Aspheric Group Research Articles

Geometric realisation of relation modules over aspherical groups

We prove that the direct sums of extensions of scalars of relation modules are geometrically realisable as the second homotopy group of a finite 2-complex. We use this to exhibit a finite 2-complex with fundamental group the (10,15) torus knot group and non-free π2, yielding exotic presentations of a group for which no such examples had previously been known. We conclude by constructing stably free non-free modules over an infinite family of Baumslag-Solitar groups; it remains to determine whether these modules are geometrically realisable by finite 2-complexes.

Effects on ocular aberration and contrast sensitivity after implantation of spherical and aspherical monofocal intraocular lens - A comparative study.

Phacoemulsification with intraocular lens (IOL) implantation is the standard of care for cataractous eyes. Monofocal IOLs are spherical or aspheric. The aspheric design of IOLs reduces the spherical and higher-order aberrations and impacts contrast sensitivity post cataract surgery. There are some studies, but data in the Indian setting with the IOLs we used is lacking. We aimed to compare the effect of implantation of spheric and aspheric foldable intraocular lenses on postoperative quality of vision, spherical aberration, and contrast sensitivity. This prospective observational study was conducted at a tertiary care hospital with an ophthalmology specialty, data collection from January 2017 to May 2018 in 100 patients. Patients meeting the inclusion criteria were selected. Their preoperative and postoperative data were collected and divided into groups based on whether spherical or aspheric IOL was implanted after cataract surgery. Variables assessed were visual acuity on days 7 and 30, spherical aberrations, and contrast sensitivity was assessed at 1-month postoperative. The mean age of the patients in this study was 64 ± 8 years with a majority of patients (60%) being females. There is no significant difference in postoperative visual acuity between the two groups. Internal SA was significantly lower (~50%) in eyes implanted with aspheric IOLs (P value = 0.004, 0.0001) compared with the spherical group. Contrast sensitivity of patients of the aspheric group was significantly better (P value <0.05). The optical design of the aspheric IOLs reduced spherical aberrations and increased contrast sensitivity.

Normal subgroups of SimpHAtic groups

A group is SimpHAtic if it acts geometrically on a simply connected simplicially hereditarily aspherical (SimpHAtic) complex. We show that finitely presented normal subgroups of the SimpHAtic groups are either: finite, or of finite index, or virtually free. This result applies, in particular, to normal subgroups of systolic groups. We prove similar strong restrictions on group extensions for other classes of asymptotically aspherical groups. The proof relies on studying homotopy types at infinity of groups in question. We also show that non-uniform lattices in SimpHAtic complexes (and in more general complexes) are not finitely presentable and that finitely presented groups acting properly on such complexes act geometrically on SimpHAtic complexes. In Appendix we present the topological two-dimensional quasi-Helly property of systolic complexes.

Optical Design of the Goaly3 Multi-Mirror Telescope System with a Wide Field of View

A Golay3 multi-mirror telescope (MMT) system is designed in this paper. The fill factor of the Golay3 MMT is derived from the angular resolution of the telescope. An initial configuration is established according to the paraxial optical theory. A three-element aspheric corrector group is designed and placed in the converging light cone to enlarge the field of view (FOV) of the Golay3 MMT. The tolerance analysis for each surface of the Golay3 MMT is conducted using the Monte Carlo method. The design results show the FOV of the Golay3 MMT system can be increased to 1.5° with the insertion of a three-element aspheric corrector group. The results of the tolerance analysis indicate that most tolerances are loose, while some decenter tolerances relating with the aspheric surfaces are relatively tight, but still within an acceptable range.

Функциональные результаты оптимизированной асферической технологии с использованием номограммы в сравнении с асферическим и стандартным алгоритмом у пациентов с миопией на отечественной эксимерлазерной установке «Микроскан-Визум»

Purpose. Comparison of FOZ (Functional-Optical Zone), Spatial-Contrast Sensitivity (SCS) under various illumination conditions, evaluation of efficacy, safety, predictability and stability in correction of myopia using the MicroScan-Visum unit in patients of comparative, control and main study groups. Material and methods. The results of FemtoLasik operations were analyzed in 78 patients with myopia (130 eyes), which were divided into the following groups: ≪Nomogram≫ (50 eyes) – the calculation was made according to the nomogram developed by the authors; ≪Aspheric≫ (30 eyes), where Q was 0.2; ≪Standard≫ (50 eyes) – using the standard method. Results. In the Nomogram group, the uncorrected visual acuity (UCVA) was 1.08±0.04, the Aspheric group – 1.06±0.02, the Standard group – 1.04±0.03. In the Nomogram group, average FOZ (functional-optical zone) value was 5.71±0.09 mm, in the Aspheric group – 5.61±0.12 mm, in the Standard group – 5.38±0,75 mm. Statistically significant differences in FOZ values between the Aspheric and Nomogram groups in the area of moderate and high myopia were 5.18±0.12 mm and 5.52±0.08 mm, respectively. The visual acuity in all light conditions by 6th month was higher than the preoperative one in all the groups except the Standard group. In the SCS analysis under photopic conditions with and without light a growth of indicators in all groups at all frequencies was observed. By 6th month under mesopic conditions without light for the Aspheric and Nomogram groups a SCS recovery was noted, with difference at 18 cyclo/deg frequency, with a slight decrease for the Aspheric group, and an increase for the Nomogram group. In the mesopic conditions with light in the Aspheric and Nomogram groups, the SCS values increased on high frequencies almost twice as opposed to the preoperative level, and also the values of the Nomogram group increased twofold as opposed to those of the Aspheric group. Conclusion. The Nomogram group showed the best characteristics of efficiency, safety, predictability and stability as opposed to the comparative and control groups.

Asphericity of Groups Defined by Graphs

A graph $\Gamma$ labelled by a set $S$ defines a group $G(\Gamma)$ whose generators are the set of labels $S$ and whose relations are all words which can be read on closed paths of this graph. We introduce the notion of aspherical graph and prove that such a graph defines an aspherical group presentation. This result generalizes a theorem of Dominik Gruber on graphs satisfying graphical $C(6)$-condition and also allows to get new graphical conditions of asphericity analogous to some classical conditions.

Aspheric versus wavefront-guided aspheric photorefractive keratectomy in eyes with significant astigmatism

To compare the refractive and higher-order aberrations (HOAs) outcomes after photorefractive keratectomy (PRK) in patients with significant astigmatism using aspheric versus wavefront-guided aspheric profiles. Ophthalmic Research Center and Department of Ophthalmology, Shahid Beheshti University of Medical Sciences, Negah Eye Hospital, Tehran, Iran. Prospective randomized case series. One eye of each patient with a refractive astigmatism more than 2.00 diopters (D) randomly received aspheric PRK. In theother eye, wavefront-guided and aspheric treatment was performed using a personalized treatment advanced algorithm. Visual acuity, refractive errors, and HOAs were compared between the 2 groups preoperatively and 12months postoperatively. The study comprised 32 patients (64 eyes). The mean preoperative refractive astigmatism was -4.07 D ± 1.64 (SD) and -4.02±1.55 D in the aspheric group and wavefront-guided aspheric group, respectively (P=.2). The mean postoperative astigmatism was -0.46±0.37 D and -0.82±0.53 D in theaspheric group and wavefront-guided aspheric group, respectively (P=.02). Postoperatively, the root mean square of total HOAs was significantly increased in both groups. However, compared with wavefront-guided aspheric PRK, aspheric PRK induced fewer HOAs (P=.003). In eyes with high astigmatism, post-PRK residual astigmatism was lower in the aspheric group than in the wavefront-guided aspheric group. The increase in HOAs was significantly higher in the wavefront-guided aspheric group than in the aspheric group.

Analysis of the Optical Quality of Spherical and Aspheric Intraocular Lenses in Simulated Nanophthalmic Eyes.

To analyze the optical performance of different implant strategies in simulated nanophthalmic eyes. An optical design software was used. Analysis included eye models that required 30.00, 45.00, and 60.00 diopters (D) intraocular lenses (IOLs) to achieve emmetropia. Spherical and aspheric IOLs were designed. They were tested either with a single implant setting S or by splitting the power into two lenses. Setting P1 had an even split of the power between the lenses and setting P2 had an uneven power split with one-third of the power in the anterior lens and two-thirds in the posterior IOL. The area under the modulation transfer function (MTF) curve was calculated and spherical aberration was recorded in each setting. Setting S had the worst optical performance in the spherical group and the best performance in the aspheric group. A statistically significant difference was found between setting S and the piggyback options (settings P1 and P2) in all analyzed variables for the spherical and aspheric groups for the 45.00 and 60.00 D IOL requirement. No statistically significant difference was found between the piggyback settings. Single aspheric IOLs had better optical performance than piggybacking lower-power aspheric IOLs. In the spherical lenses group, the results were the opposite, with the piggyback options having higher optical quality than the single IOL. MTF shows that single aspheric lenses provide the highest contrast sensitivity among all of the analyzed settings.

On asymptotically hereditarily aspherical groups

We undertake a systematic study of asymptotically hereditarily aspherical (AHA) groups, the class of groups introduced by Tadeusz Januszkiewicz and the second author as a tool for exhibiting exotic properties of systolic groups. We provide many new examples of AHA groups, also in high dimensions. We relate the AHA property with the topology at infinity of a group, and deduce in this way some new properties of (weakly) systolic groups. We also exhibit an interesting property of boundaries at infinity for a few classes of AHA groups.

Contrast visual acuity after multifocal intraocular lens implantation: aspheric versus spherical design.

To evaluate contrast visual acuity (CVA) after implantation of an aspheric apodized diffractive intraocular lens (IOL) or a spherical apodized diffractive IOL in cataract surgery. This prospective randomized controlled study with a 12-month follow-up compared the results of cataract surgery with implantation of an aspheric AcrySof ReSTOR SN6AD3 IOL (30 eyes) and a spherical AcrySof ReSTOR SN60D3 IOL (30 eyes). CVA with best distance correction was measured at 4 contrast levels (100%, 25%, 10% and 5%) under 3 levels of chart luminance [250, 85 and 25 candelas per square meter (cd/m(2))] using a multi-functional visual acuity tester (MFVA-100). At 12 months after surgery, there were no statistically significant differences in 100% CVA and 25% CVA under 250cd/m(2) (P 100%=0.875 and P 25%=0.057) and 85cd/m(2) (P 100%=0.198 and P 25%=0.193) between the aspheric group and the spherical group. However, the 10% CVA and 5% CVA were significant better in aspheric group than spherical group under 250cd/m(2) (P 10%=0.042 and P 5%=0.007) and 85cd/m(2) (P 10%=0.002 and P 5%=0.039). Under the luminance level of 25cd/m(2), no significant differences was found in the 100% CVA between the 2 group (P 100%=0.245), while aspheric group had better visual acuity in the remaining 3 contracts (P 25%=0.023, P 10%=0.026 and P 5%=0.002, respectively). [corrected] The aspheric AcrySof ReSTOR SN6AD3 IOL provided patients with better low-contrast visual acuity than the spherical AcrySof ReSTOR SN60D3 IOL.

Comparative analysis of the visual and refractive outcomes of an aspheric diffractive intraocular lens with and without toricity

To analyze and compare the postoperative visual and refractive outcomes and patients' visual satisfaction after implantation of an aspheric or an aspheric toric multifocal diffractive intraocular lens (IOL) in eyes with equivalent biometric characteristics. Private clinic, Munich, Germany. Comparative case series. Patients having cataract surgery were assigned to 1 of 2 groups: aspheric, which had AT Lisa 809M IOL implantation, and aspheric toric, which had AT Lisa 909M IOL implantation (corneal toricity ≥0.75 diopter [D]). Visual and refractive postoperative outcomes were evaluated, as was the patient's ability to perform daily tasks related to vision and the incidence of photic phenomena. The aspheric group comprised 77 eyes (42 patients) and the aspheric toric group, 26eyes (17 patients). A significant improvement in corrected distance and near visual acuity was observed postoperatively in both groups, as was a significant reduction in the astigmatic component J0 (P<.01). The aspheric toric group had significantly better uncorrected intermediate visual acuity (P=.01). In both groups, the postoperative astigmatic power vectors and spherical equivalent were within ±0.50 D in 100% of eyes and in more than 88% of eyes, respectively. No statistically significant differences were found in any subjective patient questionnaire item. There was no difference in the incidence of photic phenomena between the groups (P≥0.16). The addition of a toric surface to the aspheric diffractive multifocal platform resulted in a comparable visual performance and ability to perform visual tasks. The author has no financial or proprietary interest in any material or method mentioned.

Optimization of Process Parameters to Achieve Nano Level Surface Quality on Polycarbonate

grade plastics are increasingly being used as magnifiers in Ophthalmic Optical Instrumentation applications. In its effort to develop indigenously aspheric technology-based Ophthalmic Optical aids, the Aspheric Group at CSIO has studied the machining and surface characteristics of optical grade plastics. Generally, PMMA and polycarbonate considered as suitable candidates for aspheric Visual aids. In the study presented, optical grade polycarbonate is explored for its single-point diamond turning (SPDT) features and its profile characteristics. This study focuses on the optimization of SPDT machining parameters viz: tool feed rate, depth of cut, spindle speed for a given tool nose radius. In this study, the machining sensitivity in terms of surface roughness and profile error (Pt) is investigated. It is found that machining parameters play a major role in surface quality optimization in terms of roughness and profile. Based on optimized machining parameters, good quality aspheric lens is developed. Keywordspoint diamond turning (SPDT), Surface roughness, Profile error, machining parameters and tool path

Optical Aberrations and Contrast Sensitivity of Spherical and Aspheric Intraocular Lenses – A Prospective Comparative Clinical Study

Purpose: To compare visual acuity, aberrometry, and contrast sensitivity in eyes with spherical intraocular lens (IOL) and aspheric IOL implanted after uncomplicated phacoemulsification. Setting: Department of Ophthalmology, University Hospital, Hradec Kralove, Czech Republic. Methods: A prospective clinical study involving 90 patients (105 eyes) having cataract surgery, with implantation of spherical IOL AcrySof Natural (SN60AT) in 45 patients (50 eyes) with a mean age of 62.5 years, and aspheric IOL AcrySof IQ (SN60WF) in 45 patients (55 eyes) with a mean age of 64.5 years. A control group involved 22 eyes of similar age with clear lens crystallina. Postoperatively, visual acuity (ETDRS charts), aberrometry (ORK Wavefront Analyser, Schwind), and contrast sensitivity tests (CSV 1000, Contrast Sensitivity 8010 System) were evaluated. Statistical analyses were performed using Student t-test. Results: No statistical differences were found regarding visual acuity among eyes. A lower level of higher order aberrations was achieved in the aspheric group. In the contrast sensitivity test, no statistical differences between groups under photopic conditions were noted. In mesopic conditions better performance was observed in eyes with aspheric IOLs, mainly in low spatial frequencies (statistically significant). The control group (lens crystallina) was better in all frequencies. Conclusions: Cataract surgery outcomes cannot be measured by means of visual acuity alone. In this study, the aspheric IOLs AcrySof IQ (SN60WF) demonstrated better visual function, especially contrast sensitivity in low spatial frequences, when compared with spherical IOLs AcrySof Natural (SN60AT).

Comparison of Optical Aberrations and Contrast Sensitivity Between Aspheric and Spherical Intraocular Lenses

To compare visual acuity, aberrometry, and contrast sensitivity in patients who had a spherical intraocular lens (IOL) (SoFlex SE, Bausch & Lomb) implanted in one eye and an aspheric IOL (SofPort AO, Bausch & Lomb) implanted in the fellow eye during uncomplicated cataract surgery. A prospective, multicenter, double-blind study was performed. Forty patients (80 eyes) underwent bilateral phacoemulsification with implantation of a spherical IOL in one eye and an aspheric IOL in the fellow eye. Postoperatively, visual acuity, aberrometry, and contrast sensitivity tests were performed. Statistical analyses were performed using Student t and Wilcoxon tests, and mixed effects were used for each contrast condition situation. Thirty-nine patients (30 women, 9 men; 78 eyes) with a mean age of 69.3±6.17 years (range: 51 to 82 years) completed the study. No statistical differences were found regarding visual acuity among eyes. Lower levels of higher order aberrations were achieved in the aspheric group. No statistical difference between groups under photopic conditions was noted. In low spatial frequencies, better performance was observed with the aspheric IOL under mesopic conditions. In high spatial frequencies, the spherical IOL produced better quality of vision. Comparing mesopic conditions with glare, visual performance was statistically better using the aspheric IOL. Cataract surgery results cannot be measured by means of visual acuity alone. Quality of vision must be considered, and implantation of IOLs with low levels of spherical aberrations and better contrast sensitivity are preferred. In this study, the aspheric IOL demonstrated better visual function, especially at night, when compared with spherical IOLs.

Visual outcome and patient satisfaction after multifocal intraocular lens implantation: Aspheric versus spherical design

To evaluate visual outcomes and patient satisfaction after implantation of an aspheric apodized diffractive intraocular lens (IOL) or a spherical apodized diffractive IOL in cataract surgery. Maastricht University Medical Center, The Netherlands. Nonrandomized clinical trial. This prospective nonrandomized study with a 6-month follow-up compared the results of cataract surgery with implantation of an aspheric AcrySof ReSTOR SN6AD3 IOL and a spherical AcrySof ReSTOR SN60D3 IOL. Main outcome measures were uncorrected (UDVA) and corrected (CDVA) distance visual acuities, uncorrected (UNVA) and distance-corrected (DCNVA) near visual acuities, straylight levels, incidence of glare and halos, and contrast sensitivity levels. The mean UDVA was 0.14 ± 0.15 logMAR in the aspheric group (47 eyes) and 0.14 logMAR ± 0.17 (SD) in the spherical group (45 eyes) and the mean CDVA, -0.01 ± 0.06 logMAR and 0.02 ± 0.10 logMAR, respectively. The mean UNVA was Jaeger (J) 1 in 83.0% of patients in the aspheric group and 55.5% of patients in the spherical IOL group (P = .003). The DCNVA was J1 in 95.7% and 71.1%, respectively (P = .001). There were no significant differences between the 2 groups in contrast sensitivity levels, intraocular straylight levels, incidence of night-vision symptoms, or subjective rating of vision. Patients with the aspheric multifocal IOL had significantly better near vision than patients with the multifocal spherical IOL. The UDVA, CDVA, intraocular straylight, night-vision symptoms, and contrast sensitivity were similar between the 2 groups.

Binocular clinical comparison study of Tecnis multifocal aspheric and monofocal spherical intraocular lenses

To compare visual function in pseudophakic patients with bilateral implantation of Tecnis multifocal aspheric and conventional monofocal spherical intraocular lenses (IOL). A prospective study of 100 consecutive cases (200 eyes) was conducted. All cataract patients underwent phacoemulsification were randomized to receive multifocal aspheric IOL (Tecnis ZM900, AMO, multifocal aspheric group) or conventional spherical IOL (Akreos Adapt, Bausch & Lomb, monofocal spherical group). The following investigations were performed to assess the uncorrected and distance-corrected visual acuity of distance, intermediate and near distances, accommodative amplitude, spherical aberrations of total eye, contrast sensitivity, glare sensitivity and near stereoacuity. Patients were surveyed for visual disturbances and lifestyle visual quality. The independent-samples t test was used to compare the measure data which met normal distribution and the Mann-Whitney U test was used to compare the measure data which didn't meet. The chi-square test was applied to compare categorical variables. The uncorrected and distance-corrected bilateral visual acuity of multifocal aspheric group at 30 cm and 40 cm were 0.24 ± 0.12 and 0.22 ± 0.11 (logMAR), better than monofocal spherical group (Z = -8.261, P = 0.000; Z = -5.508, P = 0.000), but the visual acuity at other distances had no statistical difference between two groups. Patients with multifocal aspheric IOL had significantly higher accommodative amplitude than those with monofocal spherical IOL, improved about 2.3 ∼ 2.8 D (Z = -10.655, P = 0.000; Z = -2.709, P = 0.007). Mean spherical aberration of multifocal aspheric group was (0.027 ± 0.160) µm and (0.006 ± 0.083) µm, significantly lower than that of monofocal spherical group (0.269 ± 0.161) µm, (0.037 ± 0.205) µm at 5 mm and 3 mm pupil diameter (Z = -8.815, P = 0.000; Z = -2.791, P = 0.005). The difference of contrast sensitivity was not significant, but glare sensitivity was higher for monofocal spherical group than for multifocal aspheric group. Multifocal aspheric group showed statistically better uncorrected stereoacuity (72.4 ± 29.9)″ than monofocal spherical group (92.8 ± 35.7)″ (Z = -3.089, P = 0.002). The present clinical results demonstrated that Tecnis multifocal aspheric group had better near visual acuity, accommodative amplitude and near stereoacuity as compared to conventional monofocal spherical group. The aspheric design reduced spherical aberration of total eye and improved contrast sensitivity in some way.

Refractive-Error Quality of Life (RQL) in Patients with AcrySof IQ Aspherical Intraocular Lenses

Purpose To compare refractive-error quality of life, and spherical aberration in pseudophakic eyes with an aspherical intraocular lens (AcrySof IQ) vs. a conventional spherical intraocular lens (AcrySof Single-Piece). Methods 65 patients were randomized to implantation of either an aspherical IOL (Alcon AcrySof IQ) (30 eyes) or a spherical IOL (Alcon AcrySof Single-Piece (35 eyes). Three months postoperatively, complete ophthalmologic examinations including uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BCVA), and a wavefront analysis were performed. Patients completed the National Eye Institute Refractive Error Quality of life Instrument (NEI RQL) to evaluate vision-related quality of life. Results The mean postoperative best-corrected visual acuity was 0.09±0.07 logMAR in the aspherical group and 0.12±0.08 in the spherical group, and the difference was not statistically significant. Spherical aberrations were significantly lower in the aspherical group (0.12±0.23 μm), than in the spherical group (0.33±0.20 μm) ( P=0.001). Patients with aspherical AcrySof IQ IOLs implantation also experienced less difficulties driving at night ( P=0.04), but the difference was not significant after Bonferroni correction. Conclusion The NEI RQL instrument is sensitive enough to detect the visual benefit of cataract surgery. The aspherical AcrySof IQ IOL reduces both spherical aberration and total higher-order aberrations, compared with the performance achieved by the spherical AcrySof Single-Piece IOL. Although the difference between the two IOLs is not statistically significant, there is a tendency toward the association of objective optical performance of aspherical AcrySof IQ IOLs with a subjective improvement in patients’ night driving.

Ocular wavefront analysis and contrast sensitivity in eyes implanted with AcrySof IQ or AcrySof Natural intraocular lenses

This study aimed to compare ocular wavefront aberrations for pupil diameters of 4 mm and 6 mm, and contrast sensitivity, in eyes with AcrySof IQ and AcrySof Natural intraocular lenses (IOLs). Sixty eyes of 60 patients were enrolled in this prospective randomized study. After phacoemulsification the eyes received either AcrySof IQ SN60WF or AcrySof Natural SN60AT IOLs. One month after surgery, all patients underwent complete ophthalmological examination including corneal topography, wavefront analysis for pupil diameters of 4 mm and 6 mm, and contrast sensitivity measurements with the CSV 1000E instrument under photopic and mesopic conditions with and without glare. There was no statistically significant difference between groups in age, sex or other preoperative ocular characteristics (p > 0.05). Patients with AcrySof IQ IOLs had higher contrast sensitivity at 6 c.p.d. under photopic conditions, at 6 c.p.d. and 18 c.p.d. under mesopic conditions, and at 6 c.p.d., 12 c.p.d. and 18 c.p.d. under mesopic conditions with glare (p < 0.05). Corneal spherical aberration was 0.273 ± 0.074 μm in the AcrySof Natural group and 0.294 ± 0.086 μm in the AcrySof IQ group (p = 0489). Ocular spherical aberration was 0.362 ± 0.141 μm and 0.069 ± 0.043 μm (p < 0.001) for 6-mm diameter pupils and 0.143 ± 0.091 μm and 0.017 ± 0.016 μm (p < 0.001) for 4-mm diameter pupils, with AcrySof Natural and AcrySof IQ IOLs, respectively. There were no significant differences in other higher-order aberrations between the groups (p > 0.05). Aspherical AcrySof IQ IOLs significantly reduced spherical aberration for pupil diameters of both 4 mm and 6 mm and also improved contrast sensitivity more than spherical AcrySof Natural IOLs, especially in mesopic conditions.

Effect of Intraocular Lens Asphericity on Quality of Vision after Cataract Removal: An Intraindividual Comparison

To determine the effect of intraocular lens (IOL) asphericity on quality of vision after cataract removal. Intraindividual, prospective, randomized clinical trial. Twenty-six cataract patients received 2, one-piece, blue-light-filtering hydrophobic acrylic IOLs each. One eye was implanted with a spherical (SN60AT, Alcon) and the contralateral eye with an aspheric (SN60WF, Alcon) IOL with -0.2 mum spherical aberration (SA). All trial-specific measurements (corneal topography, wavefront sensing, high-contrast visual acuity [HCVA], contrast sensitivity [CS]) were performed 6 months after surgery. A paired Student t-test or Wilcoxon test was used to check intergroup differences. Absolute values and intraindividual differences (Delta(i)) of corneal and ocular higher order aberrations and best-corrected visual Strehl ratio based on the optical transfer function (BCVSOTF) values for virtual pupil diameters of 3, 4, 5, and 6 mm were computed. Photopic and mesopic HCVA, photopic, and high-mesopic CS as well as high-mesopic disability glare (DG) were measured using the Frankfurt-Freiburg Contrast and Acuity Test System. No intergroup difference of demographic data, pupillometry, and corneal aberrations were observed. Coma and trefoil root mean square and SA were significantly lower in the aspheric group resulting in higher BCVSOTF, mesopic HCVA, and photopic and high mesopic CS. All Delta(i) values with exception of photopic HCVA and DG indicated significantly better performance of the aspheric IOL. An aspheric IOL with -0.2 microm SA provide higher quality of vision than spherical IOL in terms of retinal image quality, mesopic HCVA and CS. Proprietary or commercial disclosures may be found after the references.

Efficacy of an aspheric treatment algorithm in decreasing induced spherical aberration after laser in situ keratomileusis

To determine the effectiveness of an aspheric laser in situ keratomileusis (LASIK) algorithm for myopia with and without astigmatism in minimizing postoperative induction of spherical aberration. Four sites in Asia. Patients with -1.00 to -10.00 diopters (D) of spherical myopia with -4.00 D or less of astigmatism were recruited. Patients randomly had bilateral Zyoptix aspheric algorithm (aspheric group) or bilateral conventional Zyoptix Tissue Saving algorithm (control group). A Technolas 217z100 excimer system was used for LASIK ablation. Visual effectiveness, safety, higher-order aberrations, and corneal asphericity (Q value) were evaluated postoperatively. The aspheric group comprised 86 eyes and the control group, 84 eyes. At 3 months, the high-contrast uncorrected distance visual acuity was 20/20 or better in 78% of eyes in the aspheric group and 83% of eyes in the control group. The control treatment induced 0.22 microm of spherical aberration, which was significantly higher than the 0.04 microm induced with the aspheric treatment (6.0 mm pupil) (P<.0001). The aspheric treatment induced significantly less vertical coma and trefoil (P = .02). Eyes in the aspheric group had significantly lower Q values (P<.0001). There was no statistically significant difference in the manifest refraction spherical equivalent between the 2 groups (P >.05). Although high- and low-contrast corrected distance visual acuity (CDVA) was similar between the groups, the aspheric group gained more lines of low-contrast CDVA. The aspheric algorithm was more effective than the conventional algorithm in reducing induced spherical aberration and maintaining corneal asphericity after myopic LASIK.