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| REVIEW ARTICLE |
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| Ahead of print publication |
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Toric intraocular lens: A literature review
Mithun Thulasidas1, Aishwarya Kadam2
1 Cataract and Glaucoma Services, Sankara Eye Hospital, Coimbatore, Tamil Nadu, India
2 Sankara Eye Hospital, Coimbatore, Tamil Nadu, India
| Date of Submission | 08-May-2021 |
| Date of Acceptance | 07-Oct-2021 |
| Date of Web Publication | 10-Dec-2021 |
Correspondence Address:
Mithun Thulasidas,
Cataract and Glaucoma Services, Sankara Eye Hospital, Sathy Road, Sivanandapuram, Coimbatore - 641035, Tamil Nadu
India
 Source of Support: None, Conflict of Interest: None DOI: 10.4103/tjo.tjo_43_21
Toric intraocular lenses (IOLs) are universally recommended in cataract cases with preoperative corneal astigmatism ≥1.5 D. An optimal surgical outcome depends on careful patient selection, complete preoperative evaluation, accurate IOL power calculation, precise marking of the axis, meticulous intraoperative approach, and methodical postoperative care. Understanding the importance of posterior corneal astigmatism, surgically induced astigmatism, and effective lens position in IOL power calculation and newer techniques to measure them directly have resulted in better postoperative refractive outcomes. We present a brief overview of toric IOLs along with the preoperative evaluation, IOL power calculation, different marking methods, intraoperative approach, and postoperative outcomes. Functional and anatomical outcomes, including uncorrected visual acuity, residual refractive astigmatism, and postoperative IOL misalignment, which have been reported for both toric IOLs and multifocal toric IOLs, are reviewed.
Keywords: Astigmatism, intraocular lens misalignment, multifocal toric intraocular lens, toric intraocular lens
| Introduction | |  |
The current generation of cataract surgery has become a refractive procedure, and astigmatism management became an essential part of cataract surgery. Studies have shown that a number of intraocular lenses (IOLs), especially multifocal or aspheric designs, are ineffective if residual astigmatism ≥1.0 diopter (D) is present after surgery.[1] Shimizu et al. first introduced toric IOLs in the early 1990s as three-piece nonfoldable polymethyl methacrylate implants, which can be inserted through a 5.7 mm incision.[2] Since then, toric IOLs are the most effective way of correcting astigmatism during cataract surgery due to their increased predictability and improved safety.[3],[4],[5],[6],[7],[8],[9],[10],[11],[12],[13],[14],[15],[16],[17],[18],[19],[20],[21],[22],[23],[24],[25],[26],[27],[28],[29],[30],[31],[32],[33],[34],[35],[36],[37],[38],[39],[40] About 33% of the cases undergoing cataract surgery are found to have preoperative corneal astigmatism of ≥1.0 D, with 22% having >1.5 D of astigmatism and 8% having >2.0 D of astigmatism.[9],[41],[42] Although the first models of toric IOL had high incidences of postoperative rotation, advances in the material and design of IOLs have resulted in improved rotational stability and precise visual outcomes.[12],[17],[19],[20],[27],[28],[30],[31],[32],[35]
This review provides a brief overview of toric IOLs along with the preoperative evaluation, IOL power calculation, different marking methods, intraoperative approach, postoperative outcomes, and possible complications. The literature search was performed in MEDLINE and Embase using “toric,” “toric intraocular lenses,” and “cataract surgery,” as keywords. The relevant references cited in those articles were also searched.
| Preoperative Evaluation | | |
Getting to know the patient
It is essential to ascertain the visual needs and desires of the astigmatic patients and know their expectations and past ocular and medical history to explore the potential possibilities of their ocular future. The patient should undergo a complete comprehensive ocular examination to rule out any ocular comorbidities that may interfere with the postoperative outcomes. It is difficult to obtain accurate measurements of presenting astigmatism in patients with chronic dry eye disease, narrow palpebral fissures, or deep-set eyes. It is, therefore, vital to treat existing ocular surface disease and normalize the cornea before surgical evaluation. In addition to the general complications of cataract surgery, patients should be warned of a possible refractive surprise. IOL misalignment may occur, which may warrant a secondary procedure
Currently, toric IOLs are available in cylinder powers of 1.0 D to 12.0 D (0.67 D to 8.0 D at the corneal plane) and are intended to correct preexisting regular corneal astigmatism ranging from 0.75 D to 8.0 D.[3],[4],[5],[6],[7],[8],[9],[10],[11],[12],[13],[14],[15],[16],[17],[18],[19],[20],[21],[22],[23],[24],[25],[26],[27],[35],[36] Extended series and customized toric IOLs to correct higher astigmatism are also available.[3],[27],[36],[43] Toric IOLs are universally recommended in cases with significant preoperative anterior corneal astigmatism ≥1.5 D.[44] However, in patients undergoing premium IOL implantation (multifocal IOLs) with greater visual demand, a toric multifocal IOL can be preferred for low astigmatism (≥1.0 D).[1] [Table 1] and [Table 2] show the currently available monofocal and multifocal toric IOLs.
Various studies have evaluated the effectiveness of different materials and haptic designs on the stability of IOL.[45],[46],[47],[48],[49] Draschl et al., in their study, found that the hydrophobic IOL was rotationally more stable than the hydrophilic IOL due to the tackiness of the hydrophobic material.[45] However, a recent study by Haripriya et al. observed that the hydrophilic toric IOL had comparable rates of postoperative misalignment and surgical repositioning with the hydrophobic IOL, though the rate of repositioning was nonsignificantly lower with hydrophobic IOL.[46] The advantage of a plate haptic design over open-loop haptic design of toric IOLs is still a question of debate. Patel et al. observed that plate haptic IOLs show greater rotational stability than loop haptics.[47] Nevertheless, studies by Scialdone et al. and Mihaltz et al. could not confirm this finding.[48],[49]
Contraindications for toric intraocular lens implantation
Those with irregular astigmatism caused by forme fruste keratoconus, previous trauma or surgery, dry eye syndrome, epithelial basement membrane dystrophy, Salzmann nodules, pterygium, corneal scars, or other corneal diseases are not ideal candidates. It may be better to treat them initially to regularize the corneal contour prior to astigmatic correction. However, the amount of astigmatism may be reduced with a decreased dependence on spectacles or contact lenses, and such cases may be considered for toric IOLs after proper counseling.[43],[50] Corneal tomography helps determine the effect of these conditions on astigmatism, and if the astigmatism is shown to be stable over the serial examinations, separated by at least 3–4 weeks, a toric IOL can be implanted with the help of accurate keratometry and IOL power calculation. More than one imaging modality should be used to identify inconsistent measurements, which, if present, contraindicate the use of a toric IOL.
In some cases of forme fruste keratoconus, where the manifest axis and magnitude match the corneal axis and magnitude, a toric IOL can be considered. However, those with a decentered apex, radial axis skewing, and significant superior-inferior astigmatic asymmetry are not ideal candidates.
If the irregular corneal tomographic changes are limited to the periphery with a relatively symmetric and stable central cornea (3–5 mm) as in peripheral corneal scars and mild forme fruste keratoconus, a toric IOL can be used. Nevertheless, a toric IOL should be avoided in keratoconus cases in which the patient prefers to wear a rigid contact lens after surgery as the rigid contact lens may effectively unmask the toric IOL power.
Zonular instability and posterior capsular dehiscence is an absolute contraindication as a stable capsular bag-IOL complex is essential for the rotational stability of the IOL.[51]
Insufficient pupillary dilatation is also a relative contraindication, as it may hamper the visualization of the alignment marks, which are located in the periphery of the IOL.[51]
Preoperative investigations
It is essential to evaluate and measure the ocular and optical properties of the patient's eyes, to customize the surgical approach, and to choose a specific IOL. The vital preoperative investigations include corneal tomography for corneal curvature and astigmatism, optical biometry for IOL power calculation, tear film evaluation (meibography) for dry eye, specular microscopy for corneal endothelium status, macular optical coherence tomography (OCT) for underlying retinal conditions, and visual field testing with OCT retinal nerve fiber analysis for manifest glaucoma patients and glaucoma suspects.
The amount, type, and axis of astigmatism are critical points to be considered and can be collected with the topographic evaluation of the cornea. The use of rigid and soft contact lenses should be stopped for at least 3 weeks and 1 week, respectively, before topography.[52] Multiple instruments based on different principles may be used for keratometry estimation, such as manual and automated keratometers, Placido-based corneal topographers, scanning-slit based tomographers, Scheimpflug imaging systems, wavefront aberrometers, color light-emitting diode (LED)-based systems, and anterior segment-OCT (AS-OCT).[53] Taking multiple measurements and employing at least two separate devices based on different principles increases the accuracy of keratometry estimation.[54],[55],[56] Candidates with a similar steep corneal axis on different devices are ideal for toric IOLs. The visual outcomes may not be satisfactory when a considerable difference in both the axis and magnitude of astigmatism is observed on different devices. The measurements should be rechecked and validated if astigmatism is >2.5 D, corneal power is <41.0 D or >47.0 D, or the corneal diameter is <10.75 mm or >13.0 mm.[57]
Posterior corneal astigmatism must be considered while calculating total corneal astigmatism to avoid errors in IOL power calculation. The posterior cornea acts as a minus lens, and the astigmatism is generally against-the-rule (ATR) and constant over time.[44] Furthermore, the anterior corneal astigmatism shifts from with-the-rule (WTR) in the younger age group to ATR in the elderly age group.[58],[59],[60] Depending merely on the anterior corneal curvature measurements could result in residual astigmatism after toric IOL implantation, overcorrecting by a factor of 1.38 in eyes having WTR astigmatism and undercorrecting by a factor of 0.65 in the eyes with ATR astigmatism.[60]
The keratometers and placido-based corneal topography do not measure the posterior corneal curvature, assume a fixed ratio between the anterior and posterior curvature, and are more prone to errors in keratometry estimation.[60] The slit scanning systems, Scheimpflug imaging systems, color-LED topography, and AS-OCT measure both the anterior and posterior corneal curvature and are found to be more accurate. Moreover, they are repeatable.[55],[56],[61],[62]
The image-guided systems such as VERION® and CALLISTO® Eye help in preoperative planning of the location and size of the surgical incisions, capsulorhexis, and positioning of the IOL. The CALLISTO® system also aids in planning the position of limbal relaxing incisions. VERION® unit also helps the surgeons to optimize the incision locations and toric IOL power as per their surgically induced astigmatism (SIA). Furthermore, in femtosecond laser-assisted cataract surgery (FLACS) cases, they assist in determining the position and length of arcuate incisions.[44]
The iTrace® System (Tracey Technologies, Houston, Tx) combines Placido disc corneal topography with ray tracing aberrometry and aids in preoperative planning, decision-making, and postoperative assessment in cases undergoing toric IOL implantation.[63] It gives the corneal curvature and power, measures angle alpha, and calculates the corneal, internal, and total higher-order aberrations. Moreover, the iTrace® system includes an in-built toric IOL planner, which calculates the IOL power and provides the axis of placement after considering SIA. Preoperative reference axis marking accuracy can be evaluated using the Integrated Zaldivar toric caliper and toric calculator. Furthermore, the postoperative toric IOL enhancement software provides the degree of misalignment of the IOL and the direction as well as the magnitude of the required postoperative rotation to achieve optimal results.[44]
| Intraocular lens power calculation | | |
Optical biometry is the current gold standard for IOL power calculation. Optical biometers are based on either of the three principles: partial coherence interferometry, optical low-coherence refractometry, or OCT. The main advantage of optical over ultrasound biometry is its improved accuracy by avoiding artefacts due to corneal compression, which may lead to an overestimation of the IOL power.[53],[64] Immersion ultrasound may also yield accurate results, but it is a time-consuming technique and needs an experienced operator.[65] In addition, optical biometry avoids the risk of infection and evaluates other parameters essential for newer generation formulas, such as white-to-white diameter and lens thickness. If surgery is planned in only one eye, the refractive status of the fellow eye should also be taken into account. Various studies have shown that visual acuity is superior when the residual astigmatism is ATR than WTR or oblique.[53],[66],[67]
Multiple formulae and toric calculators are available for IOL power calculation, determining the magnitude of the toric IOL and the axis of placement. An ideal formula should consider the SIA, the posterior corneal curvature, and the effective lens position (ELP). The operating surgeon must determine his SIA using standard astigmatism vector analysis or online tools.[68] ELP is defined as the effective distance between the anterior surface of the cornea and the lens plane, given that the lens was infinitely thin.[69] The ELP is considered to be the major limiting factor for refractive predictability postsurgery, as the accuracy of axial length (AL) and corneal power measurements has been widely demonstrated.[70] Improvements in IOL power calculations over the past three decades are the outcome of improved predictability of the ELP variable.
The Baylor nomogram was published first, which incorporates the posterior corneal curvature in its measurements.[60] Later, Goggin et al. developed coefficients of adjustment to adjust the anterior keratometric power while also taking into account the spherical power of the IOL.[71] The Abulafia–Koch formula introduced by Abulafia et al. incorporates a mathematical regression to estimate the effect of the posterior corneal surface.[72]
The AcrySof® online toric calculator and the iTrace® calculator employ a fixed ratio to convert IOL power to corneal plane power. This results in undercorrection of astigmatism in eyes with long AL and overcorrection in eyes with short AL. The spherical power of the IOL affects the cylindrical power at the corneal plane due to the difference in vergence of the rays. This gives rise to errors in IOLs, especially with high cylindrical powers, and when the patient has high hyperopia.[73],[74] On the other hand, the Tecnis® toric calculator incorporates the anterior chamber depth based on the AL and keratometry values, and the Holladay toric calculator considers the predicted ELP into account.[75] The Barrett toric calculator incorporates the ELP as well as the posterior corneal astigmatism. It was recently updated to introduce keratometry values from different instruments and calculate mean or median keratometry values, which further improve the results. It has better predictability than the other calculators and nomograms.[76],[77],[78] Moreover, the calculator also has the 'Barrett True K Toric Calculator', a customized method for patients who have previously undergone refractive surgery. The revised AcrySof® toric calculator incorporates the Barrett toric algorithm, and the Tecnis® calculator received FDA approval in 2016 to include posterior corneal astigmatism compensation.[44] Other newer toric calculators include the emmetropia verifying optical (EVO) toric formula and the Panacea software, both of which are yet to be tested for accuracy.[53]
Intraoperative wavefront aberrometry estimates the toric IOL power and axis of placement based on the aphakic refraction, especially in eyes with a history of refractive surgery.[44] Yesilirmak et al. in their retrospective study observed that the outcomes of optiwave refractive analysis (ORA) in postrefractive surgery (laser-assisted in situ keratomileusis) eyes were more accurate than those obtained by the standard Sanders-Retzlaff-Kraff-Theoretical (SRK-T) formula and the online American Society of Cataract and Refractive Surgery calculator.[79]
| Marking Methods | | |
The axis of the toric IOL must be aligned precisely with the axis of the corneal cylinder for optimal outcomes, which needs exact corneal marking. Different methods have been described to place the axis marks and may be categorized as manual techniques, image-guided systems, intraoperative aberrometry, and iris-detection methods.
Manual techniques
The three-step method is commonly used for toric IOL axis alignment, which involves the preoperative marking of the reference axis, intraoperative alignment of the reference marks using the degree gauge of the fixation ring, and intraoperative marking of the target axis.[80] The reference marks are usually placed in the 3 o', 6 o', and 9 o'clock positions to improve predictability, though some surgeons may prefer to mark only the horizontal 3 o' and 9 o' clock positions. A marking pen or devices such as a rotational thin slit-beam, Nuijts-Solomon bubble marker, weighted thread, or a pendulum marker may be used to perform the marking. This is followed by the intraoperative alignment of these reference marks with the degree gauge of the fixation ring, and the target axis is then marked with a corneal meridian marker intraoperatively. One-step marking may be performed using different devices such as Neuhann one-step toric bubble marker, tonometer marker, electronic toric markers, or Geuder-Gerten Pendulum marker.[81],[82]
The patient should be sitting erect with the back resting against a wall and a straight-ahead gaze while marking the axis to avoid cyclotorsion and inadvertent errors. Topical anesthesia should be administered before marking. However, the cornea should be dry before starting marking. These marking methods are associated with a significant learning curve and may show intersurgeon variability.
In order to eliminate the ink-associated problems with manual marking, Osher ThermoDot® marker (Beaver-Visitec International, BVI, Waltham, Mass.) has been introduced, which uses a bipolar cautery to create an ink-free, precise reference mark during surgery.[44] A 26-gauge needle stained with sterile blue ink can also be used to create anterior stromal puncture and mark the reference axis without smudging.[83]
Image-guided techniques
Osher introduced the concept of iris-fingerprinting in 2010, wherein the iris crypts and brush fields were used as landmarks to place the axis marks, which formed the basis for the development of various image-guided systems, like CALLISTO® Eye and Z align, VERION® system, and the TrueVision® 3D Surgical System.[84],[85],[86],[87]
The image-guided systems capture a preoperative reference image followed by intraoperative registration of the image wherein the limbal landmarks are used to match the two images. A graphic overlay is then superimposed on the surgical field along the target axis, which provides a guide for toric IOL alignment. The image-guided systems also aid in the placement of corneal incisions, the capsulorhexis size, and IOL centration.[44]
Mayer et al. evaluated the efficacy of the CALLISTO® Eye system and compared the results with those achieved using a manual marking technique. They found better IOL alignment and lower deviation from the target-induced astigmatism in the CALLISTO® Eye group than the manual marking group. The mean toric IOL misalignment was significantly lower in the digital group than in the manual group (2.0 ± 1.86° versus 3.4 ± 2.37°). The mean deviation from the target-induced astigmatism was significantly lower in the digital group (0.10 ± 0.08 D versus 0.22 ± 0.14 D). They also found the preoperative procedure and IOL alignment to be faster in the image-guided group.[88]
However, registration may be difficult in highly uncooperative patients and those with deep-set eyes or narrow palpebral apertures. Conjunctival chemosis, ballooning, and bleeding may interfere with intraoperative image registration. Furthermore, the high cost of these devices may limit widespread usage.
Intraoperative aberrometry
Intraoperative aberrometry-based devices like ORA® (WaveTec Vision Systems Inc., CA, USA) and Holos IntraOp® (Clarity Medical Systems, CA, USA) assess the phakic, aphakic, or pseudophakic refraction to give feedback for toric IOL alignment.
ORA® performs a real-time assessment of IOL power and the axis using the aphakic refraction, based on the principle of Talbot-Moire interferometry. It employs a modified refractive vergence formula for accurate IOL power calculation even in complicated postrefractive surgery cases. In addition, it helps achieve minimum residual astigmatism by providing the direction and magnitude of rotation. VerifEye® has been included in ORA with a fast-imaging processor that verifies the stability of the system before taking measurements. Holos IntraOp® also provides continuous real-time refraction throughout the surgery and helps in refining the axis of the toric IOL.[44]
Intraoperative aberrometry-based methods are 2.4 times more likely to have ≤0.50 D residual astigmatism than other standard methods (standard preoperative biometry, conventional IOL power formulas, the Acrysof® toric IOL calculator, and ink marking for positioning).[54] The anterior chamber should be uniformly filled with cohesive ocular viscoelastic devices (OVD) to maintain the intraocular pressure, and a uniform fundal glow is confirmed before taking the measurements. Intraoperative corneal edema, presence of air bubbles, clumps of dispersive OVD in the anterior chamber, or inadequate intraocular pressure and multiple radial keratotomy cuts may affect the accuracy.[89] However, the device needs a significant area or space, as it is mounted directly onto the bottom of the surgical microscope. Furthermore, the high cost involved may limit its use.
Iris-detection method
LENSAR® uses IntelliAxis Refractive Capsulorhexis to produce notches in the anterior capsulorhexis that indicate the steep axis. This iris-fingerprinting technology combined with corneal shape analysis ensures the steep corneal axis by the femtosecond laser in a way that compensates for cyclorotation.[57]
A newer smartphone application, named toriCAM®, has been shown to reduce the reference marking error to 1.28° (67%), compared to the freehand or slit-lamp-assisted marking.[90]
| Intraoperative Approach | | |
The target axis is marked at the beginning of the cataract surgery, in case of manual marking, after aligning the preoperatively placed reference marks with the degree gauge of the fixation ring. The clear corneal incisions, size, and centration of capsulorhexis, as well as IOL centration play vital roles in achieving optimal outcomes. Self-sealing clear corneal incisions ≤2.8 mm that are astigmatically neutral or induce minimal astigmatism should be created. Image-guided systems compensate for cyclotorsion and aid in the accurate placement of incisions. A continuous circular capsulorhexis, which is of adequate size (5–5.5 mm) and well-centered, provides an optimum IOL coverage and ensures the stability of the IOL postoperatively. FLACS may further improve the outcomes by providing a precise capsulotomy. Moreover, fewer higher-order aberrations were observed with FLACS than conventional phacoemulsification with toric IOL implantation.[91]
It is essential to center the IOL along the coaxially sighted corneal light reflex, as represented by the first Purkinje image when the patient is fixating on the microscope light. This provides IOL stability and prevents dysphotopsia. The final IOL alignment should be done after removing the OVD and hydrating the wounds. The IOL should be placed about 3°–5° anticlockwise of the final desired IOL position during alignment, as a majority of the open-loop IOLs can be rotated only clockwise, and a rerotation may be required if the IOL rotates clockwise of the target axis during these maneuvers. In eyes with high AL (>24 mm) and those with significant postoperative rotation of IOL, insertion of capsular tension ring may provide better rotational stability by increasing the posterior capsule-IOL contact.[92] It should be kept in mind that posterior capsular rent can lead to IOL tilt and rotation if implanted in the bag and is a relative contraindication.
| Postoperative Outcomes | | |
[Table 3] shows the overview of functional and anatomical outcomes reported in the literature after toric IOL implantation. | Table 3: Overview of functional and anatomical outcomes reported in the literature after different types of toric intraocular lens implantation
Click here to view |
Postoperative residual refractive astigmatism
Patients having a toric IOL were more likely to achieve residual refractive astigmatism <0.5 D at six months after surgery. Study outcomes showed a mean postoperative residual astigmatism ranging between -0.71 D and -0.02 D.[10],[11],[25],[28],[37],[38] A lower degree of mean residual astigmatism is observed with toric IOLs as compared to non-toric IOLs with or without limbal relaxing incisions.[9],[14],[16] Toric multifocal IOLs showed residual astigmatism <0.50 D in 80%–98% of cases.[30],[35],[40]
Postoperative uncorrected distance visual acuity
An uncorrected distance visual acuity (UDVA) of 20/40 or better is achieved in 70%–100% of cases receiving toric IOL implantation.[3],[4],[5],[6],[7],[8],[9],[10],[11],[12],[13],[14],[15],[16],[17],[18],[19],[20],[21],[22],[23],[24],[25],[26],[27],[28],[29],[30],[31],[32],[33],[34],[35],[36],[37],[38],[39],[40] The higher-order aberrations and contrast sensitivity after toric IOL implantation are similar as compared to nontoric monofocal IOLs.[14] Toric multifocal IOLs demonstrate good functional outcomes with UDVA better than 20/40 in 97% to 100% of patients, uncorrected near visual acuity better than 20/40 in 100% of patients, and spectacle independence in 79% to 100% of patients.[30],[35],[40],[93] However, dysphotopic symptoms such as glare and halos associated with multifocal IOLs may limit the overall patient satisfaction.
Mean vision-related quality of life
Satisfactory vision-related quality has been reported by patients receiving toric IOL implantation, and a mean patient satisfaction score of 9.7 ± 0.47 has been reported in a study assessing the outcomes of Tecnis® toric IOL.[21] Nanavaty et al. collected quality of life data and reported that patients with toric IOL were happier than patients who received limbal relaxing incisions.[28]
Postoperative intraocular lens rotation
One degree of misalignment causes a loss of approximately 3% of the effective cylinder power, and the entire toric effect is lost in cases with 30° of misalignment.[94] Studies found a postoperative IOL rotation of >10° in 0%–7% of eyes with AcrySof® toric IOLs, and maximum rotation occurred within the initial 10 days in the postoperative period in patients with high AL.[3],[4],[5],[6],[7],[8],[9],[10],[11],[12],[13],[14],[15],[16] Studies with Tecnis® toric IOL-implanted cases showed a postoperative rotation of >10° in only 0%–3% eyes.[7],[17],[21],[22],[23],[24],[25],[26]
Rotational stability of the IOL differs with design and material, and better stability has been observed with hydrophobic acrylic lenses. The development of strong adhesions between the IOL and lens capsule in the early postoperative period leads to greater rotational stability. The silicone IOLs have the least rotational stability, though the plate haptic design confers higher stability than conventional three-piece IOLs with polypropylene loop haptics.[95]
Early IOL rotation can be caused by retained OVDs, large capsular bag, small diameter of the haptic, and high AL. The axis of IOL implantation is also associated with postoperative rotation, and a greater incidence of IOL rotation has been observed in with-rule-astigmatism cases with a vertical axis of IOL implantation.[33] Capsulorhexis extension or fibrosis can also cause postoperative rotation.[44]
Realignment of the toric IOL is needed in cases with >10° rotation from the target axis. Rotation <10° changes the manifest refraction by only 0.5 D and usually does not warrant any resurgery.[96] The axis of implanted toric IOL may be assessed at the slit lamp with a rotating slit and rotational gauge. However, the 10° steps on the slit-lamp measuring reticule limit the accuracy of this technique. The online toric outcome analyzer (www.astigmatismfix.com) assists in determining the ideal position of the toric IOL in cases of postoperative malrotation using the patient's postoperative manifest refraction, power, and current axis of the toric IOL.[97] The iTrace® system determines the orientation of the toric IOL based on the internal ocular aberrations. A simple and inexpensive method to measure the toric IOL axis using a camera-enabled cellular phone and (ImageJ) computer software has also been described.[98]
Good results have been observed in cases with early rotation using a long cannula mounted on a balanced salt solution filled syringe to rotate the IOL through the paracentesis incision.[99] Only intraoperative marking is necessary relative to the implanted IOL. This decreases repositioning variability and maximizes outcomes after IOL rerotation. Nevertheless, cases with high residual astigmatism may need an IOL exchange, piggyback IOL implantation, or corneal ablative procedure.[100]
| Conclusion | | |
The majority of the patients receiving toric IOLs do extremely good when careful attention is given to patient selection, preoperative evaluation of astigmatism (considering posterior corneal curvature), IOL power calculation (taking into account SIA and ELP), axis marking, and surgical technique. Evaluation of corneal astigmatism by taking multiple measurements and using at least two separate devices based on different principles gives superior outcomes. The Barrett toric calculator, which includes the posterior corneal astigmatism and ELP, has better predictability than the other calculators and nomograms in toric IOL calculation. Image-guided methods for IOL alignment and newer toric IOL designs with better rotational stabilities have helped achieve more predictable outcomes. Future advancements in technology may further refine the results of toric IOL, with greater IOL stability and more accurate visual outcomes.
Financial support and sponsorship
Nil.
Conflicts of interest
The author declares that there are no conflicts of interests of this paper.
| References | | |
| 1. | Hayashi K, Hayashi H, Nakao F, Hayashi F. Influence of astigmatism on multifocal and monofocal intraocular lenses. Am J Ophthalmol 2000;130:477-82.  |
| 2. | Shimizu K, Misawa A, Suzuki Y. Toric intraocular lenses: Correcting astigmatism while controlling axis shift. J Cataract Refract Surg 1994;20:523-6. |
| 3. | Seth SA, Bansal RK, Ichhpujani P, Seth NG. Comparative evaluation of two toric intraocular lenses for correcting astigmatism in patients undergoing phacoemulsification. Indian J Ophthalmol 2018;66:1423-8. [ PUBMED] [Full text] |
| 4. | Ram J, Singh R, Gupta R, Bhutani G, Gupta PC, Sukhija J. Toric intraocular lens implantation in children with developmental cataract and preexisting corneal astigmatism. Acta Ophthalmol 2017;95:e95-100. |
| 5. | Miyake T, Kamiya K, Amano R, Iida Y, Tsunehiro S, Shimizu K. Long-term clinical outcomes of toric intraocular lens implantation in cataract cases with preexisting astigmatism. J Cataract Refract Surg 2014;40:1654-60. |
| 6. | Cervantes-Coste G, Garcia-Ramirez L, Mendoza-Schuster E, Velasco-Barona C. High-cylinder acrylic toric intraocular lenses: A case series of eyes with cataracts and large amounts of corneal astigmatism. J Refract Surg 2012;28:302-4. |
| 7. | Ferreira TB, Almeida A. Comparison of the visual outcomes and OPD-scan results of AMO Tecnis toric and Alcon Acrysof IQ toric intraocular lenses. J Refract Surg 2012;28:551-5. |
| 8. | Visser N, Ruíz-Mesa R, Pastor F, Bauer NJ, Nuijts RM, Montés-Micó R. Cataract surgery with toric intraocular lens implantation in patients with high corneal astigmatism. J Cataract Refract Surg 2011;37:1403-10. |
| 9. | Holland E, Lane S, Horn JD, Ernest P, Arleo R, Miller KM. The AcrySof Toric intraocular lens in subjects with cataracts and corneal astigmatism: A randomized, subject-masked, parallel-group, 1-year study. Ophthalmology 2010;117:2104-11. |
| 10. | Kim MH, Chung TY, Chung ES. Long-term efficacy and rotational stability of AcrySof toric intraocular lens implantation in cataract surgery. Korean J Ophthalmol 2010;24:207-12. |
| 11. | Mingo-Botín D, Muñoz-Negrete FJ, Won Kim HR, Morcillo-Laiz R, Rebolleda G, Oblanca N. Comparison of toric intraocular lenses and peripheral corneal relaxing incisions to treat astigmatism during cataract surgery. J Cataract Refract Surg 2010;36:1700-8. |
| 12. | Koshy JJ, Nishi Y, Hirnschall N, Crnej A, Gangwani V, Maurino V, et al. Rotational stability of a single-piece toric acrylic intraocular lens. J Cataract Refract Surg 2010;36:1665-70. |
| 13. | Dardzhikova A, Shah CR, Gimbel HV. Early experience with the AcrySof toric IOL for the correction of astigmatism in cataract surgery. Can J Ophthalmol 2009;44:269-73. |
| 14. | Mendicute J, Irigoyen C, Ruiz M, Illarramendi I, Ferrer-Blasco T, Montés-Micó R. Toric intraocular lens versus opposite clear corneal incisions to correct astigmatism in eyes having cataract surgery. J Cataract Refract Surg 2009;35:451-8. |
| 15. | Bauer NJ, de Vries NE, Webers CA, Hendrikse F, Nuijts RM. Astigmatism management in cataract surgery with the AcrySof toric intraocular lens. J Cataract Refract Surg 2008;34:1483-8. |
| 16. | Mendicute J, Irigoyen C, Aramberri J, Ondarra A, Montés-Micó R. Foldable toric intraocular lens for astigmatism correction in cataract patients. J Cataract Refract Surg 2008;34:601-7. |
| 17. | Jung NY, Lim DH, Hwang SS, Hyun J, Chung TY. Comparison of clinical outcomes of toric intraocular lens, Precizon vs Tecnis: A single center randomized controlled trial. BMC Ophthalmol 2018;18:292. |
| 18. | Thomas BC, Khoramnia R, Auffarth GU, Holzer MP. Clinical outcomes after implantation of a toric intraocular lens with a transitional conic toric surface. Br J Ophthalmol 2018;102:313-6. |
| 19. | Ferreira TB, Berendschot TT, Ribeiro FJ. Clinical outcomes after cataract surgery with a new transitional toric intraocular lens. J Refract Surg 2016;32:452-9. |
| 20. | Vale C, Menezes C, FirminoMachado J, Rodrigues P, Lume M, Tenedório P, et al. Astigmatism management in cataract surgery with precizon(®) toric intraocular lens: A prospective study. Clin Ophthalmol 2016;10:151-9. |
| 21. | Lubiński W, Kaźmierczak B, Gronkowska-Serafin J, Podborączyńska-Jodko K. Clinical outcomes after uncomplicated cataract surgery with implantation of the tecnis toric intraocular lens. J Ophthalmol 2016;2016:3257217. |
| 22. | Waltz KL, Featherstone K, Tsai L, Trentacost D. Clinical outcomes of TECNIS toric intraocular lens implantation after cataract removal in patients with corneal astigmatism. Ophthalmology 2015;122:39-47. |
| 23. | Lam DK, Chow VW, Ye C, Ng PK, Wang Z, Jhanji V. Comparative evaluation of aspheric toric intraocular lens implantation and limbal relaxing incisions in eyes with cataracts and≤3 dioptres of astigmatism. Br J Ophthalmol 2016;100:258-62. |
| 24. | Hirnschall N, Maedel S, Weber M, Findl O. Rotational stability of a single-piece toric acrylic intraocular lens: A pilot study. Am J Ophthalmol 2014;157:405-11.e1. |
| 25. | Mazzini C. Visual and refractive outcomes after cataract surgery with implantation of a new toric intraocular lens. Case Rep Ophthalmol 2013;4:48-56. |
| 26. | Sheppard AL, Wolffsohn JS, Bhatt U, Hoffmann PC, Scheider A, Hütz WW, et al. Clinical outcomes after implantation of a new hydrophobic acrylic toric IOL during routine cataract surgery. J Cataract Refract Surg 2013;39:41-7. |
| 27. | Kim YJ, Wee WR, Kim MK. Efficacy of 4-haptic bitoric intraocular lens implantation in asian patients with cataract and astigmatism. Korean J Ophthalmol 2019;33:36-45. |
| 28. | Nanavaty MA, Bedi KK, Ali S, Holmes M, Rajak S. Toric intraocular lenses versus peripheral corneal relaxing incisions for astigmatism between 0.75 and 2.5 diopters during cataract surgery. Am J Ophthalmol 2017;180:165-77. |
| 29. | Entabi M, Harman F, Lee N, Bloom PA. Injectable 1-piece hydrophilic acrylic toric intraocular lens for cataract surgery: Efficacy and stability. J Cataract Refract Surg 2011;37:235-40. |
| 30. | Ribeiro FJ, Ferreira TB. Comparison of visual and refractive outcomes of 2 trifocal intraocular lenses. J Cataract Refract Surg 2020;46:694-9. |
| 31. | Poyales F, Garzon N. Comparison of 3-month visual outcomes of a spherical and a toric trifocal intraocular lens. J Cataract Refract Surg 2019;45:135-45. |
| 32. | Poyales F, Garzón N, Pizarro D, Cobreces S, Hernández A. Stability and visual outcomes yielded by three intraocular trifocal lenses with same optical zone design but differing material or toricity. Eur J Ophthalmol 2019;29:417-25. |
| 33. | Ruhswurm I, Scholz U, Zehetmayer M, Hanselmayer G, Vass C, Skorpik C. Astigmatism correction with a foldable toric intraocular lens in cataract patients. J Cataract Refract Surg 2000;26:1022-7. |
| 34. | Tassignon MJ, Gobin L, Mathysen D, Van Looveren J. Clinical results after spherotoric intraocular lens implantation using the bag-in-the-lens technique. J Cataract Refract Surg 2011;37:830-4. |
| 35. | Piovella M, Colonval S, Kapp A, Reiter J, Van Cauwenberge F, Alfonso J. Patient outcomes following implantation with a trifocal toric IOL: Twelve-month prospective multicentre study. Eye (Lond) 2019;33:144-53. |
| 36. | De Silva DJ, Ramkissoon YD, Bloom PA. Evaluation of a toric intraocular lens with a Z-haptic. J Cataract Refract Surg 2006;32:1492-8. |
| 37. | Lichtinger A, Sandstedt CA, Schwartz DM, Chayet AS. Correction of astigmatism after cataract surgery using the light adjustable lens: A 1-year follow-up pilot study. J Refract Surg 2011;27:639-42. |
| 38. | Chayet A, Sandstedt C, Chang S, Rhee P, Tsuchiyama B, Grubbs R, et al. Use of the light-adjustable lens to correct astigmatism after cataract surgery. Br J Ophthalmol 2010;94:690-2. |
| 39. | Packer M, Williams JI, Feinerman G, Hope RS. Prospective multicenter clinical trial to evaluate the safety and effectiveness of a new glistening-free one-piece acrylic toric intraocular lens. Clin Ophthalmol 2018;12:1031-9. |
| 40. | Blaylock JF, Hall B. Astigmatic results of a diffractive trifocal toric IOL following intraoperative aberrometry guidance. Clin Ophthalmol 2020;14:4373-8. |
| 41. | Hoffmann PC, Hütz WW. Analysis of biometry and prevalence data for corneal astigmatism in 23,239 eyes. J Cataract Refract Surg 2010;36:1479-85. |
| 42. | Ferrer-Blasco T, Montés-Micó R, Peixoto-de-Matos SC, González-Méijome JM, Cerviño A. Prevalence of corneal astigmatism before cataract surgery. J Cataract Refract Surg 2009;35:70-5. |
| 43. | Luck J. Customized ultra-high-power toric intraocular lens implantation for pellucid marginal degeneration and cataract. J Cataract Refract Surg 2010;36:1235-8. |
| 44. | Kaur M, Shaikh F, Falera R, Titiyal JS. Optimizing outcomes with toric intraocular lenses. Indian J Ophthalmol 2017;65:1301-13. [ PUBMED] [Full text] |
| 45. | Draschl P, Hirnschall N, Luft N, Schuschitz S, Wiesinger J, Rigal K, et al. Rotational stability of 2 intraocular lenses with an identical design and different materials. J Cataract Refract Surg 2017;43:234-8. |
| 46. | Haripriya A, Gk S, Mani I, Chang DF. Comparison of surgical repositioning rates and outcomes for hydrophilic vs hydrophobic single-piece acrylic toric IOLs. J Cataract Refract Surg 2021;47:178-83. |
| 47. | Patel CK, Ormonde S, Rosen PH, Bron AJ. Postoperative intraocular lens rotation: A randomized comparison of plate and loop haptic implants. Ophthalmology 1999;106:2190-5. |
| 48. | Scialdone A, De Gaetano F, Monaco G. Visual performance of 2 aspheric toric intraocular lenses: Comparative study. J Cataract Refract Surg 2013;39:906-14. |
| 49. | Miháltz K, Lasta M, Burgmüller M, Vécsei-Marlovits PV, Weingessel B. Comparison of two toric IOLs with different haptic design: Optical quality after 1 year. J Ophthalmol 2018;2018:4064369. |
| 50. | Stewart CM, McAlister JC. Comparison of grafted and non-grafted patients with corneal astigmatism undergoing cataract extraction with a toric intraocular lens implant. Clin Exp Ophthalmol 2010;38:747-57. |
| 51. | Visser N, Bauer NJ, Nuijts RM. Toric intraocular lenses: Historical overview, patient selection, IOL calculation, surgical techniques, clinical outcomes, and complications. J Cataract Refract Surg 2013;39:624-37. |
| 52. | Thulasidas M, Teotia P. Evaluation of corneal topography and tomography in fellow eyes of unilateral keratoconus patients for early detection of subclinical keratoconus. Indian J Ophthalmol 2020;68:2415-20. [ PUBMED] [Full text] |
| 53. | Ferreira TB, Ribeiro F. How can we improve toric intraocular lens calculation methods? Current insights. Clin Ophthalmol 2020;14:1899-908. |
| 54. | Woodcock MG, Lehmann R, Cionni RJ, Breen M, Scott MC. 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;42:817-25. |
| 55. | Browne AW, Osher RH. Optimizing precision in toric lens selection by combining keratometry techniques. J Refract Surg 2014;30:67-72. |
| 56. | Hoffmann PC, Abraham M, Hirnschall N, Findl O. Prediction of residual astigmatism after cataract surgery using swept source Fourier domain optical coherence tomography. Curr Eye Res 2014;39:1178-86. |
| 57. | Sandhya N, Zacharia K, Saikumar SJ. Astigmatism correction with toric intraocular lens during cataract surgery. Kerala J Ophthalmol 2020;32:244-51. [Full text] |
| 58. | Ho JD, Liou SW, Tsai RJ, Tsai CY. Effects of aging on anterior and posterior corneal astigmatism. Cornea 2010;29:632-7. |
| 59. | Koch DD, Jenkins RB, Weikert MP, Yeu E, Wang L. Correcting astigmatism with toric intraocular lenses: Effect of posterior corneal astigmatism. J Cataract Refract Surg 2013;39:1803-9. |
| 60. | Goggin M, Zamora-Alejo K, Esterman A, van Zyl L. Adjustment of anterior corneal astigmatism values to incorporate the likely effect of posterior corneal curvature for toric intraocular lens calculation. J Refract Surg 2015;31:98-102. |
| 61. | Piñero DP, Camps VJ, de Fez D, García C, Caballero MT. Validation of posterior corneal curvature measurements with color light-emitting diode topography. Eur J Ophthalmol 2020;30:1261-7. |
| 62. | Ferreira TB, Ribeiro FJ. Comparability and repeatability of different methods of corneal astigmatism assessment. Clin Ophthalmol 2018;12:29-34. |
| 63. | Farooqui JH, Sharma M, Koul A, Dutta R, Shroff NM. Evaluation of a new electronic preoperative reference marker for toric intraocular lens implantation by two different methods of analysis: Adobe Photoshop versus iTrace. Oman J Ophthalmol 2017;10:96-9. [ PUBMED] [Full text] |
| 64. | Binkhorst RD. The accuracy of ultrasonic measurement of the axial length of the eye. Ophthalmic Surg 1981;12:363-5. |
| 65. | Olsen T, Nielsen PJ. Immersion versus contact technique in the measurement of axial length by ultrasound. Acta Ophthalmol (Copenh) 1989;67:101-2. |
| 66. | Kiss B, Findl O, Menapace R, Wirtitsch M, Petternel V, Drexler W, et al. Refractive outcome of cataract surgery using partial coherence interferometry and ultrasound biometry: Clinical feasibility study of a commercial prototype II. J Cataract Refract Surg 2002;28:230-4. |
| 67. | Nagpal KM, Desai C, Trivedi RH, Vasavada AR. Is pseudophakic astigmatism a desirable goal? Indian J Ophthalmol 2000;48:213-6. [ PUBMED] [Full text] |
| 68. | 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. |
| 69. | Olsen T. Prediction of the effective postoperative (intraocular lens) anterior chamber depth. J Cataract Refract Surg 2006;32:419-24. |
| 70. | Shammas HJ, Chan S. Precision of biometry, keratometry, and refractive measurements with a partial coherence interferometry-keratometry device. J Cataract Refract Surg 2010;36:1474-8. |
| 71. | Lundström M, Dickman M, Henry Y, Manning S, Rosen P, Tassignon MJ, et al. Risk factors for refractive error after cataract surgery: Analysis of 282 811 cataract extractions reported to the European registry of quality outcomes for cataract and refractive surgery. J Cataract Refract Surg 2018;44:447-52. |
| 72. | Abulafia A, Koch DD, Wang L, Hill WE, Assia EI, Franchina M, et al. New regression formula for toric intraocular lens calculations. J Cataract Refract Surg 2016;42:663-71. |
| 73. | Savini G, Hoffer KJ, Ducoli P. A new slant on toric intraocular lens power calculation. J Refract Surg 2013;29:348-54. |
| 74. | Savini G, Hoffer KJ, Carbonelli M, Ducoli P, Barboni P. Influence of axial length and corneal power on the astigmatic power of toric intraocular lenses. J Cataract Refract Surg 2013;39:1900-3. |
| 75. | Park HJ, Lee H, Woo YJ, Kim EK, Seo KY, Kim HY, et al. Comparison of the astigmatic power of toric intraocular lenses using three toric calculators. Yonsei Med J 2015;56:1097-105. |
| 76. | Barrett GD. An improved universal theoretical formula for intraocular lens power prediction. J Cataract Refract Surg 1993;19:713-20. |
| 77. | Abulafia A, Barrett GD, Kleinmann G, Ofir S, Levy A, Marcovich AL, et al. Prediction of refractive outcomes with toric intraocular lens implantation. J Cataract Refract Surg 2015;41:936-44. |
| 78. | Skrzypecki J, Sanghvi Patel M, Suh LH. Performance of the Barrett toric calculator with and without measurements of posterior corneal curvature. Eye (Lond) 2019;33:1762-7. |
| 79. | Yesilirmak N, Palioura S, Culbertson W, Yoo SH, Donaldson K. Intraoperative wavefront aberrometry for toric intraocular lens placement in eyes with a history of refractive surgery. J Refract Surg 2016;32:69-70. |
| 80. | Ventura BV, Wang L, Weikert MP, Robinson SB, Koch DD. Surgical management of astigmatism with toric intraocular lenses. Arq Bras Oftalmol 2014;77:125-31. |
| 81. | Woo YJ, Lee H, Kim HS, Kim EK, Seo KY, Kim TI. Comparison of 3 marking techniques in preoperative assessment of toric intraocular lenses using a wavefront aberrometer. J Cataract Refract Surg 2015;41:1232-40. |
| 82. | Elhofi AH, Helaly HA. Comparison between digital and manual marking for toric intraocular lenses: A randomized trial. Medicine (Baltimore) 2015;94:e1618. |
| 83. | Bhandari S, Nath M. Anterior stromal puncture with staining: A modified technique for preoperative reference corneal marking for toric lenses and its retrospective analyses. Indian J Ophthalmol 2016;64:559-62. [ PUBMED] [Full text] |
| 84. | Osher RH. Iris fingerprinting: New method for improving accuracy in toric lens orientation. J Cataract Refract Surg 2010;36:351-2. |
| 85. | Montes de Oca I, Kim EJ, Wang L, Weikert MP, Khandelwal SS, Al-Mohtaseb Z, et al. Accuracy of toric intraocular lens axis alignment using a 3-dimensional computer-guided visualization system. J Cataract Refract Surg 2016;42:550-5. |
| 86. | Hura AS, Osher RH. Comparing the zeiss Callisto eye and the alcon verion image guided system toric lens alignment technologies. J Refract Surg 2017;33:482-7. |
| 87. | Solomon JD, Ladas J. Toric outcomes: Computer-assisted registration versus intraoperative aberrometry. J Cataract Refract Surg 2017;43:498-504. |
| 88. | Mayer WJ, Kreutzer T, Dirisamer M, Kern C, Kortuem K, Vounotrypidis E, et al. Comparison of visual outcomes, alignment accuracy, and surgical time between 2 methods of corneal marking for toric intraocular lens implantation. J Cataract Refract Surg 2017;43:1281-6. |
| 89. | Stringham J, Pettey J, Olson RJ. Evaluation of variables affecting intraoperative aberrometry. J Cataract Refract Surg 2012;38:470-4. |
| 90. | Pallas A, Yeo TK, Trevenen M, Barrett G. Evaluation of the accuracy of two marking methods and the novel toriCAM application for toric intraocular lens alignment. J Refract Surg 2018;34:150-5. |
| 91. | Espaillat A, Pérez O, Potvin R. Clinical outcomes using standard phacoemulsification and femtosecond laser-assisted surgery with toric intraocular lenses. Clin Ophthalmol 2016;10:555-63. |
| 92. | Vokrojová M, Havlíčková L, Brožková M, Hlinomazová Z. Effect of capsular tension ring implantation on postoperative rotational stability of a toric intraocular lens. J Refract Surg 2020;36:186-92. |
| 93. | Chen X, Zhao M, Shi Y, Yang L, Lu Y, Huang Z. Visual outcomes and optical quality after implantation of a diffractive multifocal toric intraocular lens. Indian J Ophthalmol 2016;64:285-91. [ PUBMED] [Full text] |
| 94. | Ma JJ, Tseng SS. Simple method for accurate alignment in toric phakic and aphakic intraocular lens implantation. J Cataract Refract Surg 2008;34:1631-6. |
| 95. | Prinz A, Neumayer T, Buehl W, Vock L, Menapace R, Findl O, et al. Rotational stability and posterior capsule opacification of a plate-haptic and an open-loop-haptic intraocular lens. J Cataract Refract Surg 2011;37:251-7. |
| 96. | Felipe A, Artigas JM, Díez-Ajenjo A, García-Domene C, Alcocer P. Residual astigmatism produced by toric intraocular lens rotation. J Cataract Refract Surg 2011;37:1895-901. |
| 97. | Lockwood JC, Randleman JB. Toric intraocular lens rotation to optimize refractive outcome despite appropriate intraoperative positioning. J Cataract Refract Surg 2015;41:878-83. |
| 98. | Teichman JC, Baig K, Ahmed II. Simple technique to measure toric intraocular lens alignment and stability using a smartphone. J Cataract Refract Surg 2014;40:1949-52. |
| 99. | Chang DF. Repositioning technique and rate for toric intraocular lenses. J Cataract Refract Surg 2009;35:1315-6. |
| 100. | Fernández-Buenaga R, Alió JL, Pérez Ardoy AL, Quesada AL, Pinilla-Cortés L, Barraquer RI. Resolving refractive error after cataract surgery: IOL exchange, piggyback lens, or LASIK. J Refract Surg 2013;29:676-83. |
[Table 1], [Table 2], [Table 3]
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