Differences Between Simulated Keratometry and Total Corneal Power in Eyes With Keratoconus and a Formula to Improve IOL Power Calculation Results.

PURPOSE: To compare simulated keratometry (SimK) and total corneal power (TCP) in keratoconic eyes, to determine whether the differences are systematic and predictable and to evaluate an adjusted TCP-based formula for intraocular lens (IOL) power calculation. METHODS: In a consecutive series of keratoconic eyes, measurements of SimK, TCP, posterior keratometry, and anterior and posterior corneal asphericities (Q-values) were retrospectively collected. The difference between SimK and TCP was linearly correlated to the biometric parameters. In a separate sample of keratoconic eyes that had undergone cataract surgery, IOL power was calculated with the Barrett Universal II, Hoffer QST, Holladay 1, Kane, and SRK/T formulas using the SimK and an adjusted TCP power. The respective prediction errors were calculated. RESULTS: A total of 382 keratoconic eyes (271 patients) were enrolled. An increasing overestimation of SimK by TCP was detected from stage I to III, with a significant correlation between the SimK and TCP difference and SimK in the whole sample (P < .0001, r2 = 0.1322). Approximately 7% of cases presented an underestimation of SimK by TCP. IOL power calculation with the adjusted TCP improved outcomes, achieving a maximum of 80% of eyes with a prediction error within ±0.50 diopters with the Hoffer QST, Holladay 1, and Kane formulas. CONCLUSIONS: Overall, SimK overestimated TCP. Such a difference could not be predicted by any variable. The proposed TCP-adjustment formula (TCPadj = TCP + 0.56 diopters) in keratoconic eyes for IOL power calculation might be valuable for improving refractive outcomes. [J Refract Surg. 2024;40(4):e253-e259.].

Cataract Grade and Pupil: Comparison Between Conventional Phacoemulsification and Low-Energy Femtosecond Laser Assisted Cataract Surgery.

Purpose: This study presents a comparison of pupil changes according to cataract grade between low-energy femtosecond laser-assisted cataract surgery (FLACS) and conventional phacoemulsification (CP) in the same patient. Patients and Methods: Data from surgical records from patients submitted to cataract surgery with CP in one eye and FLACS in the other were retrospectively reviewed. The inclusion criterion was both eyes of the same patient having the same cataract grade in accordance with Lens Opacity Classification System (LOCS) III. Total pupil variation (TPV) was measured after recorded images, with intraindividual comparison between techniques, according to cataract grade (≤3 and >3), age and cumulative dissipated energy (CDE). Results: The study included a total of 124 eyes of 62 patients (mean age 72.65 ± 7.64 years). Analysis showed a statistically significant difference in TPV between techniques in the grade ≤3 cataract group (0.08 ± 0.22 mm²; p=0.034), with less pupil narrowing with FLACS, but not in the grade >3 group (0.01 ± 0.23 mm²; p=0.849). Regarding CDE, a significant difference (p<0.001) was found between techniques in both softer and harder cataracts, with lower values for FLACS. Correlation between CDE and TPV was significant for CP (p=0.021) but not for FLACS (p=0.922). TPV was significantly lower in older patients (age >74 years) for both techniques (p<0.001). Conclusion: There was a statistically significant difference between techniques (although of mild clinical relevance), with less reduction of pupil area with FLACS in softer cataracts (grade ≤3), as compared to CP. Higher levels of CDE are associated with more pupil narrowing in CP.

Managing low corneal astigmatism in patients with presbyopia correcting intraocular lenses: a narrative review.

Cataract surgery has become a refractive procedure in which emmetropia is the goal, with the implantation of extended depth-of-focus or multifocal intraocular lenses (IOLs) being the commonly selected option to restore vision beyond the far distance. The selection criteria for implanting these lenses can differ from those for monofocal IOLs and even between technologies, as eye characteristics can affect postoperative visual performance. Corneal astigmatism is an eye characteristic that can affect visual performance differently, depending on the implanted IOL. The magnitude of corneal astigmatism, the tolerance of the IOL to this astigmatism, economic aspects, comorbidities, and the efficacy of astigmatism treatment are factors that can make surgeons' doubt as to what astigmatism treatment should be applied to each patient. This review aims to summarize the current evidence related to low astigmatism tolerance in presbyopia-correcting lenses, the efficacy achieved through corneal incisions, and their comparison with the implantation of toric IOLs.

3D Modeling of the Crystalline Lens Complex under Pseudoexfoliation.

Pseudoexfoliation, one of the most frequent crystalline lens complex disorders, is prevalent in up to 30% of individuals older than 60 years old. This disease can lead to severe conditions, such as subluxation or dislocation of the lens, due to the weakening of the zonules. The goal for the present study was to understand the relevant biomechanical features that can lead to the worsening of an individual's visual capacity under pseudoexfoliation. To this end, finite element models based on a 62-year-old lens complex were developed, composed by the capsular bag, cortex, nucleus, anterior, equatorial, and posterior zonular fibers. Healthy and pseudoexfoliative conditions were simulated, varying the location of the zonulopathy (inferior/superior) and the degenerated layer. The accommodative capacity of the models with inferior dialysis of the zonular fibers was, on average, 4.7% greater than for the cases with superior dialysis. If the three sets of zonules were disrupted, this discrepancy increased to 14.9%. The present work provides relevant data to be further analyzed in clinical scenarios, as these models (and their future extension to a wider age range) can help in identifying the most influential regions for the reduction of the visual capacity of the lens.

Intraocular lens power calculation with ray tracing based on AS-OCT and adjusted axial length after myopic excimer laser surgery.

PURPOSE: To report the results of intraocular lens (IOL) power calculation by ray tracing in eyes with previous myopic excimer laser surgery. SETTING: G.B. Bietti Foundation I.R.C.C.S., Rome, Italy. DESIGN: Retrospective interventional case series. METHODS: A series of consecutive patients undergoing phacoemulsification and IOL implantation after myopic excimer laser was investigated. IOL power was calculated using ray-tracing software available on the anterior segment optical coherence tomographer MS-39. Axial length (AL) was measured by optical biometry, and 4 values were investigated: (1) that from the printout, (2) the modified Wang/Koch formula, and (3) the polynomial equation for the Holladay 1 and (4) for the Holladay 2 formulas. The mean prediction error (PE), median absolute error (MedAE), and percentage of eyes with a PE within ±0.50 diopters (D) were reported. RESULTS: The study enrolled 39 eyes. Entering the original AL into ray tracing led to a mean hyperopic PE (+0.56 ±0.54 D), whereas with the Wang/Koch formula, a mean myopic PE (-0.41 ±0.53 D) was obtained. The Holladay 1 and 2 polynomial equations lead to the lowest PEs (-0.10 ±0.49 D and +0.08 ±0.49 D, respectively), lowest MedAE (0.37 D and 0.25 D), and highest percentages of eyes with a PE within ±0.50 D (71.79% and 76.92%). Calculations based on the Holladay 2 polynomial equation showed a statistically significant difference compared with other methods used (including Barrett-True K formula), with the only exception of the Holladay 1 polynomial equation. CONCLUSIONS: IOL power was accurately calculated by ray tracing with adjusted AL according to the Holladay 2 polynomial equation.

Comparison of refractive and visual outcomes of 3 presbyopia-correcting intraocular lenses.

PURPOSE: To evaluate and compare the clinical outcomes after cataract surgery with implantation of 3 types of trifocal diffractive intraocular lenses (IOLs). SETTING: Hospital da Luz, Lisbon, Portugal. DESIGN: Prospective comparative case series. METHODS: Patients undergoing phacoemulsification cataract surgery with implantation of 1 of the 3 trifocal IOLs were enrolled: TECNIS Synergy (Synergy group, 30 patients), Acrysof PanOptix (PanOptix group, 30 patients), and POD F (Finevision group, 30 patients). The outcomes of distance, intermediate, and near visual acuity (VA), refraction, defocus curve, photic phenomena, and spectacle independence were evaluated at the 3-month follow-up. RESULTS: 180 eyes of 90 patients were enrolled. No statistically significant differences were found between groups in monocular distance-corrected intermediate (Synergy group 0.04 ± 0.11, PanOptix group 0.05 ± 0.09, and Finevision group 0.08 ± 0.10; P = .107) and near VA (0.01 ± 0.08, 0.01 ± 0.06, and 0.04 ± 0.10, respectively; P = .186). Similarly, no statistically significant differences among groups were found in binocular uncorrected distance (P = .572), near (P = .929), and intermediate VA (P = .327). By contrast, statistically significant differences between groups were found in the visual acuity for the vergence demands of -0.50, -1.00, -2.00, -3.50, and -4.00 diopters (P ≤ .045). No statistically significant differences among groups were found in the frequency, severity, and bothersomeness of different disturbing visual symptoms, including glare and halos (P ≥ .129). More than 87 (96%) of patients in all groups did not require the use of spectacles at any distance postoperatively. CONCLUSIONS: The 3 trifocal IOLs evaluated provided an effective visual rehabilitation with minimal incidence of photic phenomena. A trend to obtain a wider range of functional focus was observed with the TECNIS Synergy IOL.

Visual outcomes and patient satisfaction after implantation of a presbyopia-correcting intraocular lens that combines extended depth-of-focus and multifocal profiles.

PURPOSE: To evaluate clinical outcomes delivered by a new hybrid presbyopia-correcting intraocular lens (IOL): TECNIS Synergy ZFR00V IOL model (Johnson & Johnson Vision). SETTING: Hospital da Luz Lisboa, Lisbon, Portugal. DESIGN: Prospective observational study. METHODS: Patients undergoing bilateral IOL implantation were included. Visual acuity (VA) was measured for far distance, intermediate (66 cm), and near (40 cm) vision under both photopic and mesopic conditions. In addition, at the 3-month follow-up visit, the defocus curve was obtained for binocular vision, and questionnaires were administered to measure spectacle independence and level of satisfaction ( quality of vision and Catquest-SF9) with the surgical outcomes. RESULTS: 54 eyes of 27 patients were included. At the 3-month follow-up, under photopic conditions, VA values were as follows: corrected distance VA (CDVA) = -0.02 ± 0.07, distance-corrected intermediate VA = 0.03 ± 0.11, and distance-corrected near VA (DCNVA) = 0.00 ± 0.08, whereas under mesopic conditions, VA values were as follows: CDVA = -0.01 ± 0.05 and DCNVA = 0.07 ± 0.09. The binocular defocus curve revealed that mean VA was better than 0.30 logMAR within the +1.00 to -4.00 diopters (D) interval, and better than 0.10 logMAR between +0.50 and -3.00 D. All patients achieved distance vision spectacle freedom, whereas 3.7% of them said they used them in certain intermediate or near vision situations. As much as 88% of the patients reported being fairly satisfied or very satisfied. CONCLUSIONS: The TECNIS Synergy ZFR00V IOL model used for cataract surgery is capable of restoring visual function while providing very good intermediate and near vision, under both photopic and mesopic conditions, resulting in a high level of patient satisfaction.

Evaluation of posterior and total corneal astigmatism with colour-LED topography.

PURPOSE: To characterise the posterior and total corneal astigmatism using colour point-source light-emitting diodes (LED) topography. METHODS: In a prospective case series 400 eyes from 400 patients were evaluated by colour-LED topography. Only eyes with normal topographies were considered. The following parameters were studied: magnitude and distribution of SimK and posterior corneal astigmatism, correlation between SimK and posterior corneal astigmatism, and differences in magnitude and axis between total and anterior corneal astigmatism. RESULTS: The mean SimK corneal astigmatism was 1.21 ± 0.94 D. The mean posterior corneal astigmatism was 0.37 ± 0.24 D. Posterior astigmatism was vertically oriented in 68% of eyes. Twenty-two percent of eyes showed a posterior corneal astigmatism ≥ 0.50 D. The correlation coefficients between SimK and posterior corneal astigmatism were: r2 = 0.066; p = 0.371 in WTR eyes, r2 = 0.112; p = 0.173 in ATR eyes and r2 = -0.019; p = 0.879 in oblique eyes. A difference between SimK and total corneal astigmatism ≥ 0.50 D was found in 7% of eyes. A difference in axis between SimK and total corneal astigmatism ≥ 10° was found in 24% of eyes. CONCLUSIONS: The percentage of eyes with posterior corneal astigmatism ≥ 0.50 D and the differences between anterior and total corneal astigmatism were higher than those previously reported in the literature. Therefore, this study supports the consideration of total corneal astigmatism magnitude and axis is mandatory for a precise surgical correction of astigmatism.

Comparison of visual and refractive outcomes of 2 trifocal intraocular lenses.

PURPOSE: To compare clinical outcomes after cataract surgery and bilateral implantation of 2 diffractive trifocal toric intraocular lenses (IOLs). SETTING: Hospital da Luz, Lisbon, Portugal. DESIGN: Double-arm, randomized, prospective case series. METHODS: A total of 60 patients were randomly allocated to receive bilateral implantation of either the FineVision Pod FT toric IOL (PhysIOL) or the AcrySof IQ PanOptix toric IOL (Alcon). Visual and refractive outcomes, contrast sensitivity, IOL misalignment, and quality of vision outcomes (QoV questionnaire) were evaluated at 3 months postoperatively. Surgically induced astigmatic changes were evaluated by vector analysis. RESULTS: Each group (FineVision toric and AcrySof IQ PanOptix toric) comprised 30 patients (60 eyes). No significant differences between groups were found regarding uncorrected and corrected distance and near visual outcomes (P ≥ .333). Mean postoperative distance-corrected intermediate visual acuity at 60 cm was 0.04 ± 0.09 logarithm of the minimum angle of resolution (logMAR) and 0.09 ± 0.11 logMAR in the PanOptix and Pod FT group, respectively (P = .032). Mean IOL axis misalignment was 1.59 degrees ± 2.15 degrees (PanOptix group) and 1.89 degrees ± 3.31 degrees (Pod FT group) (P = .821). Mean magnitude of error of astigmatic correction was -0.09 diopters (D) and -0.11 D in the PanOptix group and Pod FT group, respectively (P = .333). Contrast sensitivity, QoV scores for the presence of photic phenomena, and the level of spectacle independence were similar in both groups (P > .05). CONCLUSIONS: Both trifocal toric IOLs allowed complete patient visual restoration, and good spectacle independence and good visual quality outcomes. The PanOptix IOL provided superior intermediate visual acuity for distances around 60 cm.

Predictability of different calculators in the minimization of postoperative astigmatism after implantation of a toric intraocular lens.

PURPOSE: To assess the efficacy of five calculators for toric intraocular lenses (IOL). METHODS: Retrospective comparative case series in cataract patients undergoing implantation of trifocal toric IOLs (PhysIOL FineVision POD FT). Inclusion criteria were age-related cataract and a corneal astigmatism between 0.90D and 4.50D. Refractive astigmatism predictability of five different toric calculators or calculation methods were compared. Furthermore, two groups were differentiated according to the type of astigmatism. The mean absolute error and the centroid errors in the predicted residual astigmatism from each calculator were evaluated. RESULTS: Fifty-one eyes of 43 patients were included in the study. For the standard toric calculator using anterior keratometry values only, the centroid prediction error was 0.39D±0.41@166º, which was reduced by the application of the PhysIOL toric calculator that includes the Abulafia-Koch regression formula and adjustment for the effective lens position (0.05D±0.34@167º), and also by the application of the Barrett toric calculator (0.07D±0.28@160º). Regarding the techniques that directly evaluate posterior corneal surface, the Holladay toric calculator, using total corneal power provided by a color-LED topographer, generated better results (0.10D±0.44@156º) than those using Scheimpflug camera data (0.23D±0.56@158º). Similar results were found for both types of astigmatism. CONCLUSION: The PhysIOL and the Barrett toric calculators taking into account the posterior corneal astigmatism by mathematical models, yielded lower astigmatic prediction errors compared to a standard toric calculator based on anterior keratometry data only. When total corneal power measurements were used, prediction errors were lower with color-LED than with Scheimpflug based topography.

Prospective Comparison of Clinical Performance and Subjective Outcomes Between Two Diffractive Trifocal Intraocular Lenses in Bilateral Cataract Surgery.

PURPOSE: To compare clinical outcomes and subjective experience after bilateral implantation of two non-toric diffractive trifocal intraocular lenses (IOLs). METHODS: In a prospective, comparative case series, patients were randomly allocated to receive bilateral implantation of either the preloaded RayOne Trifocal (Rayner, Worthing, UK) or the FineVision POD F (PhysIOL, Liège, Belgium). At the 3-month follow-up, the main outcomes were monocular and binocular uncorrected and corrected distance (UDVA, CDVA), intermediate at 80 cm (UIVA, DCIVA), and near at 40 cm (UNVA, DCNVA) visual acuities, refractive outcomes, and defocus curves. Patients' satisfaction in terms of visual disturbance was also evaluated. RESULTS: Each group comprised 30 eyes (15 patients). The mean monocular UDVA was 0.03 ± 0.11 (RayOne Trifocal) and 0.04 ± 0.08 (FineVision POD F) logMAR (P = .605); DCIVA was 0.05 ± 0.13 and 0.05 ± 0.10 logMAR, respectively (P > .999); and DCNVA was 0.02 ± 0.12 and 0.03 ± 0.11 logMAR (P = .742). A better manifest spherical equivalent was found in the RayOne Trifocal than in the FineVision POD F group (P = .035) and depth perception issues were less severe with the RayOne Trifocal IOL (P = .042). There was no significant difference in other photic phenomena between groups. CONCLUSIONS: Both IOLs provided good visual outcomes at all distances with no differences between the groups. Refractive accuracy was better for the RayOne Trifocal IOL. The results indicated that the new trifocal IOL may represent a safe and effective option for presbyopic patients. [J Refract Surg. 2019;35(7):418-425.].

Comparison of Surgically Induced Astigmatism and Morphologic Features Resulting From Femtosecond Laser and Manual Clear Corneal Incisions for Cataract Surgery.

PURPOSE: To compare the surgically induced astigmatism (SIA) vector, flattening effect, torque, and wound architecture following femtosecond laser and manual clear corneal incisions (CCIs). METHODS: In a double-armed, randomized, prospective case series, cataract surgery was performed for 600 eyes using femtosecond laser (300 eyes) or manual (300 eyes) 2.4-mm CCIs in temporal or superior oblique locations. SIA, flattening effect, torque, and the summated vector mean for SIA were calculated. Correlation with individual features was established and incision morphology was investigated by anterior segment optical coherence tomography at 3 months of follow-up. RESULTS: The SIA, flattening effect, and torque were lower in the femtosecond laser group for both incision locations, although the differences were not significant (all P > .05). The femtosecond laser group showed less dispersion of SIA magnitude and flattening effect. Temporal and superior oblique incisions resulted in flattening effect values of -0.11 and -0.21 diopters (D), respectively, in the femtosecond laser group and -0.13 and -0.34 D, respectively, in the manual group. Significant correlations with individual features were only found in the femtosecond laser group, with preoperative astigmatism being the only significant SIA predictor by multiple regression analysis (P = .003). Femtosecond laser CCIs showed less deviation from the intended length, wound enlargement, endothelial misalignment, and Descemet membrane detachments (all P < .037). CONCLUSIONS: Femtosecond laser CCIs were more reproducible. Although SIAs were smaller in femtosecond laser CCIs than in manual CCIs for both temporal and superior oblique incisions, the difference was not statistically significant. Association with individual features is highly variable. [J Refract Surg. 2018;34(5):322-329.].

Through-Focus Vision Performance and Light Disturbances of 3 New Intraocular Lenses for Presbyopia Correction.

PURPOSE: To compare the through-focus visual performance in a clinical population of pseudophakic patients implanted with two new trifocal intraocular lenses (IOLs) and one extended depth of focus IOL. METHODS: Prospective, nonrandomized, examiner-masked case series. Twenty-three patients received the FineVision® and seven patients received the PanOptix™ trifocal IOLs. Fifteen patients received the Symfony extended depth of focus IOL. Mean age of patients was 63 ± 8 years. Through-focus visual acuity was measured from -3.00 to +1.00 D vergences. Contrast sensitivity was measured with and without a source of glare. Light disturbances were evaluated with the Light Distortion Analyzer. RESULTS: Though-focus evaluation showed that trifocal IOLs performed significantly better at near distance (33 and 40 cm), and extended depth of focus performed significantly better at intermediate distance (1.0 m). Contrast sensitivity function with glare and dysphotopsia was similar between the three IOLs and subjective response to questionnaire showed a significantly higher score (worse performance) for the extended depth of focus IOL compared to both trifocal IOLs in the bothersome subscale (p < 0.05). CONCLUSIONS: Trifocal IOLs grant better performance at near distance while extended depth of focus IOL performs better at intermediate distance. Objective dysphotopsia measured with the Light Distortion Analyzer is not reduced in extended depth of focus IOL compared to trifocal IOLs.

Comparative analysis of clinical outcomes of a monofocal and an extended-range-of-vision intraocular lens in eyes with previous myopic laser in situ keratomileusis.

PURPOSE: To compare the clinical outcomes after cataract surgery with implantation of a monofocal or an extended-range-of-vision intraocular lens (IOL). SETTING: Hospital da Luz, Lisbon Portugal. DESIGN: Prospective case series. METHODS: Patients who previously had myopic laser in situ keratomileusis (LASIK) had cataract surgery with bilateral implantation of an extended-range-of-vision IOL (Tecnis Symfony) or a monofocal IOL (Tecnis ZCB00). Visual acuity, refraction, defocus curve, contrast sensitivity, photic phenomena, spectacle independence, and patient satisfaction were evaluated at 4 months postoperatively. RESULTS: The study comprised 44 patients (88 eyes), with 22 patients in each IOL group. No significant differences between groups were found postoperatively for most visual and refractive parameters (all P ≥ .27). However, binocular uncorrected intermediate and near visual acuities were significantly better in the extended-range-of-vision group (P < .01). The defocus curve of both IOLs differed more with increasing negative defocus (P < .01). No significant differences between IOLs were found in contrast sensitivity for any spatial frequency evaluated (P ≥ .05). Most of the patients did not perceive photic phenomena with either IOL. Mild glare was reported in 22.7% of the extended-range-of-vision patients and 9.1% of the monofocal group; mild halos were comparable with 13.6% in both groups. Spectacle dependence for intermediate vision and near vision was higher in the monofocal IOL group. CONCLUSION: The extended-range-of-vision IOL was a useful option to restore visual function after cataract surgery in eyes that previously had myopic LASIK surgery, offering levels of visual quality comparable to those achieved with the monofocal IOL.

Comparability and repeatability of different methods of corneal astigmatism assessment.

PURPOSE: To assess the comparability and repeatability of keratometric and astigmatism values measured by four techniques: Orbscan IIz® (Bausch and Lomb), Lenstar LS 900® (Haag-Streit), Cassini® (i-Optics), and Total Cassini (anterior + posterior surface), in healthy volunteers. PATIENTS AND METHODS: Fifteen healthy volunteers (30 eyes) were assessed by the four techniques. In each eye, three consecutive measures were performed by the same operator. Keratometric and astigmatism values were recorded. The intraclass correlation coefficient (ICC) was used to assess comparability and repeatability. Agreement between measurement techniques was evaluated with Bland-Altman plots. RESULTS: Comparability was high between all measurement techniques for minimum keratometry (K1), maximum keratometry (K2), astigmatism magnitude, and astigmatism axis, with ICC >0.900, except for astigmatism magnitude measured by Cassini compared to Lenstar (ICC =0.798) and Orbscan compared to Lenstar (ICC =0.810). However, there were some differences in the median values of K1 and K2 between measurement techniques, and the Bland-Altman plots showed a wide data spread for all variables, except for astigmatism magnitude measured by Cassini and Total Cassini. For J0 and J45, comparability was only high for J0 between Cassini and Orbscan. Repeatability was also high for all measurement techniques except for K2 (ICC =0.814) and J45 (ICC =0.621) measured by Cassini. CONCLUSION: All measurement techniques showed high comparability regarding K1, K2, and astigmatism axis. Although posterior corneal surface is known to influence these measurements, comparability was high between Cassini and Total Cassini regarding astigmatism magnitude and axis. However, the wide data spread suggests that none of these devices should be used interchangeably.

Comparison of Methodologies Using Estimated or Measured Values of Total Corneal Astigmatism for Toric Intraocular Lens Power Calculation.

PURPOSE: To compare the prediction error in the calculation of toric intraocular lenses (IOLs) associated with methods that estimate the power of the posterior corneal surface (ie, Barrett toric calculator and Abulafia-Koch formula) with that of methods that consider real measures obtained using Scheimpflug imaging: a software that uses vectorial calculation (Panacea toric calculator: http://www.panaceaiolandtoriccalculator.com) and a ray tracing software (PhacoOptics, Aarhus Nord, Denmark). METHODS: In 107 eyes of 107 patients undergoing cataract surgery with toric IOL implantation (Acrysof IQ Toric; Alcon Laboratories, Inc., Fort Worth, TX), predicted residual astigmatism by each calculation method was compared with manifest refractive astigmatism. Prediction error in residual astigmatism was calculated using vector analysis. RESULTS: All calculation methods resulted in overcorrection of with-the-rule astigmatism and undercorrection of against-the-rule astigmatism. Both estimation methods resulted in lower mean and centroid astigmatic prediction errors, and a larger number of eyes within 0.50 diopters (D) of absolute prediction error than methods considering real measures (P < .001). Centroid prediction error (CPE) was 0.07 D at 172° for the Barrett toric calculator and 0.13 D at 174° for the Abulafia-Koch formula (combined with Holladay calculator). For methods using real posterior corneal surface measurements, CPE was 0.25 D at 173° for the Panacea calculator and 0.29 D at 171° for the ray tracing software. CONCLUSIONS: The Barrett toric calculator and Abulafia-Koch formula yielded the lowest astigmatic prediction errors. Directly evaluating total corneal power for toric IOL calculation was not superior to estimating it. [J Refract Surg. 2017;33(12):794-800.].

Comparison of astigmatic prediction errors associated with new calculation methods for toric intraocular lenses.

PURPOSE: To compare the prediction errors in residual astigmatism associated with new calculation methods for toric intraocular lenses (IOLs). SETTING: Hospital da Luz, Lisbon, Portugal. DESIGN: Retrospective case series. METHODS: In eyes having cataract surgery with toric IOL implantation (Acrysof IQ), the predicted residual astigmatism by each calculation method was compared with the manifest refractive astigmatism. The prediction error in residual astigmatism was calculated by vector analysis. RESULTS: The study evaluated 86 eyes (86 patients). All calculation methods resulted in overcorrection of with-the-rule astigmatism and undercorrection of against-the-rule astigmatism. For the original Alcon calculator, the centroid prediction error was 0.43 @ 170, which was reduced by the application of the Baylor nomogram (0.35 @ 169) or the Abulafia-Koch formula (0.34 @ 170). For the Holladay toric calculator, the centroid prediction error was 0.40 @ 168, which was reduced by the Baylor nomogram (0.35 @ 169), the Abulafia-Koch formula (0.25 @ 158), and the Goggin coefficient of adjustment (0.38 @ 170). The Barrett calculator and the newly introduced Alcon calculator yielded the lowest centroid prediction errors (0.17 @ 165 and 0.19 @ 164, respectively). The centroid prediction error of ray-tracing calculations (PhacoOptics) using real posterior corneal surface measurements was 0.32 @ 171. CONCLUSIONS: The Barrett toric calculator and the new Alcon calculator yielded the lowest astigmatic prediction errors. Of the nomogram methods, application of the Abulafia-Koch formula achieved the best results. The outcomes of toric IOL implantation might be improved by using 1 of these calculation methods.

A novel color-LED corneal topographer to assess astigmatism in pseudophakic eyes.

PURPOSE: To assess the accuracy of corneal astigmatism evaluation measured by four techniques, Orbscan IIz(®), Lenstar LS900(®), Cassini(®), and Total Cassini (anterior + posterior surface), in pseudophakic eyes. PATIENTS AND METHODS: A total of 30 patients (46 eyes) who had undergone cataract surgery with the implantation of a monofocal intraocular lens (AcrySof IQ) were assessed after surgery. For each eye, subjective assessment of astigmatism and its axis was performed. Minimum, maximum, and mean keratometry and astigmatism and its axis were evaluated using the four measurement techniques. All measurements were compared with the subjective measurements. Agreement between each measurement technique and subjective assessment was evaluated using Bland-Altman plots. Linear regressions were performed and compared. RESULTS: Linear regression analysis of astigmatism axis showed very high R (2) for all models, with Total Cassini showing the least difference to the unit slope (0.052) and the least difference to a null constant (3.790), although not statistically different from the other models. Regarding astigmatism value, the Cassini and Total Cassini models were similar and statistically better than the Lenstar model. Cassini and Total Cassini showed better J0 compared with Orbscan. CONCLUSION: On linear regression models, Cassini and Total Cassini showed the best performance regarding astigmatism value. Cassini and Total Cassini also showed the least J0 deviation from the Cartesian origin compared with Orbscan, which had the lowest performance. Total corneal measurement with the color LED topographer seems to be a better technique for astigmatism assessment.