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...     

角膜内镜片的发展

圆锥角膜是一种易致盲的眼病,且发病率较高,约为1/2000,目前治疗圆锥角膜的方法主要有配戴硬性透氧性角膜接触镜(rigid gas permeable contact lens,RGP)、角膜交联术、角膜移植术等,上述治疗方法费用高、耗时长、疗效不肯定。随着科学技术的发展,角膜内镜片逐渐成为治疗圆锥角膜的一种新技术。角膜内镜片技术尝试在角膜层间植入一定度数的镜片,在治疗圆锥角膜的同时使视力得到最佳恢复。本文就角膜内镜片的研究进展及发展前景进行综述。     

Case report: Bitoric RGP lens used in the correction of astigmatism caused by trauma

A 28-year-old white male was referred to our office after having his lacerated right cornea surgically repaired following an accident. Because of the high degree of corneal toricity and irregular astigmatism present, the patient was fit with a bitoric rigid gas permeable lens that provided excellent vision.     

Intraocular lens calculations in patients with corneal scarring and irregular astigmatism

PURPOSE: To compare various methods of estimating corneal power for intraocular lens (IOL) calculation in patients with irregular corneal astigmatism. SETTING: Pepose Vision Institute, St. Louis, Missouri, USA.Case reports and review of the medical literature. RESULTS: Two patients with irregular corneal astigmatism had an IOL exchange after a "surprise" post-cataract-surgery refraction. In the first case, the patient had a post-cataract-surgery refraction of +5.50 -0.75 x 69 and in the second case, a refraction of -7.00 -1.00 x 180. The central corneal power before IOL exchange was assessed using manual keratometry, various computerized videokeratography curvature and power maps, and contact lens overrefraction. The total axial power map (Orbscan(R), Bausch & Lomb), total optical power map (Orbscan), and contact lens overrefraction method provided the most accurate estimates of central corneal power in these 2 patients. CONCLUSION: Computerized scanning-slit videokeratography, which analyzes the anterior and posterior surfaces of the cornea, and the contact lens overrefraction method gave good estimations of corneal power in patients with irregular corneal astigmatism. This type of analysis may improve the accuracy of IOL calculation in patients with corneal pathology and irregular astigmatism.     

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.     

Alternatives to toric contact lens fitting—for regular and irregular astigmatism

Although toric contact lenses have improved in design and development and their use is increasing, further consideration should be given to the alternative methods of astigmatism correction by contact lenses. Much can still be achieved by non-toric lens, both for a wide range of astigmatism and for ease of supply. A number of these alternatives are examined, their advantages and disadvantages reappraised, and the merits of lens correction compared with surgical methods considered.     

Management of irregular astigmatism

Using a liberal definition of corneal irregularity, modern videokeratoscopy may define approximately 40% of normal corneas with a toric refractive error as possessing primary irregular astigmatism. The causes of secondary forms of irregular astigmatism include corneal surgery, trauma, dystrophies, and infections. Internal refractive surface and media irregularity or noncorneal astigmatism (ocular residual astigmatism) contribute to irregular astigmatism of the entire refractive path of which crystaline lenticular astigmatism is usually the principal contributing component. Treatment options have increased in recent years, particularly, though not exclusively, through the advent of tailored corneal excimer laser ablations. However, discussion continues concerning the systematic approach necessary to enable treatment to achieve an optimal optical surface for the eye. Discussion also continues as to what constitutes the optimal corneal shape. Some refractive procedures may increase higher order aberrations in the attempt to neutralize refractive astigmatism. The way to further refinement of the commonly performed refractive techniques will ultimately lie in the integrated inclusion of a trio of technologies: topographic analysis of the corneal surface, wavefront analysis of ocular refractive aberrations, and vector planning to enable the appropriate balance in emphasis between these two diagnostic modalities. For the uncommon, irregularly roughened corneas, the ablatable polymer techniques show some promise.     

The use of the SoftPerm lens for the correction of irregular astigmatism.

We evaluated the performance of the SoftPerm combined rigid gas permeable (RGP) and hydrogel lens for the visual correction of 49 eyes (30 patients) with irregular astigmatism. Follow-up was up to 15 months. An attempt was also made to compare the SoftPerm lens to its predecessor, the Saturn II lens. The most common etiology for irregular astigmatism was keratoconus. Others etiologies were penetrating keratoplasty and refractive surgery. Visual acuity improved significantly. Only two eyes were best corrected to 20/20 before fitting whereas, 13 eyes saw 20/20 after fitting. The rate of lens replacement was 0.22 lenses per eye per month. A variety of complications occurred, including corneal staining, abrasions, and edema. Complications also reflected the relative difficulty of handling of the lens, yet no vision threatening complications occurred. Overall, the SoftPerm lens is a vast improvement over the Saturn II and is a reasonable means of correction of irregular astigmatism.     

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.     

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。     

Hyperopic LASIK following intracorneal hydrogel lens explantation

PURPOSE: To report hyperopic LASIK results after intracorneal hydrogel lens explantation in a bilateral hyperopic patient. METHODS: Slit-lamp examination showed diffuse corneal opacity around the lens edge and over the anterior lens surface affecting both eyes with uncorrected visual acuity of 0.4 in the right eye and 0.5 in the left eye. RESULTS: The intracorneal hydrogel lenses were explanted, and 6 months later hyperopic LASIK using the Schwind ESIRIS excimer laser (Schwind, Kleinostheim, Germany) was performed after lifting the same flap for the intracorneal hydrogel lens implantation. Six months after hyperopic LASIK, visual acuity recovered to the initial preoperative best spectacle-corrected levels: right eye 0.8 with +1.50 D sphere and left eye 0.9 with +1.00 -0.50 x 90 degrees. Central corneal transparency also fully recovered. CONCLUSIONS: Hyperopic LASIK is a possible alternative after intracorneal hydrogel lens explantation in hyperopic eyes.