Intraocular lens power calculation in patients with irregular astigmatism

Graefe's Archive for Clinical and Experimental Ophthalmology - Accurate intraocular lens (IOL) calculation in subjects with irregular astigmatism is challenging. This study evaluated the...     

高柱镜度数 Toric 人工晶状体植入治疗白内障合并高度散光的临床观察

评价高柱镜度数Acrysof Toric人工晶状体（SN60T6-9）植入治疗白内障合并高度散光患者的疗效及稳定性。方法白内障合并高度角膜规则散光行白内障超声乳化联合高柱镜度数Acrysof Toric人工晶状体植入手术患者13例（17只眼）,术后随访（6±1．3）个月。观察术后裸眼视力（UCVA）、最佳矫正视力（BCVA）、残余散光、人工晶状体的旋转稳定性等。结果术后3个月,平均裸眼视力为0．61±0．16,BCVA 0．70±0．18,82．3％UCVA优于0．5,62％残余散光低于0．75 D,81％低于1．00 D。残余散光为（0．69±0．26） D,Toric人工晶状体平均旋转（3．12±1．16）°。结论 Toric IOL人工晶状体能有效、安全,矫正白内障合并高度散光,具有良好的旋转稳定性。     

Corneal scarring and irregular astigmatism following refractive surgery in a corneal transplant

Background: Scarring may follow refractive surgery, causing irregular astigmatism and loss of visual acuity. Methods: A case report of scarring and irregular astigmatism occurring in a corneal transplant following photorefractive keratectomy and arcuate incisions is presented. Results: Following surgical excision of the scan unaided visual acuity improved from 1/60 to 6/12. Histopathology of the excised scar was obtained. Conclusions: Refractive surgery following corneal transplantation may produce scarring. The origin of the scar in the present case has not been established.     

硬性高透氧性角膜接触镜矫正外伤性角膜散光应用研究

目的 探讨硬性高透氧性角膜接触镜(rigid gas permeable contact lens,RGPCL)矫正外伤性角膜散光患者视力的临床应用价值.方法 对连续收集的18例眼前段外伤患者实施RGPCL验配,随访6个月以上.配戴前记录项目:年龄、性别、眼别、RGPCL验配与角膜拆线的间隔时间、晶状体状态、裸眼视力、框架镜矫正视力、伤口的大小位置、角膜前表面散光值.配戴后观察项目:RGPCL矫正视力、坚持戴镜时间、停戴原因、眼部并发症、长期配戴成功与否.长期配戴成功定义为在随访期间能坚持长期舒适配戴时间≥8 h/d.视力转换成五分制进行统计.采用SPSS 16.0软件系统,运用配对资料t检验、独立样本t检验和协方差分析进行数据统计.结果 患者年龄5～45 (20.94±13.35)岁,人工晶状体眼5只眼,无晶状体眼1只跟,其余12只眼为有晶状体眼.根据伤口位置,1区9只眼,2区9只眼.角膜伤口大小为1.50～8.33 (4.04±2.23) mm,1区和2区之间伤口大小无统计学意义(t =-0.967,P=0.348).RGPCL验配与角膜拆线的间隔时间3～22个(5.67±5.52)月.裸眼视力3.0～4.9(4.2±0.5),框架眼镜矫正视力4.0～4.9(4.6±0.3),RGPCL矫正视力4.4～5.1(4.9±0.1).RGPCL较框架镜矫正视力明显提高(t =4.143,P＜0.000).RGPCL较框架眼镜矫正视力提高1行7只眼,2～4行6只眼,≥5行4只眼.角膜分区伤口之间,RGPCL矫正视力差异无统计学意义(F=0.826,P=0.379),与框架镜矫正视力差异显著有统计学意义(F=5.128,P=0.040),RGPCL较框架镜矫正视力提高幅度差异显著有统计学意义(F=7.286,P=0.017).伤口大小对RGPCL矫正视力、框架镜矫正视力、裸眼视力及视力提高幅度等均无显著影响.随访期间,患者均未出现习惯性镜片脱落,2只眼发生点状角膜上皮炎.长期配戴成功患者4例中,10岁以下2例,10～20岁2例,无大于20岁者,其停戴原因多为初期配戴时有异物感、反复眼红以及无长期伤眼视力矫正需求等.结论 与框架眼镜相比,RGPCL矫正视力是评估伤眼最佳矫正视力更为理想的判定指标;但是,RGPCL并不是所有眼外伤患者长期视力矫正的理想方式.     

Intraocular lens calculations status after corneal refractive surgery

With the increasing number of keratorefractive surgical procedures, an increasing number of cataract surgeries in eyes after keratorefractive surgery is anticipated within a few decades. Although cataract extraction seems to be feasible without major technical obstacles, intraocular lens (IOL) power calculation turned out to be problematic. Insertion of the measured average K-readings (= "central corneal power" = keratometric diopters) after myopic radial keratotomy (RK), photorefractive keratectomy (PRK), or laser in situ keratomileusis (LASIK) into standard IOL power-predictive formulas commonly results in substantial undercorrection and postoperative hyperopic refraction or anisometropia. In this article, the major reasons for IOL power miscalculations (which are different for RK versus RRK/LASIK) are discussed based on model calculations and based on case series of cataract surgeries, methods for improved assessment of keratometric diopters as the major underlying problem are exemplary illustrated, and finally a clinical step-by-step approach to minimize IOL power miscalculations status after corneal refractive surgery is suggested. The "clinical history method" (i.e., subtraction of the spherical equivalent [SEQ] change after refractive surgery from the original K-reading) should be applied whenever refraction and K-reading before the keratorefractive procedure are available to cataract surgeons. In addition, more than one modern third-generation formula (e.g., Haigis, Hoffer Q, Holladay 2, or SRK/T) but not a regression formula (e.g., SRK I or SRK II) should be applied and the highest resulting IOL power should be used for the implant.     

角膜屈光手术后的人工晶状体度数计算

角膜屈光手术后用现行的角膜曲率检测方法测量角膜屈光力不精确,导致该类患者白内障手术时人工晶状体度数计算偏低,术后呈较严重的远视状态。随着接受准分子激光角膜屈光手术人数的增加,此问题在未来将日益突出。围绕这一问题,不少学者提出多种修正方案,以期提高角膜屈光手术后人工晶状体度数计算的准确性,本文就此进行综述。     

Contact lens fitting to correct irregular astigmatism after corneal refractive surgery

PURPOSE: To study a technique of contact lens fitting and its visual results in patients with irregular astigmatism induced by corneal refractive surgery. SETTING: Department of Cornea and Refractive Surgery, Instituto Oftalmológico de Alicante, Alicante, Spain. METHODS: This prospective noncomparative study comprised 29 eyes with irregular astigmatism after corneal refractive surgery. Different types of contact lenses were used to correct the astigmatism: hard, gas permeable, hybrid, and toric hydrophilic. Preoperative and postoperative data were analyzed for proper fitting including the preoperative keratometeric reading and corneal ablation zone. RESULTS: Proper contact lens fitting was achieved in 23 eyes (79.3%). In 6 eyes (20.7%), fitting was not possible despite an improvement in best corrected visual acuity (BCVA). Of the eyes with proper fitting, 14 (60.9%) had rigid gas-permeable lenses (9.80 mm), 6 (26.1%) had hydrophilic lenses (14.00 mm), and 3 (13.0%) had hybrid lenses (14.3 mm). Comparing the BCVA with that with spectacles, 23 eyes (79.3%) gained 2 lines or more of BCVA, 4 (13.8%) gained 1 line, and 2 (6.9%) maintained the same acuity as with spectacles. No eye lost lines of BCVA. CONCLUSIONS: Results indicate that contact lens fitting is a good-and sometimes the only-alternative for patients with induced irregular astigmatism. Rigid gas-permeable contact lenses provided the best visual performance and patient tolerance.     

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.     

Intraocular lens power calculations using corneal topography after photorefractive keratectomy

PURPOSE: To report the preoperative and postoperative palpebral fissure width in eyes undergoing laser in situ keratomileusis.METHODS: In a prospective study, 165 consecutive eyes of 87 patients (41 men and 46 women with a mean +/- standard deviation age of 32.9 (+/-9.5) years) had laser in situ keratomileusis using a Summit (Waltham, MA) APEX PLUS excimer laser and a Moria (Antony, France) LSK microkeratome. The width of palpebral fissure was measured preoperatively, 3 months or 6 months after laser in situ keratomileusis. Patients were classified into three groups as follows: hard contact lens users group (n = 61), soft contact lens users group (n = 63), and non-contact lens users group (n = 41).RESULTS: The average width of palpebral fissure increased after laser in situ keratomileusis in all three groups. The hard contact lens users group increased from 7.6 (+/-1.6) mm to 8.7 (+/-1.2) mm (P <.0001) and non-contact lens users group increased from 7.7 (+/-1.9) mm to 8.9 (+/-1.9) mm (P <.0001).CONCLUSION: These results suggest that laser in situ keratomileusis may be associated with an increase in the width of the palpebral fissure.     

个体化准分子激光上皮瓣下角膜磨镶术矫治角膜不规则散光的临床研究

目的评价眼前节全景仪引导的个体化准分子激光上皮瓣下角膜磨镶术(laser subepithelial keratomileusis,LASEK)治疗偏中心切削所致不规则散光的效果,并比较术前和术后不同时间角膜不规则状态的变化。方法收集10例(18眼)因行屈光手术而发生偏中心的患者,伴有严重的不良视觉症状,行眼前节全景仪引导的个体化LASEK治疗。所有患者在术前和术后1个月、3个月和6个月均行眼前节全景仪检查,并对手术前后所有患者的裸眼视力(uncorrected visual acuity,UCVA)、最佳矫正视力(best corrected visual acuity,BCVA)、角膜表面非球面性(Q值)、角膜表面变异指数、角膜表面垂直不对称指数等进行比较。结果 UCVA由术前0.26±0.15变为术后6个月0.85±0.11,BCVA术前0.69±0.20变为术后6个月1.02±0.04,UCVA、BC-VA与术前相比差异均有显著统计学意义(均为P=0.00)。Q值术前为0.56±0.29,术后1个月、3个月时分别为0.21±0.52、0.36±0.42,差异均有统计学意义(均为P<0.05);术后6个月为0.54±0.48,与术前相比差异无统计学意义(P>0.05)。角膜表面变异指数术前为65±11,术后6个月降低为59±8,差异有统计学意义(P<0.05)。角膜表面垂直不对称指数术前为0.78±0.12,术后6个月降低为0.24±0.18,差异也有统计学意义(P=0.04)。术后切削区中心偏移明显改善,光学区居中,并且光学区较术前有所扩大。结论眼前节全景仪引导的个体化LASEK手术矫治偏中心所致的角膜不规则散光安全、有效,能整体上改善角膜不规则状态。     

双眼角膜散光白内障分别植入多焦IOL和散光IOL的临床观察

目的：观察双眼存在不同程度角膜散光的白内障患者分别植入多焦点人工晶状体、散光人工晶状体的临床效果。

方法：观察组为年龄相关性白内障患者20例40眼,术前角膜规则散光一眼1.50～2.50(平均2.15±0.87)D,植入散光晶状体,另一眼角膜散光<1.50D,平均0.78±0.26D,植入多焦点人工晶状体(MIOL)。对照组为同期双眼均植入MIOL的20例40眼年龄相关性白内障患者,规则角膜散光≤1.00D,平均0.62±0.34D。比较术后3mo观察组的散光晶状体眼与MIOL眼的远近裸眼视力及对照组与观察组患者双眼合视的远近裸眼视力。

结果：观察组患者Toric人工晶状体眼的裸眼远、近视力分别为0.81±0.32和0.58±0.27,MIOL眼远、近视力分别为0.76±0.28和0.67±0.24,两眼间差异无统计学意义(t=0.797,P>0.05; t=1.243,P>0.05); 观察组双眼合视的远近视力分别为0.90±0.33和0.79±0.22,对照组双眼合视的远近视力分别为0.92±0.25和0.85±0.28,两者比较差异无统计学意义(t=0.601,P>0.05; t=0.875,P>0.05)。

结论：双眼存在程度不同角膜散光的白内障患者,一眼植入多焦点人工晶状体、另眼植入散光人工晶状体同样可以提高患者术后的脱镜率。     

角膜基质透镜散光标记器在角膜基质透镜植入术矫正远视及散光中的应用

目的 探讨角膜基质透镜散光标记器(简称散光标记器)在角膜基质透镜植入术矫正远视及散光中的应用.方法 前瞻性病例研究.选取2019年12月至2020年12月在南昌大学附属眼科医院屈光科就诊的满足手术要求的远视及散光患者6例6眼,年龄20～36(27.50±6.72)岁,所有患者均行飞秒激光辅助的瓣下角膜基质透镜植入术(F...     

Quantitative evaluation of regular and irregular corneal astigmatism in patients having overnight orthokeratology

PURPOSE: To quantitatively assess changes in regular and irregular corneal astigmatism in patients having overnight orthokeratology. SETTING: Matsumoto Eye Clinic, Ibaraki, Japan. METHODS: A prospective study was conducted of 64 eyes of 39 patients having overnight orthokeratology for myopia. Inclusion criteria were an uncorrected visual acuity (UCVA) of 20/20 or better after treatment and a minimum follow-up of 3 months. Using Fourier series harmonic analysis, videokeratography data were decomposed into spherical component, regular astigmatism, asymmetry (tilt or decentration), and higher-order irregularity. RESULTS: Orthokeratology significantly reduced the manifest refraction from -2.60 diopters (D) +/- 1.13 (SD) to -0.17 +/- 0.31 D (P<.0001, paired t test) and improved the UCVA from 0.82 +/- 0.30 to -0.11 +/- 0.06 logMAR (P<.0001). Regular astigmatism increased significantly from 0.53 +/- 0.23 D preoperatively to 0.63 +/- 0.40 D postoperatively (P =.0206). The asymmetry component increased significantly from 0.35 +/- 0.22 D to 0.64 +/- 0.40 D (P<.0001). Higher-order irregularity did not change significantly: 0.14 +/- 0.11 D before treatment and 0.17 +/- 0.20 D after treatment (P =.2166). The amount of myopic correction correlated significantly with the increase in the asymmetry component (Pearson correlation coefficient, R = 0.40, P =.0009) but not with the increase in regular astigmatism (R = 0.24, P =.055). CONCLUSIONS: Irregular corneal astigmatism significantly increased, even in clinically successful orthokeratology cases. The effect of the changes on visual function should be studied further.     

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。     

角膜地形图引导下准分子激光矫正角膜不规则散光及不对称性散光

目的 探讨角膜地形图引导下准分子激光个性化切削手术矫正角膜不规则散光及不对称性散光的效果和优缺点.方法 应用MEL - 70准分子激光仪及配套TOMEY -Ⅲ角膜地形图引导个性化切削系统进行准分子激光原位角膜磨镶术(LASIK)矫正不对称性或不规则角膜散光复性近视散光58例108眼.其中49例97眼为初次手术;另9例11眼为二次手术,系由不均匀切削、偏心切削或中央岛而形成的不规则散光.术前最佳矫正视力均值0.98±0.32;屈光度:球镜平均(-4.59±1.68)D,柱镜平均(-1.62±0.78)D.结果 108眼手术均顺利完成,无术中或术后并发症.术后角膜地形图显示:角膜中央3 mm切削深度平整、均匀,术后1周平均裸眼视力1.03 ±0.29.屈光度:球镜-0.50～+0.75D,平均(-0.35 ±0.29)D,柱镜0～- 0.75D,平均(-0.38 ±0.24)D.结论 TOMEY -Ⅲ角膜地形图捕捉角膜曲率信息准确,引导准分子激光个性化切削程序设计合理,系统安全可靠.用它来进行个性化LASIK可较为精确地矫正角膜不规则及不对称散光.