Polypseudophakia: from "Piggyback" to supplementary sulcus-fixated IOLs.

Polypseudophakia, the concept of using a second intraocular lens (IOL) to supplement an IOL that has already been placed in the capsular bag, was first used as a corrective measure where the power requirement was higher than that of available single IOLs. Subsequently, the technique was modified to compensate for post-operative residual refractive errors. In these early cases, an IOL designed for the capsular bag would be implanted in the sulcus.  Although these approaches were less than ideal, alternative means of correcting residual refractive errors were not without their limitations: IOL exchange can be traumatic to the eye and is not easily carried out once fibrosis has occurred, while corneal refractive surgical techniques are not suitable for all patients. Piggyback implantation was the term first coined to describe the use of two IOLs, placed together in the capsular bag. The term was later extended to include the procedure where an IOL designed for the capsular bag was placed in the sulcus. Unfortunately, the term piggyback has persisted even though these two approaches have been largely discredited. Intraocular lenses are now available which have been specifically designed for placement in the ciliary sulcus. As these newer IOLs avoid the many unacceptable complications brought about by both types of earlier piggyback implantation, it is time to employ a new terminology, such as supplementary IOL or secondary enhancement to distinguish between the placement of an unsuitable capsular bag IOL in the sulcus and the implantation of an IOL specifically designed for ciliary sulcus implantation. In addition to minimising possible complications, supplementary IOLs designed for the sulcus have expanded the options available to the ophthalmic surgeon. With these new IOLs it is possible to correct presbyopia and residual astigmatism, and to provide temporary correction of refractive errors in growing, or unstable, eyes. This article aims to review the literature available on supplementary IOL implantation in the ciliary sulcus and to summarise the evidence for the efficacy and safety of this intervention. KEY MESSAGES: What is known Polypseudophakia has been used for over 30 years to correct hyperopia or residual refractive error, but early techniques were associated with significant complications. What is new The development of specially designed sulcus-fixated supplementary IOLs significantly reduces the risks associated with these procedures, and has also opened up new opportunities in patient care. The reversibility of the procedure allows patients to experience multifocality, and to provide temporary and adjustable correction in unstable or growing eyes. The terms "secondary enhancement" or "DUET" to describe supplementary IOL implantation are preferential to "piggyback".

Refractive Lens Exchange: A Review.

In recent decades, technical advancements in lens surgery have considerably improved safety and refractive outcomes. This has led to a much broader range of indications for refractive lens exchange (RLE). Effective restoration of uncorrected distance and near visual acuity is possible with modern presbyopia correcting intraocular lenses (IOLs). Hyperopic patients who are fully presbyopic were identified as ideal candidates for RLE. For myopic patients, an increased risk of retinal detachment has been reported, which leads to a higher threshold to perform RLE in this patient group. The most frequent postoperative complications include posterior capsular opacification, deviation from the target refraction and cystoid macular edema. Thus, adequate planning of surgery, careful patient selection, as well as comprehensive counseling are crucial for successful RLE.

Cataract Classification Systems: A Review.

Cataract is among the leading causes of visual impairment worldwide. Innovations in treatment have drastically improved patient outcomes, but to be properly implemented, it is necessary to have the right diagnostic tools. This review explores the cataract grading systems developed by researchers in recent decades and provides insight into both merits and limitations. To this day, the gold standard for cataract classification is the Lens Opacity Classification System III. Different cataract features are graded according to standard photographs during slit lamp examination. Although widely used in research, its clinical application is rare, and it is limited by its subjective nature. Meanwhile, recent advancements in imaging technology, notably Scheimpflug imaging and optical coherence tomography, have opened the possibility of objective assessment of lens structure. With the use of automatic lens anatomy detection software, researchers demonstrated a good correlation to functional and surgical metrics such as visual acuity, phacoemulsification energy, and surgical time. The development of deep learning networks has further increased the capability of these grading systems by improving interpretability and increasing robustness when applied to norm-deviating cases. These classification systems, which can be used for both screening and preoperative diagnostics, are of value for targeted prospective studies, but still require implementation and validation in everyday clinical practice.

Aetiology and Management of IOL Dislocations. / Ursachen und Management von IOL-Dislokationen.

Early (< 3 months) intraocular lens (IOL) dislocation occurs due to insufficient fixation in the capsular bag, while late dislocation (≥ 3 months) is due to increasing insufficiency of the zonular apparatus. Iris-fixated IOL (IFIOL) and suture- or sutureless-fixated scleral IOL (SFIOL) are currently the most commonly used methods when IOL exchange is indicated. Different methods of scleral fixation with or without sutures have been described. The most important techniques are summarised in this paper. IFIOL and SFIOL allow comparable visual outcomes but differ in their risk profile. The decision of which method to use should be made case by case and in accordance with the surgeon's preference.

Reversible Multifocality Achieved Through Polypseudophakia. / Reversible Multifokalität durch Polypseudophakie.

Simultaneous implantation of a monofocal or monofocal toric intraocular lens (IOL) into the capsular bag and a multifocal IOL into the ciliary sulcus, referred to as duet procedure, allows us to create multifocality that is more easily reversible than the implantation of a capsular bag-fixated multifocal IOL. The optical quality and results after the duet procedure are equivalent to those of a capsular bag-fixated multifocal IOL. Patients who cannot tolerate the side effects of multifocal optics or who develop an ocular condition leading to loss of function such as age-related macular degeneration (AMD) or glaucoma in the course of their lives may benefit from the reversibility of the procedure.

Change in Subfoveal Choroidal Thickness following Cataract Surgery Imaged with Enhanced Depth Imaging Optical Coherence Tomography.

BACKGROUND: Due to its invasive nature, cataract surgery can lead to inflammatory processes in the posterior segment, which can result in prolonged recovery times, reduced functional outcomes, and late-onset complications. The aim of the current study was to identify wherever phacoemulsification parameters play a role in choroidal thickness change following cataract surgery. METHODS: This prospective single-center study enrolled 31 patients (31 eyes) scheduled to undergo routine cataract surgery. Patients with previous ocular surgeries, pathologies or general disorders affecting vision were excluded. Patients were examined preoperatively, as well as 1, 4, and 12 weeks after surgery. Corrected distance visual acuity (CDVA), intraocular pressure (IOP) as well as cumulative dissipated energy (CDE), ultrasound time (UT), and fluids used during surgery were recorded. Subfoveal choroidal thickness was measured manually by two masked independent experts using enhanced depth imaging (EDI) optical coherence tomography (OCT). Furthermore, cataract density was automatically calculated using a custom MATLAB script and an anterior segment OCT. RESULTS: Subfoveal choroidal thickness increased significantly (p < 0.001, Student's paired sample t-test) and continuously during the 12-week-long follow-up period. Both the nuclear lens density and the improvement in CDVA correlated significantly with this increase (r = 0.413, p = 0.021 and r = 0.421, p = 0.018, respectively). Neither the CDE (r = 0.334, p = 0.071), the UT (r = 0.102, p = 0.629), the amount of fluid used (r = 0.237, p = 0.27) nor the decrease in IOP (r = - 0.197, p = 0.288) showed any significant correlation with the choroidal swelling. CONCLUSION: Cataract surgery leads to an increase in subfoveal choroidal thickness. While no statistically significant correlation to the phacoemulsification parameters could be established, this might be because of a selection bias due to the technological constraints of the OCT. Nevertheless, the choroid might play a central role in early- and late-onset complications.

[Correction of aphakia in cases of insufficient capsular bag stability]. / Aphakiekorrektur bei unzureichender Kapselsackstabilität.

A variety of situations can lead to the need for an alternative method of intraocular lens (IOL) fixation if implantation in the capsular bag is not possible. Depending on the situation, sulcus-fixated IOLs, iris-fixated IOLs (IFIOLs) and scleral-fixated IOLs (SFIOLs) are available. With SFIOLs, a distinction is made between suture-fixated and sutureless-fixated techniques. This paper summarizes the advantages and disadvantages of the different approaches, including the newer methods of sutureless SFIOLs. The decision on a specific approach in the individual case depends on both the individual circumstances of the patient and the experience of the surgeon.

Functional Outcomes After Refractive Lens Exchange With Implantation of a Glistening-Free Diffractive Trifocal Intraocular Lens.

PURPOSE: To evaluate visual outcomes and patient-reported results after bilateral femtosecond-laser-assisted refractive lens exchange (RLE) with the implantation of a diffractive trifocal intraocular lens. DESIGN: Prospective interventional case series. METHODS: A study of 27 patients (54 eyes) implanted with the Clareon PanOptix (Alcon) multifocal intraocular lens during femtosecond-laser-assisted RLE in a university hospital setting. The uncorrected (UDVA) and corrected (CDVA) distance visual acuity, uncorrected (UIVA) and distance-corrected (DCIVA) intermediate visual acuity at 60 cm, uncorrected (UNVA) and distance-corrected (DCNVA) near visual acuity at 40 and 33 cm were evaluated at 3 months postoperatively and compared with the preoperative values. In addition, we assessed the postoperative defocus curve, mesopic and photopic contrast sensitivity, and patient-reported spectacle independence. RESULTS: The mean postoperative binocular UDVA was -0.02 ± 0.06 logMAR and CDVA was -0.11 ± 0.05 logMAR. The UIVA was -0.07 ± 0.05 logMAR and DCIVA was -0.07 ± 0.07 logMAR. The UNVA at 40 cm was 0.03 ± 0.09 logMAR and DCNVA was -0.02 ±â€¯0.06 logMAR; and, at 33 cm UNVA was 0.14 ± 0.10 logMAR and DCNVA was 0.11 ± 0.08 logMAR. In comparison to the preoperative binocular CDVA (-0.12 ± 0.08 logMAR), no statistically significant change was observed (P = 1.0), while all the other binocular visual acuities improved (P < .01). In the mean binocular defocus curve, the visual acuity was better than 0.10 logMAR in the range between +0.5 D and -3.0 D. The mean contrast sensitivity was within the normal range, and most patients reported complete spectacle independence. CONCLUSIONS: The RLE surgery improved uncorrected visual acuity at far, intermediate, and near distances without negatively affecting the CDVA. Patients achieved a high level of spectacle independence.

Spherical Aberration of Astigmatic Corneas in a Cataract Population.

PURPOSE: To study the distribution of spherical aberration (SA) in astigmatic corneas in a cataract population and the relationship between magnitude of corneal astigmatism and fourth-order corneal SA. METHODS: Data routinely collected using a Scheimpflug camera (Pentacam; Oculus Optikgeräte GmbH) were retrospectively analyzed. Patients with a minimum age of 60 years were included. Total corneal SA (from anterior and posterior corneal surface) was obtained for a 6-mm cor-neal area aligned with the pupil center. Exclusion criteria were insufficient measurement quality, total deviation index (Belin/Ambrósio Deviation) greater than 1.60, and corneal thickness at the thinnest point of less than 490 µm. One eye per patient was chosen randomly. Eyes were divided into low (≤ 1.00 diopters [D]), moderate (> 1.00 to ≤ 2.00 D), and high (> 2.00 D) astigmatism groups according to the Scheimpflug measurements. RESULTS: A total of 528 eyes were included in this analysis. Low astigmatism was found in 129 patients, moderate astigmatism in 265 patients, and high astigmatism in 134 patients. Mean astigmatism was 0.68 ± 0.24, 1.45 ± 0.28, and 2.91 ± 0.95 D in the low, moderate, and high astigmatism groups, respectively. Mean corneal SA in patients with moderate and high astigmatism was higher than in the low astigmatism group. The difference reached the significance level for the comparison of low and high astigmatism groups (P = .023). The fourth-order SA increased gradually with the magnitude of astigmatism with a slope of 0.015. CONCLUSIONS: SA was significantly larger in the cataract population with high corneal astigmatism. The increase of positive sign SA with the magnitude of astigmatism suggests that patients with moderate to high astigmatism may benefit more from intraocular lenses with negative sign SA correction. [J Refract Surg. 2023;39(8):532-538.].

Optical Quality and Higher Order Aberrations of Refractive Extended Depth of Focus Intraocular Lenses.

PURPOSE: To compare the optical quality and higher order aberrations of four different refractive extended depth of focus intraocular lens (EDOF IOL) models (Lentis Comfort [Teleon Surgical BV], MiniWell (SIFI), LuxSmart [Bausch & Lomb], and AcrySof IQ Vivity [Alcon Laboratories, Inc]) and a monofocal IOL (Tecnis ZCB00; Johnson & Johnson Surgical Vision, Inc). METHODS: An optical metrology instrument (OptiSpheric IOL PRO2; Trioptics GmbH) was used to study image quality metrics of the different IOLs. The modulation transfer function (MTF) was measured at pupil sizes 1 to 5 mm in 1-mm steps. Area under the MTF and simulated visual acuity were calculated for different pupil diameters. Wavefront aberrations were measured with the SHS Ophthalmic device (Optocraft GmbH), which features a Hartmann-Shack sensor. RESULTS: All EDOF lenses yielded a simulated far visual acuity of 0.00 logMAR (20/20 Snellen) or better. At the 0.20 logMAR visual acuity level, the EDOF IOLs showed an increased depth of focus of at least 0.75 diopters compared to the monofocal IOL. Pupil dependency was more pronounced with the MiniWell, LuxSmart, and Vivity, whereas the Lentis showed a more consistent behavior at different apertures. The wavefront measurement revealed increased central aberrations for the MiniWell, LuxSmart, and Vivity IOL compared to the monofocal control. CONCLUSIONS: All EDOF IOLs demonstrated increased depth of focus while maintaining good simulated visual acuity at the far focus. Pupil dependency differed between the IOL models. The wavefront analysis revealed the complex design of the different EDOF IOLs with several zones with varying aberrations. [J Refract Surg. 2023;39(10):668-674.].

Chromatic aberration and spectral dependency of extended-range-of-vision intraocular lens technology.

This study compared the optical quality and chromatic performance of refractive-diffractive intraocular lenses (IOLs) that are designed to extend the range of vision of pseudophakic patients and alter chromatic aberration. Five IOLs were evaluated, Tecnis Synergy and Triumf POD L GF, both intended to compensate for eye's chromatism, as well as Acriva Trinova Pro C-a lens that increases chromatic aberration, and AT Lisa Tri and AcrySof IQ PanOptix. An optical setup composed of a corneal model inducing monochromatic and chromatic aberrations and incorporating various spectral conditions was employed. The two chromatic-aberration correcting IOLs demonstrated the lowest far-focus dispersion, but it was negative only, with the Synergy indicating its ability to reduce eye's chromatic aberration. Although the Trinova increased far-point chromatism, it was close to the level of the PanOptix, but higher than that of the AT Lisa. All the studied models demonstrated varying optical quality in response to light color. Still, the strongest spectral dependency was associated with achromatizing technology. Therefore, chromatic aberration and wavelength dependency should be considered in IOL optimization and predicting visual function, particularly in non-white spectral conditions.

Possible Advantages of Minimal-Invasive Approaches in Rectal Cancer Surgery: A Nationwide Analysis.

(1) Background: Laparoscopic resection for colon and rectal cancer was introduced in the early 1990s; the aim of this analysis was to show possible advantages of minimal-invasive approaches in rectal cancer surgery. (2) Methods: From 2016 to 2020, all patients undergoing open, laparoscopic or robotic-assisted rectal cancer surgery in Germany were retrospectively analyzed regarding sex distribution, conversion rates and in-hospital mortality rates according to nationwide hospital billing data based on diagnosis-related groups (DRGs). (3) Results: In total, 68,112 patients were analyzed, and most commonly, low anterior rectal resections with primary anastomosis (n = 25,824) were performed with an increase of minimal-invasive procedures over the years (open: 51% to 27%; laparoscopic: 47% to 63% and robotic: 2% to 10%). In-hospital mortality rate was 2.95% (n = 2012). In total, 4.61%, 1.77%, 1.14% and 3.95% of patients with open, laparoscopic, robotic and converted-to-open surgery died during hospital stay, respectively (open vs. laparoscopic p < 0.0001; open vs. robotic p < 0.00001; laparoscopic vs. robotic p = 0.001). Conversion rates were significantly more favorable in the robotic compared to the laparoscopic group. (11.94% vs. 2.53%; p < 0.0001). (4) Conclusion: Minimal-invasive rectal cancer surgery might have some advantages in terms of a reduced in-hospital mortality, and an improved conversion rate for the robotic approach.

Comparison of Five Presbyopia-Correcting Intraocular Lenses: Optical-Bench Assessment with Visual-Quality Simulation.

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.

Comparison of a Presbyopia-Correcting Supplementary Intraocular Lens Combination and a Capsular-Bag Lens: An In Vitro Study.

We evaluated the optical quality of two approaches to trifocality: polypseudophakia versus monopseudophakia. The combination (polypseudophakia) of a monofocal Basis Z B1AWY0 and AddOn Trifocal A4DW0M intraocular lens (IOL) was compared to using one Basis Z Trifocal B1EWYN IOL, all from 1stQ GmbH. In both approaches, we measured modulation transfer function (MTF) and Strehl Ratio (SR) values at 3.0 and 4.5 mm pupil sizes. We determined the through-focus (TF) MTF at 25, 50 and 100 lp/mm for the 3 mm aperture. United States Air Force (USAF) target images were recorded. MTF measurement of the trifocal lens and the combined monofocal and trifocal AddOn IOL showed good performance at the far and near focus for the 3 mm aperture. For the 4.5 mm aperture the MTF improved for the far focus but decreased for the intermediate and near focus. TF MTF showed better contrast at the far focus for the polypseudophakic setup but at the expense of the efficiency at the near focus. However, the USAF chart images revealed only minimal differences between both approaches. The optical quality of the polypseudophakic approach was not affected by the presence of two IOLs instead of one and proved to be comparable with the performance of one capsular-bag-fixated trifocal IOL. Differences between the single vs. two-lens approach seen in the TF MTF analysis could be attributed to the optical design that varied between the trifocal models.

Impact of Phacoemulsification Parameters on Central Retinal Thickness Change Following Cataract Surgery.

Cataract surgery can lead to inflammatory processes in the retina due to its invasive nature, resulting in prolonged recovery times and reduced functional outcomes. The aim of the current study is to explore the impact that phacoemulsification parameters have on macular thickness following surgery. This prospective single-center study enrolled 46 healthy patients (46 eyes) who underwent uneventful cataract surgery. Retinal thickness was assessed using optical coherence tomography (OCT) preoperatively, as well as 1, 4, and 12 weeks after surgery. The macula was divided into a central (CMT), inner (IMT), and outer ring (OMT). Cataract density was automatically determined using an anterior segment OCT and a custom MATLAB script. Corrected distance visual acuity (CDVA), intraocular pressure (IOP) as well as cumulative dissipated energy (CDE), ultrasound time (UT), and fluids used during phacoemulsification were recorded. Retinal thickness and volume increased significantly following cataract surgery, reaching its maximum 4 weeks post-operatively. Statistically significant correlations were found between the CDE and IMT, OMT and retinal volume change (rIMT = 0.356, rOMT = 0.298, rvolume = 0.357 with p < 0.05) as well as between the ultrasound time and IMT, OMT, and retinal volume change (rIMT = 0.369, rOMT = 0.293 and rvolume = 0.409 with p < 0.05). Changes in CMT did not correlate with any surgical metrics. Additionally, no correlation was found to the amount of fluid used, whether CDVA or IOP. However, a link between nuclear cataract density and changes in OMT (r = 0.310, p < 0.05) was established. How ultrasound energy impacts the choroidea, and to what extent retinal metabolism changes after surgery, needs to be explored in future studies.

Functional outcomes after bilateral refractive lens exchange with a continuous-range-of-vision intraocular lens.

PURPOSE: To clinically evaluate a diffractive continuous-range-of-vision intraocular lens (IOL) that combines bifocal and extended depth-of-focus technologies in refractive lens exchange (RLE) patients. SETTING: University eye clinic. DESIGN: Prospective interventional clinical study. METHODS: Bilateral implantation of the TECNIS Synergy IOL was performed during a RLE procedure in 28 patients. At 3 months postoperatively, uncorrected (UDVA) and corrected (CDVA) distance visual acuities, uncorrected (UIVA) and distance-corrected (DCIVA) intermediate visual acuities at 80 cm, and uncorrected (UNVA) and distance-corrected (DCNVA) near visual acuities at 40 cm were assessed. Defocus curve testing and contrast sensitivity testing were also performed. RESULTS: Binocular UDVA and CDVA of 56 eyes (28 patients) were -0.06 ± 0.07 logMAR and -0.13 ± 0.05 logMAR, respectively. UIVA and DCIVA were -0.06 ± 0.05 logMAR and -0.08 ± 0.06 logMAR, and UNVA and DCNVA were -0.01 ± 0.07 logMAR and -0.04 ± 0.07 logMAR. The defocus curve revealed a visual acuity of 0.10 logMAR or better from +0.50 to -3.00 diopters (D). Photopic contrast sensitivity at spatial frequencies 3.0, 6.0, 12.0, and 18.0 was 1.68 ± 0.20, 1.77 ± 0.19, 1.45 ± 0.18, and 1.02 ± 0.19 log units, respectively. Mesopic contrast sensitivity at the same frequencies was 1.56 ± 0.20, 1.44 ± 0.25, 0.92 ± 0.38, and 0.44 ± 0.37, respectively. CONCLUSIONS: The Synergy IOL provided very good distance, intermediate, and near visual outcomes. A visual acuity of 0.10 logMAR or better was achieved from +0.50 to -3.0 D. Contrast sensitivity was within the normal range.

Clinical Evaluation of Reading Performance in Refractive Lens Exchange With a Diffractive Continuous-Range-of-Vision Intraocular Lens.

PURPOSE: Evaluation of reading performance with a novel presbyopia correcting intraocular lens (IOL) in refractive lens exchange using an electronic reading desk. DESIGN: Prospective interventional before-and-after clinical study. METHODS: In total, 56 eyes of 28 patients were included. Bilateral implantation of the TECNIS Synergy IOL (Johnson & Johnson Surgical Vision) during a bilateral delayed sequential refractive lens exchange procedure. Uncorrected and distance corrected reading acuity, reading distance, reading speed, and the smallest print size that could be read effectively at a set (40 cm/80 cm) and subjectively chosen near and intermediate distance were assessed using the Salzburg Reading Desk preoperatively and 6 months after surgery. RESULTS: Uncorrected near reading acuity increased from 0.61 ± 0.16 logarithm of the minimum angle of resolution (logMAR) preoperatively to 0.05 ± 0.09 logMAR postoperatively at the set near distance (40 cm) and from 0.60 ± 0.11 logMAR to 0.07 ± 0.08 logMAR at the subjectively preferred distance (39.6 ± 5.3 cm and 37.7 ± 4.3 cm). Uncorrected intermediate reading acuity was 0.39 ± 0.19 logMAR preoperatively and 0.08 ± 0.07 logMAR postoperatively at the set intermediate distance (80 cm) and 0.43 ± 0.21 logMAR preoperatively and 0.07 ± 0.08 logMAR postoperatively at the preferred intermediate distance (73.5 ± 9.5 cm and 73.3 ± 5.9 cm). CONCLUSIONS: Uncorrected intermediate and near reading function considerably improved after bilateral implantation of the TECNIS Synergy IOL. Patients preferred a closer near and intermediate distance to the set distances. However, reading function was comparable for the set and subjectively preferred distances.