高度远视白内障患者人工晶状体屈光度数计算公式的选择

目的 比较Haigis、SRKⅡ、Hoffer Q、Hollady、SRK/T公式的准确性,以期为高度远视白内障患者植入的人工晶状体(IOL)屈光度数计算提供参考.方法 比较性研究.分析了24例(31只眼)行超声乳化白内障吸除联合后房型人工晶状体植入术的高度远视白内障患者,术前分别应用A超和IOL Master测量眼轴长度,计算人工晶状体度数,术后验光获得实测屈光度数.比较应用IOLMaster测量时Haigis、SRKⅡ、Hoffer Q、Hollady、SRK/T公式预测植入人工晶状体屈光度数的准确性,以及两种生物测量方法对各公式预测误差的影响.两种测量方法间的比较采用配对t检验.结果 (1)应用IOL Master测量时,Haigis公式的平均预测误差最小(0.37±0.14),随后依次为Hoffer Q、Hollday、SRK/T、SRK Ⅱ公式,分别为-0.70±0.12,-0.97±0.15,-1.25±0.14,-1.46±0.13.Haigis公式引起轻度的过矫,而其他公式则产生不同程度的欠矫.(2)A超的预测误差偏向正值,而IOL Master的预测误差却偏向负值.在A超测量眼轴时,Hoffer Q公式较为精确(-0.39±0.16),而在使用IOL Master时,Haigis更为精确(0.37±0.14).结论 高度远视白内障患者选择IOL屈光度数的计算公式,使用IOL Master测量时,建议选择Haigis公式,而采用A超测量时,选择Hoffer Q公式则能获得较为准确的IOL屈光度数.     

长眼轴老年白内障患者人工晶状体预测公式的应用分析

目的:观察分析Haigis公式、SRK/T公式、Hoffer Q公式、Holladay 1公式和SRK Ⅱ公式在长眼轴老年性白内障患者进行人工晶状体屈光度预测时的准确性情况,以指导各公式在临床中的应用.方法:选择门诊及住院长眼轴(眼轴长度>24.5mm)老年性白内障患者81例81眼,使用IOL Master 500进行术前眼生物测量.将研究对象按照术前眼轴长度分为两组:轻度长眼轴组(24.5mm<眼轴长度≤27mm);中重度长眼轴组(眼轴长度>27mm).由同一术者完成超声乳化白内障吸除联合后房型人工晶状体植入术,手术顺利,人工晶状体植入囊袋内,无手术并发症.手术后3mo由同一检查者进行裂隙灯及综合验光仪联合显然验光,确定术后实际屈光度.将其分别与应用Haigis公式、SRK/T公式、Hoffer Q公式、Holladay 1公式和SRK Ⅱ公式计算出的预期屈光度进行比较分析,观察上述公式在不同眼轴长度组中的准确性.结果:轻度长眼轴组:SRK Ⅱ公式与其他四个公式间差异有统计学意义,Hoffer Q公式和SRK/T公式间差别有统计学意义(P<0.05),其他各公式间差异无统计学意义(P>0.05).中重度长眼轴组:SRK Ⅱ公式与其他四个公式间差异有统计学意义,Hoffer Q公式和SRK/T公式、Hoffer Q公式和Haigis公式间差异有统计学意义(P<0.05),其他各公式间差异无统计学意义(P>0.05).5个公式在两眼轴长度组中的准确性差异均有统计学意义(P<0.05).结论:对于眼轴长度>24.5~27mm的轻度长眼轴白内障患者,应用Haigis公式、SRK/T公式、Hoffer Q公式、Holladay 1公式进行预测均可获得较准确结果;对于眼轴长度超过27mm的中重度长眼轴白内障患者,Haigis公式、SRK/T公式和Holladay 1公式准确性占优.以上5个公式的预测准确性均随眼轴增长而降低.     

Pitfalls of IOL power prediction after photorefractive keratectomy for high myopia -- case report,practical recommendations and literature review

BACKGROUND AND PURPOSE: Published experience with eyes after keratorefractive correction of myopia indicates that insertion of the average keratometric readings into standard IOL power predictive formulas will frequently result in substantial undercorrection and postoperative hyperopic refraction or anisometropia after cataract surgery depending on the amount of myopia corrected previously. The purpose of this paper is to discuss the accentuated differences of various approaches to minimize IOL power miscalculations by describing a case report of a patient with excessive myopia as well as a review of the literature. PATIENT AND METHODS: A 50-year old lady presented for cataract surgery on her left eye after having PRK seven years ago elsewhere (refraction - 25.5 - 3.0/20 degrees, central keratometric power 43.0 diopters [D]). Central power before cataract extraction was measured to be 35.5 D (Zeiss Keratometer) and 36.5 D (TMS-1 topography analysis) and refraction was - 3.0 D (before onset of index myopia). Orbscan slit scanning topography analysis displayed an anterior surface power of 36.8 D and a posterior surface power of - 9.3 D. Total axial length was 31.93 mm (optical biometry using Zeiss IOL-Master). The contralateral eye after PRK suffering from a comparable excessive myopia had required an exchange of the IOL implant because of intolerable anisohyperopia of + 6.0 D after primary cataract extraction elsewhere. RESULTS: Corrected corneal power values for the left eye were calculated as follows: (1) spherical equivalent (SEQ) change at spectacle plane 19.0 D, (2) SEQ change at corneal plane 26.2 D, (3) separate consideration of anterior and posterior curvature 27.5 D, (4) consideration of the IOL power misprediction on the fellow eye 29.5 D, (5) subtraction of 24 % of the SEQ change at the spectacle plane from the actually measured keratometry value 29.7 D, (6) clinical estimate from regression analysis performed earlier 30.5 D, (7) change of anterior surface power 34.5 D. Deciding for a presumably "real" corneal power of 28.0 D the Haigis formula was used to aim for - 2.0 D since the patient preferred to read uncorrected. Thus, a 21.0 D IOL was implanted uneventfully in the capsular bag. The stable refraction postoperatively was - 3.5 - 1.0/20 degrees and visual acuity increased to 20/30. Therefore, the "real" power of that cornea must have been around 30 D. CONCLUSIONS: After corneal refractive surgery, various techniques to determine the current corneal power should be compared and the value around which results tend to cluster should be relied on to avoid hyperopia after cataract surgery with lens implantation. In those cases where keratometry and refraction before PRK/LASIK are available, the gold standard is still to subtract the change of the SEQ at the corneal plane from the preoperative central keratometric power, although in the present case report the subtraction of 24 % of the SEQ change at the spectacle plane from the measured corneal power value seemed to produce the best result. Pure subtraction of the SEQ change at the spectacle plane from the corneal power value before refractive surgery has to be avoided in eyes with excessive myopia. The most reliable corrected power value should be inserted in more than one modern third-generation formula (such as Haigis, Hoffer Q, Holladay 2, SRK/T) and the highest power IOL should be implanted. In all instances, the cataract surgeon has to make sure that the corrected K-reading is not wrongly re-converted within the IOL power calculation formula used.     

[Online First]Mid–term results of patterned laser trabeculoplasty for uncontrolled ocular hypertension and primary open angle glaucoma

AIM: To describe the safety and efficacy of patterned laser trabeculoplasty (PLT) as an adjunctive treatment in primary open angle glaucoma (POAG) and ocular hypertension (OHT) after 18-month follow-up in Hispanic population. METHODS: This was a single-center, retrospective study. All patients with OHT or POAG who underwent PLT from June 2016 to August 2016 were included in the study. Investigated parameters were intraocular pressure (IOP), the number of hypotensive medications, visual acuity, laser parameters and postoperative complications. PLT success was defined as IOP reduction ≥20% without additional medications, laser, or surgery; or a reduction in the number of medications while maintaining IOP values. RESULTS: A total of 40 PLT-treated eyes (mean baseline IOP 20.3±1.7 mm Hg) of 24 patients were analyzed (age 63.4±7.3y). The mean IOP reductions from baseline across visits (months 1, 3, 6, 9, 12 and 18) ranged from 14.1% to 20.8%. Success rate after 18-month follow-up was 61.7% with a mean IOP of 16±3.2 mm Hg (P<0.001). The number of glaucoma medications per eye (preoperative 2.1±1.1 and postoperative 2.3±1.1) and the mean best corrected visual acuity (preoperative 0.10±0.22 and postoperative 0.11±0.22), remained stable (P=0.86 and 0.42, respectively). Complications included transient IOP spikes in 4 eyes (10%) and peripheral anterior synechiae in 7 eyes (17.5%). CONCLUSION: Mid-term results of PLT show that this procedure may be an effective and safe method for the management of patients with OHT or POAG as an adjunctive therapy.     

国人正常眼轴老年白内障患者人工晶状体屈光度计算公式的准确性研究

目的:应用IOLMaster对国人正常眼轴年龄相关性白内障患者进行眼生物测量,比较SRKⅡ公式、SRK/T公式、Holladay1公式、HofferQ公式和Haigis公式对手术前人工晶状体预期屈光度计算的准确性,从而指导各公式临床应用。方法:选择门诊及住院正常眼轴(22.0～24.5mm)年龄相关性白内障患者72例(72眼),使用德国Zeiss IOLMaster进行眼生物测量。由同一术者完成超声乳化白内障吸除联合后房型三片式人工晶状体植入术,人工晶状体植入囊袋内,无手术并发症。手术后3mo由同一检查者进行裂隙灯及检眼镜检查、电脑联合散瞳检影验光,确定术后实际屈光度。比较SRKⅡ公式、SRK/T公式、Holladay1公式、HofferQ公式和Haigis公式在正常眼轴长度组中的屈光度预测值与术后实际屈光度差别。结果:Haigis公式与其他各公式间差异均有统计学意义(P<0.05),其他公式间差异均没有统计学意义。各公式预测误差<0.50D的例数比较SRK/T公式与SRKⅡ公式差别有统计学意义(P<0.05)。结论:除Haigis公式外其他4种人工晶状体屈光度计算公式对正常眼轴老年白内障患者术后屈光度预测的影响无明显差异,其中SRK/T公式预测误差较小的几率大于SRKⅡ公式。     

Genauigkeit der Linsenstärkenberechnung und Zentrierung einer asphärischen Intraokularlinse

BACKGROUND: Aspherical intraocular lenses (IOLs) are presumed to optimize the optical characteristics of IOLs. In order to profit from these characteristics, exact calculation of the IOL power and good centration of the lens are essential. METHODS: In all, 43 eyes of 43 patients with an average age of 70.9+/-8.3 years underwent implantation of a Tecnis IOL (AMO, Ettlingen) after uneventful cataract surgery with topical anesthesia. IOL power calculation was performed using the Holladay, Haigis, and SRK II formulas. Spherical equivalent refraction and centration and position of the implanted IOLs were measured 6 months postoperatively. Centration of the IOL was analyzed using digital slit lamp photographs and an image analysis program. RESULTS: Best corrected visual acuity (BCVA) increased from 0.47+/-0.25 (LogMAR) preoperatively to 0.1+/-0.11 6 months postoperatively (spherical equivalent +0.3+/-0.6 D). The intraindividual difference between target refraction and achieved postoperative refraction was 0.64+/-0.11 D for the Holladay formula, -0.21+/-0.11 D for the Haigis formula, and 0.97+/-0.15 D for the SRK II formula. The mean decentration of the IOL from the center of the corneal limbus was 0.4+/-0.1 mm. CONCLUSIONS: For the aspherical Tecnis IOL very good postoperative functional results are reported, which are supported by an accurate calculation of the IOL power and a good centration of the IOL inside the capsular bag. In this study the Haigis formula showed the lowest difference between target refraction and achieved postoperative refraction.     

IOL Master测量短眼轴眼人工晶状体计算公式准确性比较

目的 比较IOL Master测量短眼轴眼时,各个人工晶状体（IOL）计算公式（Haigis、SRKⅡ、Hoffer Q、Holladay 1以及SRK/T公式）的准确性.方法 回顾性病例系列研究.行白内障超声乳化联合IOL植入术的短眼轴患者23例（30眼）,使用IOL Master测量并且根据各个公式计算预测术后屈光度数,手术3个月后验光确定患者实际术后屈光度数,计算预测误差,采用秩和检验比较各个公式的准确性.结果 Haigis公式的预测误差平均值为（0.02±0.58）D,其中57%的绝对预测误差≤0.50 D.各个公式绝对预测误差经秩和检验发现：Haigis公式与SRK Ⅱ公式差异有统计学意义（Z=-2.861,P=0.004）,其他各个公式之间差异无统计学意义.结论 短眼轴下,Haigis公式在统计学上优于SRKⅡ公式,其临床应用的准确性也高于其他IOL计算公式.在短眼轴情况下,Haigis公式是较准确的IOL计算公式.     

不同测量仪器和不同IOL屈光度计算公式对硅油填充合并白内障眼IOL屈光度测算的比较

背景 玻璃体切割联合硅油填充眼易诱发和加速白内障的形成,白内障联合硅油取出术前人工晶状体(IOL)屈光度的准确测算是术眼获得术后良好视觉质量的关键. 目的 研究不同仪器和不同IOL计算公式在硅油填充合并白内障眼行白内障摘出联合IOL植入术前IOL屈光度测算的差异,并测算术前预测IOL屈光度与术后术眼屈光度的误差,为临床相关工作提供参考依据. 方法 采用前瞻性非随机对照的研究方法,于2011年8月至2013年10月在苏州大学附属第二医院连续纳入玻璃体切 割术后硅油填充合并白内障者36例36眼,患眼均于硅油乳化后4个月～2年拟行白内障超声乳化+IOL植入+硅油取出术,术前分别用IOLMaster及A型超声联合手动角膜曲率计(MK)测量术眼眼轴长度(AL)、角膜曲率(CC)和前房深度(ACD)等生物学参数,分别采用SRK-Ⅱ、SRK/T、Hoffer Q、Holladay 1和Haigis计算公式和预留的屈光度计算拟植入的IOL屈光度,分析和比较IOLMaster及A型超声联合MK用上述计算公式测算的IOL理论屈光度值与术后术眼实际屈光度值的平均预测误差(MPE)和平均绝对屈光误差(MAE). 结果 A型超声+MK和IOLMaster测得的AL分别为(25.21±1.02) mm和(25.43±0.90) mm,ACD分别为(3.07±0.62) mm和(3.22±0.38)mm,A型超声+MK测量的AL和ACD值明显小于IOLMaster测量结果,差异均有统计学意义(均P=0.000).IOLMaster与A型超声+MK测得的CC分别为(44.58±1.57)D和(44.56±1.62)D,差异无统计学意义(P=0.568).用IOLMaster测量时,SRK/T公式的MAE明显小于SRK-Ⅱ、Hoffer Q、Holladay 1和Haigis公式的MAE,差异均有统计学差异(P=0.017、0.009、0.012、0.001);Haigis公式的MAE明显大于SRK-Ⅱ、HofferQ和Holladay 1公式的MAE,差异均有统计学意义(P=0.026、0.035、0.021).用A型超声+MK测量时,Haigis公式的MAE明显大于与SRK-Ⅱ、SRK/T、Hoffer Q和Holladay 1公式的MAE,差异均有统计学意义(P=0.007、0.004、0.018、0.006).用SRK-Ⅱ、SRK/T、Hoffer Q和Holladay 1公式计算时,IOLMaster与A型超声+MK间测量的MAE≤1.0D眼数比较差异均无统计学意义(x2=0.107、2.250、0.845、0.084,均P＞0.05);用Haigis公式计算时,IOLMaster测量的MAE≤1.0D眼数明显多于A型超声+MK测量结果,差异有统计学意义(x2=4.431,P=0.035). 结论 使用IOLMaster时SRK/T公式测算的IOL屈光度准确性最高,用A型超声+MK测量时推荐使用SRK-Ⅱ、SRK/T、Hoffer Q和Holladay 1测算公式.     

Survey of current retinopathy of prematurity practices in China

AIM: To understand retinopathy of prematurity (ROP) screening and treatment preferences among Chinese ophthalmologists. METHODS: A Chinese language survey was administered anonymously using WebQ (Catalyst, Seattle, WA, USA) among Chinese ROP screeners from December 2016 to January 2017. RESULTS: Among 70 ophthalmologists contacted, 65 responded (93%; 78% female, mean age 40y, 57% pediatric ophthalmologists and 25% retina specialists). Most used screening criteria of birth weight ≤2 kg (62%) with variation in cut-off gestational age (≤37wk, 34%; ≤34wk, 22%; ≤32wk, 31%). RetCam (Natus Medical Incorporated, Pleasanton, CA, USA) wide-field fundus photography assisted most screeners (72%) and was exclusively used by many (29%). Among 55 ophthalmologists treating ROP, anti-vascular endothelial growth factor (VEGF) was preferred over laser for both zone I (76% vs 24%) and zone II ROP (58% vs 42%). Retina specialists (P=0.004) and ophthalmologists with >3mo of training (P=0.03) were more likely to use anti-VEGF over laser for zone I ROP. Lack of laser training (8/20, 40%), access (6/20, 30%) and anesthesia (4/20, 20%) were common barriers to laser treatment. CONCLUSION: Chinese ROP screeners favor anti-VEGF injection and RetCam imaging for ROP management. A better understanding of ROP screening and treatment informs future research and education efforts in China.     

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.     

Accuracy of intraocular lens power calculation formulas in primary angle closure glaucoma

Purpose

To compare the accuracy of intraocular lens (IOL) power calculation formulas in eyes with primary angle closure glaucoma (ACG).

Methods

This retrospective study compared the refractive outcomes of 63 eyes with primary ACG with the results of 93 eyes with normal open angles undergoing uneventful cataract surgery. Anterior segment biometry including anterior chamber depth, axial length, and anterior chamber depth to axial length ratio were compared by the IOL Master. Third generation formulas (Hoffer Q and SRK/T) and a fourth generation formula (Haigis) were used to predict IOL powers in both groups. The predictive accuracy of the formulas was analyzed by comparison of the mean error and the mean absolute error (MAE).

Results

In ACG patients, anterior chamber depth and the anterior chamber depth to axial length ratio were smaller than normal controls (all p < 0.05). The MAEs from the ACG group were larger than that from the control group in the Haigis formula. The mean absolute error from the Haigis formula was the largest and the mean absolute error from the Hoffer Q formula was the smallest.

Conclusions

IOL power prediction may be inaccurate in ACG patients. The Haigis formula produced more inaccurate results in ACG patients, and it is more appropriate to use the Hoffer Q formula to predict IOL powers in eyes with primary ACG.     

高角膜屈光力白内障患者人工晶状体屈光力的计算

目的①探讨角膜屈光力异常增大对人工晶状体（intraocular lens，IOL）屈光力计算准确性的影响。②比较不同计算公式对高角膜屈光力患者IOL屈光力计算的准确性。方法对33例（43眼）角膜屈光力高于47D的白内障患者行超声乳化白内障吸除联合IOL植入手术。术前采用Orbscan-Ⅱ眼前节分析系统测量角膜屈光力，根据高斯光学理论和临床资料推导得出IOL屈光力理论计算公式（本方法）。采用本方法、Holladay2、Holladay、Hoffer Q、SRFUT与SRK2公式对IOL屈光力进行计算，植入IOL术后人工晶状体眼实际屈光状态与术前预测值的差异为预测误差（predictive error，PE），预测误差的绝对值为绝对预测误差（absolute predictive error，AE），分别计算不同计算公式的PE与AE。用SPSS11.0软件进行如下分析：①比较不同公式AE的差异。②回归分析不同公式AE与角膜屈光力的相关性。结果①本方法、。Holladay2、Holladay、Hoffer Q、SRK／T与SRK2公式所产生的AE分别为（0.28±0.17）D、（0.24±0.18）D、（0.27±0.17）D、（0.25±0.23）D、（0.59±0.35）D及（0.83±0.48）D，SRK／T与SRK2公式产生的AE高于所研究的其他计算公式，差异具有显著性。②SRK2公式与SRK／T公式的AE分别与角膜屈光力呈正相关（SRK2公式：r^2=0.522，F=44.82，P〈0.01；SRK／T公式：r^2=0.443，F=32.63，P〈0.01），本方法、Holladay2、Holladay及Hoffer Q公式产生的AE与角膜屈光力不相关。结论对于角膜屈光力异常增大的白内障患者，SRFUT与SRK2公式的计算准确性较差，两者的计算误差与角膜屈光力大小相关，本方法、Holladay2、Holladay与Hoffer Q计算的准确性不受角膜屈光力的影响，其计算结果较为可靠。     

SRK-T Holladay Hoffer Q及Haigis公式误差分析

目的 分析第三代计算人工晶状体度数的公式SRK-T、Holladay、Hoffer Q及Haigis公式的计算误差.方法 121例白内障患者135只眼,短眼轴组(<22mm)13只眼、正常眼轴组(22-26mm)75只眼和长眼轴组(＞26mm)47只眼,术前分别用四种第三代计算人工晶状体度数的公式计算人工晶状体度数,植入合适人工晶体,术后3个月验光,减去各公式预测的屈光度数,所得数值的绝对值即各公式的计算误差,比较各公式的计算误差并分析误差来源.结果 四种第三代公式在各眼轴组中的计算误差无统计学意义,但各自均是正常眼轴组中的计算精度高,且有统计学意义,并且计算误差与眼轴长度旱直线正相关.而与角膜曲率、人工晶体常数及前房深度无明显相关性.结论 第三代计算人工晶状体度数的公式的计算误差随眼轴长度的增加而增加,高度轴性近视会出现远视屈光误差,应适当调整.     

不同生物测量方法下人工晶状体计算公式的预测准确性

目的：比较采用光学相干生物测量仪（IOLMaster）和接触式A超（AL-3000）联合角膜地形图（TMS-4）测量时,不同人工晶状体（IOL）计算公式预测的准确性。方法：前瞻性研究。选取2016 年1 月15 日至2016年5月1日来我院行白内障超声乳化吸除联合后房型IOL植入术的白内障患者133例（133眼）。术前使用IOLMaster以及AL-3000联合TMS-4进行眼轴长度（AL）、角膜曲率（K）以及前房深度（ACD）的测量,应用优化常数后的Haigis、Hoffer Q、Holladay I、SRK/T公式计算IOL度数。术后3 个月行检影和主觉验光确定实际屈光结果。不同的公式和生物测量方法预测的准确性通过以下数据评估：平均误差、屈光误差的标准差、误差范围、平均绝对误差、中位绝对误差、平均绝对误差的95% 置信区间和误差范围在±0.5 D、±1.0 D和±2.0 D的百分比。不同公式和测量方法间的比较采用方差同质检验（F 检验）。结果：使用IOLMaster测量的Haigis、Hoffer Q、Holladay I和SRK/T公式的标准差分别为0.468、0.591、0.613 和0.624,Haigis公式与后3 种公式比较差异有统计学意义（F =9.632,P =0.002;F =11.984,P =0.001;F =9.215,P =0.003）。使用AL-3000联合TMS-4测量的标准差分别为0.580、0.624、0.642和0.700,Haigis公式与SRK/T公式比较差异有统计学意义（F =5.365,P =0.021）。在AL≤22.0 mm组中,使用IOLMaster测量时,Haigis公式的标准差小于SRK/T公式,差异有统计学意义（F =7.071,P =0.012）。在AL＞26.0 mm组中,使用IOLMaster测量时,Haigis公式的标准差小于SRK/T公式,差异有统计学意义（F =6.681,P =0.012）;而Hoffer Q和Holladay I公式分别产生0.44 D和0.43 D远视漂移。结论：使用IOLMaster测量的Haigis公式对于不同AL的患者均有较好的预测准确性。     

Calculating intraocular lens geometry by real ray tracing

PURPOSE: An implementation of real ray tracing based on Snell's law is tested by predicting the refraction of pseudophakic eyes and calculating the geometry of intraocular lenses (IOLs). METHODS: The refraction of 30 pseudophakic eyes was predicted with the measured corneal topography, axial length, and the known IOL geometry and compared to the manifest refraction. Intraocular lens calculation was performed for 30 normal eyes and 12 eyes that had previous refractive surgery for myopia correction and compared to state-of-the-art IOL calculation formulae. RESULTS: Mean difference between predicted and manifest refraction for a 2.5-mm pupil were sphere 0.11 +/- 0.43 diopters (D), cylinder -0.18 +/- 0.52 D, and axis 5.13 degrees +/- 30.19 degrees. Pearson's correlation coefficient was sphere r = 0.92, P < .01; cylinder r = 0.79, P < .01; and axis r = 0.91, P < .01. Intraocular lens calculation for the normal group showed that the mean absolute error regarding refractive outcome is largest for SRK II (0.49 D); all other formulae including ray tracing result in similar values ranging from 0.36 to 0.40 D. Intraocular lens calculation for the refractive group showed that depending on pupil size (3.5 to 2.5 mm), ray tracing delivers values 0.95 to 1.90 D higher compared to the average of Holladay 1, SRK/T, Haigis, and Hoffer Q formulae. CONCLUSIONS: It has been shown that ray tracing can compete with state-of-the-art IOL calculation formulae for normal eyes. For eyes with previous refractive surgery, IOL powers obtained by ray tracing are significantly higher than those from the other formulae. Thus, a hyperopic shift may be avoided using ray tracing even without clinical history.     

IOLMASTER预设人工晶体屈光度准确性探讨

目的探讨提高预设人工晶体屈光度准确性的方法。方法对86例超声乳化联合IOL植入术前的年龄相关性白内障患者,应用IOLmaster测量眼轴长度和角膜曲率使用SRKII或SRK/T公式计算植入IOL度数术后3月检查患者屈光状态。结果术前计算IOL屈光度平均为17.90±3.45D,预设IOL屈光状态：18.31±3.50D,术后屈光状态：正视者78例（90.69%）,轻度近视6例（6.97%）,轻度远视2例（2.30%）结论应用IOLmaster测量IOL度数,具有准确性,非接触性,操作简便,安全而且病人易于接受的特点,但也有一定局限性,不能完全替代A超。     

Vitrectomy with air tamponade for surgical repair of rhegmatogenous retinal detachment by eye position guided fluid-air exchange

AIM: To observe the efficacy and safety of pars plana vitrectomy (PPV) with eye position guided fluid-air exchange (FAX) and air tamponade in the treatment of rhegmatogenous retinal detachment (RRD). METHODS: RRD patients without severe proliferative vitreoretinopathy (PVR) C1 or more were enrolled. All patients underwent PPV combining with air tamponade. During operation, the primary retinal break(s) were placed at lower site and subretinal fluid was aspirated through the break(s) at the same time when eye position guided FAX was proceeding. Sufficient laser spots were made to seal the retinal break(s) after FAX, and filtered air was left in vitreous cavity as tamponade agent finally. The main outcomes were primary and final success rates, best corrected visual acuity (BCVA), and the secondary outcomes were rate of postoperative cataract surgery and high intraocular pressure. RESULTS: A total of 37 eyes (20 males and 17 females) with a follow-up time of ≥6mo were included. The range of RRD was 5.6±1.8h, and the number of retinal breaks was 1.9±1.2. The breaks located at inferior quadrants (between 3:00 and 9:00) in 5 cases (13.5%), and both superior and inferior breaks were found in 3 cases (8.1%). A total of 25 cases (67.6%) with macular detached involvement, 9 cases (24.3%) with intraocular lens, and 8 patients (21.6%) were treated with phacoemulsification and intraocular lens implantation together. The success rate of primary retinal reattachment was 100% (37/37). At 6mo postoperatively, BCVA (logMAR) was increased from 1.13±1.07 to 0.23±0.15 (P<0.001). Phacoemulsification combined with intraocular lens implantation was performed in 2 patients (5.4%), and one of them underwent macular epiretinal membrane peeling in addition (2.7%). Furthermore, high intraocular pressure was found in 4 cases (10.8%). CONCLUSION: PPV with air tamponade by eye position guided FAX can achieve a high reattachment success rate in the management of patients with RRD, and it has the advantages of short postoperative prone time and fewer operative complications.     

Calculation of intraocular lens power after corneal refractive surgery

PURPOSE: Underestimation of required intraocular lens (IOL) power with resultant hyperopia is common in post-corneal refractive surgery eyes. A number of methods to minimize error have been proposed but most studies have been small and theoretical. METHODS: We retrospectively reviewed 34 eyes that had undergone routine phacoemulsification and IOL implantation after photorefractive keratectomy or laser in situ keratomileusis. Sixteen eyes were included in the final analysis. Using known pre- and postoperative data, four methods were used to obtain keratometric values combined with three common IOL formulae (Holladay 2, SRK/T and Hoffer Q) and Koch's published Double-K nomogram. The Double-K method was also used in conjunction with the Holladay 2 formula. Target refractions were calculated and then compared to actual postoperative results. RESULTS: The Clinical History method at the spectacle plane produced the lowest mean K-values. Shammas adjustment formula combined with the Holladay 2 and Hoffer Q produced results closest to emmetropia. The Double-K methods produced the least number of hyperopic results. Overall, all methods would have resulted in unacceptably high rates of hyperopia and deviation from target refraction. CONCLUSIONS: No method produces acceptably consistent results because modern IOL formulae were designed for presurgical eyes. Accuracy will only be improved when new IOL formulae based on the anatomy of postrefractive eyes become available. Shammas adjustment formula and regression formulae are viable alternatives especially when there is a lack of preoperative data. The Double-K methods are best suited to avoiding a hyperopic surprise.     

Intraoperative aberrometry versus preoperative biometry for intraocular lens power selection in patients with axial hyperopia

Purpose:This study was conducted to evaluate the accuracy of intraoperative aberrometry (IA) in intraocular lens (IOL) power calculation and compare it with conventional IOL formulas.Methods:This was a prospective case series. Eyes with visually significant cataract and axial hyperopia (AL <22.0 mm) underwent IA-assisted phacoemulsification with posterior chamber IOL (Alcon AcrySof IQ). Postoperative spherical equivalent (SE) was compared with predicted SE to calculate the outcomes with different formulas (SRK/T, Hoffer Q, Haigis, Holladay 2, Barrett Universal II and Hill-RBF). Accuracy of intraoperative aberrometer was compared with other formulas in terms of mean absolute prediction error (MAE), percentage of patients within 0.5 D and 1 D of their target, and percentage of patients going into hyperopic shift.Results:Sixty-five eyes (57 patients) were included. In terms of MAE, both Hoffer Q (MAE = 0.30) and IA (MAE = 0.32) were significantly better than Haigis, SRK/T, and Barrett Universal II (P < 0.05). Outcomes within ±0.5 D of the target were maximum with Hoffer Q (80%), superior to IA (Hoffer Q > IA > Holladay 2 > Hill-RBF > Haigis > SRK/T > Barrett Universal II). Hoffer Q resulted in minimum hyperopic shift (30.76%) followed by Hill-RBF (38.46%), Holladay 2 (38.46%), Haigis (43.07%), and then IA (46.15%), SRK/T (50.76%) and Barrett Universal II (53.84%).Conclusion:IA was more effective (statistically significant) in predicting IOL power than Haigis, SRK/T, and Barrett Universal II although it was equivalent to Hoffer Q. Hoffer Q was superior to all formulas in terms of percentage of patients within 0.5 D of their target refractions and percentage of patients going into hyperopic shift.     

Intraocular lens power calculation using IOLMaster and various formulas in short eyes

Purpose

To evaluate the predictability of intraocular lens (IOL) power calculations using the IOLMaster and four different IOL power calculation formulas (Haigis, Hoffer Q, SRK II, and SRK/T) for cataract surgery in eyes with a short axial length (AL).

Methods

The present study was a retrospective comparative analysis which included 25 eyes with an AL shorter than 22.0 mm that underwent uneventful phacoemulsification with IOL implantation from July 2007 to December 2008 at Seoul National University Boramae Hospital. Preoperative AL and keratometric power were measured by the IOLMaster, and power of the implanted IOL was determined using Haigis, Hoffer Q, SRK II, and SRK/T formulas. Postoperative refractive errors two months after surgery were measured using automatic refracto-keratometry (Nidek) and were compared with the predicted postoperative power. The mean absolute error (MAE) was defined as the average of the absolute value of the difference between actual and predicted spherical equivalences of postoperative refractive error.

Results

The MAE was smallest with the Haigis formula (0.37 ± 0.26 diopter [D]), followed by those of SRK/T (0.53 ± 0.25 D), SRK II (0.56 ± 0.20 D), and Hoffer Q (0.62 ± 0.16 D) in 25 eyes with an AL shorter than 22.0 mm. The proportion with an absolute error (AE) of less than 1 D was greatest in the Haigis formula (96%), followed by those in the SRK II (88%), SRK-T (84%), and Hoffer Q (80%).

Conclusions

The MAE was less than 0.7 D and the proportion of AE less than 1 D was more than 80% in all formulas. The IOL power calculation using the Haigis formula showed the best results for postoperative power prediction in short eyes.