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JOURNAL ABSTRACTS
Year : 2013  |  Volume : 1  |  Issue : 3  |  Page : 193-196

Toric intraocular lenses: A review


All India Institute of Medical Sciences, New Delhi, India

Date of Submission10-Jul-2013
Date of Acceptance10-Jul-2013
Date of Web Publication23-Aug-2013

Correspondence Address:
Rajesh Sinha
S-7, R.P. Centre, All India Institute of Medical Sciences, New Delhi
India
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Source of Support: None, Conflict of Interest: None


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How to cite this article:
Sinha R, Shekhar H, Tinwala S, Rathi A, Titiyal JS. Toric intraocular lenses: A review. J Clin Ophthalmol Res 2013;1:193-6

How to cite this URL:
Sinha R, Shekhar H, Tinwala S, Rathi A, Titiyal JS. Toric intraocular lenses: A review. J Clin Ophthalmol Res [serial online] 2013 [cited 2019 Oct 18];1:193-6. Available from: http://www.jcor.in/text.asp?2013/1/3/193/116847

Toric pseudophakic intraocular lenses (IOLs) are increasingly used in cataract surgery. They offer patients the opportunity to correct corneal astigmatism at the time of cataract surgery and achieve spectacle independence for distance vision. Now, we have multifocal toric IOLs which provide spectacle independence not only for distance vision but also for near and intermediate vision.

This review of journal abstracts gives an overview of the currently available toric and multifocal toric IOLs along with their results and complications.


  IOL Models Top


Shimuzi et al., (J Cataract Refract Surg.1994;20:523-6) evaluated the efficacy of toric IOLs implanted in the eyes of 47 patients who had preoperative against-the-rule astigmatism. The lenses, which had a cylindrical power of 2.00 diopters (D) (n= 26) or 3.00 D (n= 21), were implanted through a 5.7mm incision after cataract extraction by phacoemulsification. Best corrected visual acuity three months postoperatively was 20/25 or better in 77% of eyes. The 3.00D IOLs resulted in better correction than the 2.00D IOLs when the axis shift of the lens was less than 30°. A negative effect occurred in some eyes in which the lens axis rotated more than 30°. The maximum acceptable axis shift seems to be less than 30°.

Indications

Holland et al.,
(Ophthalmology 2010;117:2104-11) carried out a randomized, multicenter study which included 517 subjects (Toric IOL, n=256; control IOL, n=261). They concluded that favorable efficacy, rotational stability, distance vision spectacle freedom, and safety results support the use of the AcrySof® Toric IOL (Alcon Laboratories, FW, Tx) for patients with cataracts and corneal astigmatism.

Bauer et al., (J Cataract Refract Surg. 2008;34:1483-8) presented clinical data from a single-center prospective clinical trial of the AcrySof® toric (IOL)fifty-three eyes (43 patients) had implantation of an AcrySof® toric IOL. Three toric models were evaluated in cylinder powers of 1.50 diopters (D) (SN60T3; T3 group, n=16), 2.25 D (SN60T4; T4 group, n=14) and 3.00 D (SN60T5; T5 group, n=23) at the IOL plane. They concluded that implantation of the AcrySof® toric IOL proved to be an effective, safe, and predictable method of managing corneal astigmatism in cataract patients.

Kersey et al., (Cornea 2007;26:133-5) studied the change in visual acuity and refraction after cataract surgery using a toric posterior chamber intraocular lens in patients with astigmatism after penetrating keratoplasty. Seven consecutive patients with all sutures removed were included. A marked improvement in both unaided visual acuity and astigmatism was shown after the procedure. The average preoperative cylinder was 10.12D (range, 3.40-17.89D); postoperatively, which decreased to 2.75D (range, 0.75-4.25). They concluded that cataract surgery with toric intraocular lens allows the correction of high degrees of regular corneal astigmatism.

Visser et al., (Cornea 2011;30:720-3) reported 2 cases in which cataract extraction with foldable acrylic toric IOL implantation was used to correct corneal astigmatism (irregular) in patients (age > 60 years) with keratoconus and cataract. Refractive astigmatism decreased by 70% in both eyes. No IOL misalignment or other complications occurred. They concluded that cataract extraction with toric IOL implantation can be used to correct (irregular) astigmatism and to improve visual functioning in patients with mild to moderate amounts of stable keratoconus and cataract.


  IOL Calculation Top


Hill et al., (J Cataract Refract Surg. 2011;37:2181-7) evaluated simulated clinical outcomes in patients with toric IOLs calculated on the basis of dual-zone automated keratometry from an integrated optical biometer relative to manual keratometry. Patient records at four clinical sites were reviewed to identify patients who had manual keratometry and biometry with the Lenstar LS 900 recorded before toric IOL implantation and refractive follow-up data after implantation. Simulated outcomes suggest that overall results for a group of patients whose toric IOL surgery planning is performed with the dual-zone automated keratometry data from the biometer will be equivalent to those when manual keratometry is used.

Symes et al., (J Cataract Refract Surg. 2011;37:295-301) compared the mean keratometry (K) readings obtained with a conventional automated keratometer (IOL Master) and a Scheimpflug keratometer (Pentacam) in eyes having preoperative assessment for routine cataract surgery. They concluded that the equivalent K at 4.5mm had the closest match with the conventional K values.

Borasio et al., (J Cataract Refract Surg. 2006;32:565-72) carried out a prospective randomized controlled trial to determine whether there is a difference in surgically induced astigmatism (SIA) and postoperative UCVA and BCVA between two types of clear corneal incisions: the temporal and the on-axis (i.e., on the steeper corneal meridian) clear corneal incision (CCTI and CCOI, respectively). Sixty one eyes with mild to moderate corneal astigmatism (<2.58D on corneal topography) (single surgeon, 3.2mm incision) were randomized to receive CCTI or CCOI. They concluded that CCTI induced less SIA than the CCOI; however, there were no significant differences in the final UCVA and BCVA.

Masket et al., (J Refract Surg. 2009;25:21-4) evaluated the difference between 2.2-mm incision micro-coaxial phacoemulsification and traditional 3.0-mm coaxial phacoemulsification with respect to surgically induced astigmatism (SIA) after temporally oriented clear corneal incision cataract surgery. SIA with 2.2-mm micro-coaxial incisions and traditional 3.0-mm clear corneal incisions with intra-patient control resulted in statistically and clinically significant reduction in surgically induced astigmatism with the smaller incision size.

Holladay et al., (J Cataract Refract Surg. 2001;27:61-79) demonstrated analytical methods for evaluating the results of kerato-refractive surgical procedures and emphasized the importance of intraocular astigmatism. A standard data set comprising the preoperative and postoperative keratometric and refractive measurements of 100 eyes that had kerato-refractive surgery was evaluated by two methods, vector and sphero-equivalent (SEQ) analysis. The 2 analytical methods were complimentary and permit thorough and quantitative evaluation of surgically induced refractive changes (SIRCs) and allow valid statistical comparisons within and between data sets with significant clinical benefits of refractive surgery: an 8-fold increase in UCVA, an 11-fold decrease in SEQ refractive error, as well as a 9-fold and nearly a 2 1/2 -fold decrease in the magnitude and distribution of astigmatism, respectively.

Goggin et al., (Arch Ophthalmol. 2011;129:998-1003) described the refractive outcome of toric intraocular lens implantation by taking into account the effect on astigmatic outcome of the anterior chamber depth and the sphere power of the IOL and to examine whether the predictability of the toric effect can be improved. Improved outcome could be achieved by estimating the effective corneal plane cylinder power of the IOL as altered by the anterior chamber depth and pachymetry and by the IOL sphere power but this is currently not addressed by the manufacturer.

Pre-operative Marking Techniques

Visser et al.,
(J Cataract Refract Surg. 2011;37:1394-402) carried out this cohort study to determine the accuracy of a commonly used 3-step procedure for toric pseudophakic and phakic intraocular lens (IOL) implantation. Forty eyes (26 pseudophakic, 14 phakic) were analyzed. The mean errors in reference axis marking, alignment axis marking, and toric IOL alignment were 2.4 degrees ± 0.8 (SD), 3.3 ± 2.0°, 2.6 ± 2.6 °, respectively. Together these 3 errors led to a mean total error in toric IOL alignment of 4.9 ± 2.1°. They concluded that the commonly used 3-step ink-marker procedure to implant toric IOLs led to a mean error in IOL placement of approximately 5°. The error was especially relevant in cases in which higher cylinder power IOLs were implanted. In the same study they used the Surgery Guidance SG3000 system (Sensomotoric Instruments GmbH) which uses real time eye tracking based on iris and blood-vessel characteristics. Pre-operatively, a detailed image of the eye is captured in which blood-vessel and iris characteristics are visible. Simultaneously, keratometry is performed and the location of the steep and flat corneal meridians is shown in this image. Intra-operatively, the preoperative image is matched with the live surgery image from the operating microscope, based on blood-vessel and iris characteristics. An overlay showing the alignment axis is visible in the operating microscope and is used to align the toric IOL.

Osher (J Cataract Refract Surg. 2010;36:351-2) described an iris-finger printing technique, in which a pre-operative detailed image of the eye is obtained, in which the alignment axis is drawn. A printout of this image is used during surgery to align the toric IOL based on iris characteristics.

Packer (J Cataract Refract Surg. 2010;36:747-55) described technique to align toric IOLs by intra-operative wavefront aberrometry (Orange, Wavetec Vision Systems). The device is connected to the operating microscope and enables intraoperative measurement of residual refraction. This was a retrospective case-control chart review of patients who chose to have correction of pre-existing corneal astigmatism by limbal relaxing incisions (LRIs) at the time of cataract surgery or refractive lens exchange. In the aberrometry group, an Orange wavefront aberrometer was used intra-operatively to measure total ocular refractive cylinder after intraocular lens implantation and to guide LRI enhancement. The excimer laser enhancement rate was 3.3% in the aberrometry group and 16.2% in the control group.

Post-operative Alignment Measurement

Carey et al.,
(J Cataract Refract Surg. 2010;36:222-9) assessed the validity of an internal optical path difference map of a refractive power/corneal analyzer system in determining the alignment of toric IOLs. In this retrospective study, the toric IOL axis was measured three weeks post-operatively by rotating the slit lamp beam to align with the IOL axis indicator marks and using the Internal OPD Map on the Nidek OPD-Scan system. The mean IOL misalignment measured by slit lamp was 2.55 ± 2.76° and by the internal map, 2.65 ± 1.98 °. The correlation between the two methods was highly significant (r=0.99, p <.001). They concluded that both refractive power/corneal analyzer system and slit lamp observation were reliable and predictable methods of assessing IOL alignment.

Visser et al., (Invest Ophthalmol Vis Sci. 2011;52:1302-11) compared the total ocular aberrations and corneal aberrations identified with four different aberrometers in a prospective comparative study. Significant differences in measurements were found for several total ocular aberrations (defocus, astigmatism, trefoil and spherical aberration) and corneal aberrations (defocus and astigmatism). The Irx3 (Hartmann-Shack; Imagine Eyes, Orsay, France), showed the highest repeatability in measuring total ocular aberrations, followed by the Keratron (Hartmann-Shack; Optikon, Rome Italy), OPD-Scan (Automated Retinoscopy; Nidek, Gamagori, Japan) and iTrace (Ray tracing; Tracey Technologies, Houston, TX). The repeatability of the corneal aberration measurements was highest for the iTrace, followed by the Keratron and OPD-Scan. The OPD-Scan showed a lower inter-observer variability, compared with the Irx3, Keratron, and iTrace.

Clinical Results of Toric IOLs

Holland et al.,
(Ophthalmology 2010;117:2104-11) compared the AcrySof Toric IOL and an AcrySof spherical control IOL and investigated rotational stability of the AcrySof Toric IOL (Alcon Laboratories, Inc., Fort Worth, TX) in subjects with cataracts and preexisting corneal astigmatism. One year postoperatively, best spectacle-corrected distance visual acuity of ≥ 20/20 was seen in 77.7% of Toric IOL group versus 69.2% in control IOL group. Uncorrected distance visual acuity of 20/20 or better was 40.7% (Toric IOL) versus 19.4% (control IOL; p <0.05). Mean absolute residual refractive cylinder was 0.59D (Toric IOL) versus 1.22D (control IOL; p <0.0001). Mean rotation was < 4° (range, 0°-20°) for the Toric IOL. Six-month spectacle freedom was 61.0% (Toric IOL) and 36.4% (control IOL; p <0.0001). They concluded that favorable efficacy, rotational stability, distance vision spectacle freedom and safety results support the use of the AcrySof Toric IOLs for patients with cataract and corneal astigmatism.

Ahmad et al., (J Cataract Refract Surg. 2010;36:609-16) evaluated the efficacy, stability, predictability and patient-reported outcomes of bilateral toric intraocular lens implantation in cases of cataract with preexisting astigmatism. The study included 117 patients (234 eyes). The binocular UDVA was 20/40 or better in 99% of patients and 20/20 or better in 63% of patients. The mean residual refractive astigmatism was 0.4 D ± 0.4 D. The spherical equivalent was within ± 0.5D of target in 77% of eyes. At last observation, IOL alignment was within ± 5° in 91% of eyes and within ± 10° in 99%. Sixty-nine percent of patients never reported using spectacles for distance. They concluded that bilateral implantation of toric IOLs yielded excellent and stable visual outcomes that patients rated as highly satisfactory.

Gayton et al., (J Refract Surg. 2011;27:56-62) compared outcomes for uncomplicated versus complex eyes after implantation of AcrySof toric IOLs in a retrospective series of cataractous astigmatic eyes. Toric IOLs were implanted in 230 eyes of 162 adult patients. Approximately half (52%, n=120) the eyes had no complications (uncomplicated group). The other 110 (48%) eyes (complex group) had a variety of complexities. Residual cylinder was 0.40 ± 0.60 D overall (p <.01 compared to baseline) and was significantly lower (p <.01) for the uncomplicated group (0.30 ± 0.40D) than for the complex group (0.50 ± 0.80D). A larger percentage of uncomplicated eyes (26%) than complex eyes (16%) had at least 20/20 uncorrected distance visual acuity (UDVA) (p=.05). They concluded that AcrySof toric IOLs reduced cylinder and improved UDVA in both complex and uncomplicated eyes with cataract and astigmatism.

Sun et al., (Ophthalmology 2000;107:1776-81) evaluated retrospectively the results after implantation of Staar toric IOLs to correct preexisting corneal astigmatism in patients undergoing either cataract or clear lens extraction surgery. One hundred thirty eyes of 99 patients were included in the study. In the toric IOL group, 84% of eyes achieved 20/40 or better UCVA. In the spherical IOL group, 76% achieved 20/40 or better UCVA. The mean postoperative refractive cylinder was -1.03 ± 0.79 D in the toric IOL group and -1.49 ± 0.75 D in the spherical IOL group.

De Silva et al., (J Cataract Refract Surg. 2006;32:1492-8) evaluated the efficacy and rotational stability of the MicroSil 6116TU foldable 3-piece silicone toric intraocular lens (Human Optics). This prospective observational study included 21 eyes of 14 consecutive patients with more than 1.50 diopters of preexisting corneal astigmatism having cataract surgery. The mean preoperative refractive and keratometric astigmatism was 3.52D ± 1.11D and 3.08 ± 0.76D, respectively. Six months postoperatively, the logMAR UCVA in eyes without ocular comorbidity (n=14) was 0.20±0.15 (Snellen 20/32). Seventy-nine percent (11 eyes) had a visual acuity of 0.24 (Snellen 20/35) or better. The mean refractive astigmatism at 6 months was 1.23 ± 0.90D. No IOL rotated more than 5 ° during the follow-up period. They concluded that the MicroSil 6116TU toric IOL reduced visually significant keratometric astigmatism and increased spectacle independence. The IOL was stable in the capsular bag, showing no significant rotation up to 6 months postoperatively.

Entabi et al., (J Cataract Refract Surg. 2011;37:235-40) evaluated the efficacy and rotational stability of an injectable 1-piece hydrophilic acrylic toric IOL. Patients had phacoemulsification with implantation of a T-flex 623T toric IOL through a 2.8mm astigmatically neutral incision. The mean preoperative refractive astigmatism was 3.35D ± 1.20D and the mean keratometric astigmatism, 3.98D ± 1.89D, respectively. Four months postoperatively, the mean UDVA was 0.28 ± 0.23 D logMAR, improving to 0.19 ± 0.23 D logMAR CDVA. The mean difference between the intended and the actual final IOL cylinder axis was 3.44 degrees. They concluded that this toric IOL reduced visually significant keratometric astigmatism and increased spectacle independence after cataract surgery. There were no cases of significant IOL rotation in the capsular bag four months postoperatively.

Litchtinger et al., (J Refract Surg. 2011;27:639-42) carried out this study to determine whether residual astigmatism could be precisely corrected postoperatively using the Light Adjustable Lens (LAL, Calhoun Vision Inc) and to determine the stability of the adjusted refraction. All eyes achieved ± 0.50D of the targeted cylindrical adjustment. Mean spherical equivalent refraction was 0.03 ± 0.84D before adjustment and -0.06 ± 0.25D at final follow-up. The cylinder axis remained the same in 60% of eyes and all IOLs were stable within 10° rotation at 12-month follow-up. Ten eyes of 10 patients with cataract and corneal astigmatism between 1.00 and 2.00 diopters were included. Seven of 10 eyes achieved UDVA of 20/25 or better whereas all eyes achieved UDVA of 20/32 or better. Corrected distance visual acuity remained stable in all eyes.

Clinical Results of Multifocal Toric IOLs

Visser et al.,
(J Cataract Refract Surg. 2011;37:2034-42) evaluated visual outcomes and patient satisfaction after toric multifocal intraocular lens implantation in patients with cataract and corneal astigmatism. Forty-five eyes of 25 patients had cataract surgery with implantation of a toric diffractive multifocal IOL (AT Lisa). Postoperatively, the mean UDVA was 0.04 logMAR ± 0.15 and 98% of eyes achieved a UDVA of 20/40 or better. The mean uncorrected near vision (UNVA) was 0.20 ± 0.16 logMAR and the mean uncorrected (UIVA) (at 60 cm), 0.40 ± 0.16 logMAR. Residual refractive astigmatism of -1.00 diopter or less was achieved in approximately 90% of eyes. Approximately 50% of patients reported moderate glare, halos, and starburst symptoms. Spectacle independence for distance and near vision was achieved in 95% of patients and 79% of patients, respectively.

Moizis et al., (J Refract Surg. 2011;27:648-57) analyzed and compared the clinical outcomes obtained after cataract surgery with the implantation of AT LISA 909M multifocal toric IOL (Carl Zeiss Meditec) using two different types of corneal incisions. Significant reductions of refractive sphere and cylinder were observed postoperatively (p <.03), with associated visual improvements for near and distance (p <.01) in both groups.

Complications

Misalignments

Chang et al., (J Cataract Refract Surg. 2008;34:1842-7 ) prospectively compared the early rotational stability of AcrySof SN60T toric IOLs with that in a retrospective series of AA4203 toric IOLs. In the AcrySof SN60T group, 90%, 99% and 100% of the IOLs were aligned at or within 5, 10 and 15 degrees, respectively, of the desired axis and the same was seen in the AA4203 group in 70%, 90% and 97%, respectively. The mean IOL rotation was 5.56 ± 8.49 degrees in the AA4203 group and 3.35 ± 3.41 degrees in the AcrySof SN60T group (p=.0232). They concluded that based on the mean axis deviation and the number of IOLs rotating 15° or more, the AcrySof SN60T toric IOL showed statistically better rotational stability.

Visser et al., (J Cataract Refract Surg 2013;39:624-37) in their review article showed the pooled estimates for a misalignment of more than 10° for each IOL model: 20% for Staar, 13% for Rayner, 9% for Microsil, 3% for Acrysof and 0% for Acri.Comfort and light-adjustable lenses. They also reported that other complications reported in the literature are those generally associated with cataract surgery and IOL implantation: posterior capsular opacification, cystoid macular edema, peripheral vitreous detachment, macular hole and retinal detachment.




 

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