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Kristian Naeser – 1st expert on this subject based on the ideXlab platform

  • Influence of Posterior Corneal Astigmatism on Total Corneal Astigmatism in Eyes With Keratoconus
    Cornea, 2016
    Co-Authors: Giacomo Savini, Kristian Naeser, Domenico Schiano-lomoriello, A. Mularoni

    Abstract:

    To measure posterior corneal Astigmatism (PCA) and investigate its influence on total corneal Astigmatism (TCA) in eyes with keratoconus.
    Keratometric Astigmatism (KA), PCA, and TCA were investigated by means of a dual Scheimpflug analyzer in patients with keratoconus. Vector analysis was carried out with the Naeser polar value method.
    We enrolled 119 eyes. PCA magnitude averaged 0.77 ± 0.43 diopters (D) and exceeded 0.50, 1.00, and 2.00 D in 73.9%, 21.8%, and 16.8% of eyes, respectively. PCA averaged 0.95 ± 0.48, 0.55 ± 0.28, and 0.70 ± 0.35 D in eyes with with-the-rule (WTR), against-the-rule (ATR), and oblique Astigmatism. The steepest posterior meridian was oriented vertically (between 61 and 119 degrees) in 55.5% of eyes, thus generating ATR Astigmatism. The difference between the location of the steepest meridian of KA and that of TCA was >10 degrees in 8.4% of eyes. On average, KA overestimated TCA in eyes with WTR Astigmatism by 0.16 D and underestimated TCA in eyes with ATR Astigmatism by 0.22 D. The PCA power oriented along the steeper anterior corneal meridian averaged −0.83 ± 0.40, −0.40 ± 0.37, and −0.53 ± 0.43 D for WTR, ATR, and obliquely astigmatic eyes, respectively. Linear regression disclosed a statistically significant correlation (P < 0.0001, r2 = 0.16) between the meridional powers of TCA and PCA. In eyes with keratoconus, PCA displays large, variable values and is correlated to TCA. The influence of PCA on TCA cannot be disregarded when planning Astigmatism correction by toric intraocular lenses.

  • an analysis of the factors influencing the residual refractive Astigmatism after cataract surgery with toric intraocular lenses
    Investigative Ophthalmology & Visual Science, 2015
    Co-Authors: Giacomo Savini, Kristian Naeser

    Abstract:

    PURPOSE: To investigate the influence of posterior corneal Astigmatism, surgically-induced corneal Astigmatism (SICA), intraocular lens (IOL) orientation, and effective lens position on the refractive outcome of toric IOLs. METHODS: Five models were prospectively investigated. Keratometric Astigmatism and an intended SICA of 0.2 diopters (D) were entered into model 1. Total corneal Astigmatism, measured by a rotating Scheimpflug camera, was used instead of keratometric Astigmatism in model 2. The mean postoperative SICA, the actual postoperative IOL orientation, and the influence of the effective lens position were added, respectively, into models 3, 4, and 5. Astigmatic data were vectorially described by meridional and torsional powers. A set of equations was developed to describe the error in refractive Astigmatism (ERA) as the difference between the postoperative refractive Astigmatism and the target refractive Astigmatism. RESULTS: We enrolled 40 consecutive eyes. In model 1, ERA calculations revealed significant cylinder overcorrection in with-the-rule (WTR) eyes (meridional power = -0.59 ± 0.34 D, P < 0.0001) and undercorrection in against-the-rule (ATR) eyes (0.32 ± 0.42 D, P = 0.01). When total corneal Astigmatism was used instead of keratometric Astigmatism (model 2), the ERA meridional power decreased in WTR (-0.13 ± 0.42 D) and ATR (0.07 ± 0.59 D) eyes, both values being not statistically significant. Models 3 to 5 did not lead to significant improvement. CONCLUSIONS: Posterior corneal Astigmatism exerts the highest influence on the ERA after toric IOL implantation. Basing calculations on total corneal Astigmatism rather than keratometric Astigmatism improves the prediction of the residual refractive Astigmatism.

  • an analysis of the factors influencing the residual refractive Astigmatism after cataract surgery with toric intraocular lenses
    Investigative Ophthalmology & Visual Science, 2015
    Co-Authors: Giacomo Savini, Kristian Naeser

    Abstract:

    Abstract To investigate the influence of posterior corneal Astigmatism, surgically-induced corneal Astigmatism (SICA), intraocular lens (IOL) orientation, and effective lens position on the refractive outcome of toric IOLs. Five models were prospectively investigated. Keratometric Astigmatism and an intended SICA of 0.2 diopters (D) were entered into model 1. Total corneal Astigmatism, measured by a rotating Scheimpflug camera, was used instead of keratometric Astigmatism in model 2. The mean postoperative SICA, the actual postoperative IOL orientation, and the influence of the effective lens position were added, respectively, into models 3, 4, and 5. Astigmatic data were vectorially described by meridional and torsional powers. A set of equations was developed to describe the error in refractive Astigmatism (ERA) as the difference between the postoperative refractive Astigmatism and the target refractive Astigmatism. We enrolled 40 consecutive eyes. In model 1, ERA calculations revealed significant cylinder overcorrection in with-the-rule (WTR) eyes (meridional power = -0.59 ± 0.34 D, P

Giacomo Savini – 2nd expert on this subject based on the ideXlab platform

  • Influence of Posterior Corneal Astigmatism on Total Corneal Astigmatism in Eyes With Keratoconus
    Cornea, 2016
    Co-Authors: Giacomo Savini, Kristian Naeser, Domenico Schiano-lomoriello, A. Mularoni

    Abstract:

    To measure posterior corneal Astigmatism (PCA) and investigate its influence on total corneal Astigmatism (TCA) in eyes with keratoconus.
    Keratometric Astigmatism (KA), PCA, and TCA were investigated by means of a dual Scheimpflug analyzer in patients with keratoconus. Vector analysis was carried out with the Naeser polar value method.
    We enrolled 119 eyes. PCA magnitude averaged 0.77 ± 0.43 diopters (D) and exceeded 0.50, 1.00, and 2.00 D in 73.9%, 21.8%, and 16.8% of eyes, respectively. PCA averaged 0.95 ± 0.48, 0.55 ± 0.28, and 0.70 ± 0.35 D in eyes with with-the-rule (WTR), against-the-rule (ATR), and oblique Astigmatism. The steepest posterior meridian was oriented vertically (between 61 and 119 degrees) in 55.5% of eyes, thus generating ATR Astigmatism. The difference between the location of the steepest meridian of KA and that of TCA was >10 degrees in 8.4% of eyes. On average, KA overestimated TCA in eyes with WTR Astigmatism by 0.16 D and underestimated TCA in eyes with ATR Astigmatism by 0.22 D. The PCA power oriented along the steeper anterior corneal meridian averaged −0.83 ± 0.40, −0.40 ± 0.37, and −0.53 ± 0.43 D for WTR, ATR, and obliquely astigmatic eyes, respectively. Linear regression disclosed a statistically significant correlation (P < 0.0001, r2 = 0.16) between the meridional powers of TCA and PCA. In eyes with keratoconus, PCA displays large, variable values and is correlated to TCA. The influence of PCA on TCA cannot be disregarded when planning Astigmatism correction by toric intraocular lenses.

  • an analysis of the factors influencing the residual refractive Astigmatism after cataract surgery with toric intraocular lenses
    Investigative Ophthalmology & Visual Science, 2015
    Co-Authors: Giacomo Savini, Kristian Naeser

    Abstract:

    Abstract To investigate the influence of posterior corneal Astigmatism, surgically-induced corneal Astigmatism (SICA), intraocular lens (IOL) orientation, and effective lens position on the refractive outcome of toric IOLs. Five models were prospectively investigated. Keratometric Astigmatism and an intended SICA of 0.2 diopters (D) were entered into model 1. Total corneal Astigmatism, measured by a rotating Scheimpflug camera, was used instead of keratometric Astigmatism in model 2. The mean postoperative SICA, the actual postoperative IOL orientation, and the influence of the effective lens position were added, respectively, into models 3, 4, and 5. Astigmatic data were vectorially described by meridional and torsional powers. A set of equations was developed to describe the error in refractive Astigmatism (ERA) as the difference between the postoperative refractive Astigmatism and the target refractive Astigmatism. We enrolled 40 consecutive eyes. In model 1, ERA calculations revealed significant cylinder overcorrection in with-the-rule (WTR) eyes (meridional power = -0.59 ± 0.34 D, P

  • an analysis of the factors influencing the residual refractive Astigmatism after cataract surgery with toric intraocular lenses
    Investigative Ophthalmology & Visual Science, 2015
    Co-Authors: Giacomo Savini, Kristian Naeser

    Abstract:

    PURPOSE: To investigate the influence of posterior corneal Astigmatism, surgically-induced corneal Astigmatism (SICA), intraocular lens (IOL) orientation, and effective lens position on the refractive outcome of toric IOLs. METHODS: Five models were prospectively investigated. Keratometric Astigmatism and an intended SICA of 0.2 diopters (D) were entered into model 1. Total corneal Astigmatism, measured by a rotating Scheimpflug camera, was used instead of keratometric Astigmatism in model 2. The mean postoperative SICA, the actual postoperative IOL orientation, and the influence of the effective lens position were added, respectively, into models 3, 4, and 5. Astigmatic data were vectorially described by meridional and torsional powers. A set of equations was developed to describe the error in refractive Astigmatism (ERA) as the difference between the postoperative refractive Astigmatism and the target refractive Astigmatism. RESULTS: We enrolled 40 consecutive eyes. In model 1, ERA calculations revealed significant cylinder overcorrection in with-the-rule (WTR) eyes (meridional power = -0.59 ± 0.34 D, P < 0.0001) and undercorrection in against-the-rule (ATR) eyes (0.32 ± 0.42 D, P = 0.01). When total corneal Astigmatism was used instead of keratometric Astigmatism (model 2), the ERA meridional power decreased in WTR (-0.13 ± 0.42 D) and ATR (0.07 ± 0.59 D) eyes, both values being not statistically significant. Models 3 to 5 did not lead to significant improvement. CONCLUSIONS: Posterior corneal Astigmatism exerts the highest influence on the ERA after toric IOL implantation. Basing calculations on total corneal Astigmatism rather than keratometric Astigmatism improves the prediction of the residual refractive Astigmatism.

Li Wang – 3rd expert on this subject based on the ideXlab platform

  • Astigmatism induced by intraocular lens tilt evaluated via ray tracing
    Journal of Cataract and Refractive Surgery, 2018
    Co-Authors: Mitchell P Weikert, Abhinav Golla, Li Wang

    Abstract:

    Purpose To evaluate Astigmatism induced by aspheric and toric intraocular lens (IOL) tilt using a ray-tracing model. Setting Cullen Eye Institute, Baylor College of Medicine, Houston, Texas, USA. Design Experimental study. Methods Ray-tracing eye models with aspheric IOLs (16.0 diopters [D], 22.0 D, and 28.0 D) and toric IOLs (16.0 D, 22.0 D, and 28.0 D each with toricities of 1.50 D, 3.75 D, and 6.00 D) were used. The IOLs were tilted from 1 to 10 degrees horizontally around a 90-degree vertical meridian. Toric IOLs were aligned at 90 degrees and 180 degrees to correct with-the-rule (WTR) and against-the-rule (ATR) corneal Astigmatism, respectively. Astigmatism at the corneal plane induced by IOL tilt was calculated. Results Induced Astigmatism increased with increasing IOL tilt and power. Horizontal tilt around a vertical meridian induced ATR Astigmatism. For 5 degrees of tilt, induced Astigmatism was 0.08 D, 0.11 D, and 0.14 D for 16.0 D, 22.0 D, and 28.0 D aspheric IOLs, respectively. Ten degrees of IOL tilt produced 0.33 D, 0.44 D, and 0.56 D of induced Astigmatism for 16.0 D, 22.0 D, and 28.0 D aspheric IOLs, respectively. Tilting toric IOLs aligned at 90 degrees around a vertical meridian increased the magnitude of induced ATR Astigmatism. Tilting toric IOLs aligned at 180 degrees decreased the magnitude of induced WTR Astigmatism. Conclusions Tilting aspheric IOLs horizontally around a vertical meridian induced ATR Astigmatism. Tilting toric IOLs aligned at 90 degrees increased ATR Astigmatism, resulting in overcorrection. Tilting toric IOLs aligned at 180 degrees decreased WTR Astigmatism, producing undercorrection.

  • contribution of posterior corneal Astigmatism to total corneal Astigmatism
    Journal of Cataract and Refractive Surgery, 2012
    Co-Authors: Douglas D Koch, Mitchell P Weikert, Mariko Shirayama, Richard Jenkins, Li Wang

    Abstract:

    Purpose To determine the contribution of posterior corneal Astigmatism to total corneal Astigmatism and the error in estimating total corneal Astigmatism from anterior corneal measurements only using a dual-Scheimpflug analyzer. Setting Cullen Eye Institute, Baylor College of Medicine, Houston, Texas, USA. Design Case series. Methods Total corneal Astigmatism was calculated using ray tracing, corneal Astigmatism from simulated keratometry, anterior corneal Astigmatism, and posterior corneal Astigmatism, and the changes with age were analyzed. Vector analysis was used to assess the error produced by estimating total corneal Astigmatism from anterior corneal measurements only. Results The study analyzed 715 corneas of 435 consecutive patients. The mean magnitude of posterior corneal Astigmatism was −0.30 diopter (D). The steep corneal meridian was aligned vertically (60 to 120 degrees) in 51.9% of eyes for the anterior surface and in 86.6% for the posterior surface. With increasing age, the steep anterior corneal meridian tended to change from vertical to horizontal, while the steep posterior corneal meridian did not change. The magnitudes of anterior and posterior corneal Astigmatism were correlated when the steeper anterior meridian was aligned vertically but not when it was aligned horizontally. Anterior corneal measurements underestimated total corneal Astigmatism by 0.22 @ 180 and exceeded 0.50 D in 5% of eyes. Conclusions Ignoring posterior corneal Astigmatism may yield incorrect estimation of total corneal Astigmatism. Selecting toric intraocular lenses based on anterior corneal measurements could lead to overcorrection in eyes that have with-the-rule Astigmatism and undercorrection in eyes that have against-the-rule Astigmatism. Financial Disclosure The authors received research support from Ziemer Group. In addition, Dr. Koch has a financial interest with Alcon Laboratories, Inc., Abbott Medical Optics, Inc., Calhoun Vision, Inc., NuLens, and Optimedica Corp.

  • correction of Astigmatism during cataract surgery toric intraocular lens compared to peripheral corneal relaxing incisions
    Journal of Refractive Surgery, 2010
    Co-Authors: Jed T Poll, Douglas D Koch, Li Wang, Mitchell P Weikert

    Abstract:

    PURPOSE: To compare the efficacy of astigmatic correction achieved at the time of cataract surgery using toric intraocular lens (IOL) implantation versus peripheral corneal relaxing incisions. METHODS: A retrospective review assessed the outcomes of phacoemulsification cataract surgery performed between January 2006 and January 2008 by a single surgeon. Patients receiving a toric IOL (toric IOL group) or peripheral corneal relaxing incisions (relaxing incisions group) were included in the study. Main outcome variables included postoperative uncorrected distance visual acuity (UDVA) and manifest refractive cylinder. Each treatment modality was stratified by amount of preoperative keratometric Astigmatism into three groups (low, moderate, and high Astigmatism) for comparative analysis. RESULTS: A total of 192 eyes were included in the study; 77 received a toric IOL and 115 received peripheral corneal relaxing incisions. Preoperative data were not significantly different between the two groups except regarding keratometric Astigmatism, which was higher in the toric IOL group (P<.05). Average postoperative Astigmatism was 0.42 diopters (D) and 0.46 D in the toric and relaxing incisions groups, respectively. In subgroup analysis, no statistical significance separated the two treatment options in terms of amount of surgically induced Astigmatism or residual Astigmatism. Eyes with Astigmatism ≥2.26 D were more likely to achieve 20/40 UDVA from a toric IOL. CONCLUSIONS: Toric IOL implantation and peripheral corneal relaxing incisions yielded similar results regarding surgical correction of Astigmatism at the time of phacoemulsification cataract surgery. Both treatment modalities achieved comparable results with mild-to-moderate Astigmatism. Higher degrees of Astigmatism favor use of a toric IOL.