Phacoemulsification with intraocular lens (IOL) implantation is one of the most common procedures in eye surgery [1, 2]. In addition to monofocal IOLs, premium IOLs (i.e., aspheric, multifocal, and toric) currently gain popularity. Increased active life expectancy and increased patients’ demands for both distance and near vision in developed countries in part account for this phenomenon. Good uncorrected visual acuity (UCVA) and freedom from glasses are major requirements for cataract surgery. However, many patients are unhappy with their results since they do not achieve target refraction and have poor UCVA [3-5]. In these patients, optimal management strategy is to correct residual refractive errors to achieve desired visual outcomes. This is particularly important for premium IOLs.
Currently, several approaches are applied in clinical practice to correct residual ametropia after IOL implantation. They can be subdivided into two categories, i.e., corneal and intraocular. Corneal options involve laser in situ keratomileusis (LASIK) and photorefractive keratectomy (PRK). Intraocular options involve piggyback IOL implantation and IOL exchange [6, 7]. Published data on the benefits of LASIK and PRK to correct small spherical and cylindrical refractive errors and piggyback IOL implantation and IOL exchange to correct high spherical refractive errors are available [6-9]. Considering few large comparative studies on ametropia correction after cataract surgery by LASIK and PRK, we have performed a literature search in Russian and English databases throughout the time of existence of laser refractive surgery (about 20 years). There are numerous studies on the safety and predictability of laser refractive surgery to correct residual ametropia after cataract surgery [3, 8, 9-16], refractive lens exchange [17-20], implantation of phakic IOLs , and piggyback IOL implantation . Results of the studies on LASIK and PRK for ametropia correction on pseudophakic eyes are listed in Table 1. However, IOL model is not specified in most studies.
The aim of this study was to analyze the outcomes of residual ametropia correction by LASIK and PRK on pseudophakic eyes depending on IOL model.
57 patients (79 eyes) after cataract surgery (n = 37) or refractive lens exchange (n = 42) with IOL implantation (2012-2017) were enrolled in this prospective open study. 45.6% (n = 26) were women and 54.5% (n = 31) were men. Mean age was 50.8 ± 13.9 (19-79) years.
Preoperative eye examination included automated refractometry (Tonoref II, Nidek, Japan), visual acuity and IOP measurements, computer perimetry (HFA-750i, Zeiss, Germany), corneal topography (Pentacam, Oculus, Germany), B-scan ultrasonography and ultrasound pachymetry (US-400, Nidek, Japan), and optical coherence biometry to measure axial length, corneal curvature, and anterior chamber depth (IOLMaster, Zeiss, Germany). Dilated fundus examination and, as needed, optical coherence tomography (RTVue-100, Optovue, USA) were performed to prevent intra- and postoperative complications.
LASIK (n = 72, 91.1%) and PRK (n = 7, 8.9%) were performed using standard protocols. Femto-assisted laser eye surgery (FS200 WaveLight, Alcon, USA) was performed on 6 eyes (7.6%). IOL power ranged from 13 D to 30 D (21.7 ± 3.4 D). In most patients (97.5%), target refraction was ±0.25 D. In two patients, target refraction was -1.5 D and -2.5 D. Follow -up was 6 to 9 (7.1 ± 1.2) months.
Among preoperative ocular comorbidities, age-related macular degeneration associated with high myopia and staphyloma (n = 2, 2.5%), central retinal degeneration (n = 12, 15.2%), early glaucoma (n = 1, 1.2%), amblyopia (n = 21, 26.6%), and Fuchs’ dystrophy (n = 2, 2.5%) were diagnosed.
Each eye was assessed separately using the following criteria: pre- and postoperative spherical and cylindrical components, keratometry readings (K1 and K2) and their axes, UCVA and best-corrected visual acuity (BCVA) at 4 meters, intra- and postoperative complications, IOL stability and if repositioning was required. In addition, indices of efficacy and safety were assessed. Index of safety is calculated as mean postoperative BCVA divided by mean preoperative BCVA. Index of efficacy is calculated as mean postoperative UCVA divided by mean preoperative BCVA.
All patients were subdivided into groups according to IOL model. Monofocal IOLs were various models of spheric and aspheric IOLs (Alcon, USA). Multifocal IOLs were Acrysof ReStor (Alcon, USA), AT LISA tri (Carl Zeiss, Germany), and Lentis M-plus 313 (Oculentis, Germany). In group I (28 patients, 38 eyes), spheric and aspheric monofocal IOLs were implanted. In group II (29 patients, 39 eyes), multifocal IOLs were implanted. Clinical and functional characteristics of patients are listed in Table 2.
The groups were similar in all parameters (p > 0.05) excepting cylindrical component (-1.45 ± 0.43 D in group I and -0.4 ± 0.29 D in group II, p = 0.046).
Postoperatively, all patients were prescribed with hyaluronic acid-containing eye drops (3 or 4 times daily for 6 months).
Statistical analysis was performed using Microsoft Excel 2010 and Statistica software v. 10.1 (StatSoft, USA). Arithmetic mean (M), standard deviation (SD), minimum and maximum values, and range of variation/Rv (i.e., difference between min and max) were calculated. Student’s T-test was used to compare mean values and to assess reliability of the results. Fisher’s exact test was used to compare occurrences of the parameter. Differences between the samples were considered statistically significant at p < 0.05 (95% confidence interval).
In group I, distance UCVA significantly improved from 0.31 ± 0.14 to 0.72 ± 0.22 (p < 0.05). Postoperatively, no significant changes in distance BCVA were revealed. No significant changes in spherical component were revealed as well (0.21 ± 1.47 D preoperatively and 0.23 ± 0.76 D postoperatively, p > 0.1). Target refraction ± 0.5 D was achieved in 81.6% of patients (n = 31). After 6 months, cylindrical component significantly reduced from -1.45 ± 0.43 D to -0.18 ± 0.80 D. No significant changes in keratometry readings were revealed (K1: 42.4 ± 2.7 D preoperatively and 42.1 ± 2.6 D postoperatively; K2: 44.3 ± 2.4 D preoperatively and 43.5 ± 2.1 D postoperatively); this phenomenon is accounted for by minor spherical component to be corrected. Distance UCVA better than 0.5 was achieved in 94.7% of patients (n = 36). Index of safety was 0.99. Index of efficacy was 0.87.
In group II, distance UCVA significantly improved from 0.43 ± 0.17 to 0.80 ± 0.18 (p < 0.05). Postoperatively, no significant changes in distance BCVA were revealed. Some decrease in spherical (from 0.42 ± 1.28 D to 0.27 ± 0.51 D) and cylindrical (from -0.4 ± 0.29 D to -0.17 ± 0.58 D) components was reported after 6 months, however, the differences were insignificant (p > 0.05). Target refraction was achieved in 82.1% of patients (n = 32). No significant changes in keratometry readings were revealed postoperatively (p > 0.1). Distance UCVA better than 0.5 was achieved in 97.4% of patients (n = 38). Index of safety was 0.99. Index of efficacy was higher than in group I (0.96) being accounted for by more careful patient selection for multifocal IOLs.
Comparative analysis of the outcomes in the groups has demonstrated that laser eye surgery provides significantly greater reduction of cylindrical component in group I as compared with group II (p < 0.05) if there are differences in this parameter at baseline. Postoperatively, distance UCVA has significantly improved in both groups (p < 0.05). The rate of target refraction achievement was similar (p > 0.1).
Our findings are similar to the results of other studies. Y.Y. Fan еt al. have studied the outcomes of PRK for refractive error correction after the implantation of aspheric, multifocal, and toric IOLs. The authors have demonstrated significant improvement of distance UCVA and no changes in spherical and cylindrical components in the group of aspheric and multifocal IOLs . The lack of postoperative changes in spherical component is accounted for by the correction of both myopia and hyperopia at baseline. We have demonstrated significant reduction of cylindrical component in group I while toric IOLs were not included in the analysis. The results of other studies were similar [12, 13]. Distance UCVA better than 0.5 was achieved in 94.7% of patients in group I and 97.4% of patients in group II. These outcomes are better than in most studies [3, 10, 11, 13] and similar to the results of Kim еt al. , Jin еt al. , and Muftuoglu еt al. .
Residual ametropia after IOL implantation can be corrected by LASIK and PRK. In monofocal IOL group, significant decrease in cylindrical component was demonstrated. Procedure efficacy in terms of target distance UCVA achievement was independent of IOL model. The rates of target refraction achievement were similar in the groups. Index of safety was 0.99 in both groups. Index of efficacy was 0.87 in group I and 0.96 in group II (more careful patient selection for multifocal IOLs accounts for the difference).
About the authors:
1Evgeny P. Gurmizov — MD, PhD, Head Doctor, ORCID iD 0000-0002-3438-3404;
2Kirill B. Pershin — MD, PhD, Professor, Medical Director, ORCID iD 0000-0003-3445-8899;
2Nadezhda F. Pashinova — MD, PhD, Head Doctor, ORCID iD 0000-0001-5973-0102;
2Alexander Yu. Tsygankov — MD, PhD, Scientific Advisor of Medical Director, ORCID iD 0000-0001-9475-3545.
1 LLC “Diagnostic Center “Vision”. 3/1, Marksistskaya str., Moscow, 109147, Russian Federation.
2 LLC “SovMedTech”. 6, Apraksin lane, St. Petersburg, 191023, Russian Federation.
Contact information: Alexander Yu. Tsygankov, e-mail: firstname.lastname@example.org. Financial Disclosure: no author has a financial or property interest in any material or method mentioned. There is no conflict of interests. Received 26.01.2019.