Quantifying Corneal Topographic Astigmatism (CorT Total) in Keratoconic Eyes.

Purpose: To determine optimal corneal regions from which to derive corneal topographic astigmatism (CorT) in kerato-conic eyes.

Methods: In this retrospective study, potential measures of corneal astigmatism are calculated from raw total corneal power data (179 eyes from 124 patients) from a corneal tomographer. The measures are derived from annular corneal regions varying in both extent and center position, and evaluated according to the variability of the ocular residual astigmatism (ORA) in the cohort.

Hemidivisional vector planning to reduce and regularize irregular astigmatism by laser treatment.

Purpose: To demonstrate how hemidivisional vector planning of refractive laser treatments of astigmatism can be used to directly address idiopathic corneal irregular astigmatism that has an asymmetrical, non-orthogonal bow tie topography appearance.

Design: Case study.

Methods: The cornea is conceptually divided into two hemidivisions along the flat meridian of the corneal topographic astigmatism (CorT), which means that each hemidivision will approximately correspond to one lobe of the asymmetric, non-orthogonal topographic bow tie.

Assessing Total Keratometry Astigmatism, Simulated Keratometry, and Total Corneal Topographic Astigmatism Against Manifest Refractive Cylinder.

Purpose: To evaluate how the Total Keratometry astigmatism measure from a swept-source optical biometer compares with simulated keratometry astigmatism from the same device, and total corneal topographic astigmatism (CorT Total) derived from a Scheimpflug tomographer.

Methods: For normal virgin eyes, the ocular residual astigmatism (ORA) magnitudes were determined based on Total Keratometry, simulated keratometry from the same optical biometer (SimK), and CorT Total and simulated keratometry (SimK) from a Scheimpflug tomographer. The ORA magnitudes for each type of measure were summarized into the standard deviations (ORAsd) and means (ORAmean).

Optimized CorT Total to compare Scheimpflug vs dual Scheimpflug/Placido imaging devices.

Purpose: To compare the manufacturer-provided measures of total corneal power (TCP) generated by Scheimpflug and dual Scheimpflug/Placido imaging compared with corneal topographic astigmatism calculated on the basis of measured TCP data (CorT Total).

Setting: Emory University, Atlanta, Georgia, USA.

Design: Retrospective case series.

Corneal Topographic Astigmatism Based on Total Corneal Power Data (CorT Total): A Benchmark for Total Corneal Astigmatism.

Purpose: To evaluate how closely manufacturer-provided measures of total corneal astigmatism correspond with the manifest refractive cylinder, as compared to a benchmark of corneal topographic astigmatism calculated on the basis of measured total corneal power (TCP) data (CorT Total).

Methods: The SD of the ocular residual astigmatism magnitude (ORAsd) was evaluated for normal virgin eyes based on an optimized benchmark CorT Total and the various measures of total corneal astigmatism provided by 3 different Scheimpflug tomographers.

Results: The CorT Total corresponded with the manifest refractive cylinder at least as well as all the measures of total corneal astigmatism provided by the tomographers [Sirius CorT Total ORAsd: 0.

Role of Hemidivisional Corneal Topographic Astigmatisms (CorTs) in the Regularization and Reduction of Irregular Astigmatism.

Purpose: To demonstrate how the concept of hemidivisional corneal topographic astigmatism (hemiCorT) enables the planning of hemidivisional corneal treatments to reduce irregularity and overall astigmatism.

Methods: Whole-of-cornea corneal topographic astigmatism (CorT) is calculated from topography data derived from a corneal topographer or tomographer. The cornea is conceptually divided into 2 hemidivisions along the flat meridian of the CorT.

Planning for Coupling Effects in Bitoric Mixed Astigmatism Ablative Treatments.

Purpose: To demonstrate how to determine the historical coupling adjustments of bitoric mixed astigmatism ablative treatments and how to use these historical coupling adjustments to adjust future bitoric treatments.

Methods: The individual coupling adjustments of the myopic and hyperopic cylindrical components of a bitoric treatment were derived empirically from a retrospective study where the theoretical combined treatment effect on spherical equivalent was compared to the actual change in refractive spherical equivalent. The coupling adjustments that provided the best fit in both mean and standard deviation were determined to be the historical coupling adjustments.

Asymmetric Corneal Flattening Effect After Small Incision Cataract Surgery.

Purpose: To determine whether the flattening effect of corneal incisions differs between the right and left eye.

Methods: A retrospective study of preoperative and postoperative corneal astigmatism was performed for patients who had bilateral cataract surgery by a right-handed surgeon. The change in corneal astigmatism was attributed to the 2.

Corneal topographic astigmatism (CorT) to quantify total corneal astigmatism.

Purpose: To evaluate the performance of corneal topographic astigmatism (CorT) based on total corneal power measurements.

Methods: Anterior, posterior, and total corneal power measurements of 526 virgin eyes obtained using the CSO Sirius tomographer (Costuzione Strumenti Oftalmici, Scandicci, Florence, Italy) were analyzed. Individual CorTs were created from each set of data.

Corneal coupling of astigmatism applied to incisional and ablative surgery.

Purpose: To redefine measures of corneal coupling for use with incisional and ablation procedures for astigmatism.

Setting: Private clinics, Melbourne, Victoria, Australia.

Design: Retrospective nonrandomized study.

Refractive surprise after toric intraocular lens implantation: graph analysis.

Purpose: To determine the refractive cylinder effect of rotating a toric intraocular lens (IOL) and identify the sources of refractive astigmatic surprise after toric IOL implantation.

Setting: Private practice, Melbourne, Australia.

Design: Experimental study.

New method of quantifying corneal topographic astigmatism that corresponds with manifest refractive cylinder.

Purpose: To derive a method of quantifying corneal topographic astigmatism (CorT) that accurately represents manifest refractive cylinder.

Setting: Private practice, Melbourne, Australia.

Design: Retrospective study.

Measuring torsional eye movements by tracking stable iris features.

We propose a new method to measure torsional eye movements from videos taken of the eye. In this method, we track iris features that have been identified as Maximally Stable Volumes. These features, which are stable over time, are dark regions with bright borders that are steep in intensity.