Synchrony dual-optic accommodating intraocular lens. Part 1: optical and biomechanical principles and design considerations

PURPOSE: To describe a dual-optic accommodating intraocular lens (IOL) based on theoretical considerations. SETTING: University and independent research group. METHODS: Ray-tracing analysis using optical modeling software (ZEMAXTM, Focus Software Inc., Tucson, Ariz) in a theoretical model eye was used to analyze lens configurations to optimize the accommodative and magnification effects of axial lens displacement. Finite-element modelling using a commercially available PC-based software package (COSMOS DesignSTAR) was applied to design the biomechanical parameters of the inter-optic articulations and optics. RESULTS: Ray-tracing analysis indicated that a dual-optic design with a high plus-powered front optic coupled to a minus posterior optic produced greater change in conjugation power of the eye compared to a single-optic intraocular lens and that magnification effects were unlikely to account for improved near vision. Finite-element modelling indicated that the 2 optics can be linked by spring-loaded haptics that allow anterior and posterior axial displacement of the front optic in response to changes in ciliary body tone and capsular tension. CONCLUSION: A dual-optic design linked by spring haptics increases the accommodative effect of axial optic displacement with minimal magnification effect and has promise for improving the performance of accommodative intraocular lenses.     

Pseudophakic accommodation with translation lenses – dual optic vs mono optic

PURPOSE: To investigate the pseudophakic accommodation effect in dual and mono optic translation accommodative intraocular lenses (AIOL) using linear matrix methods in the paraxial space. METHODS: Dual (anterior optic of power +32 D linked to a compensatory posterior optic of negative power) and mono lens power was determined in the non-accommodated state using linear geometric optics based on the Gullstrand model eye. The position of the AIOL was calculated from a regression formula. Pseudophakic accommodation was assessed with three systems: (1) forward shift of the mono optic lens, (2) anterior translation of the anterior optic in the dual optic lens system with an unchanged position of the posterior minus lens and (3) symmetrical anterior and posterior translation of the anterior and posterior lens. The Gullstrand model eye was modified by changing the axial length (and proportionally changing the phakic anterior chamber depth) to investigate the accommodative effect in myopic and hyperopic eyes. RESULTS: The dual optic lens system (2) yields a nearly constant accommodation amplitude of 2.4-2.5 D mm(-1) movement over the total range of axial lengths. The mono optic lens (1) provides a higher accommodative effect only in extremely short eyes (high refractive power of the lens), whereas for normal eyes (1.4-1.5 D mm(-1) movement) and for long (myopic) eyes the accommodative effect is much less than the dual optic lens. The dual optic lens system under condition (3) yields less accommodation amplitude compared with the dual optic system under condition (2) over the total range of axial length but provides higher accommodation amplitude compared with the mono optic lens system (1) with axial lengths greater than 22.3 mm (lens power 25.5 D). In the accommodated state, with lens translation of 1 mm, the absolute value of the lateral magnification increases with the refractive power of the mono optic lens (1) and decreases in both dual optic lens systems (under conditions 2 and 3). CONCLUSIONS: A mathematical strategy is presented for calculation of the accommodative effect of mono-optic and dual optic AIOL. The dual optic lens yielded a nearly constant accommodation amplitude of about 2.4-2.5 D mm(-1) translation, whereas the mono optic lens yielded an accommodative response of <2 D mm(-1) translation in long myopic or normal eyes. Only in extremely short eyes is the accommodative amplitude of the mono-optic lens higher than the dual optic lens.     

Refractive lensectomy and accommodating lens implantation in a case of hyperopia

We present a 39-year-old woman with high hyperopia who developed an intolerance to contact lenses due to dry-eye syndrome and Grave's disease. Refractive lensectomy with implantation of a custom-made +31.00 diopter (D) accommodating intraocular lens (IOL) (1CU, HumanOptics) was performed in both eyes. This foldable IOL has modified haptics with transmission elements that allow axial movement of the IOL optic and capsular bag secondary to contraction of the ciliary muscle. The calculated pseudophakic accommodation induced by the anterior shift of a +31.00 D IOL is 2.20 D per millimeter of axial displacement. After 6 months, the accommodative range determined by defocusing was 3.00 D. The subjective near point with best distance correction was 32.00 cm. Refractive lensectomy and implantation of an accommodating IOL based on focus shift may be a refractive solution in eyes with high hyperopia and a short axial length.     

Image quality in polypseudophakia for extremely short eyes

AIM: To evaluate the image quality produced by polypseudophakia used for strongly hypermetropic and nanophthalmic eyes. METHODS: Primary aberration theory and ray tracing analysis were used to calculate the optimum lens shapes and power distribution between the two intraocular lenses for two example eyes: one a strongly hypermetropic eye, the other a nanophthalmic eye. Spherical aberration and oblique astigmatism were considered. Modulation transfer function (MTF) curves were computed using commercial optical design software (Sigma 2100, Kidger Optics Ltd) to assess axial image quality, and the sagittal and tangential image surfaces were computed to study image quality across the field. RESULTS: A significant improvement in the axial MTF was found for the eyes with double implants. However, results indicate that this may be realised as a better contrast sensitivity in the low to mid spatial frequency range rather than as a better Snellen acuity. The optimum lens shapes for minimum spherical aberration (best axial image quality) were approximately convex-plano for both lenses with the convex surface facing the cornea. Conversely, the optimum lens shapes for zero oblique astigmatism were strongly meniscus with the anterior surface concave. Correction of oblique astigmatism was only achieved with a loss in axial performance. CONCLUSIONS: Optimum estimated visual acuity exceeds 6/5 in both the hypermetropic and the nanophthalmic eyes studied (pupil size of 4 mm) with polypseudophakic correction. These results can be attained using convex-plano or biconvex lenses with the most convex surface facing the cornea. If the posterior surface of the posterior intraocular lens is convex, as is commonly used to help prevent migration of lens epithelial cells causing posterior capsular opacification (PCO), then it is still possible to achieve 6/4.5 in the hypermetropic eye and 6/5.3 in the nanophthalmic eye provided the anterior intraocular lens has an approximately convex-plano shape with the convex surface anterior. It was therefore concluded that consideration of optical image quality does not demand that additional intraocular lens shapes need to be manufactured for polypseudophakic correction of extremely short eyes and that implanting the posterior intraocular lens in the conventional orientation to help prevent PCO does not necessarily limit estimated visual acuity.     

Biometry and intraocular lens power calculation

This article surveys the literature of 1 year, between July 2003 and August 2004, on the topic of biometry and intraocular lens power calculation for cataract surgery. There is an increasing demand for low postoperative refractive error with rising patient expectations, especially with patients who have already undergone refractive surgery, and with developing intraocular lens technologies such as multifocal, accommodating, or toric intraocular lenses. Optical biometry has become an invaluable tool for axial length measurement, especially for a setting with a less experienced biometrist. Introduction of ray tracing for power calculation and new methods of dealing with power calculation in eyes that have undergone previous refractive surgery seem promising. New intraocular lens designs that allow adjusting the axial optic position and therefore the effective refractive power of the intraocular lens have been evaluated in animal studies.     

Proposed mechanism for retinal tears after LASIK: an experimental model

OBJECTIVE: To demonstrate axial length changes associated with anterior shift of the lens/iris diaphragm and anterior vitreous base in human cadaver eyes during suction ring application preceding Moria LASIK, and to propose that these changes may be associated with anterior retinal tears. DESIGN: Human eye study. MATERIALS: Eight human eye bank eyes ranging in age from 65 to 73 years. Two eyes had a history of intraocular surgery involving cataract extraction and intraocular lens implantation. INTERVENTION: Measurements of intraocular pressure via internal manometer and Tono-Pen, anterior chamber depth, and axial length before and after application of a Moria LASIK suction ring. MAIN OUTCOME MEASURES: Change in anterior chamber depth and axial length after Moria LASIK suction ring application. RESULTS: Axial length increases (mean change = 1.125 mm, P = 0.02) after application of the suction ring, whereas anterior chamber depth shows no significant difference (mean change = -0.01 mm, P = 0.98), suggesting anterior movement of the vitreous base resulting in traction on the anterior retina. CONCLUSION: Axial length increase with anterior displacement of the vitreous base during suction ring placement might predispose susceptible eyes to anterior retinal tears during and after LASIK.     

小眼球高度远视眼透明晶状体摘除联合后房型Piggyback人工晶状体植入

目的：探讨小眼球高度远视眼的透明晶状体摘除联合后房型Piggyback人工晶状体植入术的疗效及人工晶状体度数的计算方法。方法：1例双眼极短眼轴合并高度远视、慢性闭角型青光眼患者行透明晶状体摘除联合后房型二片 30.0D Piggyback人工晶状体植入,术前双眼行YAG激光虹膜周切,术后一周右眼眼压高,行小梁切除术。术后一周、一月和三月分别视力、屈光状态,眼压和前房深度。利用光路追迹法计算人工晶状体度数。结果：术后三月最佳矫正视力与术前一致,屈光状态等效球镜度右 2.75D、左 2.88D,前房深度右眼、左眼分别由术前1.87mm、1.93mm加深到术后3.02mm和3.20mm,眼压正常。结论：对小眼球合并高度远视、慢性闭角型青光眼行透明晶状体手术联合二片后房型IOL植入,不仅能较好地解决屈光问题,而且有利于控制青光眼的发作和发展。利用光路追迹法计算IOL度数的方法是可取。     

Phacoemulsification and implantation of an accommodating IOL after PRK

PURPOSE: To present a case of phacoemulsification and implantation of an accommodating intraocular lens (IOL) in a patient with cataract formation after previous refractive surgery. METHODS: A 50-year-old man, who initially had photorefractive keratectomy to correct moderate myopia, developed a cataract in one eye. He subsequently underwent phacoemulsification and implantation of a 1CU accommodating IOL, as he wished to remain spectacle independent. RESULTS: The patient's distance vision was fully restored. However, accommodative function, which was assessed using subjective and novice objective techniques, was only partially restored. CONCLUSIONS: Although the accommodating IOL fully restored the patient's distance vision, accommodative function was only partially restored.     

Staining of zonules during posterior chamber lens implantation in a cadaver eye model.

A cadaver eye model was used to study the effects of extracapsular lens removal and implantation on the zonules and capsule. Five staining solutions were instilled in the posterior and anterior chambers of human cadaver eyes and washed out three to five minutes later. Gomori's chrom hematoxylin-eosin most clearly revealed the zonules. Three eyes stained in this way had lens removal (including the continuous circular capsulorhexis technique for anterior capsulectomy) and intraocular lens implantation. The effects of the surgery on the zonules and capsule were clearly visualized and appeared quite satisfactory. This staining technique may prove useful in other cadaver eye models.     

Using the lens haptic plane concept and thick-lens ray tracing to calculate intraocular lens power

PURPOSE: To develop a methodology for intraocular lens (IOL) power calculation in which the task of predicting the postoperative position of the IOL is separated from the calculation itself. SETTING: Pharmacia, Groningen, The Netherlands. METHODS: The minimum biometry input needed for IOL power calculation is the mean anterior corneal radius and axial length of the eye. The lens haptic plane (LHP) is the plane where the IOL haptics make contact with eye tissue. It is an anatomical site (eg, the equator of the capsular bag) and is independent of the IOL model. The position of the IOL optic in relation to the LHP is determined from the exact design of the IOL. Gullstrand's eye model is adopted to obtain the posterior corneal radius, thickness of the cornea, and refractive indices of the eye media. Thick-lens ray tracing in the paraxial limit is used for the optical calculation. RESULTS: A spreadsheet is given for the calculation. CONCLUSIONS: The methodology developed allows for IOL power calculation from first principles (ie, using true physical distances, radii, and refractive indices as input for the optical calculation).     

先天性晶状体脱位31例的手术治疗观察

目的：通过对先天性晶状体脱位行手术治疗的患者进行临床分析及手术方式选择、手术后效果分析,探讨先天性晶状体脱位患者的手术方式的选择及术中术后并发症的防治。
　　方法：回顾性分析我院自2010-01-01/2015-01-01的5 a间先天性晶状体脱位行手术治疗的患者共31例57眼,进行临床分析及手术方式选择、手术后效果、并发症分析。
　　结果：先天性晶状体脱位临床最常见的类型为单纯性晶状体半脱位和Marfan综合征晶状体半脱位。57眼中1眼为Marchesani综合征继发性青光眼导致视神经萎缩,术后视力无改善,其余56眼(98%)术后视力均较术前有不同程度提高。手术方式：晶状体超声乳化摘除+人工晶状体植入术3眼(5%);晶状体超声乳化摘除+囊袋张力环植入+人工晶状体植入术8眼(14%),其中1眼行囊袋张力环巩膜缝合固定;经角膜切口晶状体切除联合前部玻璃体切除+人工晶状体缝线固定术39眼(68%),其中2眼联合小梁切除术,未植入人工晶状体;晶状体囊内摘除联合前部玻璃体切除+人工晶状体缝线固定术5眼(9%);经睫状体平坦部切口晶状体切除联合玻璃体切除术+硅油注入术2眼(4%)。
　　结论：先天性晶状体脱位经过手术治疗大多数患者均可取得较为满意的术后效果。对于晶状体半脱位范围<90°者,可单纯行晶状体超声乳化摘除+人工晶状体植入术;晶状体半脱位范围90°~180°者,行晶状体超声乳化摘除+囊袋张力环植入+人工晶状体植入术;晶状体半脱位范围>180°者,经角膜切口晶状体切除联合前部玻璃体切除+人工晶状体缝线固定术,术后效果优于晶状体囊内摘除联合前部玻璃体切除+人工晶状体缝线固定术;根据患者晶状体脱位程度,尽量选择切口较小的微创的手术方式是手术取得成功的关键。     

负度数折叠式人工晶状体植入术治疗白内障合并轴性高度近视

目的:探讨超声乳化白内障吸除联合负度数人工晶状体植入术治疗白内障合并高度近视的临床疗效。方法:对30例41眼白内障合并高度近视患者行超声乳化白内障吸除联合负度数折叠式人工晶状体植入术,随访6mo,观察术中和术后并发症、术后视力、眼底情况。结果:术前平均眼轴长度为32.11mm。术后视力<0.1者3眼,0.1～0.5者26眼,>0.5者12眼。术中2眼晶状体后囊膜破裂;1眼角膜水肿,未见视网膜脱离。24眼眼底有明显的高度近视眼底病变。结论:超声乳化白内障吸除联合负度数人工晶状体植入术是治疗白内障合并高度近视眼安全、有效的方法。     

Biometry of phakic intraocular lens using Scheimpflug photography

PURPOSE: To examine lateral and axial positioning of phakic intraocular lenses (IOLs) with iris fixation in the anterior chamber and to examine short-term stability of the IOL position. SETTING: The Netherlands Opthalmic Research Institute, Amsterdam, the Netherlands. METHODS: Thirty patients participated in the study. Thirty-one eyes were implanted with the 204 type myopia IOL, 14 eyes with the 206 myopia IOL, and 8 eyes with the 203 hyperopia IOL. Scheimpflug slitlamp photographs were made through the optical axis along 4 meridians of the eyes. Ray tracing was used to obtain the lateral and axial position of the IOLs. RESULTS: Centration of the IOL with respect to the pupil's center and the tilt angle of the IOL with respect to the optical axis of the eye were measured. Standard deviation of decentration was 0.21 mm vertically and 0.16 mm horizontally. Standard deviation of tilt was 1.30 degrees vertically and 0.90 degrees horizontally. Tilt and decentration are proportional to each other. Vaulting, the distance between the crystalline lens and the IOL, was constant over a period of 24 months, ranging from 0.2 to 0.8 mm, depending primarily on the radius of curvature of the crystalline lens. A geometric model for this dependence was formulated. CONCLUSION: Phakic IOLs with iris fixation can be positioned in the eye with submillimeter precision. Axial position of iris-fixated phakic IOLs over time is excellent. Axial position and vaulting can be predicted when the radius of curvature of the crystalline lens is known. The IOL behaves as if mounted slightly above a sphere-the anterior surface of the crystalline lens.     

Magnification changes in scanning laser tomography

PURPOSE: It is important when evaluating glaucomatous optic disc progression in longitudinal images that image magnification remains unchanged. We studied the effect of changed lens power on magnification in scanning laser tomography. The relative contribution to magnification of axial length, eye-scanner distance, and image-to-image scaling was also assessed. METHODS: A simulated optic disc in a model eye was imaged using the Heidelberg Retina Tomograph. Lens power was alterable by exchanging intraocular lenses (IOL) mounted at the lens plane of the eye to mimic changes in the crystalline lens. IOL power of +20.0D and axial length of 21.5 mm was compatible with emmetropia. The optic disc was imaged through IOLs differing in power (+16.0D to +25.0D) but with axial length kept constant. IOL power was then held constant and imaging was repeated for various axial lengths (17.5-23.5 mm). Model eye-scanner distance was varied with each test sequence. The distances between landmarks on the disc was measured before and after contour lines were exported. RESULTS: Image size varied with IOL power and axial length (r > 0.98; P < 0.0001), with the magnification effect of a +1D increase in lens power equivalent to a third the magnification effect of a 1-mm increase in axial length. Magnification tended to increase with myopia (IOL power > +20.0D) and was accentuated by longer eye-scanner distances. Image-to-image scaling corrected some magnification though this varied with ametropia. CONCLUSIONS: Changed lens power, axial length, and eye-scanner distance can affect the size of the optic disc in scanning laser tomography images. The exported contour line partly compensates for changed magnification.     

Intraocular lens calculation for cataract treated with photorefractive keratectomy using ray tracing method

PURPOSE: Conventional methods (such as the SRK-II formula) do not accurately calculate the power of the intraocular lens (IOL) after refractive surgery. Therefore, we compared a new formula including a ray tracing method to the conventional method for foldable IOL lens implantation. METHOD: Foldable IOLs (MA 60 BM) were implanted in 26 patients (32 eyes) using the phakoemulsification technique. The power of the IOL was measured preoperatively using the SRK-II formula in all cases. From the results of postoperative refractive errors of these cases, the power of IOL calculated by the ray tracing method was compared to the SRK-II formula. Cataract patients first treated with photorefractive keratectomy (PRK) received IOL implants using our ray tracing method and their postoperative refraction was measured. RESULTS: The average postoperative refractive error was 1.32 D in SRK-II formula, 0.95 D in the ray tracing method with Ray 1 used and 0.89 D with Ray 2 used. Postoperative refraction of both eyes first treated with PRK was--1.00 D. CONCLUSION: The average postoperative refractive error was reduced in the ray tracing method using Olsen's predicted ACD (Ray 2) compared to SRK-II formula. This new tracing method appears to be useful for determination of IOL power and it may be applied for IOL calculation for cataract surgery after refractive surgery.     

Intraocular Lens Calculation for Cataract Treated with Photorefractive Keratectomy Using Ray Tracing Method

Purpose: Conventional methods (such as the SRK-II formula) do not accurately calculate the power of the intraocular lens (IOL) after refractive surgery. Therefore, we compared a new formula including a ray tracing method to the conventional method for foldable IOL lens implantation.Method: Foldable IOLs (MA 60 BM) were implanted in 26 patients (32 eyes) using the phakoemulsification technique. The power of the IOL was measured preoperatively using the SRK-II formula in all cases. From the results of postoperative refractive errors of these cases, the power of IOL calculated by the ray tracing method was compared to the SRK-II formula. Cataract patients first treated with photorefractive keratectomy (PRK) received IOL implants using our ray tracing method and their postoperative refraction was measured.Results: The average postoperative refractive error was 1.32 D in SRK-II formula, 0.95 D in the ray tracing method with Ray 1 used and 0.89 D with Ray 2 used. Postoperative refraction of both eyes first treated with PRK was -1.00 D.Conclusion: The average postoperative refractive error was reduced in the ray tracing method using Olsen's predicted ACD (Ray 2) compared to SRK-II formula. This new tracing method appears to be useful for determination of IOL power and it may be applied for IOL calculation for cataract surgery after refractive surgery.     

New Management of Angle—closure Glaucoma by Phacoemulsification with Foldable Posterior Chamber Intraocular Lens Implantation

Objective: To investigate the management oi angle-closure glaucoma byphacoemulsification with foldable posterior chamber intraocular lens (PC-IOL)implantation.Design: Retrospective, noncontrolled interventional case series.Participants: In 36 eyes with angle-closure glaucoma (ACG) , there were 18 eyes withprimary acute angle-closure glaucoma (PACG) , 14 eyes with primary chronicangle-closure glaucoma (PCCG) , 3 eyes with secondary acute angle-closure glaucoma(SACG) and 1 eye with secondary chronic angle-closure glaucoma (SCCG).Intervention: Phacoemulsification with posterior chamber intraocular lens implantation.Main Outcome Measures: Postoperative visual acuity, IOP, axial anterior chamberdepth.Results: After a mean postoperative follow-up time of 8. 81±7. 45 months, intraocularpressure was reduced from a preoperative mean of 23. 81 ±17. 84 mmHg to apostoperative mean of 12. 54 4. 73 mmHg ( P =0. 001). Mean anterior chamber depthwas 1. 75 ± 0. 48 mm preoperatively and 2. 29 ?0. 38 mm postoperatively     

Anterior chamber depth and change in axial intraocular lens position after cataract surgery with primary posterior capsulorhexis and posterior optic buttonholing

PURPOSE: To compare axial position changes of the intraocular lens (IOL) by measuring anterior chamber depth (ACD) after small-incision cataract surgery with primary posterior continuous curvilinear capsulorhexis (PPCCC) and posterior optic buttonholing (POBH) of the IOL and after conventional cataract surgery with phacoemulsification and in-the-bag IOL implantation. SETTING: Department of Ophthalmology, Medical University of Vienna, Austria. METHODS: This prospective comparative study comprised 23 patients (46 eyes) with age-related cataract who had bilateral cataract surgery and implantation of an acrylic IOL (YA-60BB, Hoya). In randomized order, cataract surgery with PPCCC and POBH of the IOL was performed in 1 eye of each patient. In the fellow eyes, conventional phacoemulsification cataract surgery with in-the-bag IOL implantation was performed. The ACD was measured 1 to 2, 6, and 24 hours as well as 7 and 30 days postoperatively using high-resolution partial coherence laser interferometry. A baseline measurement was taken preoperatively in all patients. RESULTS: Ten patients completed 10 to 12 months of follow-up. Postoperatively, the axial IOL position was stable in eyes with PPCCC-POBH (P>.05). In contrast, a significant axial shift of the IOL in the anterior direction was observed in control eyes with in-the-bag IOL implantation (P<.001). The resulting refractive shift was significantly higher in control eyes than in eyes with PPCCC-POBH (P<.001). CONCLUSION: Combined PPCCC and POBH for cataract surgery significantly reduced postoperative anterior movement of the IOL.     

Central retinal artery occlusion after radial optic neurotomy in a patient with central retinal vein occlusion

PURPOSE: To describe a patient with a central retinal vein occlusion (CRVO) who developed central retinal artery occlusion after radial optic neurotomy. DESIGN: Interventional case report. METHODS: A 70-year-old woman with CRVO underwent a radial optic neurotomy on her right eye. Her preoperative visual acuity in the affected eye was 20/400. RESULTS: Radial optic neurotomy was performed after phacoemulsification and aspiration for a cataract with intraocular lens implantation. At the insertion of a CRVO knife, pulsating bleeding occurred from the cup of the optic disk; the bleeding was stopped within 2 minutes by elevating the intraocular pressure to 80 mm Hg. On the following day, the patient noticed that she had lost light perception. Fluorescein angiography showed a marked delay of arterial filling, indicating a central retinal artery occlusion. Retinal circulation returned to normal 2 months later; however, her vision was still no light perception. CONCLUSIONS: Ophthalmologists should be aware that severe complications such as central retinal artery occlusion can be associated with radial optic neurotomy, which is an unproven surgical procedure with a questionable pathophysiologic mechanism.     

人工晶状体光学部囊袋后嵌入治疗儿童先天性白内障

目的 评价人工晶状体（IOL）囊上植入、光学部囊袋后嵌入治疗儿童白内障的临床效果。设计 回顾性病例系列。研究对象 15例（17眼）儿童先天性白内障患者。方法 超声乳化白内障吸除后，后囊连续环形撕囊，直径约4mm，将IOL光学部嵌于后囊后，襻位于囊袋上，使囊袋闭锁。主要指标裸眼视力、眼压、IOL位置及并发症。结果 术中17眼按设计的手术方式顺利完成。术后6个月5眼IOL位置从囊袋后向前移位至囊袋前，这其中有4眼发生视轴区混浊，余13眼在随访期间均未出现视轴区混浊。术后6个月的主要并发症为IOL表面沉着物：1级3眼（18％），2级7眼（41％）。虹膜前粘连1眼（6％），后粘连4眼（24％）。瞳孔变形5眼（29％）。结论 应用囊上植入、光学部囊袋后嵌入IOL治疗儿童白内障安全有效，可有效预防后发性白内障的发生。