Refractive accuracy after intraocular lens implantation in pediatric cataract

AIM: To analyze the factors that influence the prediction error (PE) after intraocular lens (IOL) implantation in pediatric cataract. METHODS: The medical records of cataract patients of no more than 14 years old who had primary IOL implantation were reviewed from 2006 to 2010. The PE, absolute value of PE (APE), and predictability between in different axial length, mean corneal curvature, corneal astigmatism, and age at the surgery were analyzed. RESULTS: Seventy-five children (119 eyes) were included, with a mean age of (5.09±2.54) years. At the follow-up of (1.19±0.69) months, the mean postoperative PE was (-0.22±1.12) D, and APE was (0.87±0.73)D. The PE in eyes with an axial length ＞20mm but ≤22mm were significantly under-corrected than that in eyes with longer axis, and the APE in eyes with an axial length ≤20mm was more obvious compared with the others. The correlations between PE and axial length, as well as corneal astigmatism, and between APE and axial length were significant. The predictability was significantly poorer in the eyes with an axial length ≤20mm than the others. CONCLUSION: The axial length is closely related with the PE after IOL implantation in pediatric cataract patients, especially when it is ≤20mm, PE is more significant. The formula that is more suitable to very short axial length should be explored.     

Effect of lens constants optimization on the accuracy of intraocular lens power calculation formulas for highly myopic eyes

AIM: To evaluate the effect of different lens constant optimization methods on the accuracy of intraocular lens (IOL) power calculation formulas for highly myopic eyes. METHODS: This study comprised 108 eyes of 94 consecutive patients with axial length (AL) over 26 mm undergoing phacoemulsification and implantation of a Rayner (Hove, UK) 920H IOL. Formulas were evaluated using the following lens constants: manufacturer’s lens constant, User Group for Laser Interference Biometry (ULIB) constant, and optimized constant for long eyes. Results were compared with Barrett Universal II formula, original Wang-Koch AL adjustment method, and modified Wang-Koch AL adjustment method. The outcomes assessed were mean absolute error (MAE) and percentage of eyes with IOL prediction errors within ±0.25, ±0.50, and ±1.0 diopter (D). The nonparametric method, Friedman test, was used to compare MAE performance among constants. RESULTS: Optimized constants could significantly reduce the MAE of SRK/T, Hoffer Q, and Holladay 1 formulas compared with manufacturer’s lens constant, whereas the percentage of eyes with IOL prediction errors within ±0.25, ±0.50, and ±1.0 D had no statistically significant differences. Optimized lens constant for long eyes alone showed non-significant refractive advantages over the ULIB constant. Barrett Universal II formula and formulas with AL adjustment showed significantly higher accuracy in highly myopic eyes (P<0.001). CONCLUSION: Lens constant optimization for the subset of long eyes reduces the refractive error only to a limited extent for highly myopic eyes.     

Comparison of Visual Quality after Implantation of Big Bag and Akreos Adapt Intraocular Lenses in Patients with High Myopia

Purpose: To compare vision quality following phacoemulsification cataract extraction and implantation of a Big Bag or Akreos Adapt intraocular lens(IOL) in patients diagnosed with high myopia complicated with cataract.Methods:.This was a randomized prospective control study.The patients with high myopia complicated with cataract, with axial length ≥28 mm,.and corneal astigmatism ≤1D were enrolled and randomly divided into the Big Bag and Akreos Adapt IOL groups. All patients underwent phacoemulsification cataract extraction and lens implantation..At 3 months after surgery,.intraocular high-order aberration was measured by a Tracey-i Trace wavefront aberrometer at a pupil diameter of 5mm in an absolutely dark room and statistically compared between two groups. The images of the anterior segment of eyes were photographed with a Scheimpflug camera using Pentacam three-dimensional anterior segment analyzer..The tilt and decentration of the IOL were calculated by Image-pro plus 6.0imaging analysis software and statistically compared between two groups.Results:.In total,.127 patients(127 eyes),..including 52 males and 75 females, were enrolled in this study. The total high-order aberration and coma in the Akreos Adapt group(59 eyes)were significantly higher compared with those in the Big Bag(P <0.05)..The clover and spherical aberration did not differ between the two groups(P>0.05). The horizontal and vertical decentration were significantly smaller in the Big Bag lens group than in the Akreos Adapt group(both P<0.05), whereas the tilt of IOL did not significantly differ between the two groups(P>0.05).Conclusion:.Both Big Bag and Akreos Adapt IOLs possess relatively good intraocular stability implanted in patients with high myopia. Compared with the Akreos Adapt IOL, the Big Bag IOL presents with smaller intraocular high-order aberration. Coma is the major difference between the two groups.     

Refractive outcomes after vitrectomy combined with phacoemulsification of idiopathic macular holes

AIM:To report the refractive outcomes after vitrectomy combined with phacoemulsification and intraocular lens(IOL)implantation(phaco-vitrectomy)in idiopathic macular holes(IMH).METHODS:A total of 56 eyes with IMH(IMH group)that underwent phaco-vitrectomy and 44 eyes with age-related cataract(ARC group)that underwent cataract surgery were retrospectively reviewed.The best corrective visual acuity(BCVA),predicted refractive error(PRE),actual refractive error(ARE),axial length(AL),were measured in both groups before and 6 mo after operation.The power calculation of IOL and the predicted refractive error(PRE)were calculated according to the SRK/T formula.The difference of PRE and ARE between the two groups were compared and analyzed.RESULTS:In the IMH group,the diameters of macular holes were 271.73±75.85μm,the closure rate was 100%.The pre-and post-operative BCVA were 0.80±0.35 and 0.40±0.35 log MAR.The PRE of A-ultrasound and IOL Master in the IMH group was-0.27±0.25 and 0.10±0.66 D.The postoperative mean absolute prediction error(MAE)was observed to be 0.58±0.65 and 0.53±0.37 D in the IOL Master and A-ultrasound(P=0.758).The PRE and ARE of the IMH group were 0.10±0.66 D and-0.19±0.64 D(P=0.102).The PRE and ARE of the ARC group was-0.43±0.95 and-0.31±0.93 D(P=0.383).The difference between PRE and ARE was-0.33±0.81 and 0.09±0.64 D in the IMH and ARC groups(P=0.021).The proportion of myopic shift was 67.9%in the IMH group and 27.3%in the ARC group(P=0.004).CONCLUSION:The myopic shift can be observed in patients with IMH after phaco-vitrectomy.     

Comparative evaluation of rotational stability of toric IOLs with four-eyelet vs two-eyelet capsular tension rings in eyes with high myopia

AIM:To compare the rotational stability of Toric intraocular lens(IOLs)implantation combined with foureyelet or two-eyelet capsular tension rings(CTRs)in eyes with high myopia and cataract.METHODS:This prospective randomized controlled interventional study in cluded 33 eyes which had preoperative corneal astigmatism≥1.5 D and ocular axial length≥25.5 mm.These eyes were randomly divided into two groups to undergo phacoemulsification and toric IOL implantation with either four-eyelet CTR implantation(group A,n=16)or two-eyelet CTR implantation(group B,n=17).Uncorrected visual acuity(UCVA),best-corrected visual acuity(BCVA),phoropter examination results,and toric IOL rotation degrees were tested 6 mo after the surgery.RESULTS:In both groups,the toric IOL was in the capsular sac 6 mo after surgery.The difference between the two groups in terms of visual outcome was not found to be statistically significant(P>0.05)at a follow-up of 6 mo.The mean residual astigmatism values were 0.56±0.22 D and 0.92±0.24 D in A and B groups,respectively(P<0.001).The mean rotation degree of IOL was 1.00°±0.73°in group A and 3.53°±1.46°in group B(P<0.001).CONCLUSION:In cataract patients with high myopia and astigmatism,four-eyelet CTR can effectively increase the rotation stability of toric IOLs,achieving the desired goal of correcting corneal astigmatism.     

Evaluation of functional outcome and stability of sutureless scleral tunnel fixated IOLs in children with ectopia lentis

AIM:To evaluate functional outcome of sutureless scleral tunnel intraocular lens(SSTIOL)in children with crystalline lens subluxation of more than 7 clock hours.METHODS:A prospective interventional study was conducted consisting of 45 eyes of 44 children in age group 6-18 y having>7 clock hours of lens subluxation who underwent lensectomy-vitrectomy followed by SSTIOL implantation.Primary outcome was improvement in best corrected visual acuity(BCVA)and secondary outcomes were assessment of intraocular lens(IOL)tilt using ultrasound biomicroscopy(UBM),mean change in astigmatism at last follow-up of 1 y and associated complications.RESULTS:The mean preoperative and postoperative BCVA was 1.05±0.28 and 0.64±0.45(log MAR)respectively(P=0.001)at last follow-up.The mean astigmatism preoperatively and postoperatively was-4.17±2.69 D and-1.86±1.25 D respectively(P=0.011).Significant IOL tilt(>5 degrees)was present in 5 cases.The mean percentage endothelial loss was 3.65%±1.92%.The most serious complication encountered was retinal detachment seen in 2 cases.CONCLUSION:SSTIOL implantation provides efficient visual rehabilitation in children provided there is stringent case selection.We recommend caution in children having white-to-white distance>12 mm and presence of peripheral retinal degenerations.     

Accuracy of optimized Sirius ray-tracing method in intraocular lens power calculation

AIM:To evaluate the accuracy and predictability of ray tracing-assisted intraocular lens(IOL) calculation function in Sirius internal software and further improve the accuracy by optimizing the calculation of predicted lens position(PLP).METHODS:This retrospective study recruited 52 eyes of 49 patients.All of the cases with cataract had undergone phacoemulsification combined with IOL implantation.SRK-T,Haigis formula,and Sirius ray-tracing method were all used for each eye’s IOL calculation.The mean absolute value of prediction error(prediction error=predicted refraction-postoperative refraction) was defined as mean absolute prediction error(MAPE) and was determined for each method.Calculation of PLP was optimized by effective lens position(ELP).Optimized PLP was entered to Sirius internal software again to verify whether the method was improved.RESULTS:Compared with SRK-T and Haigis formulas,less accuracy was shown in Sirius ray-tracing method(P=0.001).The ELP of the IOL moved forward compared to PLP(P<0.001).The MAPE of the ELP-inputted Sirius ray-tracing method was reduced.ELP and PLP were well correlated.Taking ELP as y and PLP given by Sirius soft as x,a linear regression formula y=0.1637 x+3.1741 was concluded(R²=0.1066,P=0.018).It was shown that the optimized Sirius ray-tracing method(optimized PLP entered),compared with SRK-T and Haigis formulas,worked with the same accuracy(P=0.038).CONCLUSION:The original Sirius ray tracing method is not satisfactory enough.However,in normal eyes,the optimized Sirius ray-tracing method in IOL calculation was as accurate as SRK-T and Haigis formulas.     

Comparison of polymethylmethacrylate versus hydrophobic acrylic lenses for primary intraocular lens implantation in pediatric cataract surgery

AIM: To compare the visual results and postoperative complications of polymethylmethacrylate (PMMA) and hydrophobic acrylic intraocular lenses (IOLs) in children who underwent cataract extraction with primary IOL implantation. METHODS: This retrospective study included 117 eyes of 63 children with bilateral pediatric cataract undergoing cataract surgery and primary IOL implantation. The patients were divided into two groups, Group I included 58 eyes of 30 patients with PMMA IOLs; Group II included 59 eyes of 33 patients with hydrophobic acrylic IOLs. The clinical features, refraction errors, best corrected visual acuity (BCVA) and surgical complications were compared between two groups. RESULTS: The mean age at the time of surgery was 5.8 (2-12)y and mean follow up period was 40.5 (6-196)mo. Postoperatively, BCVA was ≥0.5 in 80 eyes (68.4%) and this was comparable in two groups. Visual axis opacification was seen in 28 eyes (48.3%) in Group I and 16 eyes (27.1%) in Group II and this difference was statistically significant (P=0.018). Postoperative IOL dislocation and posterior synechia formation were also noted. When all postoperative complications were considered, there were significantly less complications in the acrylic IOL group than PMMA IOL group (P=0.020). CONCLUSION: Pediatric cataract surgery with primary IOL implantation is a safe procedure. Hydrophobic acrylic IOLs may lead to less postoperative complications compared to PMMA IOLs.     

Evaluation of axis alignment and refractive results of toric phakic IOL using image-guided system

AIM: To evaluate accuracy of axis alignment and refractive results of toric phakic intraocular lens(IOL) implantation using a digital imaging system. METHODS: This retrospective study investigated toric implantable collamer lens(ICL) implantation in 30 eyes of 21 patients with myopic astigmatism more than 2.0 D guided with digital imaging system. Data were collected during the first week after phakic IOL implantation.RESULTS: Thirty eyes of 21 patients were included in our study. Patients includes 9 males and 12 females. The mean age of the patients was 26.5±7.1(range 21-44)y. The mean preoperative manifest astigmatism was 3.2±1.7(range from 2.25 to 4.75) D. The mean postoperative uncorrected distance visual acuity(UCDVA) were 0.07±0.07(range from 0.1 to 0.0) log MAR. The mean postoperative residual refractive cylinder was 0.25±0.29(range 0-0.75) D. Eyes with postoperative residual refractive cylinder of 0.5 D or less represented 80%(24 eyes). The mean postoperative toric IOL misalignment measured by the OPD scan III was 1.9°±1.45°(range from 0 to 5°). CONCLUSION: Image guided system allows accurate alignment of toric ICL. This is associated with good postoperative visual acuity and low residual refractive astigmatism which correlates with the precision of toric phakic IOL alignment.     

IOL Master引导下白内障术后散光和视力影响

Objective To study and analyze the impact on corneal astigmatism and visual acuity during individualized phaeoemulsification with intraocular lens implantation guided by IOL Master. Methods Thirty-eight patients (50 eyes) were treated with phacoemulsification through 3.0mm clear corneal incision with the steepest meridian according to IOL Master (group A) or auto-refractor/A-scan (group B). All patients were divided randomly and equally. The corneal astigmatism and visual acuity between group A and B were compared after the operation. Results The astigmatism of group A, B were (1.01± 0.10)D and (0.95 ± 0.13)D before operation, (1.33± 0.13)D and (1. 25 ± 0.15)D 1 day after operation, (1.15± 0.14)D and (1.07 ± 0.13) D after 1 week, (0.90 ± 0.13)D and (0.87 ± 0.12)D after 1 month, (0.89± 0.12)D and (0.80± 0.11)D after 3 months, respectively. There was no significant difference in the estimated values of astigmatism before and after operation (P ＞0.05), so between the methods of IOL Master and auto- refractor (P ＞0.05). In group A the naked visual acuity above 0.8 were 8 eyes 1 month, and 10 eyes 3 months after operation, better than group B with 2 eyes and 3 eyes. There was significant difference in the estimated values of visual acuity between the methods of IOL Master and A-scan (P ＜0.05). Conclusions Individualized phaeoemulsification with intraocular lens implantation guided by IOL Master can reduce corneal astigmatism and improve the visual impact.     

Accuracy of intraocular lens power calculation in paediatric cataract surgery

AIMS: To determine the accuracy of intraocular lens (IOL) power calculation in a group of pseudophakic children. METHODS: A retrospective analysis of biometric and refractive data was performed on 52 eyes of 40 infants and children, who successfully underwent cataract extraction and IOL implantation. The following parameters were included: age at the time of surgery, keratometry, axial length, estimated refraction, and the power of IOL implanted. The postoperative refractive outcome was taken as the spherical equivalent of the refraction at 3 months after surgery. The prediction error was taken as the absolute difference between the estimated and actual postoperative refraction. The data were analysed to assess the effects of age at the time of surgery, keratometry, and axial length on the accuracy of calculation of IOL power. RESULTS: For the overall group the mean and median prediction errors were 1.40 D and 0.84 D (SD 1.60). The mean and median prediction errors in eyes with axial lengths > or =20 mm were 1.07 D and 0.71 D (SD 0.98) and in eyes <20 mm were 2.63 D and 2.61 D (SD 2.65). The mean and median prediction errors in eyes in children aged > or =36 months were 1.06 D and 0.68 D (SD 1.02) and in children aged <36 months was 2.56 D and 2.29 D (SD 2.50). The differences between the prediction errors for both axial length and age were statistically significant (p<0.05). CONCLUSIONS: For the overall group IOL power calculation is satisfactory. In eyes with axial lengths less than 20 mm and in children less than 36 months of age larger errors can arise. This study demonstrates the need for an IOL formula specifically designed for paediatric use.     

先天性白内障人工晶状体植入术后屈光状态及程度改变

目的 分析不同年龄段先天性白内障患者人工晶状体植入术后近视漂移及眼轴增长情况。设计 回顾性病例系列。研究对象 31例（53眼）先天性白内障患儿,平均（3.21±1.56）岁时接受一期或二期人工晶状体植入术。方法 对以上患儿按手术年龄分为两组：Ⅰ组＜3岁（16例,27眼）,Ⅱ组≥3岁（15例,26眼）;按每次随访年龄分为三组：A组＜4岁（11例,18眼）,B组4~6岁（17例,30眼）,C组＞6岁（9例,15眼）。术后随访（28.74±11.67）个月,检查患儿屈光状态及眼轴增长情况。主要指标 屈光变化及眼轴长度变化。 结果 术后近视漂移程度：A组平均（1.18±0.98） D/年,B组平均（0.80±0.81） D/年,C组平均（0.71±0.82） D/年（F=3.532,P=0.032）;但B组与C组差异无统计学意义（P=0.605）。眼轴长度增加：Ⅰ组平均（1.22±0.76） mm,Ⅱ组平均（0.82±0.46） mm（P=0.030）。目标屈光度误差：Ⅰ组平均（1.64±1.32） D,Ⅱ组平均（0.55±1.16） D（P=0.009）。同一随访时间内屈光变化量与眼轴变化量呈中度相关（r=0.596,P<0.001）。结论 先天性白内障人工晶状体植入术后近视漂移程度随年龄增加而减小,年龄越小则眼轴增长及近视漂移幅度越大,在一定程度上,眼轴长度增加的幅度会影响到近视漂移的程度。（眼科, 2014, 23： 80-85）     

应用优化计算方法与计算机软件计算角膜屈光手术后人工晶状体屈光力

目的 对准分子激光角膜屈光手术后人工晶状体屈光力的计算方法进行优化,并开发为计算机软件,评价其准确性与可靠性.方法 对人工晶状体屈光力计算方法进行优化,包括：角膜屈光力的矫正计算 人工晶状体有效位置的计算与双K值法（double-K method）的应用 标准化计算公式的应用.将计算方法编写为计算机应用软件（IOL calculator for post-refractive cases）.应用该软件对49例角膜屈光手术后的白内障患者的人工晶状体屈光力进行计算,以白内障手术后实际屈光状态为标准,预测屈光状态与实际屈光状态之间的差异为预测误差,预测误差的绝对值为绝对预测误差.以SPSS 11.0软件分析预测误差与绝对预测误差的平均值与分布.结果 白内障手术后屈光状态为-2.50～0.75 D,平均为（-0.78±o.83）D,3眼（6.1%）为正视,36眼（73.5%）为近视,10眼（20.4%）为远视.预测误差为-1.26～1.96 D,平均（-0.02±0.75）D,接近于正视性屈光状态.绝对预测误差为0～1.96 D,平均（0.62±0.42）D,绝对预测误差≤0.5 D者19眼（38.8%）,＞0.5 D且≤1.0 D者22眼（44.9%）,＞1.0 D且≤1.5 D者7眼（14.3%）,＞1.5 D 且≤2.0 D者1眼（2.0%）.结论 通过优化计算方法与开发计算机软件,可以充分简化准分子激光角膜屈光手术后人工晶状体屈光力的计算过程,并提高计算的准确性与可靠性.     

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.     

Intraocular lens power calculations in patients with extreme myopia

PURPOSE: To determine the variables that might contribute to improved intraocular lens (IOL) power calculations preoperatively in cataract patients with extreme myopia. METHODS: This retrospective study included 50 patients with extreme myopia and axial lengths longer than 27.0 mm. All patients had clear corneal phacoemulsification by the same surgeon and implantation of the Domilens SiFlex 1 IOL (power range -6.0 to +5.0 diopters [D]). The performances of the SRK/T, Hoffer Q, Holladay 1, and Holladay 2 formulas in predicting an IOL power that would meet the target refraction of +/-1.00 D were compared. RESULTS: The formulas tended to suggest underpowered IOLs, more severe in eyes with axial lengths greater than 30.00 mm. These eyes accounted for most of the minus-power IOLs implanted. Back calculations of axial lengths in patients with minus-power IOLs showed that, on average, emmetropia could have been predicted by choosing shorter axial lengths (up to 2.72 mm shorter) than those used in the original IOL power calculations. Preoperative B-scan ultrasonography demonstrated the presence of a posterior pole staphyloma temporal to the optic nerve in several patients who required minus-power IOLs, which suggests that axial length measurement problems were a major source of IOL calculation errors in these patients. CONCLUSIONS: In eyes with axial lengths longer than or equal to 27.0 mm, current third- and fourth-generation lens calculation formulas have a tendency to over minus patients between -1.0 and -4.0 D. The formulas appear to perform better for plus-power IOL implantation than for minus-power IOL implantation. The use of B-scan ultrasonography to locate posterior pole staphylomas may improve the accuracy of IOL calculations in eyes with extreme myopia.     

Accuracy of intraocular lens power calculations in eyes with axial length <22.00 mm

Background: To assess the accuracy of Haigis, Holladay 1, Hoffer Q and SRK/T formulae in eyes with axial length of <22.00 mm. Design: Retrospective comparative analysis. Participants: 163 eyes of 97 patients undergoing phacoemulsification and intraocular lens (IOL) implantation. Methods: Ocular biometry was performed using IOLMaster laser interferometry. Predicted refractive outcomes before and after lens constant adjustment were compared to actual refractive outcomes. Main Outcome Measures: Mean prediction (ME) and mean absolute errors (MAE) with standard deviations (±SD). Results: Mean preoperative spherical equivalent was +5.44D ± 1.97D. Mean axial length was 21.20 mm ± 0.60 mm. Using standard IOL constants the MAE for Hoffer Q (0.62D, ±0.52D) and Holladay 1 (0.66D ± 0.52D) were significantly lower than SRK/T (MAE 0.91D ± 0.64D; P = <0.0005 and P = 0.001 respectively), but not Haigis (MAE 0.82D ± 0.83D, P = 0.071 and 0.22 respectively). MAEs for all formulae were significantly reduced by IOL constant adjustment (all P = <0.001). Following this there was no statistically significant difference in MAEs between formulae (range 0.50–0.57D, P = 0.57). Increasing MAE was significantly associated with reducing axial length and increasing IOL power for all formulae. For bilateral cases, prediction errors between eyes were significantly correlated across all formulae (all P = <0.0001) and explained 32–42% of the variance in prediction error between eyes. Conclusions: Prediction of postoperative refraction in patients with short axial lengths is challenging and at the limit of current, popular IOL formulae. There is now a clear need for prospective studies to assess latest generation IOL formulae such as Holladay 2 or Olsen in small eyes.     

Intraocular lens power calculation using ray tracing following excimer laser surgery

PURPOSE: To evaluate intraocular lens (IOL) power calculation using ray tracing in patients presenting with cataract after excimer laser surgery. METHODS: Ten eyes of seven consecutive patients who presented for cataract surgery following excimer laser treatment without any pre-refractive biometry data were enrolled in this prospective clinical study. Preoperatively, IOL power calculation was performed using a ray tracing software called OKULIX. Keratometry data (C-Scan) were imported and axial length (IOLMaster) was entered manually. Accuracy of IOL power calculation was investigated by subtracting attempted and achieved spherical equivalent. RESULTS: Mean spherical equivalent was -3.51+/-2.77 D (range -10.38 to -0.5 D) preoperatively and -1.01+/-1.08 D (range -2.5 to +0.75 D) postoperatively. Mean error was 0.31+/-0.84 D, mean absolute error was 0.74+/-0.46 D, and IOL calculation errors ranged from -1.39 to +1.47 D. A total of 40% of eyes were within +/-0.5 D, 70% within +/-1.0 D, and 100% within +/-1.5 D. Three eyes with corneal radii over 10 mm showed calculation errors exceeding +/-1.0 D. Mean best-corrected visual acuity increased from 20/60 to 20/30 postoperatively. Conclusions: IOL power calculation after excimer laser surgery can be difficult, especially when pre-refractive keratometry values are not available. In these cases, ray tracing combined with corneal topography measurements provides reliable and satisfactory postoperative results. However, it is advisable to be careful when calculating IOL power for eyes with corneal radii exceeding 10 mm because of slightly higher prediction errors.     

IOLMaster biometry: refractive results of 100 consecutive cases

AIMS: To study the refractive outcome of cataract surgery employing IOLMaster biometry data and to compare it with that of applanation ultrasonography in a prospective study of 100 eyes that underwent phacoemulsification with intraocular lens implantation. METHODS: The Holladay formula using IOLMaster data was employed for the prediction of implanted intraocular lenses (IOLs). One month after cataract surgery the refractive outcome was determined. Preoperative applanation ultrasonography data were used retrospectively to calculate the IOL prediction error. The two different biometry methods are compared. RESULTS: 100 patients, 75.42 (SD 7.58) years of age, underwent phacoemulsification with IOL implantation. The optical axial length obtained by the IOLMaster was significantly longer (p<0.001, Student's t test) than the axial length by applanation ultrasound, 23.36 (SD 0.85) mm v 22.89 (0.83) mm. The mean postoperative spherical equivalent was 0.00 (0.40) D and the mean prediction error -0.15 (0.38) D. The mean absolute prediction error was 0.29 (0.27) D. 96% of the eyes were within 1 D from the intended refraction and 93% achieved unaided visual acuity of 6/9 or better. The Holladay formula performed better than the SRK/T, SRK II, and Hoffer Q formulas. Applanation ultrasonography after optimisation of the surgeon factor yielded a greater absolute prediction error than the optimised IOLMaster biometry, 0.41 (0.38) D v 0.25 (0.27) D, with 93% of the eyes within 1 D from the predicted refraction. CONCLUSION: IOLMaster optical biometry improves the refractive results of selected cataract surgery patients and is more accurate than applanation ultrasound biometry.     

Retrospective evaluation of ocular axial length after unilateral cataract surgery with intraocular lens implantation in children and adolescents

PURPOSE: To evaluate the postoperative ocular axial length in children, who had unilateral cataract extraction with intraocular lens implantation. MATERIAL AND METHODS: In this retrospective study we studied 20 children (12 boys and 8 girls) in age from 7 to 20 years (mean 14 +/- 3.65 years), who had undergone surgery for unilateral cataract: 8 children had congenital cataract; 7 patients had traumatic cataract; in 5 cases there were secondary cataract: 3 children had cataract after uveitis, in 1 child cataract was due to steroid therapy because of nephrotic syndrome and 1 patient had neurodermatic cataract. In 16 cases PMMA lens was used, heparinized lens was implanted in 3 eyes and acrylic lens in 1 eye. The power of implants was from + 19 D to +24 D (mean 20.98 +/- 1.6 D). All measurements of axial length were obtained using ultrasound A scan. Examination was done from 14 months to 7.5 years after surgery (mean 3.5 +/- 1.55 years). The axial length in the operated eyes was compared with axial length of the fellow nonoperated eyes. RESULTS: Mean axial length in operated eyes was 22.58 +/- 1.56 mm. Mean axial length in fellow eyes was 22.96 +/- 1.42 mm. There were no significant differences between operated and nonoperated eyes (p>0.05). CONCLUSIONS: Cataract extraction with intraocular lens implantation does not influence rate of axial growth in children and adolescents.     

No-history method of intraocular lens power calculation for cataract surgery after myopic laser in situ keratomileusis

PURPOSE: To prospectively evaluate the no-history method for intraocular lens (IOL) power calculation in 15 cataractous eyes that had previous myopic laser in situ keratomileusis (LASIK) and for which the pre-LASIK K-readings were not available. SETTING: Private practice, Lynwood, California, USA. METHODS: The predicted IOL power was calculated in each case. Also calculated were the mean arithmetic and absolute IOL predictor errors, range of the prediction errors, and number of eyes in which the error was within +/-1.00 diopter (D). RESULTS: The mean arithmetic IOL prediction error was -0.003 D +/- 0.63 (SD), and the mean absolute IOL prediction error was 0.55 +/- 0.31 D (range -0.89 to +1.05 D). Fourteen eyes (93.3%) were within +/-1.00 D. The results of the Shammas post-LASIK formula compared favorably to the results obtained with the optimized Holladay 1 (P = .42), Hoffer Q (P = .25), Haigis (P = .30), and Holladay 2 (P = .19) formulas and were better than the results obtained with the optimized SRK/T formula (P = .0005). CONCLUSION: The no-history method is a viable alternative for IOL power calculation after myopic LASIK when the refractive surgery data are not available.