Comparative Analysis of Postoperative Visual Outcomes of Light-Adjustable Lens, Toric Monofocal, and Spherical Monofocal Intraocular Lenses

Abstract

This retrospective study compares postoperative visual outcomes among 150 eyes treated with Light-Adjustable Lenses (LAL), toric monofocal lenses, and spherical monofocal lenses at Discover Vision Centers in Missouri and Kansas. The study included individuals with an average age of 68.9 years (25–82 years) who had cataract extraction (CE) within the past five years. Patients with prior corneal refractive procedures, including Radial Keratotomy (RK), Photorefractive Keratectomy (PRK), Laser-Assisted In Situ Keratomileusis (LASIK) or Small Incision Lenticule Extraction (SMILE) were excluded. Sixty-four percent of eyes with LALs achieved uncorrected distance visual acuity (UCDVA) better than 20/20 after the final lock-in, 46.0% with toric monofocal lenses, and 32.0% with spherical monofocal lenses. LAL-treated eyes also showed lowest residual refractive error, with a final mean spherical equivalent of 0.0 ± 0.353D, outperforming toric (0.08 ± 0.386D) and spherical monofocal lenses (0.20 ± 0.631D). These results suggest that LALs offer superior outcomes, though further research is warranted.

Introduction

A cataract is the gradual clouding of the normal clear crystalline lens and is the leading cause of vision loss in the United States (US). Most cataracts are intrinsically age-related, affecting more than 20.5 million Americans above the age of 40. Annually, 6.1 million cataract extractions (CE) are performed, making it the most commonly performed ambulatory surgery in the US.¹

To provide informed consent it is mandatory to educate patients on the various options available to them with respect to the changing landscape of intraocular lens (IOL) technology. When considering lifestyle and personal preferences, understanding the differences between options can play a significant role in pre-operative choice and post-operative patient satisfaction.

Spherical monofocal lenses are the most frequently implanted IOLs in cataract surgery. While these lenses are able to provide clear vision at one focal point, they cannot correct astigmatism or allow for any postoperative adjustments. Patients may have to wear glasses for both near or distance vision to correct residual refractive errors.^2,3 Data shows that spherical monofocal lenses can offer acceptable visual outcomes for the majority of patients, but the inability to address astigmatism poses limitations for patients with visually significant corneal astigmatism.^4,5

Toric monofocal lenses incorporate astigmatism correction into the design of the lens.^2,6 Roughly 50% of patients have visually significant astigmatism that must be corrected to optimize uncorrected vision. Toric lenses provide improvement in uncorrected distance visual acuity (UCDVA) and decrease residual astigmatism when compared with spherical monofocal lenses.⁷

The Light Adjustable Lens (LAL) is an IOL design that incorporates technology that is unique in its ability to allow postoperative adjustments to spherical and astigmatic lens power. LALs enable fine-tuning of lens power postoperatively. LALs use photosensitive macromers in the lens, that when presented with specific wavelengths of ultraviolet light, can be reshaped. Adjusting LALs requires up to three sessions following the surgery in which the lens power is modified to effect the desired refractive power.⁸ Refraction adjustability after implantation affords improved uncorrected postoperative visual acuity compared to traditional nonadjustable technology. Studies show that patients with LALs display a higher chance of achieving UCDVA better than 20/20 when contrasted with both spherical or toric monofocal lenses.⁹ In addition, there is a lower level of residual refractive errors with LALs which enhances overall visual clarity, reduces dependence on any corrective eyewear and increases patient satisfaction with postoperative outcomes.^10,11

The objective of this retrospective study is to provide a comparative analysis of the outcomes associated with the newer technology of LALs versus the currently available spherical and toric monofocal lenses. Emphasizing efficacy, suitability, and comfort for patient populations, we aim to provide insights of the changing field of cataract surgery. By evaluating monocular UCDVA and manifest refraction spherical equivalent (MRSE), this study seeks to define outcome differences and better understand patient outcomes in cataract surgery.

Methods

Study Design: Pre- and Postoperative Patient Chart Review

This is an observational study of retrospective data obtained from 2019 to 2024 at Discover Vision Centers’ surgical outpatient centers in Missouri and Kansas. The study includes a total of 150 eyes of 99 healthy adults, averaging 68.9 years of age (25–82 years), who received LAL, toric, or spherical monofocal IOLs. All individuals in each group were consecutive patients. Exclusion criteria include patients who underwent prior RK, PRK, LASIK and SMILE. Patients with diagnosed comorbidities of macular degeneration and glaucoma were also excluded from this analysis. This study is in accordance with the tenets of the Declaration of Helsinki. Written consent from patients was not required due to the nature of retrospective review and de-identified data.

All patients underwent comprehensive preoperative ophthalmic exams with dilation to confirm diagnosis of a visually significant cataract and relevant measurements prior to CE. Visual acuity was measured with standard visual acuity charts with 100% contrast and reported using 20/20 for standard vision. Topographic values were measured using the ZEISS Atlas Topographer and ZEISS IOL Master. Preoperative refractive measurements were measured with the ZEISS i.Profiler Plus Autorefractor and manual phoropter refractions. Patient biometry values were determined with the ZEISS IOLMaster 500, using Holladay II formulas for calculation of suitable IOL power to a target manifest refraction of plano, or 0.0 diopters.

The primary postoperative outcomes of this study are monocular UCDVA, monocular mean residual sphere and cylinder, and monocular mean spherical equivalent (SEQ) at their appropriate final refractive postoperative exam. The measurements and manifest refractions of patients who received spherical or toric monofocal lenses were obtained from their postop 1-month visit, while LAL patient postop refractive values were measured at their visit status-post their second lock-in treatment.

Surgical Procedure and Lens Types

All procedures were performed by the same surgeon with the same protocols at two ambulatory surgical centers. The patient’s surgical eye was prepped in holding with topical anesthesia of proparacaine 0.5% and dilated with phenylephrine 2.5%/Tropicamide 1%. All patients also received Ofloxacin preoperatively in the surgical eye. Once in the operating room, the eye was prepped with Betadine and draped in a sterile fashion. A lid speculum was placed and proparacaine 0.5% was administered over the corneal surface. Clear corneal entry was achieved with a 3.0 mm temporal incision and 1.0 mm sideport incision. One percent preservative-free lidocaine was injected intracamerally to prepare for clear corneal phacoemulsification. Once the residual cortex was removed, the appropriate posterior chamber IOL was inserted through the clear corneal incision. Specific lenses and relevant models included in the study are LAL^®, LAL+™ (RxSight). Toric monofocal IOLs include: TECNIS^® Toric I ZCT 150, 225, 300, 400, TECNIS^® Toric II ZCU 150, 225, 300, 375, 450, 525, 600 (Johnson and Johnson Vision) and SA6AT9 AcrySof^® Toric (ALCON). The LI61AO Sofport^® (Bausch and Lomb) is the spherical monofocal IOL studied.

Postoperative drops of topical steroid and antibiotics were prescribed accordingly depending on patient tolerance, usually Pred-Forte with tapering and Ciprofloxacin. Patients were educated on the importance of compliance with postoperative drop scheduling prior to, and following CE. The imperativeness of wearing RxSight UV protective glasses during their postop phase prior to lock-ins was emphasized to patients with LALs, explaining that UV light sources, including the sun, can modify the prescription of the lens and lead to unexpected visual outcomes. All LAL patients received three different types of RxSight UV protective glasses: one clear, one clear with bifocal and one tinted.

No sooner than 17 days after surgery, LAL patients underwent adjustment treatments with the digital Light Delivery Device (LDD) ultraviolet light at 365 nm to modify the shape of the lens, adjusting refractive power to desired targets. Adjustments were performed until the patient was satisfied with their vision and ready to lock-in. All 50 eyes underwent a primary adjustment. Twenty-six eyes (52%) received at least two adjustment treatments and then proceeded with lock-in. Sixteen eyes (32%) had tertiary and six eyes (12%) had quaternary adjustments prior to lock-in. Patients were instructed that after the final light treatments, there can be no additional refractive changes.

Results

Of the 150 eyes of 99 adults included in the study, 50 eyes received LALs, 50 eyes received toric monofocal, and the remaining 50 eyes had spherical monofocal IOLs implanted. The mean age of eligible patients for this report was 68.9 years, with a gender ratio of 68.7% female (103 eyes) to 31.3% male (47 eyes). Table 1 provides more information regarding patient demographics as well as pre- and postoperative refractive data of mean sphere, cylinder, and spherical equivalent in diopters.

Table 1.

Pre- and postoperative demographic and refractive data of patients.

Pre-Operative Data of Subjects (n = 150)
	LAL	Toric Monofocal	Spherical Monofocal
Eyes (n)	50	50	50
Sex (M/F)	18/32	17/33	12/38
Age (Years)	65.5	69.5	71.7
Mean sph (D)	−3.4 ± 5.632	−3.63 ± 3.312	−1.65 ± 3.835
Mean cyl (D)	1.2 ± 0.974	1.86 ± 1.419	0.95 ± 0.645
Mean sph equiv (D)	−2.8 ± 5.356	−2.70 ± 3.186	−1.18 ± 3.924
Post-Operative Refractive Data of Subject (n= 150)
	LAL	Toric Monofocal	Spherical Monofocal
Mean sph (D)	−0.2 ± 0.392	−0.14 ± 0.398	−0.18 ± 0.657
Mean cyl (D)	0.3 ± 0.397	0.44 ± 0.387	0.76 ± 0.609
Mean sph equiv (D)	0.0 ± 0.353	0.08 ± 0.386	0.20 ± 0.631

Comparison of Postoperative UCDVA Between Groups

After CE, at least 90% of all eyes, regardless of lens type, reached monocular UCDVA ≥ 20/40. At the stable, finalized postop visit after the second lock-in treatment, 32 eyes (64.0%) of the LAL group had UCDVA ≥ 20/20, compared to the 23 eyes (46%) of the toric monofocal group, and 16 eyes (32%) of the spherical monofocal group (Figure 1).

Figure 1.

Comparison of monocular UCDVA in the LAL, toric, spherical monofocal treatment groups at their postop visit.

Comparison of Postoperative Refractive Diopters Between Groups

Seventy-four percent of LAL eyes were within 0.25D of target plano spherical equivalent, higher than that of the toric monofocal (50%) and spherical monofocal (38%) groups. Ninety-two percent of LAL eyes were within 0.50D of plano spherical equivalent, compared to 82% of the toric and 64% of the spherical monofocal groups (Table 1). The bar graph in Figure 2 summarizes the accuracy of spherical equivalent refraction outcomes between each lens type.

Figure 2.

Accuracy of spherical equivalent refraction between different treatment groups status post cataract surgery.

LAL patients achieved decreased residual mean cylinder and MRSE (0.3 ± 0.397D, 0.0 ± 0.353D). When looking at the difference between the preop and postop values, there is also a greater change in preop mean residual cylinder values compared to postop (Figure 3). The standard deviation in mean sphere, cylinder, and SEQ are reduced in LAL patients compared to that of spherical and toric monofocal values.

Figure 3.

Comparison of change in mean cylinder (D) between pre- and postop CE for different treatment groups.

Discussion

With constant evolutions of cataract surgery and IOL technology, physicians continue to explore ways to improve visual outcomes for their patients. Whether that be through improved surgical techniques, Femtosecond laser-assisted cataract surgery (FLACS), or the use of different lens types, the field of ophthalmology continually strives to improve the most commonly performed surgical procedures of cataract extraction with IOL placements. With new advancements, it is important to compare the various surgical treatment options and their respective visual outcomes in an effort to properly validate superiority and to educate patients prior to consenting to surgery.

In our study, when looking at monocular UCDVA, compared to the spherical and toric monofocal lenses, the LAL consistently had a higher proportion of eyes reaching better unaided visual acuity. In fact, it was found that LAL patients (64%) were twice as likely to reach 20/20 or better monocular UCDVA compared to the spherical monofocal IOL eyes (32%). This is consistent with the FDA studies of 600 subjects where 70.1% of LAL patients achieved 20/20 compared to 36.3% of the control, spherical monofocal IOL group.¹²

Generally, patients with mild to no corneal astigmatism perform well with a spherical IOL. However, a study of 2,415 patients, all within the prevalent age group for CE, found that on average, 64.4% of patients had corneal astigmatism between 0.25 to 1.25D, and 22.2% had more than 1.50D.¹³ Furthermore, astigmatic changes increase with age as much as 10% in a span of a 12-year period.¹⁴ This underlines the importance of astigmatic management with CE by calculating the most appropriate IOL power for each individual, but also choosing the lens type to improve overall visual acuity of the general patient population.

Yamauchi et al. showed that toric monofocal lenses had significantly better postoperative binocular UCDVA, compared to non-toric spherical IOLs of the same material, a finding seen in our results as well as other studies.^15,16 Residual astigmatism is a common refractive error that is observed even after uncomplicated CE and if not addressed, these unexpected outcomes contribute to overall patient dissatisfaction.^17,18 Toric monofocal lenses, compared to spherical monofocal lenses (0.20 ± 0.631D), do remain an effective option to manage corneal astigmatism as seen in our results, achieving MRSE of 0.08 ± 0.386D, but studies have found that residual astigmatism and residual spherical refractive errors are still observed even with toric lenses. This can be due to incorrect preoperative measurements of corneal astigmatism and the inability to predict postoperative astigmatic results, especially in those with low astigmatism. The postoperative residual refractive errors and residual astigmatism can also be due to the misalignment of the lens implanted, postoperative rotation of the toric IOL despite accurate alignment at the time of surgery, or due to surgically induced astigmatism after wound healing of the incision.^17,19,20 These postoperative results bring up the question of how to adjust the residual astigmatism that can be caused after CE and IOL placement. LAL technology and the ability to adjust the implanted lens even after the procedure can help improve these unexpected visual outcomes.

Our study illustrates that although LAL, spherical monofocal and toric monofocal lenses improve overall visual outcomes in all eyes, LAL lenses excel with the smallest postop mean residual cylinder value of 0.3 ± 0.397D (Figure 3). This data was similar to another study where 100% of patients, who started with 0.75 to 2.0D of corneal astigmatism, achieved MRSE within 0.25D of emmetropia nine months status post LAL adjustments and lock-in.²¹ While toric monofocal lenses also improve postoperative MRSE and overall vision, they are still limited to 82% within 0.5 D and 50% within 0.25 D of target, compared to 92% of LALs being within 0.5 D and 74% within 0.25 D of target refraction.

Additionally, LAL lenses had the greatest reduction in mean SEQ, with a beginning preoperative MRSE of −2.8 ± 5.356D to a postoperative 0.0 ± 0.353D of targeted emmetropia, showing not only the smallest MRSE, but also the most efficiency of reducing MRSE compared to spherical and toric monofocal lens types. Hengerer et al. also found similar findings in LAL patients but with an extended follow-up period of 18 months. Their study found a final MRSE of 0.03 ± 0.17 D in LAL patients thus showing the long-term refractive stability of these IOLs.²²

It is important to understand that the results of LALs rely on patient compliance. Patients are required to wear UV-protective glasses in any presence of ambient outdoor UV light sources for up to four to six weeks or until lock-in is complete. If not, the photosensitive lenses are at risk of photopolymerization and unexpected refractive outcomes. A case study from 2023 discussed a 61-year-old man who required an explanation of his LAL due to self-reported non-compliance of UV glasses wear and resulting uncontrolled polymerization of the LAL.²³ The introduction of ActivShield in the lens has markedly decreased chances of auto adjustment.²⁴ Patient compliance should be addressed and taken into consideration as physicians recommend the lens to potential candidates.

Conclusion

The visual outcomes of monocular UCDVAs and reduced residual cylinder and MRSE of patients who received LALs objectively exhibit superior results to those of spherical and toric monofocal lenses. A recent study presented at the Association for Research in Vision and Ophthalmology meeting in April 2023 also found that LALs are more cost-effective when compared to surgery with conventional monofocal lenses. The study analyzed the incremental cost-effectiveness ratio (ICER) in dollars per quality-adjusted life years (QALY) gained post surgery and found that patients who received LALs, although more expensive upfront, saw better post-surgical vision outcomes due to its adjustability after implantation. Considering the long-term cost benefits when deciding between different IOL types is important, which can further contribute to overall patient satisfaction.²⁵ Additional research of increased sample size, long-term postoperative refractive stability are required. Qualitative patient satisfaction studies are also welcomed.