眼与无IOL眼屈光度增长。方法 对21例(26眼)IOL眼和24例(30眼)无IOL眼的儿童进行随访后回顾性分析。结果 俩组平均手术年龄、眼轴长和平均随访时间均无显著差异,/值分别为0.55、0.44和0.8,均P>0.05。平均屈光度增员IOL组为-1.42D,无IOL组为-1.35D;两组比较无显著差异,t=0.54,P>0.05。结论 虽然IOL组与无IOL组的年均屈光度增长无统计学差异,但IOL组的屈光度增长确实略高于无IOL组,这有助于预测儿童白内障术后未来的眼屈光状态。     

Measuring corneal power for intraocular lens power calculation after refractive surgery. Comparison of methods

PURPOSE: To find a more accurate and predictable method for intraocular lens (IOL) power calculation in eyes after refractive surgery. SETTING: Department of Ophthalmology, Kangnam St. Mary's Hospital, Seoul, Korea. METHODS: The accuracy of the following methods for calculating IOL power in 132 eyes after PRK or LASIK was compared: manual keratometry, hard contact lens, refraction-derived keratometry at the corneal plane, and the refraction-derived keratometry at the spectacle plane. Based on this comparison, the IOL power was calculated in the 2 eyes of a patient using refraction-derived keratometry at the spectacle plane with the SRK II formula. Cataract surgery with IOL implantation was then performed. RESULTS: The largest corneal power values were obtained using a manual keratometer and the smallest using refraction-derived keratometry at the spectacle plane (P <.001). In the patient having cataract surgery with IOL implantation, near target refraction was achieved with minimal error in IOL power. CONCLUSIONS: If the corneal power is known before refractive surgery, the use of the smallest value of those obtained using refraction-derived keratometry and the hard contact lens method is recommended. However, if the corneal power before refractive surgery is unknown, the use of the hard contact lens method is recommended.     

Laser in situ keratomileusis and photorefractive keratectomy for residual refractive error after phakic intraocular lens implantation

PURPOSE: To determine the visual and refractive outcome of photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK) in eyes with prior posterior chamber phakic intraocular lens implantation for high myopia. METHODS: We studied a series of 37 consecutive eyes of 31 patients who underwent LASIK or PRK for residual refractive error following collamer posterior chamber intraocular lens (IOL) (Staar Surgical Implantable Contact Lens) implantation into a phakic eye. Twenty-eight eyes had LASIK and nine eyes had PRK. Mean follow-up was 8.1 +/- 4.7 months after laser ablation (range, 3 to 18 mo). RESULTS: The preoperative mean spherical equivalent refraction prior to phakic posterior chamber IOL implantation was -17.74 +/- 4.89 D (range, -9.75 to -28.00 D). Following phakic IOL implantation and prior to LASIK or PRK, mean spherical equivalent refraction was -2.56 +/- 2.34 D (range, -0.25 to -8.75 D). One month following LASIK or PRK, mean spherical equivalent refraction was -0.24 +/- 0.52 D (range, -1.50 to +1.50 D), 3 months following LASIK or PRK, mean spherical equivalent refraction was -0.19 +/- 0.50 D (range, -1.50 to +1.00 D). The refraction was within +/-1.00 D of emmetropia in 36 eyes (97.2%) and within +/-0.50 D in 31 eyes (83.7%). Three eyes developed anterior subcapsular opacities several weeks after laser ablation, one eye developed macular hemorrhage 4 weeks after laser ablation, and one eye had corticosteroid induced ocular hypertension. CONCLUSIONS: LASIK or PRK can be used to treat the residual refractive error following posterior chamber phakic IOL implantation.     

Refractive outcome of silicone oil removal and intraocular lens implantation using laser interferometry

PURPOSE: To evaluate the refractive outcome of silicone oil removal and intraocular lens (IOL) implantation using laser interferometry. METHODS: Thirteen silicone oil-filled eyes of 12 patients were included in the study. IOL power calculation was performed using laser interferometry (IOLMaster V1.1; Carl Zeiss, Jena, Germany). All of these eyes underwent silicone oil removal and cataract extraction with IOL implantation. Post-operative refraction was evaluated. RESULTS: The mean deviation of the final post-operative refraction (spherical equivalent) was -0.30+/-0.91 D (range, -1.87 to +1.3) at 12 weeks. The mean axial length of the eyes was 22.99+/-0.84 mm (range, 22.07-25.24 mm). No major complications occurred intra- or post-operatively. CONCLUSION: Laser interferometry appears to be a feasible and satisfactorily accurate method to calculate IOL power in some silicone oil-filled eyes. Further studies comparing this technique to others are warranted.     

Analysis of intraocular lens power calculation for eyes with previous myopic LASIK

PURPOSE: To evaluate the effectiveness of a manual keratometry (K) adjusted value for intraocular lens (IOL) power calculation in patients who underwent cataract surgery following previous myopic LASIK. METHODS: Sixteen eyes of 14 consecutive patients who underwent cataract surgery after previous LASIK were evaluated retrospectively. All IOL powers were calculated using an adjusted K value (K minus 1.0 diopter [D]) with the Binkhorst II formula aiming for -0.75 to -1.00 D final refraction. Additionally, the IOL power for each eye was retrospectively calculated using K, refractive-derived K, and adjusted K with the Binkhorst II, Holladay I, and SRK/T formulas. The final refraction was used as a criterion of accuracy of each approach. RESULTS: Uncorrected visual acuity > or = 20/40 was achieved in 14 (87.5%) of 16 eyes. The mean postoperative spherical equivalent refraction was -0.41 +/- 0.57 D (range: +0.50 to -2.00 D). Twelve (75%) of 16 eyes were within +/- 0.50 D of emmetropia and 15 (94%) of 16 eyes were within +/- 1.00 D. No eye was > +1.00 D. CONCLUSIONS: Using an adjusted K with the Binkhorst II formula, aiming for -0.75 to -1.00 D, and with the Holladay I formula, aiming for -0.50 to -1.00 D, measuring K with a regular manual keratometer permits determination of an IOL power after myopic LASIK without the need of preoperative LASIK refractive data.     

Refraction changes after cataract extraction with IOL implantation in the eyes with previous performed vitrectomy

PURPOSE: To determine differences between the predicted and postoperative refraction after cataract extraction with intraocular lens implantation in the eyes, which previous underwent vitrectomy. MATERIAL AND METHODS: Fifty three eyes of 52 patients underwent the analysis: twenty five in group I, nineteen in group II and nine eyes with previous scleral buckling in group III. All the eyes had ECCE and IOL with PMMA implantation after vitrectomy. In groups II and. III silicone oil tamponade was used and removed before cataract extraction. Thirty eyes of the control group K underwent cataract surgery and IOL implantation alone. The IOL power calculation was performed with SRK II formula. The predicted and postoperative refractions were compared. The follow-up was minimum 4 months (on average 15 +/- 12.71 months). RESULTS: The postoperative refractions were significantly shifted toward myopia than it was predicted--1.41 +/- 1.21 D in group I, -0.81 +/- 2.11 D in group II and -3.03 +/- 1.49 D in group III. In the control group K the difference was--0.07 +/- 0.91. CONCLUSIONS: Myopic shift of postoperative refraction after cataract surgery should be considered, when calculating the IOL power in the eye after vitreoretinal procedures.     

Accuracy and predictability of intraocular lens power calculation after laser in situ keratomileusis

PURPOSE: To study the accuracy and predictability of intraocular lens (IOL) power calculation in eyes that had laser in situ keratomileusis (LASIK). SETTING: Gimbel Eye Centre, Calgary, Alberta, Canada. METHODS: Refractive outcomes in 6 cataract surgery and lensectomy eyes after previous LASIK were analyzed retrospectively. Target refractions based on measured and refraction-derived keratometric values were compared with postoperative achieved refractions. Differences between target refractions calculated using 5 IOL formulas and 2 A-constants and achieved refractions were also compared. RESULTS: The refractive error of IOL power calculation in postoperative LASIK eyes was significantly reduced when refraction-derived keratometric values were used for IOL power calculation. Persistent residual hyperopia still occurred in some cases; this was corrected by hyperopic LASIK. Refractive results appeared more accurate and predictable when the Holladay 2 or Binkhorst 2 formula was used for IOL power calculation. CONCLUSION: Hyperopic error after cataract surgery in post-LASIK eyes was significantly reduced by using refraction-derived keratometric values for IOL power calculation. Persistent hyperopic error was corrected by hyperopic LASIK.     

Intraocular lens power calculation after incisional and thermal keratorefractive surgery

PURPOSE: To evaluate the efficacy of corneal topography in determining the central corneal refractive power in intraocular lens (IOL) power calculations after incisional and thermal keratorefractive surgery. SETTING: Oregon Eye Institute, Eugene, Oregon, USA. METHODS: This retrospective review comprised 20 eyes (14 patients) that had cataract extraction with IOL implantation or refractive lens exchange after radial keratotomy, hexagonal keratotomy, or laser thermal keratoplasty. The effective refractive power (EffRP) of the Holladay Diagnostic Summary on the EyeSys Corneal Analysis System was used to determine the central corneal refractive power, which was input into the Holladay 2 IOL calculation formula. RESULTS: Eighty percent of eyes achieved a postoperative spherical equivalent refraction within +/-0.50 diopter of emmetropia. CONCLUSION: The use of the EffRP increases the likelihood of an acceptable refractive outcome after cataract or refractive lens exchange surgery in eyes with a history of keratorefractive surgery.     

Intraocular lens power calculations after laser in situ keratomileusis

PURPOSE: To compare the accuracy of several techniques for calculating intraocular lens (IOL) power after laser in situ keratomileusis (LASIK). METHODS: Retrospective review of 10 eyes from nine patients undergoing phacoemulsification after LASIK. Corneal power (K) was measured by manual keratometry (MK), refractive history (RH), contact lens overrefraction (CTL), videokeratography (VK), and an average of the refractive history and contact lens methods (AVG 2). Results were compared with the back-calculated K value generated by the Holladay IOL Consultant program. Age-matched patients undergoing phacoemulsification without previous refractive surgery served as controls. RESULTS: Mean spherical equivalent postoperative refraction was +0.21 diopter (D) (SD, 1.54; range, -2.25 to +2.25 D) for patients undergoing cataract extraction after LASIK versus -0.56 D (SD, 0.66; range, -2.375 to +0.5 D; p= 0.16) for controls. Thirty percent of cases versus 90% of controls were within 1 D ( p= 0.002) of emmetropia. Forty percent of cases versus no controls were more than 1 D hyperopic ( p= 0.08). The mean differences for each method compared with the back-calculated K values were MK, +0.82 D; VK, +1.24 D; RH, -0.76 D; CTL, +0.91 D; AVG 2, +0.08 D. The mean absolute deviations from the back-calculated K values were MK, 1.91 D; VK, 2.01 D; RH, 1.68 D; CTL, 1.62 D; AVG 2, 1.42 D. CONCLUSION: Significant refractive errors occurred with each of the methods investigated for determining IOL power after LASIK. RH, CL, or AVG 2 provided the most accurate results.     

Intraocular lens calculation for cataract treated with photorefractive keratectomy using ray tracing method

PURPOSE: Conventional methods (such as the SRK-II formula) do not accurately calculate the power of the intraocular lens (IOL) after refractive surgery. Therefore, we compared a new formula including a ray tracing method to the conventional method for foldable IOL lens implantation. METHOD: Foldable IOLs (MA 60 BM) were implanted in 26 patients (32 eyes) using the phakoemulsification technique. The power of the IOL was measured preoperatively using the SRK-II formula in all cases. From the results of postoperative refractive errors of these cases, the power of IOL calculated by the ray tracing method was compared to the SRK-II formula. Cataract patients first treated with photorefractive keratectomy (PRK) received IOL implants using our ray tracing method and their postoperative refraction was measured. RESULTS: The average postoperative refractive error was 1.32 D in SRK-II formula, 0.95 D in the ray tracing method with Ray 1 used and 0.89 D with Ray 2 used. Postoperative refraction of both eyes first treated with PRK was--1.00 D. CONCLUSION: The average postoperative refractive error was reduced in the ray tracing method using Olsen's predicted ACD (Ray 2) compared to SRK-II formula. This new tracing method appears to be useful for determination of IOL power and it may be applied for IOL calculation for cataract surgery after refractive surgery.     

Intraocular Lens Calculation for Cataract Treated with Photorefractive Keratectomy Using Ray Tracing Method

Purpose: Conventional methods (such as the SRK-II formula) do not accurately calculate the power of the intraocular lens (IOL) after refractive surgery. Therefore, we compared a new formula including a ray tracing method to the conventional method for foldable IOL lens implantation.Method: Foldable IOLs (MA 60 BM) were implanted in 26 patients (32 eyes) using the phakoemulsification technique. The power of the IOL was measured preoperatively using the SRK-II formula in all cases. From the results of postoperative refractive errors of these cases, the power of IOL calculated by the ray tracing method was compared to the SRK-II formula. Cataract patients first treated with photorefractive keratectomy (PRK) received IOL implants using our ray tracing method and their postoperative refraction was measured.Results: The average postoperative refractive error was 1.32 D in SRK-II formula, 0.95 D in the ray tracing method with Ray 1 used and 0.89 D with Ray 2 used. Postoperative refraction of both eyes first treated with PRK was -1.00 D.Conclusion: The average postoperative refractive error was reduced in the ray tracing method using Olsen's predicted ACD (Ray 2) compared to SRK-II formula. This new tracing method appears to be useful for determination of IOL power and it may be applied for IOL calculation for cataract surgery after refractive surgery.     

角膜屈光术后人工晶状体度数计算的临床观察

目的：探讨角膜近视屈光术后白内障患者的人工晶状体度数的计算方法,观察初步的临床效果。方法：回顾性分析2013－03／2015－06于我院行白内障手术同时伴有角膜近视屈光手术史的患者14例23眼。根据患者既往角膜手术方式分为 LASIK （ laser in situ keratomileusis）组9例15眼,RK（ radial keratotomy）组5例8眼。将每例患者的角膜地形图中央2．5 mm最低点曲率值,带入SRK－T公式,按照预留－1．00～－1．50 D选择人工晶状体度数,完成常规的白内障超声乳化联合人工晶状体植入术。术后随访3mo,观察术后视力、矫正视力和屈光状态。计算出术后人工晶状体计算公式的预测屈光误差,分别与www．iolcalc．org网站上的Shammas公式和Barrett True K公式进行比较,观察其应用效果,采用独立样本t检验进行统计分析。结果：LASIK组和RK组相比,两组患者术后3 mo的裸眼视力（LogMAR）分别是0．15±0．11、0．21±0．16,术后屈光度分别是－0．43±1．04、－1．52±1．01D,SRK－T公式预测屈光误差分别是－0．71±0．80、0．43±0．99,LASIK组均优于RK组且两组间差异均有统计学意义（ P＜0．05）。将本研究方法分别与Shammas公式和Barrett True K公式相比,观察各种公式的预测屈光误差,本研究方法的屈光误差最小,但是差异无统计学意义（P＞0．05）。结论：应用研究方法的术后屈光状态均为轻度近视,适用于因近视行角膜屈光手术的白内障患者进行人工晶状体度数的选择,此方法对于LASIK手术史患者的人工晶状体度数预测性更佳。     

角膜屈光矫正手术后白内障手术

目的:探讨角膜屈光矫正手术后白内障手术的诊疗特点。方法:对2005/2008年间于我院就诊的4例角膜屈光矫正手术后白内障患者行白内障超声乳化吸出术+人工晶状体植入术。依据患者提供的角膜屈光手术资料,分别采用临床病史法或角膜后表面曲率法计算矫正角膜曲率及人工晶状体度数。术后随访观察角膜情况、手术并发症、裸眼视力、最佳矫正视力、术后屈光状态等。结果:术后最佳矫正视力较术前明显提高。术后稳定屈光度与手术前预留屈光状态比较误差范围为-1.00～+1.25D。结论:对角膜屈光手术后的白内障患者施行白内障超声乳化吸出术+人工晶状体植入术是可行的。然而只有了解这类患者病情特点,掌握手术前后诊疗方法,准确计算人工晶状体度数,才能达到满意的疗效。     

Clear lens extraction with intraocular lens followed by photorefractive keratectomy or laser in situ keratomileusis

OBJECTIVE: To study photorefractive keratectomy (PRK) or laser in situ keratomileusis (LASIK) after clear lens extraction (CLE) with intraocular lens (IOL) implantation for hyperopia or astigmatism. DESIGN: Retrospective, noncomparative interventional case series. PARTICIPANTS: Sixty-five eyes (55 subjects) had CLE with posterior chamber IOL implants for hyperopia up to 12.25 diopters (D); 31 eyes were retreated with PRK, and 34 eyes were retreated with LASIK for residual ametropias. INTERVENTION: For PRK and LASIK, the refractive surgery was performed with the slit-scanning excimer laser Nidek EC-5000, Nidek Co., Tokyo, Japan. MAIN OUTCOME MEASURES: Manifest refraction, best-spectacle and uncorrected Snellen visual acuity, haze, and halos were evaluated before surgery and at 1, 3, 6, and 12 months postoperative. RESULTS: Forty-seven eyes were evaluated at the 12-month postoperative examination: 96% of these eyes had spherical equivalents (SE) within +/-2 D of emmetropia, 79% of eyes had SE within +/-1 D of emmetropia and 51% of eyes had SE within +/-0.50 D of emmetropia. Eighty-five percent of the eyes at 12 months postoperative had uncorrected visual acuity of 20/40 or better, and 46% of eyes had uncorrected visual acuity of 20/20 or better. Eighty-seven percent of the eyes at 12 months postoperative had uncorrected visual acuity within 1 Snellen line of their initial best spectacle-corrected visual acuity (BSCVA) before all treatment. No eye lost 2 Snellen lines of BSCVA at 3, 6, or 12 months after PRK or after LASIK. CONCLUSIONS: IOL implantation for CLE, although an invasive technique, resulted in better refractive outcomes without laser-related clinical complications after PRK or LASIK adjustment.     

Combined posterior chamber phakic intraocular lens and laser in situ keratomileusis: bioptics for extreme myopia.

PURPOSE: To examine the efficacy, predictability, stability, and safety of combined posterior chamber phakic intraocular lens (IOL) implantation and laser in situ keratomileusis (LASIK) in eyes with extreme myopia. METHODS: We analyzed the results of 67 eyes that received a posterior chamber hydrogel-collagen plate phakic IOL (STAAR Collamer Implantable Contact Lens) and also underwent secondary LASIK for the correction of extreme myopia. Mean follow-up was 3 months after the LASIK portion of the procedure (range, 1 day to 6 mo after LASIK). RESULTS: Mean preoperative spherical equivalent refraction was -23.00 +/- 3.60 D (range, -18.75 to -35.00 D), and mean refractive cylinder was 1.50 +/- 1.20 D (range, 0 to 5.00 D). Mean spherical equivalent refraction after IOL implantation and before LASIK was -6.00 +/- 2.80 D (range, -2.00 to -14.38 D) and mean refractive cylinder 1.50 +/- 1.10 D (range, 0 to 5.00 D). Mean postoperative spherical equivalent refraction at last examination after the LASIK portion of the two-part phakic IOL-LASIK procedure was -0.20 +/- 0.90 D (range, +1.75 to -5.13 D), and mean refractive cylinder was 0.50 +/- 0.50 (range, 0 to 2.25 D). Eighty-five percent (57 eyes) were within +/- 1.00 D and 67% (45 eyes) were within +/- 0.50 D of emmetropia at last examination. The refractions remained stable with a statistically insignificant change (P > .05 at each interval) during follow-up. Postoperative uncorrected visual acuity at last examination was 20/20 or better in 3% (2 eyes) and 20/40 or better in 69% (46 eyes). A gain of 2 or more lines of spectacle-corrected visual acuity was seen in 51 eyes (76%) and no eyes lost 2 or more lines of spectacle-corrected visual acuity at last examination. CONCLUSION: Combined posterior chamber phakic IOL implantation with the STAAR Collamer plate lens and LASIK (bioptics) is an effective and reasonably predictable method for correcting myopia from -18 to -35 D. Gains in spectacle-corrected visual acuity were common, and results demonstrated good short-term safety and refractive stability.     

Prediction error and accuracy of intraocular lens power calculation in pediatric patient comparing SRK II and Pediatric IOL Calculator

Background  

Despite growing number of intraocular lens power calculation formulas, there is no evidence that these formulas have good predictive accuracy in pediatric, whose eyes are still undergoing rapid growth and refractive changes. This study is intended to compare the prediction error and the accuracy of predictability of intraocular lens power calculation in pediatric patients at 3 month post cataract surgery with primary implantation of an intraocular lens using SRK II versus Pediatric IOL Calculator for pediatric intraocular lens calculation. Pediatric IOL Calculator is a modification of SRK II using Holladay algorithm. This program attempts to predict the refraction of a pseudophakic child as he grows, using a Holladay algorithm model. This model is based on refraction measurements of pediatric aphakic eyes. Pediatric IOL Calculator uses computer software for intraocular lens calculation.     

Changes in refraction and ocular dimensions after cataract surgery and primary intraocular lens implantation in infants

PURPOSE: To study refraction and axial length changes after cataract extraction and primary intraocular lens (IOL) implantation in children younger than 1 year of age. SETTING: Two regional hospitals. METHODS: After determining the IOL power for emmetropia, 80% of the value was used to choose the IOL for implantation to counter anticipated myopic shift with age. The main outcome measures were changes in refraction and axial length 3 years after surgery. RESULTS: Thirty-four eyes of 20 children (mean age 6.7 months +/- 3.9 [SD]) were studied. Refraction in the immediate postoperative period was +4.53 +/- 1.45 diopters (D). Three years after surgery, the mean refraction was -2.49 +/- 3.08 D (P<.001). Twenty-two eyes (64.7%) had surgery during the first 6 months of life (group 1) and had a shorter axial length at surgery (mean 18.92 +/- 1.32 mm) compared with 12 eyes (35.3%) that received surgery between 7 and 12 months (group 2, mean 20.29 +/- 1.00 mm) (P = .007). However, the final axial length was greater in group 1 (mean 22.67 +/- 1.04 mm) than in group 2 (mean 21.23 +/- 0.26 mm) (P = .019). CONCLUSIONS: Primary IOL implantation is an option for children having cataract surgery in the first year of life. Significant myopic shifts occurred, and this seemed to be more pronounced in younger children. It appears that rethinking current strategies for IOL power calculation may be required to achieve more optimal refractive outcomes.