Alan Cayless
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View article: Keratometry and the Central Radius with Aspheric Corneal Surfaces
Keratometry and the Central Radius with Aspheric Corneal Surfaces Open
For corneal representations with a conoid surface or where central corneal radius is required e.g. for paraxial calculations, the keratometric radius of curvature could easily be converted to the central radius based on corneal asphericity…
View article: Predictive Correction Model for Corneal Back Surface Astigmatism With <scp>IOLMaster700</scp> Keratometry Data in a Cataractous Population
Predictive Correction Model for Corneal Back Surface Astigmatism With <span>IOLMaster700</span> Keratometry Data in a Cataractous Population Open
Background To develop and validate various models to predict total keratometry ( TK ) power vector components TKC0 and TKC45 from classical keratometry (K) KC0 and KC45 based on a large dataset of pre cataract surgery IOLMaster 700 measure…
View article: Repeatability of Corneal Astigmatism and Equivalent Power with the MS-39 Tomographer Derived from Model Surface Fitting in a Cataractous Population
Repeatability of Corneal Astigmatism and Equivalent Power with the MS-39 Tomographer Derived from Model Surface Fitting in a Cataractous Population Open
We investigated the repeatability of the MS-39 in determining power vector components—the spherical equivalent (SEQ) and astigmatic powers (C0 and C45) and asphericity (Q)—of corneal epithelium, stroma, and endothelium in a large patient c…
View article: A two‐step formula constant optimization strategy for minimal standard deviation and zero mean prediction error in <scp>IOL</scp> power calculation
A two‐step formula constant optimization strategy for minimal standard deviation and zero mean prediction error in <span>IOL</span> power calculation Open
Purpose To investigate the precision and accuracy performance of a two‐step approach for optimizing lens formula constants (FC) with a refractive offset correction (RO) as a second tuning parameter. Methods Using IOLMaster 700 biometric da…
View article: Repeatability of corneal measurements from the Casia2 anterior segment tomographer in a cataractous population
Repeatability of corneal measurements from the Casia2 anterior segment tomographer in a cataractous population Open
Purpose The purpose of this study was to investigate the repeatability of corneal power and thickness measures in a large patient cohort. Methods In this retrospective non-randomised cross sectional single-centre study we evaluated a datas…
View article: Repeatability of corneal curvature with the MS-39 anterior segment tomographer in a cataractous population
Repeatability of corneal curvature with the MS-39 anterior segment tomographer in a cataractous population Open
Purpose The purpose of this study was to investigate the repeatability of optical coherence tomography in measuring radius of curvature (ROC) and asphericity (Q) of corneal epithelium, stroma and endothelium in a large patient cohort. Meth…
View article: Deciphering the performance of different surface models for corneal topography
Deciphering the performance of different surface models for corneal topography Open
Purpose To study the performance of different corneal surface models to be used for ray tracing. Models based on geometric surfaces and polynomial fits were compared and the differences discussed. Methods For this simulation study, five ch…
View article: Jackknife and bootstrapping resampling techniques to evaluate the precision of lens formula constants
Jackknife and bootstrapping resampling techniques to evaluate the precision of lens formula constants Open
Purpose The purpose of this study was to develop a method for evaluating intraocular lens (IOL) formula constant uncertainties using two modern statistical techniques—jackknife and bootstrap resampling. Methods Using two datasets (dataset …
View article: Repeatability of biometric measures from the LenStar LS900 in a cataractous population
Repeatability of biometric measures from the LenStar LS900 in a cataractous population Open
Purpose To investigate the repeatability of biometric measures and assess interactions between their uncertainties for use in an error propagation model, using patient data. Methods Cross-sectional non-randomised study evaluating a dataset…
View article: Considerations on the Haigis formula: Are better outcomes possible with tuning?
Considerations on the Haigis formula: Are better outcomes possible with tuning? Open
Purpose To design a vergence‐based lens power formula based on the classical Haigis formula for better outcomes while retaining the original formula architecture. Methods Four new formula variants (A–D) incorporating a sum of segments corr…
View article: Evaluation of keratometric and total corneal astigmatism measurements from optical biometers and anterior segment tomographers and mapping to reconstructed corneal astigmatism vector components
Evaluation of keratometric and total corneal astigmatism measurements from optical biometers and anterior segment tomographers and mapping to reconstructed corneal astigmatism vector components Open
Purpose To investigate different measures for corneal astigmatism in the context of reconstructed corneal astigmatism (recCP) as required to correct the pseudophakic eye, and to derive prediction models to map measured corneal astigmatism …
View article: Prediction of refraction error after toric lens implantation with biometric input data uncertainties and power labelling tolerances
Prediction of refraction error after toric lens implantation with biometric input data uncertainties and power labelling tolerances Open
Background The purpose of this study was to simulate the impact of biometric measure uncertainties, lens equivalent and toric power labelling tolerances and axis alignment errors on the refractive outcome after cataract surgery with toric …
View article: Performance Evaluation of a Simple Strategy to Optimize Formula Constants for Zero Mean or Minimal Standard Deviation or Root-Mean-Squared Prediction Error in Intraocular Lens Power Calculation
Performance Evaluation of a Simple Strategy to Optimize Formula Constants for Zero Mean or Minimal Standard Deviation or Root-Mean-Squared Prediction Error in Intraocular Lens Power Calculation Open
This simple formula constant optimization scheme performs excellently for 4 disclosed formulae and one nondisclosed formula in our 2 monocentric datasets with zero MPE or minimal RMSPE as metrics. Multicentric studies with other study popu…
View article: The Homburg‐Adelaide toric IOL nomogram: How to predict corneal power vectors from preoperative IOLMaster 700 keratometry and total corneal power in toric IOL implantation
The Homburg‐Adelaide toric IOL nomogram: How to predict corneal power vectors from preoperative IOLMaster 700 keratometry and total corneal power in toric IOL implantation Open
Purpose The purpose of this study is to compare the reconstructed corneal power (RCP) by working backwards from the post‐implantation spectacle refraction and toric intraocular lens power and to develop the models for mapping preoperative …
View article: Evaluating keratometry and corneal astigmatism data from biometers and anterior segment tomographers and mapping to reconstructed corneal astigmatism
Evaluating keratometry and corneal astigmatism data from biometers and anterior segment tomographers and mapping to reconstructed corneal astigmatism Open
Background To compare results from different corneal astigmatism measurement instruments; to reconstruct corneal astigmatism from the postimplantation spectacle refraction and toric intraocular lens (IOL) power; and to derive models for ma…
View article: Performance of a simplified strategy for formula constant optimisation in intraocular lens power calculation
Performance of a simplified strategy for formula constant optimisation in intraocular lens power calculation Open
Purpose To investigate the performance of a simple prediction scheme for the formula constants optimised for a mean refractive prediction error. Methods Analysis based on a dataset of 888 eyes before and after cataract surgery with IOL imp…
View article: Vector analysis of corneal astigmatism in cataractous eyes based on IOLMaster 700 biometry
Vector analysis of corneal astigmatism in cataractous eyes based on IOLMaster 700 biometry Open
Purpose The purpose of this study was to investigate the effect of the corneal back surface by comparing the keratometric astigmatism (K, derived from the corneal front surface) of a modern optical biometer against astigmatism of Total Ker…
View article: Surrogate optimisation strategies for intraocular lens formula constant optimisation
Surrogate optimisation strategies for intraocular lens formula constant optimisation Open
Purpose To investigate surrogate optimisation (SO) as a modern, purely data‐driven, nonlinear adaptive iterative strategy for lens formula constant optimisation in intraocular lens power calculation. Methods A SO algorithm was implemented …
View article: Science for society
Science for society Open
Chapter 8 presents an introduction and sections on: education and outreach in an interdisciplinary environment; science with and for the citizens; open communication and responsible citizens; science and ethics; the limits of science
View article: Repeatability of biometric measures from the IOLMaster 700 in a cataractous population
Repeatability of biometric measures from the IOLMaster 700 in a cataractous population Open
Purpose The purpose of this study was to investigate the repeatability of biometric measures and also to assess the interactions between the uncertainties in these measures for use in an error propagation model, using data from a large pat…
View article: Calculation of Phakic and Pseudophakic Additional Lenses
Calculation of Phakic and Pseudophakic Additional Lenses Open
Calculation of add-on intraocular lens (IOL) power, both for phakic and pseudophakic eyes, can be done based on refraction, spectacle vertex distance, corneal curvatures, and IOL plane position. In this chapter, a Gaussian optical matrix f…
View article: Monte-Carlo simulation for calculating phakic supplementary lenses based on a thick and thin lens model using anterior segment OCT data
Monte-Carlo simulation for calculating phakic supplementary lenses based on a thick and thin lens model using anterior segment OCT data Open
Background Phakic lenses (PIOLs, the most common and only disclosed type being the implantable collamer lens, ICL) are used in patients with large or excessive ametropia in cases where laser refractive surgery is contraindicated. The purpo…
View article: Limitations of constant optimization with disclosed intraocular lens power formulae
Limitations of constant optimization with disclosed intraocular lens power formulae Open
Purpose: To investigate the effect of formula constants on predicted refraction and limitations of constant optimization for classical and modern intraocular lens (IOL) power calculation formulae. Setting: Tertiary care center. Design: Ret…
View article: Prediction of corneal power vectors after cataract surgery with toric lens implantation–A vector analysis
Prediction of corneal power vectors after cataract surgery with toric lens implantation–A vector analysis Open
Background Intraocular lenses are typically calculated based on a pseudophakic eye model, and for toric lenses (tIOL) a good estimate of corneal astigmatism after cataract surgery is required in addition to the equivalent corneal power. Th…
View article: Prediction of IOL decentration, tilt and axial position using anterior segment OCT data
Prediction of IOL decentration, tilt and axial position using anterior segment OCT data Open
Background Intraocular lenses (IOLs) require proper positioning in the eye to provide good imaging performance. This is especially important for premium IOLs. The purpose of this study was to develop prediction models for estimating IOL de…
View article: Prediction of spectacle refraction uncertainties with discrete IOL power steps and manufacturing tolerances according to ISO using a Monte Carlo model
Prediction of spectacle refraction uncertainties with discrete IOL power steps and manufacturing tolerances according to ISO using a Monte Carlo model Open
Purpose The purpose of this study was to develop a concept for predicting the effects of both discrete intraocular lens (IOL) power steps (PS) and power labelling tolerances (LT) on the uncertainty of the refractive outcome (REFU). Design …
View article: Impact of uncertainties in biometric parameters on intraocular lens power formula predicted refraction using a <scp>Monte‐Carlo</scp> simulation
Impact of uncertainties in biometric parameters on intraocular lens power formula predicted refraction using a <span>Monte‐Carlo</span> simulation Open
Purpose The purpose of this study was to investigate the uncertainty in the formula predicted refractive outcome REFU after cataract surgery resulting from measurement uncertainties in modern optical biometers using literature data for wit…