A post-operative manifest refractive error as close as possible to target is key when performing cataract surgery with intraocular lens (IOL) implantation, given that residual astigmatism and refractive errors negatively impact patients’ vision and satisfaction. This review explores refractive outcomes prior to modern biometry; advances in biometry and its impact on patients’ vision and refractive outcomes after cataract surgery; key factors that affect prediction accuracy; and residual refractive errors and the impact on visual outcomes. There are numerous pre-, intra-, and post-operative factors that can influence refractive outcomes after cataract surgery, leaving surgeons with a small “error budget” (i.e., the source and sum of all influencing factors). To mitigate these factors, precise measurement and correct application of ocular biometric data are required. With advances in optical biometry, prediction of patient post-operative refractory status has become more accurate, leading to an increased proportion of patients achieving their target refraction. Alongside improvements in biometry, advancements in microsurgical techniques, new IOL technologies, and enhancements to IOL power calculations have also positively impacted patients’ refractory status after cataract surgery.

Purpose: The use of monochromatic light in the assessment of intraocular lenses (IOLs) has been criticized for not representing the real-world situation. This study aimed to measure and compare the image quality of 3 extended depth-of-focus (EDOF) IOL models in monochromatic and polychromatic light. Setting: David J Apple Laboratory, Heidelberg, Germany. Design: In vitro study. Methods: An optical metrology instrument was used to study image quality metrics of diffractive IOLs with chromatic aberration correction (Symfony and AT Lara) and a refractive lens (Mini Well). The modulation transfer function (MTF) was measured in green and polychromatic light at a 2.0 mm, 3.0 mm, and 4.0 mm aperture. The EDOF IOL's tolerance to defocus was tested against a monofocal lens. Results: The mean MTF of the EDOF IOL at far distance was decreased in polychromatic compared with monochromatic light. The largest effect was found in the refractive lens; however, at intermediate distance, only small differences occurred. In their tolerance to defocus, the EDOF IOLs were superior to the monofocal IOL. The diffractive IOL had higher MTFs than that of the refractive IOL at 2 primary foci, the refractive IOL's optical quality varied less with defocus at 3.0 mm. The refractive lens was the most susceptible to changes in aperture size. Conclusion: The diffractive EDOF IOL was more resistant to chromatic effects than the refractive IOL. The EDOF IOLs provided an extended through-focus performance compared with the monofocal IOL, but differences in optical design, particularly pupil dependency, should be considered when refining IOL selection for patients.

To study the effect of glistenings on the optical quality of a hydrophobic acrylic intraocular lens (IOL). David J. Apple Laboratory, Heidelberg, Germany. An in vitro laboratory study. An accelerated aging protocol was used to induce glistenings (microvacuoles) in 38 hydrophobic acrylic IOLs. The IOLs were warmed to 45°C and then cooled to 37°C. Image analysis of light-microcopy photographs determined the number and size of microvacuoles (MV). A classification was applied based on the glistening number per mm2: grade 0 (none), grade 1 (1-100), grade 2 (101-200), grade 3 (201-500) and grade 4 (more than 500). An optical bench was used to measure each IOL's modulation transfer function (MTF) and Strehl ratio to evaluate the impact of glistenings on image quality. Glistenings were observed in all IOLs. The mean glistening numbers ± SD (MV/mm2) in grades 1 through 4 were 74 ± 12.7, 142 ± 22.2, 297 ± 76.2, and 1509 ± 311.9, respectively. The mean glistening sizes in grades 1 through 4 were 13.28 ± 3.85 μm, 15.88 ± 2.08 μm, 16.85 ± 3.23 μm, and 15.27 ± 2.25 μm, respectively. Statistical analysis showed that grades 1 through 3 did not change the optical quality; however, in grade 4, the MTF and the Strehl ratio were significantly affected. A limited number of glistenings (<500 MV/mm2) had no effect on the image quality. Although statistically significant deteriorations in the MTF and the Strehl ratio were observed in grade 4, the effects found were small and are unlikely to affect the visual quality.

Presbyopia correction through implantation of a trifocal intraocular lens (IOL) is a modality offered to both cataract and refractive-lens exchange patients. To maximize postoperative satisfaction, IOL selection needs to be made based on patients’ requirements aligned with the available technology. Five Trifocal IOLs were assessed in this study, and their differentiating features were identified: Triumf POD L GF, AT Lisa Tri, Tecnis Synergy, AcrySof IQ PanOptix, and Acriva Trinova Pro C. The optical quality was assessed using the modulation-transfer-function principle. Simulated defocus curves were derived from a non-linear formula. Far-focus simulated visual acuity (simVA) was 0.03 logMAR or better for all the studied IOLs, showing minimal differences. However, each IOL’s intermediate focus position differed across a range from 61 cm to 80 cm; and for the near focus, it was 36 cm to 44 cm. Triumf demonstrated improved intermediate point at the expense of the near focus resulting in a lower predicted near VA. PanOptix exhibited the shortest range of vision without a clear distinction between intermediate and near-point. The remaining lenses presented three foci of comparable optical quality and, thus, simVA performance. Each model, however, revealed a different aperture-change response. Trinova function improved at intermediate but was worse at near for larger pupils. The opposite was observed for AT Lisa. Synergy’s optical quality change was predominantly associated with lower pupil diameter. In conclusion, the trifocal IOLs can be differentiated according to their secondary-foci position, light-energy distribution, and pupil-size-related behavior. The observed differences may translate directly into a clinical effect showing that the trifocal IOLs vary in their ability to deliver optimal vision at different distances, with some providing improved intermediate while others favor reading distance. The knowledge gained through this objective testing can support IOL selection, postoperative patient counselling and increase the chance of spectacle independence after surgery.

To assess the optical quality of intraocular lenses (IOLs) explanted because of opacification after the intraocular injection of gas. David J. Apple Laboratory, Heidelberg, Germany. Experimental study. Four hydrophilic acrylic IOLs were studied, each with a centrally localized round opacification pattern associated with the intraocular use of gas. Laboratory analysis included gross examination with a light microscope, followed by alizarin and von Kossa staining. Optical quality was assessed by examining the modulation transfer function (MTF) and straylight. Results were compared with those of a control IOL and normative data for straylight of the crystalline lens. The following parameters were derived from image analysis: opacified surface fraction, light loss in the opacified surface, and the area and number of granules. The relationship between straylight increase and those parameters was studied. Fine granules were identified on the IOL surface and subsurface. The granules stained positive for calcium, and the MTF levels of 2 IOLs dropped markedly. The other 2 showed relatively minor changes. The straylight was extremely increased in 3 IOLs up to (and above) a level of that of a cataractous lens. A proportional relationship was found between straylight and the morphological parameters from image analysis. Intraocular lenses with centrally localized opacification have a strong potential for deteriorating optical performance. However, the optical quality might differ depending on the morphology of opacification. A serious straylight increase was found in most of these IOLs, suggesting that affected patients may suffer from glare-related symptoms.