Wei-Wei Xu, Jun-Qing Wang, Ye Tao, Zhao-Hui Li

?

·Original article·

Rotational stability of AcrySof toric intraocular lens: high-precision method for lens axis control

Wei-Wei Xu, Jun-Qing Wang, Ye Tao, Zhao-Hui Li

Department of Ophthalmology,Chinese PLA General Hospital, 28 Fuxing Road, Haidian District, Beijing 100853, China

Correspondence to:Zhao-Hui Li. Department of Ophthalmology, Chinese PLA General Hospital, 28 Fuxing Road, Haidian District, Beijing 100853, China. zhaohuili650@hotmail.com

目的：通過一種高精度方法評價AcrySof散光型人工晶體的旋轉(zhuǎn)穩(wěn)定性。

方法：收錄90例年齡相關(guān)性白內(nèi)障伴中、高度散光患者(104眼)，施行白內(nèi)障超聲乳化聯(lián)合AcrySof散光型人工晶體植入術(shù)?；颊咴谝?guī)定的復(fù)查時間接受必要的檢查。通過KR-1W視覺質(zhì)量分析儀檢測AcrySof散光型人工晶體的穩(wěn)定性。觀察指標(biāo)包括裸眼遠(yuǎn)視力(UDVA)、最佳矯正遠(yuǎn)視力 (CDVA)以及顯然驗光結(jié)果。通過配對T檢驗及ANOVA檢驗分析結(jié)果。

結(jié)果：研究共納入104眼，從術(shù)前檢查至最后一次術(shù)后復(fù)查持續(xù)24個月。7次復(fù)查時間點觀察到AcrySof散光型人工晶體的位置沒有顯著變化，P=0.863；所有患者的裸眼遠(yuǎn)視力(logMAR,4.39±0.27至4.77±0.22;P<0.001)、最佳矯正遠(yuǎn)視力(logMAR, 4.54±0.25至4.93±0.14;P<0.001)以及顯然驗光[度(D), -1.27±0.98至-0.97±0.71,P=0.003]均有顯著改善。術(shù)后調(diào)制傳遞函數(shù)(MTF)較術(shù)前提高。

結(jié)論：研究顯示AcrySof散光型人工晶體具有很好的旋轉(zhuǎn)穩(wěn)定性。該種人工晶體可以減少顯然驗光的柱鏡度數(shù)、提高視力并改善視力相關(guān)的生活質(zhì)量。

引用：許薇薇，王均清，陶冶，李朝輝. 通過檢測人工晶狀體軸位評價AcrySof散光型人工晶狀體的穩(wěn)定性.國際眼科雜志2016;16(9):1603-1608

Abstract

?AIM: To evaluate the rotational stability of AcrySof toric intraocular lens (IOL) after cataract surgery, by an high-precision method.

?METHODS: A total of 104 eyes of 90 patients with age related cataract and moderate to high regular astigmatism underwent phacoemulsification and implantation of AcrySof toric IOL (SN6AT series; Alcon, Fort Worth, TX, USA). Patients underwent comprehensive examinations at standard intervals. The rotational stability of AcrySof toric intraocular lens was evaluated using visual quality analyser KR-1W(Topcon, Tokyo, Japan). Uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA) and manifest refraction were also recorded. The outcomes were analysed by paired-samples T test and ANOVA Test.

?RESULTS: From preoperatively to the last visit (24mo), 104 eyes were included in the clinical trial. The AcrySof toric IOL axis orientation (at seven visits) did not show significant change,P=0.863. All of the eyes had significant improvement in UDVA (logMAR, 4.39±0.27 to 4.77±0.22;P<0.001), CDVA (logMAR, 4.54±0.25 to 4.93±0.14;P<0.001) and manifest refraction astigmatism [diopters (D), -1.27±0.98 to -0.97±0.71,P=0.003]. There was an increase in MTF results between preoperative and postoperative evaluations.

?CONCLUSION: The AcrySof toric IOL shows good rotational stability. It can reduce manifest refraction cylinder and improve visual acuity and vision-related quality of life permanently.

?cataract; astigmatism; lens implantation; intraocular; refractive errors

INTRODUCTION

Cataract surgery has dramatically improved patients’ visual acuity and vision-related quality of life[1-2]. However, corneal astigmatism is a key factor associated with good visual outcomes. It has been estimated that 30% of cataract patients have more than 0.75 diopters (D) of corneal astigmatism, that 22% have more than 1.50 D, and that 8% have more than 2.00 D[3-4]. Data from China shows that 67.7% of 60-90y old people have 0.25-1.25 D corneal astigmatism; and that 27.5% have more than 1.25 D[5].Since post-surgical residual astigmatism can compromise uncorrected distance visual acuity (UDVA), correction of corneal astigmatism is a critical element of modern cataract surgery. Corneal astigmatism can be surgically treated with adjustment of wound size and location, peripheral corneal relaxing incisions, additional clear corneal cataract incision along the steep meridian, laser refractive surgery[6]. All these methods have limitations including the degree of astigmatism that can be treated and long-term mechanical instability. Postoperative outcomes are subject to many variables such as age; magnitude; and incision number, depth, and length[7]. Toric intraocular len (IOL) implantation is another valuable option for astigmatism correction. Previous researches indicate that phacoemulsification and AcrySof toric IOL(SN6AT series; Alcon, Fort Worth, TX, USA) implantation is an effective, predictable and safe option to correct pre-existing astigmatism in cataract surgery[7-11]. Shift of controlling axis could impair visual acuity significantly. Postoperatively, IOL misalignment from its intended position can be assessed using a slit-lamp with a rotating slit and rotational gauge. This method requires sufficient mydriasis to see the marks on the IOL optic. An obvious limitation in accuracy is the 10-degree steps on the slit-lamp’s measuring reticule[6]. In our research, we used visual quality analyser KR-1W (Topcon, Tokyo, Japan), to measure the axis of AcrySof toric IOL in capsule. In our present study, we use KR-1W visual quality analyzer to measure ocular astigmatism and internal astigmatism. KR-1W visual quality analyzer use Hartmann-Shack principle, which could get computer optometry, wave front aberration and corneal topography data at the same time. It is much preciser than visual quality analyzer which based on Ray Trace principle. We got very precise data of the IOL position and analysed the change of the axis to evaluate the rotation stability. We also analysed the visual quality of the patients who received AcrySof toric IOL implantation.

SUBJECTS AND METHODS

This prospective observational study included 104 eyes of 90 consecutive patients with cataract and preexisting regular corneal astigmatism greater than 1.00 D who had implantation of the AcrySof toric IOL at the People’s Liberation Army General Hospital, China, between Jan. 2012 and Apr. 2013. The tenets of the Declaration of Helsinki were followed in the research.

Informed consent was obtained from all patients. Institutional Review Board approval was obtained. Inclusion criteria included cataract, age between 50 and 75y, and preoperative regular corneal astigmatism greater than 1.00 D. Exclusion criteria included preoperative astigmatism greater than 5.00 D, history of glaucoma or retinal detachment, corneal disease, previous corneal or intraocular surgery, abnormal iris, pupil deformation, macular degeneration or retinopathy, neuroophthalmic diseases, and history of ocular inflammation. Before cataract surgery, patients had a complete ophthalmologic examination including slitlamp examination, ophthalmoscopy through dilated pupils, manifest and cycloplegic refractions, applanation tonometry and keratometry. Axial length and keratometry were measured with the Zeiss Humphrey IOL Master (Carl Zeiss Meditec AG, Germany). Calculation of IOL power and axis placement to achieve emmetropia was performed using a program available from the IOL manufacturer (www.acrysoftoriccalculator.com). Preoperative keratometry and biometry data, incision location, and the surgeon’s estimated surgically induced corneal astigmatism were used to determine the appropriate AcrySof toric IOL model, spherical equivalent (SE) lens power, and axis of placement in the eye. The SRK/T formula was used for spherical IOL power calculation in most patients. If axial length was over 28 mm, Haigis formula was used. If axial length was less than 22 mm, Hoffer Q formula was used for spherical IOL power calculation. The targeted refraction was emmetropia. All surgery was performed by the same experienced surgeon (Z.L.) using topical anesthesia. With the patient seated at the slitlamp, the corneal limbus was marked at the 0-degree and 180-degree positions with a sterile string needle and after vertical alignment of the patient’s head. Next, with the patient lying on the surgical table, the steep corneal meridian was identified and marked using a sterile marker with the aid of the pre-placed reference points. Phacoemulsification was performed through a 2.4 mm temporal corneal incision. In all cases, the target capsulorhexis diameter was 5.50 mm to 6 mm, this to ensure overlap of the IOL border. After phacoemulsification, a foldable AcrySof toric IOL was inserted in the capsular bag using the Monarch Ⅱ injector (Alcon Laboratories Inc., USA). The IOL was rotated to align the cylinder axis with the marked steep corneal meridian. No sutures were used to seal the wound. The AcrySof toric IOL is an open-loop, modified single piece, acrylic polymer IOL with L-shaped haptics. In our research, selection of the adequate toric IOL is made using Acrysof toric calculator (www.acrysoftoriccalculator.com) which works on the basis of preoperative corneal astigmatism for the power and axis parameters. This program could consider a combination of relaxing incisions and toric IOL implantation depending on the astigmatism degree and power availability of the toric IOL. The IOL is available in 5 models: SN6AT2, SN6AT3, SN6AT4, SN6AT5, SN6AT6. After the operations, tobramycin and dexamethasone drop were used 4 times per day for 1wk and then 3 times per day for a second week. IOL axis, UDVA, corrected distance visual acuity (CDVA), refraction and keratometry were recorded. Intraocular lens rotation was measured by visual quality analyser KR -1W(Topcon, Tokyo, Japan). Postoperative assessments were performed at 1d, 1mo, 3mo, 6mo, 12mo, 1.5y and 2y intervals. All examinations were performed by the same ophthalmic technician. Data analysis was performed using SPSS (version 19.0 SPSS Inc., USA). The paired-samples T test and ANOVA Test were used to compare IOL axis position and refractive outcomes. Differences were considered statistically significant when thePvalue was less than 0.05.

RESULTS

One hundred and four eyes of 90 consecutive patients were enrolled in this study. Table 1 shows the patients’ demographics. The mean age was 67.4±10.7y (SD) (range 50 to 75y). The mean preoperative cylinder was -2.51±1.27 D (range -1.00 to -3.50).

Visual OutcomesTable 2 shows the mean preoperative and postoperative UDVA and CDVA. Two years postoperatively, the mean UDVA (logMAR) was 4.76±0.22. The CDVA (logMAR) improved slightly to 0.39±0.23 (approximately 20/20). Figure 1 summarizes the last visit UDVA and CDVA values. A total of 61.8% had UDVA≥20/30, and 97.1% had CDVA≥20/30. There was an increase in MTF results between preoperative and postoperative evaluations. Figure 2 shows modulation transfer function curve at preoperative and postoperative.Figure 2 shows the mean MTF at 5, 10, 15, 20, 25, and 30 c/pd. There was an obvious increase in the MTF between preoperation and postoperation values at any spatial frequency with 3.0 mm pupils (5, 10, 15, 20, 25, and 30 cpd;P=0.000,P=0.000,P=0.000,P=0.000,P=0.002, andP=0.003, respectively) and 5.0 mm pupils (P=0.000,P=0.000,P=0.000,P=0.000,P=0.004, andP=0.002, respectively).

Rotational StabilityOne-way ANOVA was used to analyze change in axial lens position after AcrySof toric IOL implantation. F=0.019,P=1.000. Figure 3 shows change in IOL axel position after implantation. We analysed the differences between groups and found that most IOL rotation occurred in the first month. Figure 4 shows that for 2.9% of the eyes, 20 rotation occurred after a period of 2y, with 1.9% occurring in the first month. None of the eyes had secondary surgery to reposition the IOL axis within the 2y postoperative period. The mean toric IOL axis rotation was 4.12±4.35 degrees (range 0 to 36 degrees). Seven eyes (6.7%) had significant IOL rotation (≥10 degrees)，the rest of the eyes (93.3%) had rotation less than 10 degrees (Figure 5).

DISCUSSION

Corneal astigmatism can be surgically managed using corneal, relaxing, or limbal incisions and excimer laser keratectomy. Limitations, advantages, and disadvantages have been fully discussed in the literature[12]. The use of toric IOLs to correct corneal astigmatism is one surgical option. The major requirement for a toric IOL is rotational stability. Several researches measure the IOL axis as described by Javier Mendicuteetal[7]. Intraocular lens rotation is measured at the slitlamp in 1-degree steps using an eyepiece for angle measurement through pupils dilated with tropicamide. A thin coaxial slit is projected in front of the eye and rotated until the thin slit projection overlapped the axis marks of the IOL. Results from this method could be influenced by several factors, such as the skill of investigator and the position of patient’s head and eyes. In addition to this, the degree scale of slitlamps are not accurate and this also leads to inaccurate data. All these factors influence the consistency of results. In

Table 1Patients’ demographics

CharacteristicValuePatients(n)90Meanage(a)±SD67.4±10.7range(y)50to75Sex(M/F)26/64Eyes(n)104OD/OS49/55Preoperativecylinder(D) Mean±SD-2.51±1.27D Range-1.00to-3.50DMeanpreoperativekeratometry(D)±SD K143.19±1.57 K245.57±1.79SphericalIOLpower(D) Mean±SD20.63±2.35 Range16.00to24.50

OD: right eye; OS: left eye; IOL: intraocular lens.

Figure 1Cumulative UDVA and CDVA.

our research, we measured IOL axis shift by visual quality analyser KR-1W. Precise data was used to report the efficacy and rotational stability of this toric IOL. KR-1W by measuring IOL axis directly. This avoided the inaccuracies of manual measurement. The data from this method was more precise and more consistent.

Follow up extended to 2y after IOL implantation in the first eye. The mean toric IOL axis rotation was 4.12±4.35 degrees (range 0 to 36 degrees). This is consistent with the results of other researches[13-15]. Weinandetal[16]researched rotational stability of intraocular lens by a digital fundus camera, which was also reported as an high-precision rotation control. In their report, the median IOL rotation was 0.7 degree (range 0.1 to 1.8 degrees), which is less than ours. However, they included only 17 eyes.

It was identified that all three patients, who had significant IOL rotation (>20 degrees), had suffered trauma of head or face. Two of them were struck by an infant. This is an interesting phenomenon, as in China it is common for older people to take care of their grandchildren. They spend a lot of time taking care of their grandchildren, hence several accidents and severe cases occurred because of the grandchildren

Table 2Visual acuity before and 2y after AcrySof toric IOL implantation(Mean±SD)

ParameterPreoperativePostoperativeDifferencesPUDVA(logMAR)4.38±0.274.76±0.220.38±0.26<0.001CDVA(logMAR)4.54±0.254.92±0.130.39±0.23<0.001

UDVA: uncorrected distance visual acuity; CDVA: corrected distance visual acuity.

Figure 2The modulation transfer function curve at preoperative and postoperative visitsThere was an increase in MTF results between preoperative and postoperative evaluations. A is the MTF curve before cataract operation; B is the curve after cataract operation. The MTF results increase no matter in 3mm pupil or 5mm pupil, which suggested the improvement of visual quality.

Figure 3Mean postoperative IOL axel positionIOL rotation was 4.12±4.35 degree 2y after implantation. Error bars indicate 1 standard deviation (SD). Axel= Mean postoperative AcrySof toric IOL axel position.

Figure 4Cumulative IOL rotation degree.

Figure 5Toric IOL axis shift 2y after surgery. Scattergram of toric IOL axis shift in each eye.

Figure 6Vector analysis of keratometric data. Keratometric changes were minimal before and after operation; thus, the reduction in astigmatism was the result of toric IOL implantation.

were uncontrollably active and subconsciously caused the traumas which could lead to luxation of lens and retinal detachment. All of the three patients examined had subluxation of lens. There were 12.7% of the patients, who had IOL rotation more than 10 degrees. This finding was above expectations, however it is felt that, now identified, it might relate to traditional Chinese culture and this phenomenon will reoccur repeatedly in future. Additionally, the number of patients who need cataract surgery is very large and therefore it is necessary for Chinese Ophthalmology surgeon to warn the population of the potential of this kind of accident.

There is a high variability in IOL rotation as a function of the toric IOL model and haptic design. C-loop or plate haptics are prone to rotate from the intended axis postoperatively[17-19]. While Z-design haptics have good stability[15]. With improvement of material and facture technique, rotation stability of IOL has been better and better. We used AcrySof toric IOL in this research. It is an open-loop, modified singlepiece, acrylic polymer IOL with L-shaped haptics. Our data showed this IOL had low rate of postoperative rotation (5.77%≥10°). The axis rotation was 4.12±4.35 degree, which was slightly higher than Javier Mendicuteetal[7]reported. However, this included three patients who suffered trauma to the head or face. Modified mean axis rotation, the axis rotation was 3.73±2.77 degree. Our results suggested that the modified L-shaped haptic design of the AcrySof toric IOL showed satisfactory rotation stability. Trauma, severe coughing or some other movements could lead to IOL rotation. Thus, surgeons should inform the patients to avoid these factors. It has been reported that rotation of toric IOLs depends on the implantation axis[20]. However, in our study, we did not find statistically significant correlation between intraoperative axis alignment and postoperative rotation. Figure 4 showed that most rotation happened in the first month after IOL implantation. During this period, the attachment between the IOL and the capsular bag was not very tight. Once the anterior and posterior capsules fuse, IOL rotation is less frequent. To reduce IOL rotation in early stage, viscoelastic need to be washed away completely, with our experience, stick a dual irrigation-aspiration probe under IOL then irrigate and aspirate carefully, after all, press IOL gently next to posterior subcapsular. Also to reduce astigmatism, a minimal incision on corneal should be carefully designed, we analysed the confounding variables according to it. Figure 6 assess whether surgically induced corneal refractive change plays a role in surgically induced refractive change. The figure shows that keratometric astigmatism was distributed randomly before and after IOL implantation without significant differences (P>0.1).

In our study, 94.2% of patients achieved 20/40 or better UDVA. In a study by Sunetal[21], 98.4% of eyes achieved 20/40 or better UCVA after Staar TF IOL implantation. Ruhswurmetal[20]reported a lower percentage (67.6%) using the same IOL. Tilletal[13]reported that 66% of patients had an UCVA of 20/40 or better after Staar TF or TL IOL implantation. Eyes in our study had a 61% reduction in astigmatism after toric IOL implantation(mean preoperative corneal astigmatism -2.38±1.36D). This is consistent with reported results[14,21]. Differences between IOL models and preoperative astigmatism values are responsible for the variability in the percentage of astigmatism reduction and visual acuity outcomes between toric IOLs[7].

Data from KR-1W were high precise. The results in our study show that implantation of the AcrySof toric IOL is an effective surgical option to correct preexisting corneal astigmatism during cataract surgery. In addition to this, apart from regular postoperation care, we also remind patient to be extra precautious in avoiding ocular trauma caused by their grandchildren in the daily activities.

REFERENCES

1 Friedman DS, O’Colmain BJ, Muoz B, Tomany SC, McCarty C, de Jong PT, Nemesure B, Mitchell P, Kempen J. Prevalence of age-related macular degeneration in the United States.ArchOphthalmol2004;122(4):564-572

2 Ryan A, Hartnett C, Lanigan B, O’Keefe M. Foldable iris-fixated intraocular lens implantation in children.ActaOphthalmol2012;90(6):e458-e462

3 Hoffmann PC, Hütz WW. Analysis of biometry and prevalence data for corneal astigmatism in 23,239 eyes.JCataractRefractSurg2010;36(9):1479-1485

4 Ferrer-Blasco T, Montés-Micó R, Peixoto-de-Matos SC, González-Méijome JM, Cervio A. Prevalence of corneal astigmatism before cataract surgery.JCataractRefractSurg2009;35(1):70-75

5 Chen W, Zuo C, Chen C, Su J, Luo L, Congdon N, Liu Y. Prevalence of corneal astigmatism before cataract surgery in Chinese patients.JCataractRefractSurg2013;39(2):188-192

6 Ventura BV, Wang L, Weikert MP, Robinson SB, Koch DD. Surgical management of astigmatism with toric intraocular lenses.ArqBrasOftalmol2014;77(2):125-131

7 Mendicute J, Irigoyen C, Aramberri J, Ondarra A, Montés-Micó R. Foldable toric intraocular lens for astigmatism correction in cataract patients.JCataractRefractSurg2008;34(4):601-607

8 Hill W. Expected effects of surgically induced astigmatism on AcrySof toric intraocular lens results.JCataractRefractSurg2008;34(3):364-367

10 Doors M, Budo CJ, Christiaans BJ, Luger M, Marinho AA, Dick HB, Güell JL, Nuijts RM. Artiflex Toric foldable phakic intraocular lens: short-term results of a prospective European multicenter study.AmJOphthalmol2012;154(4):730-739.e2

11 Langenbucher A, Viestenz A, Szentmáry N, Behrens-Baumann W, Viestenz A. Toric intraocular lenses--theory, matrix calculations, and clinical practice.JRefractSurg2009;25(7):611-622

12 Kohnen T, Kasper T, Terzi E. Intraocular lenses for the correction of refraction errors. Part II. Phakic posterior chamber lenses and refractive lens exchange with posterior chamber lens implantation.Ophthalmologe2005;102(11):1105-1117

13 Till JS, Yoder PR Jr, Wilcox TK, Spielman JL. Toric intraocular lens implantation: 100 consecutive cases.JCataractRefractSurg2002;28(2):295-301

14 Chang DF. Early rotational stability of the longer Staar toric intraocular lens: fifty consecutive cases.JCataractRefractSurg2003;29(5):935-940

15 De Silva DJ, Ramkissoon YD, Bloom PA. Evaluation of a toric intraocular lens with a Z-haptic.JCataractRefractSurg2006;32(9):1492-1498

16 Weinand F, Jung A, Stein A, Pfützner A, Becker R, Pavlovic S. Rotational stability of a single-piece hydrophobic acrylic intraocular lens: new method for high-precision rotation control.JCataractRefractSurg2007;33(5):800-803

17 Sauder G. Secondary toric intraocular lens implantation in pseudophakic eyes. The add-on IOL system.Ophthalmologe2007;104(12):1041-1045

18 Visser N, Gast ST, Bauer NJ, Nuijts RM. Cataract surgery with toric intraocular lens implantation in keratoconus: a case report.Cornea2011;30(6):720-723

19 Patel CK, Ormonde S, Rosen PH, Bron AJ. Postoperative intraocular lens rotation: a randomized comparison of plate and loop haptic implants.Ophthalmology1999;106(11):2190-2195

20 Ruhswurm I, Scholz U, Zehetmayer M, Hanselmayer G, Vass C, Skorpik C. Astigmatism correction with a foldable toric intraocular lens in cataract patients.JCataractRefractSurg2000;26(7):1022-1027

21 Sun XY, Vicary D, Montgomery P, Griffiths M. Toric intraocular lenses for correcting astigmatism in 130 eyes.Ophthalmology2000;107(9):1776-1781

通過檢測人工晶狀體軸位評價AcrySof散光型人工晶狀體的穩(wěn)定性

許薇薇，王均清，陶冶，李朝輝

100853 北京市海淀區(qū)復(fù)興路北京市海淀區(qū)復(fù)興路28號解放軍總醫(yī)院眼科)

許薇薇 ，解放軍醫(yī)學(xué)院，博士，主治醫(yī)師，研究方向：屈光手術(shù)、角膜疾病。

李朝輝，解放軍醫(yī)學(xué)院，碩士，副主任醫(yī)師，副教授，研究方向：白內(nèi)障、晶狀體疾病. zhaohuili650@hotmail.com

白內(nèi)障；散光；人工晶體植入；眼內(nèi)；屈光不正

10.3980/j.issn.1672-5123.2016.9.02

Xu WW, Wang JQ, Tao Y, Li ZH. Rotational stability of AcrySof toric intraocular lens: high-precision method for lens axis control.GuojiYankeZazhi(IntEyeSci) 2016;16(9):1603-1608

2016-04-21Accepted： 2016-06-23