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Authors; Candyce Hamel, and Sharon Bailey.
A cataract is an opacity of the lens and is the leading cause of reversible visual impairment worldwide.1 The lens of the eye has a unique structure and unlike other epithelia, it cannot shed nonviable cells. These cells compress in the eye over time and lose their transparency.2 Cataracts occur frequently with increasing age. In 2019 to 2020, Statistics Canada reported that 17.9% (n = 1,143,000) of people over the age of 65 were diagnosed with cataracts by a health professional.3 However, in children and adults, cataracts may also be caused by poor nutrition, disease, medication, trauma, and excessive exposure to sunlight.2,4,5 Bilateral congenital cataracts have been reported in infants with low birth weight (< 2,000 g).5 The development of cataracts is painless, but cataracts may cause blurred or distorted vision, glare problems, and blindness.2 Approximately 90% of blindness in developed countries can be attributed to cataracts.4
There are no proven medical therapies to treat cataracts,2 but cataract surgery (i.e., removal of the lens and replacement with a synthetic lens, called an IOL)4 is an effective procedure and can restore normal vision in most patients.2,4 In adults, surgery may be indicated if the symptoms interfere with daily activities and is not usually based on a specific level of VA.2,4 In children, the management of cataracts depends on factors such as the child’s age and the potential for interference with visual development.5 The most common technique used for cataract surgery is phacoemulsification (e.g., 99% of cataract surgeries in the US use phacoemulsification),4 where a small incision is made to remove the natural lens, which is then replaced with the IOL.2 In adults, surgery is most often performed in an outpatient setting using a topical anesthetic with monitored sedation, while the pediatric population typically requires general anesthetic sedation.2,6
There are 3 main IOL types: monofocal, multifocal or accommodating, and toric. Monofocal and multifocal lenses refer to the focus of the lens. More specifically, a monofocal lens usually targets distance vision and patients often still require spectacles for near activities. A multifocal lens is designed to minimize dependence of spectacles after surgery at multiple focal lengths. Toric lenses aim to eliminate or reduce preoperative astigmatism and can reduce or eliminate the need for astigmatism-correcting spectacles or contact lenses.2 Multifocal and toric lens are considered premium lenses and may not be covered by public and/or private insurance plans, with the extra expense paid by the patient. Because cataract surgery is performed only once, the type of IOL implanted is important and should be discussed between the patient and the surgeon. Factors that may influence this decision are the amount of preexisting astigmatism, the desired level of spectacle independence, and budget.2
In 2020, CADTH produced a Rapid Response report that evaluated premium versus standard IOLs.7 Five SRs and 2 RCTs were included. Although some of the included studies within the 2020 report would be relevant to this rapid review, all were published before 2018, with others comparing multifocal or accommodating lenses to monofocal lenses.
As there is a potential reduction in the requirement for astigmatism-correcting spectacles with toric IOLs, albeit with an increased cost to the patient or private insurance (if it was covered), evidence regarding the clinical effectiveness is required. The objective of this review is to summarize the evidence regarding the clinical effectiveness of the monofocal toric IOL compared to the monofocal nontoric IOL implanted during cataract surgery.
What is the clinical effectiveness of cataract surgery using monofocal toric IOLs versus conventional monofocal IOLs with or without astigmatism-correcting spectacles for people with cataracts?
An information specialist conducted a literature search on key resources including MEDLINE, Embase, the Cochrane Database of Systematic Reviews, the International HTA Database, and the websites of Canadian and major international health technology agencies, as well as a focused internet search. The search approach was customized to retrieve a limited set of results, balancing comprehensiveness with relevancy. The search strategy comprised both controlled vocabulary, such as the National Library of Medicine’s MeSH (Medical Subject Headings), and keywords. Search concepts were developed based on the elements of the research questions and selection criteria. The main search concepts were IOLs, cataract surgery, and toric lenses. CADTH-developed search filters were applied to limit retrieval to health technology assessments, systematic reviews, meta-analyses, or indirect treatment comparisons, any types of clinical trials or observational studies, and guidelines. The search was completed on September 18, 2023, and limited to English-language documents published since January 1, 2018.
One reviewer screened citations and selected studies. In the first level of screening, titles and abstracts were reviewed and potentially relevant articles were retrieved and assessed for inclusion. The final selection of full-text articles was based on the inclusion criteria presented in Table 1.
Selection Criteria.
Articles were excluded if they did not meet the selection criteria outlined in Table 1, they were duplicate publications, or were published before 2018. Systematic reviews in which all relevant studies were captured in other more recent or more comprehensive systematic reviews were excluded. Primary studies retrieved by the search were excluded if they were captured in 1 or more included systematic reviews. Guidelines with an unclear methodology were also excluded.
The included publications were critically appraised by 1 reviewer using the following tools as a guide: A MeaSurement Tool to Assess systematic Reviews 2 (AMSTAR 2)8 for systematic reviews and the Downs and Black checklist9 for randomized and nonrandomized studies. Summary scores were not calculated for the included studies; rather, the strengths and limitations of each included publication were described narratively.
A total of 375 citations were identified in the literature search. Following screening of titles and abstracts, 352 citations were excluded and 23 potentially relevant reports from the electronic search were retrieved for full-text review. Three potentially relevant publications were retrieved from the grey literature search for full-text review. Of these potentially relevant articles, 15 publications were excluded for various reasons and 11 publications met the inclusion criteria and were included in this report. These comprised 1 SR, 3 RCTs, and 7 nonrandomized studies. Appendix 1 presents the PRISMA10 flow chart of the study selection.
Additional references of potential interest are provided in Appendix 5.
This report includes 1 SR,11 3 RCTs,12-14 and 7 nonrandomized studies (1 prospective and 6 retrospective).15-21
Additional details regarding the characteristics of the included publications are provided in Appendix 2.
One SR published in 2022 was identified.11 The search date was up to July 25, 2021. The review included 12 RCTs, published between 2009 and 2015. All 12 RCTs were relevant to this current review.
The 3 RCTs were published in 2023,12 2021,13 and 2020.14 One prospective study published in 202316 and 6 retrospective studies were published between 2021 and 2023.15,17-21
The SR was published by a first author from China and does not report where the primary studies were conducted.11 The RCTs were conducted in Austria,12 China,13 and the UK.14 The prospective nonrandomized study was conducted in China,16 2 retrospective studies were conducted in China,17,18 with 1 retrospective study each conducted in Italy,15 Egypt,19 Japan,20 and Korea.21
The SR11 included RCTs if the study population were patients with cataracts and corneal astigmatism. Most primary studies included patients with a mean age of 60 years or older. One subgroup in 1 study had patients 49 years and older. Other study and patient characteristics, like setting and comorbidities, were not presented. Eleven of the 12 studies included patients with a mean corneal divergence of more than 1.00 diopters (D), with 3 studies with corneal divergence of more than 2.00 D.
Patients in the 3 RCTs were 161 eyes of 126 male and females (as described in the original source) with mean ages of 69.5 years or older. Two RCTs were conducted in a hospital,12,13 with the other study not specifying where the surgery occurred, but patients were recruited from clinics.14 To be eligible for the study, baseline astigmatism ranged from 0.75 D to 1.5 D,12 1.0 D to 2.0 D,13 and at least 2.0 D.14
Patients in the 1 prospective and 6 retrospective studies were 543 eyes of 483 males and females (as described in the original source). Six of 7 studies were in adults, with a mean age of 53 years or older 15,16,18,19,21 and 1 study including patients 80 years or older.17 One study was performed in a pediatric population, with a mean age of 7.8 years.20 One study did not report the setting for surgery,15 1 study was performed in an ophthalmic centre at a university,16 and all other surgeries were performed in hospitals.17-21 One study included patients with preoperative astigmatism of 1.0 D or less.15 Three studies included patients with minimum levels of astigmatism, 0.75 D or more,17 more than 1.0 D,16 and more than 1.5 D.21 Two studies included patients with a range of astigmatism, 0.75 D to 1.5 D18 and 1.0 D to 4.0 D.19 The study in the pediatric population did not specify the level of astigmatism for inclusion.20
The SR11 the RCT by Liu et al. (2021),13 and 5 of the retrospective studies (Bellucci [2023],15 Wang [2023],17 Ding [2022],18 El-Shehawy [2022],19 Young Shin [2021]21) compared phacoemulsification or ultrasonic emulsification cataract surgery with 1 group receiving toric lenses and the other group receiving nontoric lenses. The RCT by Hienert et al. (2023)12 reported using “standard cataract surgery” with either toric or nontoric IOLs, and the RCT by Stanojcic et al. (2020)14 did not report the type of cataract surgery performed. One retrospective study, in the pediatrics population, reported using the optic capture technique.20 The prospective nonrandomized study by Fan et al. (2023)16 compared femtosecond laser-assisted cataract surgery and phacoemulsification cataract surgery combined with either toric IOLs or nontoric IOLs.
Astigmatism, reported in Ds, was reported several different ways. A list of all astigmatism-related outcomes are presented in Appendix 2, with a subset of these outcomes reported here. In the SR by Chi et al. (2022),11 astigmatism was reported as corneal astigmatism. In the RCTs, astigmatism was reported as subjective refraction astigmatism (at a 6-month follow-up),12 autorefraction astigmatism (at a 6-month follow-up),12 cylinder (at a 4-week follow-up),14 spherical equivalent (at 4-week and 3-month follow-ups),13,14 corneal astigmatism (at a 3-month follow-up),13 and surgically induced astigmatism (at 4-week, 3-month, and 6-month follow-ups).12-14 In the prospective and retrospective nonrandomized studies, astigmatism was reported as cylinder (at 2-month, 2- to 4-month, and 3-month follow-ups),15,17,18,21 spherical equivalent (at 2-month, 2- to 4-month, and 3-month follow-ups),15-19,21 corneal astigmatism (at 2-month and 2- to 4-month follow-ups),15,21 residual refractive astigmatism (at a 3-month follow-up),16,19 postoperative refractive astigmatism (defined as surgically induced plus corneal) (at a 2- to 4-month follow-up),15 surgically induced astigmatism (at 2- to 4-month and 3-month follow-ups),15,18,19 and internal astigmatism in the pseudophakia (at a 2- to 4-month follow-up).15
Uncorrected VA was reported in 10 of the 11 included studies, but were reported at distance (at 4-week, 2- to 4-month, 3-month, and 6-month follow-ups), intermediate (at a 3-month follow-up), and near (at 2- to 4-month and 3-month follow-ups) VA.
Uncorrected distance VA: The SR,11 the 3 RCTs,12-14 and 5 of the nonrandomized studies15,17-19,21 reported uncorrected distance VA. The SR did not report the distance at which this was measured.11 Two RCTs measured distance VA at 4 m,12,14 while the third did not report the distance.13 One retrospective study reported VA at a distance of 6 m,21 while the other 4 retrospective studies did not report the distance at which this was measured.15,17-19
Uncorrected intermediate VA: The prospective nonrandomized study16 reported uncorrected intermediate VA at 80 cm.
Uncorrected near VA: Two retrospective studies15,21 and the prospective nonrandomized study16 reported on uncorrected near VA. The prospective nonrandomized studies reported near VA at a distance of 40 cm.16 One retrospective study reported near VA at a distance of 33 cm,21 and 1 retrospective study did not report the distance at which this was measured.15
All 11 included studies reported best-corrected or corrected distance VA (at 4-week, 2- to 4-month, 3-month, 6-month, and 1-year follow-ups). The SR did not report the distance this was measured.11 Two RCTs reported that the distance measured was at 4 m,12,14 while the third did not report the distance.13 The prospective nonrandomized study reported best-corrected distance VA at 5 m.16 The retrospective study reported this at 4 m,15 5 m,20 and 6 m.21 The other 3 retrospective studies did not report the distance at which this was measured.17-19
The RCT by Hienert et al. (2023)12 reported on a patient questionnaire (at a 6-month follow-up) that asked the patients to evaluate which eye (1 eye received a toric lens and the other received a nontoric lens) was superior for car driving, recognizing faces, reading text in TV, seeing irregularity on the street, reading mobile phone, playing cards, cooking, crafting, and reading a book. The RCT by Stanojcic et al. (2020)14 reported on Cat-PROM5 Rasch-calibrated score, 3-Level EQ-5D index score, and EQ-5D visual analogue scale at 4-weeks follow-up. The range of the scale for each of these tools was not provided.
The RCT by Stanojcic et al. (2020)14 and 2 retrospective studies20,21 reported on intraoperative complications. The SR,11 2 RCTs,13,14 and 4 retrospective studies18-21 reported on postoperative complications. The RCT by Hienert et al. (2023)12 reported on adverse events. Follow-up times for postoperative complications and adverse events were not reported, with the exception of Hienert et al. (2023), which reported these times at a 6-month follow-up.12
The SR was assessed using the A MeaSurement Tool to Assess systematic Reviews 2 (AMSTAR 2) tool.8 The SR11 had several strengths, including searching 8 electronic databases, supplemental searching of professional journals, and contacting experts, which decreases the risk of missing relevant studies. The quality of reporting was sufficient in some areas; for example, the elements of PICO were well described, a PRISMA flow diagram was provided, the source of funding for the review was provided, and the authors declared their conflicts of interest. The quality of conduct was well performed and reported for some areas; for example, the methods for extraction and risk of bias were performed by 2 independent reviewers. Publication bias was assessed for all meta-analysis, regardless of the number of studies included in the analysis, which may not provide an accurate indication of publication bias (i.e., if there were fewer than 10 studies). Three of 4 meta-analyses had fewer than 10 studies. There were also limitations, including no statement that the methods were established before the review conduct (and no protocol mentioned), and it was unclear what languages of the primary studies were included and how study selection was performed. A list of the excluded studies was not provided, but high-level reasons were provided in the PRISMA flow diagram. Finally, the source of funding of the primary studies was not provided.
The RCTs12-14 were assessed using the Downs and Black checklist.9 The strengths in the RCTs were well-defined objectives, detailed descriptions of the inclusion and exclusion criteria, a description on how randomization was performed, detailed descriptions of the surgical procedure and both lenses, and all reported specific P values. There were also differences in the quality of conduct and reporting in the RCTs. In 2 RCTs, patients and examiners were masked to the intervention group,12,14 with the other RCT described as an open-label study,13 but it was unclear who was aware of the intervention assignments. Sample size calculations (with a sufficient number of patients recruited),12,13 estimates of variability (e.g., standard deviations),13,14 and baseline patient characteristics13,14 were each provided in 2 RCTs. Across all 3 RCTs,12-14 the surgery occurred in a single facility and the patients had baseline astigmatism in specific ranges, which may limit the generalizability of the surgical procedure and study population. Outcome reporting was poor in all 3 RCTs. For example, the number of outcomes reported in the results section were more than what was described in the methods section12-14 or the trial registry.12 Most12,14 or all13 outcome results did not include the number of patients who contributed to the outcome.
The prospective nonrandomized study and retrospective studies15-21 were assessed using the Downs and Black checklist.9 There were several strengths in these studies; for example, the objectives, inclusion and exclusion criteria, surgical procedures, and IOL types were well described in all studies. Additionally, estimates of variability (e.g., standard deviations) and specific P values were reported in all studies. However, there was variability in conduct and reporting across the studies; for example, 7 studies reported detailed baseline patient characteristics,15-21 4 studies reported a sample size calculation,15-17,19 and 1 study reported the number of patients contributing to the outcomes.17 In all 7 studies, it is unclear if the facility(ies) where the surgeries occurred were representative of all cataract surgeries. Similarly, in most studies, patients had specific ranges of astigmatism (e.g., ≤ 1 D15) or it was not reported,16 which may not be representative all of patients with astigmatism. One study included patients 80 years and older17 and 1 study included pediatric patients,20 which may limit the generalizability of these studies. As the patients in these 7 studies were not randomized to an intervention group, it is possible there were unmeasured baseline differences between the groups, and no studies reported an adjusted analysis. Six of 7 studies were retrospective;15,17-21 therefore, it is likely that patients and assessors would have been aware of lens type during surgery and follow-up. In the prospective study,16 patients selected which lens was implanted. Although this would not impact objective outcomes, it may influence subjective outcomes. Most15,18,20,21 or all16,19 outcomes did not describe the number of patients that contributed to the outcome. Finally, surgical complication and adverse events were not reported in 3 studies.15-17
Additional details regarding the strengths and limitations of the included publications are provided in Appendix 3.
Appendix 4 presents the main study findings.
Astigmatism was reported several different ways. They are presented in the following as reported in these studies.
Corneal astigmatism: The SR11 meta-analysis included 4 results from 3 RCTs (1 RCT included 2 groups) and reported a non-statistically significant difference favouring toric over nontoric IOLs (mean difference [MD] = −0.34; 95% confidence interval [CI], −0.83 to 0.15; P = 0.18; I2 = 96%). One RCT13 and 2 retrospective studies15,21 reported no significant difference in the mean level of astigmatism between the 2 groups.
Subjective refraction astigmatism: One RCT12 reported a statistically significant difference in the median and average level of astigmatism favouring the toric IOL group over the nontoric IOL group at a 6-month follow-up, 0.25/0.23 D compared to 0.50/0.53 D, respectively (P = 0.04).
Autorefraction astigmatism: One RCT12 reported a statistically significant difference in the median and average level of astigmatism favouring the toric IOL group over the nontoric IOL group at a 6-month follow-up, 0.50/0.52 D compared to 1.00/1.17 D, respectively (P < 0.001).
Cylinder: One RCT14 and 2 retrospective studies17,21 reported a statistically significant lower mean (standard deviation [SD]) astigmatism in the cylinder, favouring the toric IOL group over the the nontoric IOL group. However, 2 retrospective studies reported no difference between groups.15,18
Spherical equivalent: Two RCTs13,14 and 5 of the 6 nonrandomized studies15-18,21 reported no difference in the spherical equivalent between those who received toric and those who received nontoric IOLs. El-Shehawy (2022)19 reported a statistically significant difference favouring the toric IOL group over the nontoric IOL group.
Surgically induced astigmatism: Results differed between the RCTs and the nonrandomized studies. The 3 RCTs12-14 reported no difference between the toric and nontoric groups. One retrospective study18 reported a statistically significant difference, with higher levels of surgically induced astigmatism in the toric IOL group. Two retrospective studies15,19 reported the mean for each group but did not provide a statistical value (e.g., P value) to measure if there was difference between groups; however, in 1 study, the mean was higher in the toric IOL group than in the nontoric IOL group, 3.47 (SD = 1.14) and 1.66 (SD = 1.46), respectively.
Postoperative refractive astigmatism: One retrospective study15 defined postoperative refractive astigmatism as surgically induced plus corneal components and reported a lower mean astigmatism favouring the toric IOL group over the nontoric IOL group; however, the difference was not statistically significant.
Residual refractive astigmatism: One prospective nonrandomized study16 and 1 retrospective study19 reported statistically significant differences between the toric and nontoric groups, with the toric group having lower levels of residual refractive astigmatism.
Internal astigmatism in the pseudophakia: One retrospective study15 reported no difference between the toric and nontoric groups.
Visual acuity was measured using the Logarithm of the Minimum Angle of Resolution (LogMAR) scoring system, with visual acuity decreasing as the LogMAR value increases. It was measured using distance, intermediate distances, and near distances in the included studies.
Uncorrected distance visual acuity: The SR11 meta-analysis included 12 RCTs and reported a statistically significant difference between toric and nontoric IOLs (MD = −0.05; 95% CI, −0.09 to −0.00; P = 0.03; I2 = 85%). All 3 RCTs also reported statistically significant differences, with the toric group having lower LogMAR values than the nontoric group. Four15,17,19,21 of the 5 retrospective studies reported statistically lower LogMAR scores in the toric IOL group than in the nontoric IOL group. One retrospective study18 reported higher LogMAR scores in the toric group, but the difference was not statistically significant.
Uncorrected intermediate visual acuity: The prospective nonrandomized study16 reported a statistically significant lower LogMAR score in the toric group than in the nontoric group.
Uncorrected near visual acuity: One prospective nonrandomized study16 and 1 retrospective study21 reported statistically significant lower LogMAR scores in the toric group than in the nontoric group. The retrospective study15 with patients with preoperative astigmatism of 1.0 D or lower did not report a statistically significant difference.
Corrected distance visual acuity was reported across all 11 included studies with LogMAR scores.
The SR11 meta-analysis included 7 results from 6 RCTs (1 RCT included 2 groups) and reported no difference between toric and nontoric IOLs (MD = −0.00; 95% CI, −0.02 to 0.01; P = 0.77; I2 = 0%). Results across the RCTs differed; 1 RCT14 reported a statistically significant lower LogMAR score in the toric group compared to the nontoric group, and 2 RCTs12,13 reported no difference. Five of 7 nonrandomized studies reported no difference,16-18,20,21 1 study15 did not provide a statistical value (e.g., P value) to measure if there was difference between groups, and 1 study reported a statistically significant difference, with the toric group reporting a lower LogMAR score than the nontoric group.19 Specific to the retrospective study that included the pediatric population, there was no difference between groups.
Two RCTs reported on patient-centred outcomes. The RCT by Hienert et al. (2023),12 which randomized eyes to toric or nontoric IOLs, asked patients a series of questions comparing the 2 eyes. Patients could have answered no difference between eyes, or if 1 eye was better than the other for car driving, recognize faces, reading text in TV, seeing irregularity on the street, reading mobile phone, playing cards, cooking, crafting, and reading a book. Generally, the toric eye was superior to the nontoric eye, but there were high levels of “no difference” reported across these questions. In the RCT by Stanojcic et al (2020),14 23 of the 77 patients were included in the patient-centred outcomes. There was a statistically significant difference in the Cat-PROM5 Rasch-calibrated score, although the study did not report which group reported better scores (e.g., no score values were provided for this tool and no text around which group had better scores). There was no difference in the 3-Level EQ-5D index score and the EQ-5D visual analogue scale between the toric and nontoric groups.
Intraoperative complications: One RCT14 reported 2 patients who had intraoperative complications in the toric IOL group and 0 in the nontoric group, this was not statistically significant (P = 0.49). Two retrospective studies reported on intraoperative complications; 1 study reported no herniation of the vitreous in the anterior chamber20 and 1 study reported no complications during surgery, such as rupture of the capsule.21
Postoperative complications: The SR11 reported on postoperative complications, which mainly included persistent edema, pupillary block, retinal detachment, and endophthalmitis. There were fewer postoperative complications in the toric group, which reached statistical significance (MD = 0.47; 95% CI, 0.23 to 0.96; P = 0.04; I2 = 0%). Few postoperative complications were reported in the RCTs. In Stanojcic et al. (2020),14 3 patients in the toric group had cystoid macular edema and 1 patient in the toric group had mild posterior capsule opacification. Liu et al. (2021)13 reported that there were no surgical complications. In the 2 retrospective studies that reported this outcome, there were no complications reported.18,21 Tachibana et al. (2021) reported no increase in postoperative intraocular pressure.20 El-Shehawy et al. (2022)19 reported corneal edema, uveitis, posterior capsular opacification, and immediate postoperative anterior chamber reactions in some patients, although there did not appear to be differences between the toric and nontoric groups.
Adverse events: Hienert et al (2023)12 reported that no serious adverse events occurred during the study.
One SR, 3 RCTs, 1 prospective nonrandomized study, and 6 retrospective studies that compared toric to nontoric IOLs combined with cataract surgery were identified. There were some important limitations with the evidence identified in this review.
Although a formal test for heterogeneity (e.g., I2 value) was not performed for the narrative summaries, it is important to note that there were differences between the studies that may affect the overall results across the studies. For example, in the RCT studies, Hienert et al. (2023)12 and Liu et al. (2021)13 included patients with preoperative astigmatism values of 2.0 D or less (0.75 D to 1.5 D and 1.0 D to 2.0 D, respectively), whereas Stanojcic et al. (2020)14 included patients with preoperative astigmatism of 2.0 D or greater. Follow-up duration also differed, ranging from 4 weeks in Stanojcic (2020),14 3 months in Liu (2021),13 and 6 months in Hienert (2023).12 In the nonrandomized studies, Bellucci (2023)15 included patients with a preoperative astigmatism value of less than 1.0 D, Fan et al. (2023) performed femtosecond laser-assisted cataract surgery before phacoemulsification cataract surgery, Wang et al. (2023)17 included patients aged 80 years and older, and Tachibana et al. (2021)20 reported on a pediatric population. Follow-up durations also differed in these studies.
Most nonrandomized studies (i.e., the prospective and retrospective nonrandomized studies) reported no differences between baseline characteristics. However, as patients were not randomized to toric or nontoric IOL, there is opportunity for unmeasured and residual confounding, and none of these studies performed adjusted analyses. El-Shehawy et al. (2022)19 reported no statistical baseline difference between the 3 groups in the study; however, there appears to be baseline differences between the 2 groups relevant to this review. For example, the toric group mean baseline spherical equivalent was −5.3 D (SD = 5 D) compared to the nontoric group baseline spherical equivalent of −1.3 D (SD = 3.7 D). This study reported statistically significant differences in all outcomes (among those where P values were reported).
Outcomes were reported in several different ways using different measures across the studies. Astigmatism is used here as an example; however, this was seen in uncorrected visual acuity, corrected visual acuity, and harms outcomes, although to a lesser degree. A comprehensive list of outcomes for astigmatism can be found in Appendix 2, but several here are provided as an example: residual corneal astigmatism, subjective refraction astigmatism, autorefraction astigmatism, surgically induced astigmatism, astigmatism cylinder range in 0.25 D steps (e.g., 0.25 D, 0.50 D, 0.75 D, 1.0 D), spherical equivalent refraction (attempted, absolute achieved, spherical equivalent error, absolute spherical equivalent error), refractive astigmatism (by Snellen visual acuity), target-induced astigmatism versus surgically induced astigmatism (Snellen lines), correction index, refractive astigmatism angle of error (change in Snellen lines), target induced astigmatism vector, difference vector. For feasibility, astigmatism was extracted from the included studies reported 9 different ways. A more consistent terminology would reduce the number of outcomes and increase the number of studies in each outcome, thereby increasing the precision in the results.
Few studies reported on patient-centred outcomes (e.g., quality of life). Among the 2 RCTs that reported these, 1 did not use a validated tool12 and the other used 3 validated tools,14 but did not provide any details on how to interpret the results (e.g., no scale or indication if a lower score is worse or better), requiring the reader to look externally to interpret the findings. Additionally, in this study, not all patients contributed to this outcome (23 of 77 patients).14
The SR did not list where the primary studies were conducted. The primary studies identified in this review were conducted in Austria, China, Egypt, Italy, Japan, Korea, and the UK. As there may be differences in surgical procedures and insurance coverages, studies conducted in other counties may limit the generalizability to the Canadian context.
One SR,11 3 RCTs,12-14 and 7 nonrandomized studies (1 prospective and 6 retrospective)15-21 evaluated the clinical effectiveness of toric compared to nontoric IOLs combined with cataract surgery.
It is difficult to make conclusions across studies and outcomes due to the variation in how outcomes are reported or due to a lack of studies reporting outcomes. For example, all studies reported on at least 1 measure of astigmatism, with mixed results across the studies depending on how the outcome was reported. Both subjective and autorefraction astigmatism reported statistically significant results, favouring those who received toric IOLs in 1 RCT.12 There were mixed results across the studies that reported cylinder, with 3 studies reporting a statistically significant lower mean level of astigmatism in the toric group,14,17,21 and 2 studies reporting no difference between groups.15,18 Seven of 8 studies reported no difference in the spherical equivalent,13-18,21 except for 1 study19 that had a baseline difference in this measure. There was no difference in corneal astigmatism in the SR,11 the 1 RCT,13 and 2 retrospective studies.15,21 Therefore, depending on the measurement of astigmatism that is most relevant to the patient, it is unclear if toric IOLs significantly reduce the level of astigmatism in patients who have undergone cataract surgery compared to nontoric IOLs. Furthermore, 2 RCTs reported on patient-centred outcomes,12,14 limiting conclusions relating to quality of life and visual function outcomes. A working group of international experts in cataract outcomes and registries published the results of a modified Delphi process in 2015, which included a list of postoperative outcomes for cataract surgery. This study can be found on the Core Outcomes Measures in Effectiveness Trials (COMET) initiative database using the search term cataract. Refractive outcomes is listed and the working group suggested to include the target refraction and the actual postoperative refractive error.22 Additionally, patient-reported visual function should be reported using Rasch-calibrated score from Catquest-9SF or other Rasch-calibrated PROM. This was reported in 1 RCT.14 As all primary studies in this review were published after 2015, more studies should have included this outcome.
Toric IOLs were favoured over nontoric IOLs in most studies when evaluating uncorrected visual acuity (i.e., without glasses or contact lenses). This was measured in distance, intermediate distances, and near distances. However, not all statistically significant differences are clinically meaningful to a patient. The American Academy of Ophthalmology reports that most people have between 0.5 D and 0.75 D of astigmatism and that people with a measurement of ≥ 1.5 D typically required corrective lenses to have a clear vision.23 Therefore, even a statistically significant difference between toric and nontoric IOLs may not result in a clinically meaningful difference (i.e., patients may still require corrective lenses in both groups). In a 2018 CADTH Rapid Response report,7 the 1 primary study that reported on uncorrected distance visual acuity reported statistically significant differences, favouring toric IOLs, between those who received medium-to-high and low-toric lenses compared to nontoric lenses. In this 2018 CADTH report, although not a direct link between outcomes, in general, spectacle independence was found to be better in patients with premium IOLs compared to monofocal IOLs. Spectacle independence was favoured in the toric group among the 2 SRs that included studies that compared toric to nontoric IOLs.
The additional costs or availability of toric IOLs may have impacted the results in the nonrandomized studies. It was not always reported why patients received toric or nontoric lenses, but among the studies where this was reported, it was selected by the patient,16,21 or as a result of the timing of the surgery (pre or post 2012).20
Study sizes ranged from as few as 26 eyes in 20 patients up to 159 eyes in 159 patients, 3 primary study RCTs were published between 2018 and 2023,12-14 and among the studies that reported the setting, almost all were performed in a single centre, with 1 studies being performed in more than 1 clinic or hospital.19 Based on the primary studies identified in this review, larger multicentre RCTs should be performed that compare toric to nontoric lenses. These studies should, at a minimum, report on the core outcomes as suggested in the publication by Mahmud et al. (2015).22 This may increase the generalizability of the results and provide a better indication of objective, subjective, and patient-important outcomes in studies that compared the clinical effectiveness of toric and nontoric IOLs implanted during cataract surgery.
confidence interval
diopters
intraocular lens
Logarithm of the Minimum Angle of Resolution
mean difference
randomized controlled trial
standard deviation
systematic review
visual acuity
Contributor: Calvin Young
Selection of Included Studies.
Note that this appendix has not been copy-edited.
Characteristics of Included Systematic Review.
Characteristics of Included Primary Clinical Studies.
Note that this appendix has not been copy-edited.
Strengths and Limitations of Systematic Reviews Using AMSTAR 28.
Strengths and Limitations of Clinical Studies Using the Downs and Black Checklist.
Note that this appendix has not been copy-edited.
Summary of Findings by Outcome — Astigmatism.
Summary of Findings by Outcome — Uncorrected Visual Acuity.
Summary of Findings by Outcome — Corrected Distance Visual Acuity.
Summary of Findings by Outcome — Patient-Centred Outcomes.
Summary of Findings by Outcome — Harms Outcomes.
Note that this appendix has not been copy-edited.
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