Publications by authors named "Noel Alpins"
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.
Graefes Arch Clin Exp Ophthalmol
September 2022
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.
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).
Comment on: Rethinking the optimal methods for vector analysis of astigmatism.
J Cataract Refract Surg
January 2021
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.
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.
Quality of images with toric intraocular lenses.
J Cataract Refract Surg
March 2018
Purpose: To objectively evaluate the image quality obtained with toric intraocular lenses (IOLs) when misaligned from the intended axis.
Setting: University Eye Clinic and the Department of Industrial and Information Engineering, University of Trieste, Trieste, Italy.
Design: Experimental study.
Purpose: To evaluate clinical outcomes of laser in situ keratomileusis (LASIK) with an aberration-neutral profile centered on the estimated visual axis (considering 70% of the pupil offset toward the corneal vertex) comparing vector planning with manifest refraction planning for the treatment of myopic astigmatism.
Setting: Muscat Eye Laser Center, Muscat, Sultanate of Oman, Muscat, Oman.
Design: Retrospective case series.
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.
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.
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.
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.
J Cataract Refract Surg
November 2014
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.