surgical management of astigmatism for cataract patients ......astigmatism. if surgeons treat...

Surgical Management of Astigmatism for Cataract Patients: Pre, Intra, and Post-Operative Protocols for Success

Supplement Dec 2016/Jan 2017

SATURDAY 10 SEPTEMBER 2016COPENHAGEN, DENMARK

Surgical Management of Astigmatism for Cataract Patients: Pre, Intra, and Post-Operative Protocols for Success1

Preoperative Tools and Diagnostics: Improved Treatment Planning for Toric IOL PatientsFine-tuning preoperative assessments can help advance toric IOL outcomes.

BÉATRICE COCHENER, MD, PHD

To optimise outcomes from toric intraocular lens (IOL) implantation, surgeons need to improve each element of their preoperative assessment—examining how they measure astigmatism, the tools they use, and how they perform their

diagnostic examination.

MEASURING ASTIGMATISMAn estimated 47% of the population between 8 and 70 years of age have been reported to have astigmatism of at least 0.75 D, with more than 24% having bilateral astigmatism. More than one-third have astigmatism greater than 1.0 D, and two-thirds have high spherical ametropia when cataracts are diagnosed.1

To measure astigmatism, surgeons focus principally on the cornea, determining the anterior and posterior curvature, thickness, and corneal refractive indices.

The anterior curvature is measured with keratometers and computerized video keratographers, which compensate for the posterior corneal surface using a modified refractive index. The measurement of the anterior curvature is converted to the refractive

The first supplement in this series features the presentations of our panel of experts who focused on questions cataract surgeons commonly ask about managing astigmatism before, during, and after surgery. Within these pages, you will learn more about treatment planning with toric intraocular lenses, the effect of surgically induced astigmatism and the posterior cornea on outcomes, intraoperative alignment techniques and technologies, and addressing postoperative error.

The new forthcoming ESCRS and EuroTimes online portal provides a wealth of additional educational content, including the video replay of the lectures, faculty interviews, question-and-answer sessions, and related content from ESCRS meetings and EuroTimes articles.

We invite you to take advantage of these resources to learn how you can improve your protocols and procedures, a step that will benefit your patients and your practice.

Dr. Spalton is president of the ESCRS and consultant ophthalmic surgeon at the London Clinic Eye Centre. He may be reached at [email protected].

This autumn, the ESCRS launched a new type of educational programming for cataract and refractive surgeons. This evidence-based series, supported by a number of companies, will enable us to provide independent, category-based education. It is driven by delegate responses from the ESCRS Clinical Survey.

“This evidence-based series, supported by a number of companies, will enable us to provide independent, category-based education”

Figure 1. Axial specular topography allows surgeons to qualify the astigmatism. Image shows against-the-rule astigmatism, which is slightly irregular

“Practice Pearl: One-third of the overall population has more than 1.0 D of astigmatism that impacts visual performance. Only corneal astigmatism can be corrected by toric IOLs, requiring the use of video topography when performing preoperative measurements. Successful calculation requires a good correlation among the K reading, K topography, and K biometry in terms of cylinder value and axis.”

Introduction: Managing Astigmatism Each Step of the WayNew programme emphasises independent, category-based education.

DAVID SPALTON, FRCS, FRCP, FRCOPHTH

Surgical Management of Astigmatism for Cataract Patients: Pre, Intra, and Post-Operative Protocols for Success 2

Meanwhile, we can combine Placido measurements, elevation with Scheimpflug, and biometry, which can be transferred to calculation software based on ray tracing that can predict wavefront errors, avoiding errors from empirical formulas in difficult cases.

However, reduction of total higher-order aberrations is limited even if aspheric IOLs are well positioned.4 Regardless of the IOL model used, online calculator software is used for calculations.

POSSIBLE PITFALLSWhen implanting toric IOLs, the primary pitfall is treating the wrong astigmatism. If surgeons treat lenticular astigmatism with a toric IOL, they will induce astigmatism. Removing the crystalline lens corrects lenticular astigmatism without a toric IOL.

Corneal warpage and irregular asymmetrical astigmatism are contraindications to toric multifocal IOLs.5 It is also critical to assess and treat the ocular surface before performing preoperative measurements because an unstable tear film can lead to incorrect calculations.

CONCLUSIONTo achieve improved outcomes from toric IOLs, surgeons need to take a close look at their preoperative assessments. Because we need to treat corneal astigmatism, topography is necessary, and we also need to measure posterior corneal astigmatism.

REFERENCES1. Ferrer-Blasto T. Prevalence of corneal astigmatism before cataract surgery. J Cataract Refract Surg. 2009; 35:70-75. 2. Koch DD, et al. Contribution of posterior corneal astigmatism to total corneal astigmatism. J Cataract Refract Surg. 2012; 38:2080-2087.3. Bregnhøj JF, et al. Refractive, anterior corneal and internal astigmatism in the pseudophakic eye. Acta Ophthalmol. 2015; 93:33-40.4. Einighammer J, et al. Customized aspheric intraocular lenses calculated with real ray tracing. J Cataract Refract Surg. 2009; 35:1984-1994.5. Young G. Prevalence of astigmatism in relation to soft contact lens fitting. Eye Contact Lens. 2011 ;37 :20-25.

Professor Cochener is head of the Ophthalmology Department at Brest University Hospital, France, president of the French Academy of Ophthalmology, secretary of EuCornea, and president-elect of ESCRS. She may be reached at [email protected]. She is a clinical investigator for Alcon, Santen, TearScience, PhysIOL, Thea, Allergan, Cutting Edge, and Abbott Medical Optics.

“When implanting toric IOLs, the primary pitfall is treating the

wrong astigmatism”

Figure 2. Aberrometry measurement as a result of corneal and internal aberrations

power of the entire cornea by empirical estimation of the thickness and posterior curvature.

Refractive astigmatism, measured with automated refraction as a subjective refraction, determines the total ocular astigmatism.

Keratometry can be measured manually and digitally. Manual keratometry measures corneal power between two points, however, it does not measure the central part of the cornea, so this is extrapolated as regular. This is a simple way to detect irregular astigmatism.

Automated keratometry is similar to manual methods in terms of principles and limits. Axial specular (Placido) topography qualifies astigmatism (regularity, symmetry, orientation) and confirms the corneal origin (Figure 1). Surgeons must compare this with the refraction because only corneal astigmatism can be corrected with toric IOLs. It has a blind zone in the central area (approximately 1.6 mm), and the sim-K measurement is calculated on the central 3-mm zone.

Elevation topography is based on the slit scanning (rotation) on the cornea. There is no central blind zone. The peripheral camera measures the central keratometry without extrapolation. It also provides access to the posterior surface.

Researchers have reported that disregarding the posterior surface can lead to inaccurate calculation of the overall corneal astigmatism.2,3 Posterior corneal curvature now can be estimated with the Purkinje images, scanning slit imaging, Scheimpflug imaging and optical coherence tomography, or reflection topography. These technologies measure the total corneal refractive power (anterior, posterior curvature, thickness).

Astigmatism is just one optical aberration. Aberrometry enables surgeons to define and analyze higher-order aberrations.

IMPROVING CALCULATIONSA variety of topographers extrapolate corneal aberrometry (Figure 2). Based on mathematics, they can recalculate and estimate the aberrometry of the cornea. They can be linked to IOL calculation software, integrating topography and adjusting the IOL asphericity. This will be a new option in the future.


(Carl Zeiss Meditec) postoperative prediction error.4 When corneal astigmatism was calculated based only on the anterior corneal surface, the WTR group frequently was overcorrected by 0.5 D and in the ATR group it was often undercorrected by 0.3 D.

Although it is important to measure the posterior and anterior curvature, we still cannot obtain actual measurements and measurements vary by system.

ADDITIONAL FACTORSWhen implanting toric IOLs, we need to keep in mind that a small amount of ATR astigmatism (average of 3/8 D) occurs during a 10-year period.5 Therefore, we may need to compensate for this with a small amount of WTR astigmatism.

Furthermore, IOL power and anterior chamber depth determine effective toricity. With a deeper chamber and lower IOL power, there is less toric effect, and with a shallower chamber and higher power there is greater toricity. At the extremes of each, as much as 0.5 D of variation can occur in each direction.

TORIC IOL SELECTIONThe correct formula guides selection of the best toric IOL for an individual patient. Formulas need to take into consideration the effect of posterior corneal astigmatism, IOL power and anterior chamber depth on effective toricity.

Using the Baylor Toric Nomogram, surgeons can adjust for WTR and ATR astigmatism, however, it does not include anterior chamber depth and IOL power.4 Other formulas are available, but some do not take into consideration factors such as the posterior cornea. Surgeons should always aim for undercorrection with toric IOL implantation.

CONCLUSIONTo obtain optimal results with toric IOLs, we will need to have the correct formula, including the posterior corneal surface, and we need to target a slight undercorrection.

REFERENCES1. Hayashi K, et al. Effect of astigmatism on visual acuity in eyes with a diffractive multifocal intraocular lens. J Cataract Refract Surg. 2010; 36:1323-1329.2. Holladay JT, Moran JR, Kezirian GM. Analysis of aggregate surgically induced refractive change, prediction error, and intraocular astigmatism. J Cataract Refract Surg. 2001; 27:61-79.3. Koch DD, et al. Contribution of posterior corneal astigmatism to total corneal astigmatism. J Cataract Refract Surg. 2012; 38:2080-2087.4. Koch DD, et al. Correcting astigmatism with toric intraocular lenses: effect of posterior corneal astigmatism. J Cataract Refract Surg. 2013; 39:1803-1809.5. Hayashi et al. Long-term change in corneal astigmatism after sutureless cataract surgery. Am J Ophthalmol. 2011; 151:858-865.

Dr. Kohnen is professor and chair, Department of Ophthalmology, Goethe-University, Frankfurt, Germany. He may be reached at [email protected]. Dr. Kohnen is a consultant for Abbott Medical Optics, Alcon, Carl Zeiss Meditec, Geuder AG, Oculus Optikgerate GmbH, Schwind Eye-Tech Solutions, Staar Surgical, and Ziemer, and has received funding from Abbott Medical Optics, Alcon, Carl Zeiss Meditec, Oculus, And Schwind Eye-Tech Solutions.

Residual astigmatism significantly impacts patients’ visual acuity after implantation of intraocular lenses (IOLs).1 To make the most of toric intraocular lenses (IOLs), we need to recognize and manage the factors that contribute to

postoperative astigmatism.

UNDERSTANDING THE INFLUENCESAs part of this process, surgeons need to optimize their lens constants because patients will not achieve the true benefit of the IOL if the sphere is not correct.

Surgically induced astigmatism also should be calculated, which is most likely minimal with a 2.2- to 2.4-mm incision. To analyze astigmatism, we need to understand double-angle plots, which were described by Holladay et al.2

During preoperative testing, we need to take into account least three data points: power calculation, topography for alignment, and the patient’s glasses to determine whether there is less with-the-rule (WTR) or more against-the-rule (ATR) astigmatism. If there are discrepancies in the first two, the surgeon must remeasure.

POSTERIOR CORNEAL ASTIGMATISMResearch has shown that the mean magnitude of posterior corneal astigmatism is approximately -0.3.3 If not identified, posterior astigmatism contributes to ATR astigmatism and leads to incorrect measurements. Figures 1 and 2 show the effect of the posterior corneal curvature on the magnitude of WTR and ATR astigmatism.

Posterior corneal astigmatism can be measured with a combined placido disk and dual Scheimpflug corneal analyzer.

When Koch et al. studied outcomes in 42 eyes in which IOLs were implanted, they used a double angle plot calculation and the IOLMaster

Figure 1. Magnitude of WTR astigmatism induced by posterior astigmatism

Figure 2. Magnitude of ATR astigmatism induced by posterior astigmatism

The Role of Surgically Induced Astigmatism and the Posterior Cornea in Achieving Our Goals for Toric IOL PatientsA number of factors may undermine efforts to achieve ideal outcomes.

THOMAS KOHNEN, MD


Intraoperative Alignment: Technologies and Techniques to Navigate to Your Best Option and OutcomesLow-tech and high-tech tools can help improve toric IOL outcomes.

OLIVER FINDL, MD, MBA

Although toric intraocular lenses (IOLs) can effectively treat astigmatism, outcomes may be hampered if residual astigmatism is present.

This may result from improper placement of the IOL, using the incorrect lens, poor measurements or calculations, surgically induced astigmatism, cyclorotation, IOL rotation, and other factors (Figure 1).1-3

A number of manual and digital techniques can help surgeons improve IOL orientation, which is critical to success when implanting a toric IOL (Figure 2).

INCREASING PRECISIONManual marking has been the standard technique to mark orientation and the steep axis. Research has shown that the pendulum marker and marking at the slitlamp using a needle, two of the most popular manual techniques, produced similar results, with approximately 3 degrees of alignment error.4

We were involved with the development of the digital system Callisto Eye (Carl Zeiss Meditec AG, Germany) for several years. It allows not only precise positioning of the toric IOL at the end of surgery, but also improves the flow of these patients in the surgical setting. Meanwhile, there are also similar systems from other manufacturers.

Comparing digital and manual methods, Elhofi et al. found less postoperative deviation from targeted induced astigmatism and misalignment of the toric IOL with a digital vs. manual technique.5 However, Montes de Oca et al. reported that alignment results when using a manual technique to guide femtosecond laser marks compared

with a three-dimensional computer-guided visualization system were similar in patients receiving toric IOLs.6

Total cataract refractive suites with image-guided systems have been developed to increase accuracy and efficiency. Data are captured before surgery in the clinical area and transferred automatically to the surgical stations to potentially reduce errors. Systems use these data to size the capsulorrhexis, locate the incisions, and orient the IOL.

SURGICAL PEARLSTo ensure optimal postoperative results with toric IOLs, it is important to remove all viscoelastic from the capsular bag and from behind the IOL.

Intraoperative aberrometry has been used to guide implantation. The pseudophakic calculation is used for alignment and residual error. However, to date, there is little peer-reviewed literature about this technique. Factors such as pressure from the lid speculum, hydration of the incisions during surgery as well as an unphysiological tear film during surgery may result in errors of these measurements.

Huelle et al. reported that refraction with intraoperative aberrometry in aphakic eyes seems to be reliable when the anterior chamber is stable and pressurized.7 In addition, Woodcock et al. stated that more eyes had refractive astigmatism within 0.50 D after surgery.8

CONCLUSIONOphthalmologists need to improve the way they approach toric IOL implantation. An array of improved manual and automated tools can help surgeons optimize refractive outcomes from toric IOLs.

REFERENCES1. Koch DD, et al. Contribution of posterior corneal astigmatism to total corneal astigmatism. J Cataract Refract Surg. 2012; 38:2080-2087.2. Viestenz A, et al. Evaluating the eye’s rotational stability during standard photography: effect on determining the axial orientation of toric intraocular lenses. J Cataract Refract Surg. 2005; 31:557-561.3. Viestenz A, et al. Impact of the eye’s cyclorotation on axial orientation analysis of toric intraocular lenses: recommendations for an optimized evaluation of rotational stability of toric IOLs. Klin Monatsbl Augenheilkd. 2006; 223:134-140. 4. Popp N, et al. Evaluation of 4 corneal astigmatic marking methods. J Cataract Refract Surg. 2012;38:2094-2099.5. Elhofi AH, et al. Comparison between digital and manual marking for toric intraocular lenses: a randomized trial. Abdulrahman. K, ed. Medicine. 2015;94: e1618.6. Montes de Oca I, et al. Accuracy of toric intraocular lens axis alignment using a 3-dimensional computer-guided visualization system. J Cataract Refract Surg. 2016; 42:550-555.7. Huelle JO, et al. First clinical results on the feasibility, quality and reproducibility of aberrometry-based intraoperative refraction during cataract surgery. Br J Ophthalmol. 2014; 98:1484-1491. 8. Woodcock M, et al. Intraoperative aberrometry versus standard preoperative biometry and a toric IOL calculator for bilateral toric IOL implantation with a femtosecond laser: One-month results. J Cataract Refract Surg. 2016; 42:817-825.

Dr. Findl is chief of the Department of Ophthalmology, Vienna Hanusch Hospital, and founder of the Vienna Institute for Research in Ocular Surgery (VIROS), Austria. He may be reached at [email protected]. Dr. Findl is a scientific advisor for Carl Zeiss Meditec AG.

“Practice Pearl: Orientation of a toric intraocular lens is critical to its refractive outcome. New technological developments such as digital tracking techniques in the microscope allow precise positioning and enhance workflow in the surgical setting.”

Figure 1. The importance of stability of toric IOLs and effect of rotation on vision

Figure 2. Low-tech vs high-tech marking tools

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In a 62-year-old patient who had toric IOL implantation elsewhere to correct 2.5 D of corneal astigmatism, the IOL was misaligned 15 degrees and the patient had an eccentric capsulorrhexis. We realigned the IOL at 111 degrees, which resulted in UDVA of 20/25 (0.8). However, in time the IOL tilted, resulting in -1.75 D of refractive astigmatism because of the eccentric capsulorrhexis. We performed additional laser refractive surgery, and the patient was satisfied with UDVA of 20/20 (1.0).

Furthermore, surgeons also can address residual astigmatism by creating arcuate incisions with a femtosecond laser.

CONCLUSIONOvercorrection can be a significant problem with toric IOLs. To prevent this, surgeons need to know their surgically induced astigmatism, use a second-generation IOL calculator that includes posterior astigmatism and effective lens position, and recognize that surgically induced astigmatism and posterior astigmatism depend on the amount of anterior astigmatism.

When managing residual astigmatism, surgeons need to identify the origin. If the IOL is misaligned, one should determine whether rotation would be beneficial. For errors greater than 1.25 D, an IOL exchange usually is preferred.

REFERENCES1. Ofir S, et al. Surgically induced astigmatism assessment: comparison between three corneal measuring devices. J Refract Surg. 2015; 31:244-247.2. Koch DD, et al. Contribution of posterior corneal astigmatism to total corneal astigmatism. J Cataract Refract Surg. 2012; 38:2080-2087.3. Norrby S. Sources of error in intraocular lens power calculation. J Cataract Refract Surg. 2008; 34:368-376.4. Visser N , et al. Toric vs aspherical control intraocular lenses in patients with cataract and corneal astigmatism: a randomized clinical trial. JAMA Ophthalmol. 2014; 132:1462-1468.5. Visser N, et al. Toric intraocular lenses: historical overview, patient selection, IOL calculation, surgical techniques, clinical outcomes, and complications. J Cataract Refract Surg. 2013; 39:624-637.

Dr. Nuijts is professor of cornea and refractive surgery at the University Eye Clinic, Maastricht University Medical Center, Maastricht, The Netherlands He may be reached at [email protected]. Dr. Visser is a cornea fellow at the University Eye Clinic, Maastricht University Medical Center. She may be reached at [email protected]. Dr. Nuijts is a speaker for Abbott Medical Optics, AcuFocus, Alcon, Asico, Bausch + Lomb, Gebauer, Human Optics, Ophtec, and PhysIOL. He is a consultant and receives other income from Alcon (lecturer) and Asico (patent), and he is a consultant for Bausch + Lomb and TheaPharma. Dr. Visser has no financial disclosures.

To achieve success with toric intraocular lenses (IOLs), surgeons not only need to understand the sources of residual astigmatism, but know how to manage residual astigmatism.

SOURCES OF RESIDUAL ASTIGMATISMResidual astigmatism results from a number of factors, such as preoperative morbidity, errors in preoperative measurements, surgically induced astigmatism, calculation inaccuracies, and marking errors and misalignment.1-3

In our research, we found that 70% of patients receiving toric intraocular lenses (IOLs) had an uncorrected visual acuity of 20/25 or better and 84% were spectacle independent for distance.4 However, 26% of eyes still had more than 1.0 D and 54% more than 0.5 D of residual astigmatism. In an overview that we published, 53% of eyes had at least 0.5 D of residual astigmatism.5

Examining with-the-rule astigmatism in our toric IOL database of more than 300 eyes, we found that the higher the power implanted, the more overcorrection occurred. However, with against-the-rule astigmatism, we saw less undercorrection.

MANAGING RESIDUAL ASTIGMATISMWhen we looked at misalignment in our database, approximately 92% of eyes were within 5 degrees and 4% within 5 and 10 degrees. Four percent had more than 10 degrees of misalignment. Only 2% were realigned; a lens exchange was performed in 1% and a laser enhancement in 1%.

If realignment of the toric IOL is necessary to treat residual astigmatism, software programs, such as the Berdahl and Hardten calculator (http://astigmatismfix.com), provide the ideal toric IOL position.

A 21-year-old patient who had juvenile cataract had a good outcome after implantation of a toric IOL in her right eye. However, in her left eye an alignment axis of 90 degrees was planned, but the lens was misaligned 10 degrees at 80 degrees, resulting in residual astigmatism. Her uncorrected distance visual acuity (UDVA) was 20/50 (0.40) and corrected distance visual acuity (CDVA) was 0.25/ -1.75 x 55 degrees: 20/22 (0.9-) (Figure 1). We entered the patient’s results into the Berdahl and Hardten calculator; when we placed the IOL in the suggested position, the patient had a good outcome (UDVA: 20/26 [0.75]; CDVA [S -0.50]: 20/20).

IOL exchange is another option. In a case of stellate cataract in a 38-year-old patient with 1.8 D of with-the-rule astigmatism, a 22.5-D IOL was advised for an expected residual cylinder of -0.02 D. Postoperatively, residual refraction was S +1.25 D, with little residual refractive astigmatism, and the axis was in a good position. When we exchanged the IOL for a higher sphere power lens, the patient achieved UDVA of 20/13 (1.5) (Figure 2).

Laser enhancements also can correct residual astigmatism.

Figure 1. Data for patient with toric IOL that required repositioning.

Managing Postoperative Error With Toric IOLs: Pearls for SuccessTreating residual astigmatism is a critical part of achieving patient satisfaction.

RUDY M.M.A. NUIJTS, MD, PHD, AND NIENKE VISSER, MD

Figure 2. Berdahl and Hardten calculator recommendations for patient with hyperopic surprise after implantation of a toric IOL.


Conclusions

This evidence-based information can help surgeons refine their preoperative, intraoperative, and postoperative cataract surgery protocols to manage astigmatism more precisely.

Astigmatism is a common condition. An estimated 47% of the population between the ages of 8 and 70 have astigmatism of 0.75 D or greater and 24% of cases are bilateral. In addition, more than one-third have astigmatism that exceeds 1.0 D.1

In diagnosing astigmatism, cataract surgeons need to focus principally on the cornea, rather than internal astigmatism. If lenticular astigmatism is treated with a toric intraocular lens (IOL), astigmatism will be induced. Lenticular astigmatism is corrected by removal of the natural lens.

If discrepancies occur during preoperative assessments (i.e., optical biometry, topography, examination of patient’s glasses, and others that are necessary), the surgeon should repeat the measurements.

Posterior astigmatism is an important consideration. Researchers have reported that if it is not taken into account, total corneal astigmatism may be calculated incorrectly.2,3 In more than 700 corneas, Koch et al. found that the anterior curvature was steep vertically in more than half and the posterior curvature was steep vertically in approximately 87%.2

To achieve optimal outcomes, surgeons need to optimize their lens constants and calculate their surgically induced astigmatism.4 A number of additional factors may result in residual astigmatism, such as cyclorotation and IOL rotation.

Intraoperatively, surgeons can use either manual or digital marking

techniques to improve orientation of the IOL. Some researchers have reported that digital methods are more effective, however, others have stated that results were similar.5,6

When correcting astigmatism with a toric IOL, European surgeons can choose from among several alternatives. A few of those options include toric lenses manufactured by Abbott Medical Optics (AMO), Alcon, and Rayner.

With the AMO Tecnis Toric IOL, 94% of eyes had 0.50 or less residual refractive cylinder.7 Monocular corrected distance visual acuity was 20/20 or better in 88%.7 In addition, the IOL has shown rotational stability; the mean axis change was 2.74 degrees during a period of 6 months.8

With the Alcon AcrySof IQ IOL, 94% achieved uncorrected distance vision of 20/40 or better, and more than 81% were within 5 degrees of the intended axis.9,10

In patients in whom the Rayner T-Flex Aspheric Toric IOL was implanted, 96% of eyes had 20/40 uncorrected distance vision or better and 52% had 20/25 or better 3 months after surgery. More than 92% had IOL rotation less than 10 degrees.11

Intraoperative aberrometry has been used to guide IOL implantation, however, additional research is necessary.

Despite a surgeon’s best efforts, residual astigmatism may remain after surgery. To manage postoperative error, surgeons need to identify the cause.

R e s i d u a l astigmatism may be treated with laser vision correction or arcuate incisions created with a femtosecond laser. If realignment of the toric IOL is necessary, software programs such as the Berdahl and Hardten calculator (http://astigmatismfix.com/) provide the ideal toric IOL position. If residual error exceeds 1.25 D, IOL exchange often is performed.

REFERENCES1. Ferrer-Blasto T. Prevalence of corneal astigmatism before cataract surgery. J Cataract Refract Surg. 2009; 35:70-75. 2. Koch DD, et al. Contribution of posterior corneal astigmatism to total corneal astigmatism. J Cataract Refract Surg. 2012; 38:2080-2087.3. Bregnhøj JF, et al. Refractive, anterior corneal and internal astigmatism in the pseudophakic eye. Acta Ophthalmol. 2015; 93:33-40.4. Holladay JT, Moran JR, Kezirian GM. Analysis of aggregate surgically induced refractive change, prediction error, and intraocular astigmatism. J Cataract Refract Surg. 2001; 27:61-79.5. Elhofi AH, et al. Comparison between digital and manual marking for toric intraocular lenses: a randomized trial. Abdulrahman. K, ed. Medicine. 2015;94: e1618.6. Montes de Oca I, et al. Accuracy of toric intraocular lens axis alignment using a 3-dimensional computer-guided visualization system. J Cataract Refract Surg. 2016; 42:550-555.7. Black D. Efficacy of hydrophobic acrylic toric IOL to correct astigmatism in cataract patients. Presented at 2015 ASCRS-ASOA Symposium and Congress.8. TECNIS® Toric 1-Piece IOL [package insert]. Santa Ana, Calif.: Abbott Medical Optics Inc.9. AcrySof® IQ Toric IOL Directions for Use.10. U.S. Food and Drug Administration. Summary of Safety and Effectiveness Data P930014/S15, AcrySof® Toric IOL. http://www. accessdata.fda.gov/cdrh_docs/pdf/P930014S015b.pdf. 11. Alberdi R, et al. Rotational stability and visual quality in eyes with Rayner toric intraocular lens implantation. J Refract Surg. 2012; 28:696-700.

AMO Tecnis Toric IOL

Alcon AcrySof IQ IOL

Rayner T-Flex Aspheric Toric IOL

Supported by an unrestricted educational grant from Alcon, Rayner & Abbott

Supplement Dec 2016/Jan 2017

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surgical management of astigmatism for cataract patients ......astigmatism. if surgeons treat...

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