Matrix-based calculation scheme for toric intraocular lenses.

BACKGROUND AND PURPOSE: While a number of intraocular lens power prediction formulas are well established for determination of spherical lenses, no common strategy is published for the computation of toric intraocular lenses. The purpose of this study is to describe a paraxial computing scheme using 4 x 4 system matrices to describe the 'optical system eye' containing astigmatic refractive surfaces with their axes at random. METHODS: Based on the definition of a centred optical system in the paraxial Gaussian space containing astigmatic surfaces using 4 x 4 refraction and translation matrices, we derived a methodology for calculating the refractive power of thin and thick toric intraocular lenses by solving a linear equation system. In a second step, we derived a methodology for prediction of the residual spectacle refraction after implantation of any toric lens implant with any orientation. RESULTS: The capabilities of this computing scheme are demonstrated with three examples. In example 1 we calculate a 'thin toric lens' for compensation of a corneal astigmatism to achieve a spherical target refraction. In example 2 we compute a 'thick toric lens', which has to compensate for an oblique corneal astigmatism and rotate the spectacle cylinder to the 'against the rule' position to enhance near vision. In example 3 we predict the residual refraction at the corneal plane after implantation of a thick toric lens, when the cylinder of the lens implant is compensating the corneal cylinder in part and the axis of implantation is not fully aligned with the axis of the corneal astigmatism. CONCLUSION: We present an en bloc matrix-based strategy for the calculation of thick or thin toric intraocular lenses, with the flexibility of crossing an unlimited number of cylinders with restrictions to paraxial optics. The resulting system matrix S is written as a product of 4 x 4 refraction and translation matrices. Residual refraction at the corneal (contact lens) or spectacle plane can be derived by inverting the order of matrices for calculation of the system matrix.     

Repeated rotation of a toric implantable collamer lens: A case report

Introduction:Implantable collamer lens have been used widely worldwide, and have been accepted by more and more doctors and patients due to good safety, stability, and effectiveness. However, there is still a problem of crystal rotation. The large angle rotation (over 10°) would weaken the original astigmatism correction effect and even induce irregular astigmatism, seriously affecting the visual quality of patients. Herein, we reported a case who had 2 times of crystal rotations after toric implantable collamer lens (TICL) implantation.Patient concerns:The patient was a 38-year-old man who underwent TICL implantation for the correction of high myopic astigmatism in eyes. He presented a sudden decrease in the visual acuity (VA) of the left eye 4 months after the TICL implantation. The uncorrected visual acuity (UCVA) was 8/20 (refraction, +2.25 −5.25 × 68).Diagnosis:Rotation of TICL was diagnosed. The toric marks with a rotation of 75° counter-clockwise from the original position were observed.Interventions:The TICL was re-set to the original position, leading to the UCVA of 12/20 in the left eye (refraction, −0.00 −0.75 × 131), with the vaulting of 589 μm. Ten months after the TICL relocation, the patient again presented a sudden decrease in the VA of the left eye, with the UCVA of 2/20 (refraction, +2.25 −5.00 × 66). Again, the toric marks with a rotation of 75° counter-clockwise from the original position was observed, just at the same position as the last rotation. This time, the TICL was removed. The axis and power were recalculated, and a new TICL was implanted, with the rotation of 73° counter-clockwise from the horizontal line of the temporal side.Outcomes:The patient obtained a final UCVA of 12/20 in the left eye (refraction, +0.50 −0.50 × 26), which remained stable in the 6-month follow-up period, with the vaulting of 602 μm.Lessons:Rotation is a common complication after TICL surgery. Relocation or replacement of TICL are safe and efficient ways to recover VA due to TICL rotation.     

Trifocal toric intraocular lenses in eyes with low amount of corneal astigmatism

AIM: To evaluate the refractive and visual outcomes following cataract surgery and implantation of a trifocal toric intraocular lens (IOL) in eyes with low degrees of corneal astigmatism. METHODS: Twenty six eyes of 22 patients who underwent implantation a trifocal toric IOL (FineVision PODFT, PhysIOL s.a., Liege, Belgium) were enrolled. Phacoemulsification with femtosecond laser, capsular tension ring insertion and intraoperative aberrometry were performed in all cases. All IOLs used showed a cylinder power of 1.00 D. Main outcome measures were refractive error and corrected distance visual acuity (CDVA) and uncorrected distance visual acuity (UDVA) values. Eyes were evaluated at 4mo post-surgery. RESULTS: Totally 50% of eyes showed a spherical equivalent (SE) within ±0.13 D and all of them within ±0.50 D. The mean SE and refractive cylinder were -0.02±0.23 and -0.16±0.22 D, respectively. Vector analysis revealed that 100% of eyes were within ±0.50 D for the SE and cylindrical components (J0 and J45). Refractive changes were not correlated with keratometric changes (P>0.05) showing that the reduction in astigmatism comes from the trifocal toric IOL. Of 81% and 96% of eyes showed UDVA and CDVA of 20/20, respectively. The postoperative mean values of monocular distance Snellen decimal UDVA and CDVA were 0.97±0.05 and 0.99±0.02 (about 20/20), respectively. CONCLUSIONS: The present study suggests that the use of this trifocal toric IOL in patients with low amount of astigmatism provides accurate refractive outcomes and enables them to achieve excellent visual acuity.     

非球面散光型和非球面型人工晶状体植入术后效果

目的：比较非球面散光型和非球面型人工晶状体（IOL）植入术后效果。方法：前瞻性非随机对照研究。 选择2016年5月至2018年1月在抚顺市眼病医院白内障科就诊的术前角膜散光为1.25 D以上的年龄相关性白内障患者106例（172眼）。根据自愿原则,其中50例（80眼）患者行超声乳化白内障吸除术后植入Acrysof IQ Toric IOL（SN6AT）作为Toric组,56例（92眼）患者植入AcrySof IQ IOL（SN60WF） 作为对照组。术前Toric组和对照组散光分别为（2.08±0.74）D、（2.14±0.95）D。术后6个月评估2组患者的裸眼远视力（UDVA）、矫正远视力（CDVA）、脱镜率、残余眼散光和轴位旋转、对比敏感度、 波前像差、视觉满意度问卷调查等。采用t检验、Mann-Whitney U检验、χ2 检验进行数据分析。结果：9例失访,失访率为8.5%,最终纳入对照组为51例（84眼）,Toric组为46例（73眼）。术后6个月对照组和Toric组的UDVA（LogMAR）分别为0.22±0.14和0.15±0.20,差异有统计学意义（t=-2.14, P<0.001）;CDVA（LogMAR）分别为0.11±0.09和0.09±0.08,差异无统计学意义;Toric组看远脱镜率为77.8%（21/27）,对照组为27.3%（9/33）,二者差异有统计学意义（χ2 =15.15,P<0.001）。Toric组残余眼散光为（0.77±0.39）D,对照组为（1.99±1.12）D,二者差异有统计学意义（t=-7.56,P<0.001）; Toric组的轴位旋转4.6°±5.7°。Toric组低阶像差低于对照组,差异有统计学意义（U=1.57,P=0.006）。 2组术后明视、暗视、暗视眩光情况下对比敏感度、视觉满意度调查问卷比较差异均无统计学意义。 结论：与非球面型IOL相比,非球面散光型可有效、安全地矫正白内障患者的术前角膜散光,稳定性好,大大提高术后脱镜率,且低阶像差更低。     

Visual outcome and refractive status with monofocal toric intraocular lens implantation to correct astigmatism during cataract surgery

Purpose:Measurement, calculations, visual assessment, and refractive status after monofocal toric intraocular lens (IOL) implantation were the purpose of this study.Methods:This was a hospital-based interventional prospective study, where 40 eyes were included with astigmatism of more than 2D. They underwent biometric assessment using Lenstar. Toric IOL power calculation was done based on Barrett''s Toric calculation method. Preoperative axis marking was done using both bubble marker and direct slit beam to avoid cyclotorsion in sleeping position. On table, axis marking was reassessed. Post phacoemulsification, monofocal Supra Phob Toric IOL was rotated till its marking matches corneal axis marking. Postoperative best-corrected visual acuity was measured at 1 and 3 months.Results:Mean of refractive astigmatism reduced from 3.55 ± 0.97 preoperatively to 0.81 ± 0.28 at 1 month and 0.79 ± 0.27 at 3 months postoperatively. In total, 92.5% had residual astigmatism less than 1D at 3 months postoperatively, while 7.5% eyes had residual astigmatism more than 1D. In total, 72.5% patients had IOL rotation of less than or equal to 5°, 20% patients had it between 6° and 10° and 7.5% eyes had more than 10° at day 7 postoperatively, which required IOL repositioning.Conclusion:Accurate measurement of parameters and proper calculation reduce the postoperative residual astigmatism after toric IOL.     

Toric intraocular lens for correction of high corneal astigmatism in cataract patients

AIM: To evaluate the efficacy of Bi-Flex toric intraocular lens (T-IOL; Medicontur, Medical Engineering, Ltd., Inc.) implantation to correct preexisting astigmatism in patients having cataract surgery. METHODS: This retrospective consecutive study included 22 eyes of 16 patients with more than 2.50 diopters (D) of corneal preexisting astigmatism having cataract. Preoperative and postoperative uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), objective and subjective refraction and keratometric and topographic cylinder were measured. Postoperative the toric IOL axis was evaluated using vector analysis. RESULTS: Postoperatively, subjective refractive cylinder was reduced significant (P<0.05) from 4.05±1.53 D to 1.35±0.86 D. The component J0 reduced in magnitude from -0.81±2.02 D to -0.12±0.62 D (P<0.05). Both, UCVA and BCVA improved significantly at 1mo after surgery (P<0.05 in both cases). After the surgery, the UCVA and BCVA were 0.24±0.19 and 0.06±0.08, respectively. The mean toric IOL axis rotation was 2.95±5.25 degree, with rotation less than 10 degrees in 86.36% of eyes. No differences in mean keratometric values obtained before and after surgery were found (P>0.05 for J0 and J45). CONCLUSION: Implantation of the Bi-Flex toric IOL is a safe and effective method to correct the preexisting regular astigmatism (greater than 2.50D).     

High Water Content Soft Toric Lenses*

ABSTRACT: A retrospective evaluation of the fitting of soft toric contact lenses using high water content materials was conducted in a New Zealand contact lens practice. A 97% success rate was achieved over a 6 month review period. Factors contributing to this success were the use of a pre-fitting tolerance test and careful lens verification procedures.     

Comparative clinical outcomes of Tecnis toric IOL implantation in femtosecond laser-assisted cataract surgery and conventional phacoemulsification surgery

AIM: To compare the short-term visual outcomes, residual refractive cylinder, and rotation stability after Tecnis toric intraocular lens (IOL) implantation during femtosecond laser-assisted cataract surgery (Femto phaco) and conventional phacoemulsification surgery (Conventional phaco). METHODS: In a prospective cohort study, Conventional phaco and Femto phaco (anterior capsulotomy and lens fragmentation by a femtosecond laser) with Tecnis toric IOL implantation were performed in 40 eyes from 36 patients and 37 eyes from 33 patients, respectively. The uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), and manifest refraction were assessed during 1d, 1wk, and 1mo follow-ups. The orientation of the Tecnis Toric IOL was evaluated during 1wk and 1mo follow-ups. RESULTS: There were no significant differences in UDCA or CDVA between two groups at 1mo postoperatively, though relatively more subjects had UDVA values of 20/25 or better in Femto phaco group than in the Conventional group (P>0.05). A lower but not significantly lower rate of having more than 5° of IOL rotation was observed in Femto phaco group at the 1-month follow-up, while a significant lower rate of residual astigmatism of ≤1 D was observed in Femto phaco group. CONCLUSION: The Femto phaco group has significantly more subjects with the residual astigmatism of ≤1 D, but there are no significant differences in rotation stability and visual outcomes as compared with the Conventional phaco group after the application of the Tecnis toric IOL in this cohort.     

中央孔型后房型人工晶状体植入术治疗中高度近视合并散光的临床观察

目的 观察散光型中央孔型后房型人工晶状体(TICL-V4c)植入术治疗中高度近视合并散光的临床效果、稳定性及安全性。方法 回顾性研究,收集2018-11至2020-12于北京同仁医院行TICL-V4c植入术治疗中高度近视合并散光患者35例(59眼),分析患者术前及术后1周、1年的视力及屈光度变化,通过散光矢量分析术后散光矫正的有效性和安全性,并观察记录术后并发症。结果 术后1年裸眼视力为0.00(-0.08,0.00),裸眼视力≥1.0的占比88.14%,手术安全指数为1.20(1.00,1.25),有效指数为1.14(1.00,1.20),术后等效球镜明显改善且效果稳定,术后平均散光得到有效且稳定的矫正。散光经CRAVY矢量分析,术后J0得到良好矫正,J45未见明显改变。结论 TICL-V4c治疗中高度近视合并散光有效、稳定且安全。     

Verion导航与手动标记对Toric人工晶状体植入术后角膜散光矫正的影响

目的：比较Verion导航系统与手动标记对散光矫正型人工晶状体（Toric IOL）植入术矫正角膜散光效果的影响。方法：前瞻性随机对照研究。选取2015 年2 月至2017 年2 月在江苏省常州市第三人民医院就诊的白内障合并规则性角膜散光> 1.0 D的患者80例（80眼）。使用随机数字表法将患者随机分配到观察组（40例）和对照组（40例）。观察组使用Verion数字导航系统引导术中Toric IOL的植入,对照组术前在裂隙灯显微镜下手动标记用于指导Toric IOL的植入。2 组患者均行超声乳化白内障吸除联 合Toric IOL植入术,观察患者术前及术后3个月的裸眼远视力（UCDVA）（ LogMAR）、最佳矫正远视力（BCDVA）（ LogMAR）、角膜散光以及术后3个月的实际与预期残余散光、Toric IOL轴位。计量资料组间比较采用独立样本t检验,计数资料组间比较采用卡方检验。结果：对照组术后平均UCDVA为0.13±0.13,观察组术后平均UCDVA为0.11±0.11,2 组间差异无统计学意义（t=-0.96,P=0.34）。实际与预期残余散光的偏差绝对值对照组为（0.21±0.12）D,观察组为（0.12±0.11）D,2 组间差异有统计学意义（t=-3.71,P=0.001）。术后对照组裂隙灯显微镜下Toric IOL实际轴位与预期安放轴位偏差绝对值为4.6°±3.0°,观察组为2.2°±1.6°,2组间差异有统计学意义（t=-3.69,P=0.001）。结论：在Toric IOL植入术中应用Verion数字导航系统相较于传统手动标记技术可明显减小术后实际与预期散光的差值,减少术后Toric IOL轴位与预期轴位的偏离。