To our knowledge, this study is the first large Spanish cohort RWE study (+8000 eyes) that investigated the incidence of Nd:YAG capsulotomy after cataract surgery with different single-piece, monofocal, acrylic IOLs over 3 years. This research also serves to fill the gap with respect to infrequently studied IOLs in the PCO literature; in a recent systematic review on Nd:YAG capsulotomy [9], out of the 65 IOLs assessed in 67 publications, it was just the Alcon AcrySof lens that was present from the cohort of lenses assessed in this study. The overall incidence of Nd:YAG capsulotomy 3 years after cataract surgery was approximately 14%, and the rates were significantly lower for Alcon AcrySof IOLs (5%) compared to the other IOLs implanted at the study sites (31.1% for AJL LLASY60, 23.2% for IOL Tech Stabibag, 23.1% for Medicontur Bi-flex, and 21.2% for Zeiss Asphina, Fig. 2a) (P < 0.0001 for each comparison). The incidence of Nd:YAG capsulotomy increased from year 1 to year 3 post surgery, but was consistently about 80% lower for Alcon AcrySof compared to the other included IOLs. All non-Alcon IOLs were associated with over five-fold higher odds for Nd:YAG capsulotomy compared to Alcon AcrySof. At IOL level, Nd:YAG capsulotomy rates were highest for AJL LLASY60, followed by Medicontur Bi-flex, IOL Tech Stabibag (all hydrophilic), and Zeiss Asphina (hydrophilic with hydrophobic surface), and the lowest rates for Alcon AcrySof (hydrophobic) IOLs (Fig. 2a). Differences in Nd:YAG capsulotomy rates between the IOLs became more pronounced from 1 year to 3 years post cataract surgery. Our findings suggest a protective effect provided by Alcon AcrySof IOLs compared with other IOLs. This effect could be due to the specific material characteristics [10], as suggested by previous RWE studies, which showed lower PCO and Nd:YAG capsulotomy rates for hydrophobic compared with hydrophilic IOLs, with consistently superior outcomes for hydrophobic AcrySof IOLs compared to other IOLs [17,18,19,20,21,22]. The Nd:YAG capsulotomy rates in the current study were comparable to previous studies for the Alcon AcrySof IOLs (5% vs. 2.4% [21] and 3.9%), but more pronounced differences were present for the included IOLs that had hydrophilic surface characteristics (26.8% vs. 10.9% [21]). For IOLs with hydrophilic materials, we found the highest Nd:YAG capsulotomy incidence of 31.1% for AJL LLASY60 IOLs and the lowest for Medicontur Bi-flex and IOL Tech Stabibag (both ~23%). In comparison, the hydrophilic Zeiss Asphina IOLs with hydrophobic surface characteristics showed only a slightly lower Nd:YAG rate (21.2%), which was comparable to recent reports of Nd:YAG 3 years after cataract surgery by others (24.6%).
Our results indicate that the hydrophobic surface material is not as effective in preventing PCO as an entirely hydrophobic lens. Hydrophobic acrylic materials have a low water content and high fibronectin bio-adhesion properties. This bioactivity is thought to result in a sandwich pattern of adhesion between a single layer of lens epithelial cells, the posterior capsule, and the IOL body, thus allowing for better binding compared to other IOL materials, which could protect against PCO development [23, 24]. Possibly, the prevailing high water content (25%) may account for inferior fibronectin binding, while the existence of a rounder edge design may also play a role [25]. However, it is possible that other lens characteristics might account for the differences in performance with respect to Nd:YAG between IOLs. For instance, it has been suggested that the ‘stepped’ sharp edge, which extends beneath the uninterrupted broad haptic junction of the IOLs, may delay, but cannot prevent the occurrence of PCO. A recent comparison of PCO in square edged IOLs has reported more beneficial outcomes for IOLs with a radius of curvature of less than 10 μm, while the radius of curvature of Asphina is 13.7 μm. In contrast, and although both the Zeiss Asphina and AcrySof models have a similar edge design (square edge, non-360°), the AcrySof lens has a radius of curvature (8.5μm) smaller than 10 μm, which may offer a further rationale as to why AcrySof models have demonstrated lower PCO rates. Also, IOLs manufactured with sharp optic edges have been shown to be more effective in preventing PCO by creating a mechanical barrier at the capsular bend compared to round-edged IOLs. Compared with the hydrophobic IOLs, the high water content and specific manufacturing process of hydrophilic IOLs has been suggested to result in a rounder edge profile, which could account for higher rates of PCO and subsequent Nd:YAG [26]. Besides, differences in the Nd:YAG incidence rates by different IOLs in our study could also be due to other IOL properties, for instance, different lens size or haptic design characteristics between the stableforce vs. plate, tri-, or c-loop haptic designs of the hydrophilic IOLs, as previously suggested by other RWE studies [19]. The findings highlight the need for further research to fully understand the clinical consequences of IOL choice and material characteristics.
While the direction of the current findings was in line with previous work, the overall Nd:YAG capsulotomy incidence was substantially higher, which might be due to the specific sample characteristics [19, 21, 22]. Moreover, while the investigation of risk factors for Nd:YAG capsulotomy was not our main aim, the multivariate analysis showed that diabetic retinopathy, younger age at cataract surgery, and female gender were associated with higher risk for PCO, in line with the findings previously reported by others [21]. High myopia was associated with an increased risk of Nd:YAG capsulotomy in the univariate analysis (see Supplementary Material); however, this association did not persist in the adjusted multivariate analysis. Conflicting results have been reported with respect to whether myopia is related to PCO development [27, 28].
The average incidence of post-Nd:YAG capsulotomy complications within 6 months for the study cohort was 7.1% (95% CI 5.9–8.3); the most frequently observed complications were posterior vitreous detachment, macular atrophy, and cystoid macular oedema.
This study is the first to report on RWE evidence from Spain relating to the incidence of Nd:YAG capsulotomy associated with single-piece monofocal IOLs, showing significant differences in Nd:YAG rates between IOLs. The strengths of this study are the inclusion of a large sample that has been followed over 3 years post cataract surgery and the presentation of novel RWE insights on specific postoperative Nd:YAG capsulotomy treatment outcomes associated with different IOLs in a Spanish patient population. Another strength of our study is that the two hospitals that contributed data (Ribera Salud hospitals) are the hospitals in Spain that have fully adopted electronic medical record and resource management systems, which offered a unique opportunity to conduct this retrospective study using secondary data feasible in a Spanish setting. In addition, the Ribera Salud hospital network is a leading healthcare system using the capitation model in Spain. This model attracts patients to stay long within the care system and accumulates more longitudinal and complete follow-up data, which can be utilized by future RWE studies.
While our findings are important, they need to be interpreted in the light of the methodological consideration that the RWE data may over-represent more severe cases, given that these might be seen more frequently compared to cases with mild PCO or those who responded well to surgical treatment. A further limitation relates to potential biases that may arise from certain variables that may also play a role in PCO formation that were not controlled for in the conducted multivariate analysis. Examples of such factors from recent work include axial length, topical steroids, and nonsteroidal anti-inflammatory medications (NSAIDs) [29] and the dioptric power of the IOL implanted at the time of surgery [30]. Moreover, potential biases associated with between-eye correlation were not controlled for in this research; future work could consider these factors as part of the statistical analyses.
To conclude, the finding that Alcon AcrySof IOLs are associated with a lowest incidence of Nd:YAG capsulotomy compared to all other IOLs implanted at the study site has important clinical implications. Crucially, IOL choice may reduce patient burden and improve quality of life after cataract surgery. In addition, a reduced need for Nd:YAG capsulotomy after cataract surgery is likely to reduce clinical risks and subsequent healthcare costs. Further research is needed to investigate the relationship between specific IOL design characteristics and other confounding factors that may impact Nd:YAG capsulotomy rates and the related clinical risks and treatment costs associated with the procedure.
Summary
What was known before
What this study adds
-
This study extends previous insights to a Spanish cohort and shows that Alcon AcrySof IOLs are associated with lower Nd:YAG capsulotomy rates compared to other single-piece monofocal lenses, which include AJL LLASY60, Medicontur Bi-flex, and IOL Tech Stabibag, which are hydrophilic IOLs, and Zeiss Asphina, which are hydrophilic IOLs with hydrophobic surface.
