Cataract surgery is one of the most frequently performed surgical procedures globally and in this surgical procedure, intraocular lens (IOL) implantation constitutes an essential part of it. The main objective of cataract surgery is to achieve clear vision by extracting the opacified natural lens and replacing it with an artificial intraocular lens (IOL). Monofocal IOLs have been the gold standard for most patients undergoing cataract correction for many years, as they provide excellent distance vision. However, with the growing elderly population and increasing demand for less spectacle dependence, multifocal IOLs are becoming popular, particularly trifocal IOLs that aim to provide clear distances for far, intermediate, and near focal points [1, 2].

Standard Monofocal IOLs are successfully used for distant vision but require patients to don reading glasses for near and, in some instances, intermediate activities, like using a computer [3]. This has increased interest in developing multifocal lenses that can provide an extended range of vision and minimize spectacle dependence. Trifocal IOLs are a newer version of multifocal lenses that offer separate vision points for distance, intermediate, and near vision; this helps patients more fully engage in their day-to-day lives without dependence on spectacles. These lenses employ diffractive or refractive optical designs to divide incoming light into separate focal points to improve the quality of vision at multiple distances [4, 5].

Although trifocal IOLs have been increasingly used, some concerns about their optical quality remain, especially with respect to halos, glare, and decreased contrast sensitivity [6]. Optical quality metrics (modulation transfer function [MTF] and Strehl ratio) are lower in multifocal intrascleral IOLs than in monofocal IOLs in clinical behavior and prevalence [7]. These questions and a trade-off between the optics and extended range of vision may limit the indications for trifocal IOLs in some patient groups.

While generally high, multifocal IOL satisfaction (including trifocal designs) remains limited in some clinical formats due to concerns regarding visual disturbances and optical quality [8]. Clinical and optical outcomes of trifocal IOLs have not been as widely researched as those of monofocal lenses, which addresses the superior ability of trifocal lenses to provide near and intermediate acuity post-operatively. However, comparative studies directly comparing their effectiveness are still limited.

This study seeks to compare visual results, optical quality, and patient-reported satisfaction between monofocal and trifocal IOLs implanted in patients undergoing cataract surgery, helping to fill the existing gap in the literature regarding the potential clinical advantages and drawbacks of trifocal IOLs.

OBJECTIVE

The objective of this study was to compare the visual outcomes and optical quality of monofocal versus trifocal IOLs in cataract surgery patients, focusing on postoperative visual acuity, optical quality metrics.

This comparative observational study was conducted at Bangabandhu Sheikh Mujib Medical University, Bangladesh. It included 50 patients, 25 of whom received monofocal intraocular lenses (IOLs) and 25 of whom received trifocal IOLs. The study population consisted of patients who underwent cataract surgery and required intraocular lens implantation.

Selection Criteria:

Inclusion Criteria

• Patients aged 40 years and above.
• Diagnosed with age-related cataract.
• Underwent uneventful phacoemulsification surgery.
• Willing to participate and provide informed consent.

 Exclusion Criteria

• History of ocular trauma or prior intraocular surgery.
• Presence of glaucoma, diabetic retinopathy, or macular degeneration.
• Pre-existing corneal astigmatism >1.5D.
• Any systemic condition affecting visual function.

 Data Collection Procedure

Data collection included comprehensive preoperative and postoperative evaluations. Preoperatively, patients underwent visual acuity testing, refraction, slit-lamp examination, and optical biometry to determine IOL suitability. Standard phacoemulsification surgery was performed, with monofocal or trifocal IOLs implantation. Postoperatively, 1 month and 3 assessments evaluated best-corrected visual acuity (BCVA), contrast sensitivity, optical quality metrics (MTF, Strehl ratio, aberrations), and patient satisfaction. Informed consent ensured participant confidentiality and adherence to research guidelines.

Statistical Analysis

Data analysis was performed using SPSS version 18.0. Descriptive statistics were used to summarize baseline characteristics. Independent t-tests assessed differences in continuous variables between groups, while chi-square tests analyzed categorical variables. A p-value <0.05 was considered statistically significant

Table 1: Baseline characteristics (n=50)

Table 1 presents the baseline characteristics of study participants, comparing monofocal and trifocal IOL groups. The average age in the monofocal group was 57.2 ± 5.7 years, while the trifocal group had a higher average of 62.8 ± 6.1 years. Gender distribution was similar between groups, with a slight female majority. Preoperative spherical equivalent and best-corrected visual acuity (BCVA) were comparable, with no significant differences observed.

Table 2: Postoperative visual activity (n=50)

Table 2 presents postoperative visual acuity outcomes at three distances (distance: 4 meters, intermediate: 60 cm, near: 40 cm). For distance vision, mean visual acuity was 0.02 ± 0.03 for the monofocal group and 0.03 ± 0.04 for the trifocal group, with no significant difference (p = 0.32). However, for intermediate vision, the trifocal IOL group had significantly better acuity (0.12 ± 0.04) compared to the monofocal group (0.19 ± 0.05) (p < 0.001). Similarly, near vision was significantly better in the trifocal group (0.13 ± 0.05) than the monofocal group (0.24 ± 0.06) (p < 0.001).

Table 3: Optical quality metrics (n=50)

Table 3 summarizes optical quality measures: Modulation Transfer Function (MTF at 50 lp/mm), Strehl ratio, and aberrations. The monofocal IOL group had a higher MTF (0.75 ± 0.02) than the trifocal IOL group (0.42 ± 0.03), with a statistically significant difference (p < 0.001). The Strehl ratio was significantly higher in the monofocal group (0.18 ± 0.01) compared to the trifocal group (0.13 ± 0.01) (p < 0.001). Aberrations were more pronounced in the trifocal IOL group (0.21 ± 0.03) than the monofocal group (0.15 ± 0.02) (p < 0.001).

Table 4: Patients satisfaction and spectacle dependence (n=50)

 Table 4 presents patient satisfaction and spectacle dependence outcomes. The mean overall satisfaction score was significantly higher in the trifocal IOL group (8.9 ± 1.0) compared to the monofocal IOL group (7.6 ± 1.1) (p < 0.001). For spectacle independence, 87% of trifocal group patients reported no need for spectacles, compared to 54% in the monofocal group (p = 0.01). Halo and glare complaints were more common in the trifocal group (19%) than the monofocal group (5%), though not statistically significant (p = 0.13).

This study compared the visual outcomes and optical quality of monofocal and trifocal intraocular lenses (IOLs) in cataract surgery. Our findings revealed significant differences between the two types of lenses, particularly in intermediate and near visual acuity, optical quality, and patient satisfaction.

The most important outcome of this study was the better intermediate and near visual acuity of the trifocal IOL group compared with the monofocal IOL group. In particular, trifocal IOL patients had markedly superior vision at 60 cm and 40 cm (p < 0.001) compared to monofocal lenses. Our result is consistent with previous works, which indicate that trifocal IOLs enhance intermediate and near vision at the price of reduced distance vision [9]. Because the trifocal IOL can enable patients to enjoy good vision at three distances, it can potentially add significant value in the everyday environment, especially with near vision and mid-range vision activities like reading or computer activities, as also shown by Avitabile et al. [3].

However, the distance vision between the two groups did not significantly differ, corroborating findings from Steinert et al. (1999), who pointed out that trifocal IOLs are made to provide more than enhancing near vision whilst maintaining the quality of distance vision [2]. These results stand out, given that the difference in distance visual acuity leaned towards monofocal IOLs at 1 year (p = 0.32), suggesting that the distance versus multifocal trade-off isn't definitive.

Optical quality metrics further demonstrated the differences between the 2 IOL types. Trifocal IOLs had significantly lower MTF and Strehl ratio values and higher aberrations than monofocal IOLs. This is in accordance with previous work indicating that the optical performance of multifocal IOLs is generally poorer than that of monofocal lenses [10, 11]. The low MTF and Strehl ratio may be attributed to the high aberrations associated with trifocal IOLs because these parameters are vulnerable to the effect of higher-order wavefront aberration in both the different types of visual optics and when entering the human eye, which is a known problem of multifocal lenses [12]. The optical deficiencies may also explain other visual complaints, such as halos and glare, which were more frequent in trifocal IOL than in monofocal IOL patients (19% vs. 5%, respectively). However, they did not reach statistical significance in our cohort (p = 0.13). This finding agrees with previous studies conducted by Woodward et al. who reported the multifocal IOLs to produce higher number of complaints regarding visual disturbances especially in low-light conditions [13].

Optical shortcomings notwithstanding, patient satisfaction was significantly higher in the group receiving trifocal than monofocal IOLs (mean satisfaction = 8.9 versus 7.6, respectively, p < 0.001). Trifocal IOL patients also had better spectacle independence, with 87% of patient’s spectacle-free compared with 54% of the monofocal group (p = 0.01). Such findings highlight the strong satisfaction level among patients receiving trifocal IOLs, given that trifocal lenses can generally fulfil both reading and intermediate requirements without spectacles based on data from Bellucci, Quinn & Mastrota [14, 15]. The greater spectacle independence in trifocal IOLs is especially relevant to those choosing multifocal IOLs who desire freedom from glasses after surgery.

Trifocal IOLs offer significant advantages in intermediate and near vision and patient satisfaction but with optical compromises that can affect overall visual quality. These data emphasize the need to assess refractive targets, visual results, and patient-centric choice for IOLs. Further long-term studies on overall visual and optical quality outcomes involving trifocal IOLs would enhance the understanding of their ability to improve visual performance in patients undergoing cataract surgery beyond the more common metrics, with respect to contrast sensitivity and retinal straylight.

Trifocal intraocular lenses significantly improved intermediate and near visual acuity and reduced spectacle dependence relative to monofocal lenses, although the latter demonstrated better optical quality. These results provide additional context regarding IOL performance and aid in patient-centered lens selection. Trifocal IOLs represent an important option for greater independence but with a slight increase in optical aberrations. In conclusion, this study highlights that optimized individualized IOL selection is critical to optimize outcomes, and the trifocal lens remains a good option for improved postoperative vision outcomes and patient satisfaction.

 Limitations of the study

This study is limited by its relatively small sample size and short-term follow-up. To assess long-term visual outcomes and complications, further research with more extensive, multicenter cohorts and longer follow-up periods is needed. Additionally, a broader range of optical quality metrics and patient-reported outcomes should be explored to enhance understanding of IOL performance in diverse populations.

Acknowledgment

I would like to express my sincere gratitude for the invaluable support and cooperation provided by the staff, participants, and my co-authors/colleagues who contributed to this study.

 Financial support and sponsorship: No funding sources.

Conflicts of interest: There are no conflicts of interest.

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