Purpose To compare the accuracy of four different intraocular lens (IOL) power calculation formulas for eyes with mean keratometry values greater than 46 diopters (D). Methods Forty five eyes from 45 patients who were candidates for senile cataract surgery with mean keratometry values greater than 46 D were included. Calculation of the IOL power was performed by the Lenstar. The implanted IOL in all cases was Acrysof SA60AT. The average absolute value of the differences between the actual and predicted spherical equivalent (SE) of the postoperative refractive error (mean absolute error: MAE) was calculated using 4 formulas (Haigis, Holladay 1, Hoffer Q, and SRK/T) with optical IOL constants from the User Group for Laser Interference Biometry constants. Results The MAE was smallest in the SRK/T formula (0.39 D ± 0.35) followed by those of the Holladay 1 (0.44 D ± 0.32), Haigis (0.45 D ± 0.35) and Hoffer Q (0.5 D ± 0.38) formulas. However, there was no statistically significant difference between the MAE among different formulas. The SRK/T formula predicted more eyes within ± 0.5 D of the SE (77.8%) compared to other formulas. Conclusion In eyes with steep corneas, there were no statistically significant differences among the accuracies of the four common IOL power calculation formulas.

Accuracy of Various Intraocular Lens Power Calculation Formulas in Steep Corneas.

To the Editor: We read with great interest the article by Camps et al, published in your journal. We congratulate the authors because calculating the intraocular lens (IOL) power in patients who had undergone refractive surgery is very challenging, and it will become more important over the years when a greater number of patients who underwent this kind of surgery will age. We would like to make a comment on this article, because in the Introduction, the authors stated that a variety of adjustment in keratometric estimations have been proposed in eyes that have undergone myopic corneal refractive surgery, some of them considering data before the surgery and others not considering the preoperative data. Among the methods that do not require the use of preoperative parameters or the amount of treatment to calculate the IOL power, the authors acknowledged only 3 articles, 2 published by Shammas et al and 1 by Savini et al. To the best of our knowledge, with these characteristics, at least 19 methods have been described. Some can be used without limitations, such as those described by Ferrara et al, Haigis, Jin et al, Kim et al, Latkany et al, Rosa et al, and Shammas et al; whereas, the others require the use of special devices. Regarding the study by Savini, actually, the authors in the cited article did not propose a real K adjustment, but they tested the data currently provided by the Pentacam camera to determine whether they could be used in a reliable way in the IOL power calculation of patients who underwent corneal refractive surgery. Unfortunately, they found that “none of the data provided by the Pentacam camera can accurately replace those obtained with the clinical history method, either because of a statistically significant difference in the mean values or poor agreement,” and found that none of them could be used in a reliable way for such a purpose. Our concern is why the authors decided to make such citations, excluding all the others.

Algorithm for the estimation of the corneal power in eyes with previous myopic laser refractive surgery.

AIM: To evaluate the prediction error in intraocular lens (IOL) power calculation for a rotationally asymmetric refractive multifocal IOL and the impact on this error of the optimization of the keratometric estimation of the corneal power and the prediction of the effective lens position (ELP). METHODS: Retrospective study including a total of 25 eyes of 13 patients (age, 50 to 83y) with previous cataract surgery with implantation of the Lentis Mplus LS-312 IOL (Oculentis GmbH, Germany). In all cases, an adjusted IOL power (PIOLadj) was calculated based on Gaussian optics using a variable keratometric index value (nkadj) for the estimation of the corneal power (Pkadj) and on a new value for ELP (ELPadj) obtained by multiple regression analysis. This PIOLadj was compared with the IOL power implanted (PIOLReal) and the value proposed by three conventional formulas (Haigis, Hoffer Q and Holladay I). RESULTS: PIOLReal was not significantly different than PIOLadj and Holladay IOL power (P>0.05). In the Bland and Altman analysis, PIOLadj showed lower mean difference (-0.07 D) and limits of agreement (of 1.47 and -1.61 D) when compared to PIOLReal than the IOL power value obtained with the Holladay formula. Furthermore, ELPadj was significantly lower than ELP calculated with other conventional formulas (P<0.01) and was found to be dependent on axial length, anterior chamber depth and Pkadj. CONCLUSION: Refractive outcomes after cataract surgery with implantation of the multifocal IOL Lentis Mplus LS-312 can be optimized by minimizing the keratometric error and by estimating ELP using a mathematical expression dependent on anatomical factors.

/pdf/error-induced-by-the-estimation-of-the-corneal-power-and-the-15oat5t0b3.pdf

Error induced by the estimation of the corneal power and the effective lens position with a rotationally asymmetric refractive multifocal intraocular lens

Purpose: To evaluate the predictability of the refractive correction achieved with a positional accommodating intraocular lenses (IOL) and to develop a potential optimization of it by minimizing the error associated with the keratometric estimation of the corneal power and by developing a predictive formula for the effective lens position (ELP). Materials and Methods: Clinical data from 25 eyes of 14 patients (age range, 52-77 years) and undergoing cataract surgery with implantation of the accommodating IOL Crystalens HD (Bausch and Lomb) were retrospectively reviewed. In all cases, the calculation of an adjusted IOL power (P IOLadj ) based on Gaussian optics considering the residual refractive error was done using a variable keratometric index value (n kadj ) for corneal power estimation with and without using an estimation algorithm for ELP obtained by multiple regression analysis (ELP adj ). P IOLadj was compared to the real IOL power implanted (P IOLReal , calculated with the SRK-T formula) and also to the values estimated by the Haigis, HofferQ, and Holladay I formulas. Results: No statistically significant differences were found between P IOLReal and P IOLadj when ELP adj was used (P = 0.10), with a range of agreement between calculations of 1.23 D. In contrast, P IOLReal was significantly higher when compared to P IOLadj without using ELP adj and also compared to the values estimated by the other formulas. Conclusions: Predictable refractive outcomes can be obtained with the accommodating IOL Crystalens HD using a variable keratometric index for corneal power estimation and by estimating ELP with an algorithm dependent on anatomical factors and age.

/pdf/positional-accommodative-intraocular-lens-power-error-11mznu7v2v.pdf

Positional accommodative intraocular lens power error induced by the estimation of the corneal power and the effective lens position

The author David P. Pinero has been supported by the Ministry of Economy, Industry and Competitiveness of Spain within the program Ramon y Cajal, RYC-2016-20471. Additionally he received an unrestricted grant from Johnson and Johnson Vision for the performance of this research.

/pdf/interchangeability-of-corneal-curvature-and-asphericity-2k85fd1hwm.pdf

Interchangeability of corneal curvature and asphericity measurements provided by three different devices

PURPOSE To evaluate theoretically in normal eyes the influence on IOL power (PIOL) calculation of the use of a keratometric index (nk) and to analyze and validate preliminarily the use of an adjusted keratometric index (nkadj) in the IOL power calculation (PIOLadj). METHODS A model of variable keratometric index (nkadj) for corneal power calculation (Pc) was used for IOL power calculation (named PIOLadj). Theoretical differences (ΔPIOL) between the new proposed formula (PIOLadj) and which is obtained through Gaussian optics ((Equation is included in full-text article.)) were determined using Gullstrand and Le Grand eye models. The proposed new formula for IOL power calculation (PIOLadj) was prevalidated clinically in 81 eyes of 81 candidates for corneal refractive surgery and compared with Haigis, HofferQ, Holladay, and SRK/T formulas. RESULTS A theoretical PIOL underestimation greater than 0.5 diopters was present in most of the cases when nk = 1.3375 was used. If nkadj was used for Pc calculation, a maximal calculated error in ΔPIOL of ±0.5 diopters at corneal vertex in most cases was observed independently from the eye model, r1c, and the desired postoperative refraction. The use of nkadj in IOL power calculation (PIOLadj) could be valid with effective lens position optimization nondependent of the corneal power. CONCLUSIONS The use of a single value of nk for Pc calculation can lead to significant errors in PIOL calculation that may explain some IOL power overestimations with conventional formulas. These inaccuracies can be minimized by using the new PIOLadj based on the algorithm of nkadj.

Minimizing the IOL power error induced by keratometric power.

Handle everyday research tasks with reliable, citation-backed results

Your personal Research Agent to handle research tasks with citation-backed results

Popular Tasks used by Researchers

How can I help with your research?

Meet SciSpace

Get more enhanced response by uploading the PDFs you want me to reference.

No relevant PDFs in your library

SciSpace is the AI research assistant for academics. Run systematic literature reviews on 280M+ papers, and write papers with cited sources. Trusted by 1M+ students, PhDs & researchers.

SciSpace | AI for Research

Analyze PDFs

Code & Manuscripts

Funding & Grants

Literature & Patents

Medical & Clinical Data

Systematic Review

Visualize & Present

Web & Data

Build a Google Scholar-like website for your research.

Build a website

Create charts and images for your research

Create a Chart

Write a paper for submission to a journal

Draft a manuscript

Patent Search

Design eye-catching scientific posters in minutes.

Scientific Poster Generation

Systematic Literature Review

One task is running at the moment. Your messages will be shown right after.

Drag and drop or click here to browse

Loved by <highlight>1 million+</highlight> researchers

Extract a list of specific topics and their sources from unstructured text

Topics

Compare and analyze relevant papers that matches with your search

Papers

Get insights from PDFs and bookmarked papers from your library

My library

Recent searches

Try searching for:

Catch AI-generated content in scholarly and non-scholarly content

{ai} Detector

Ai Writer

Get PDF Summaries, highlighted text explanations 

Chat with PDF

Effortlessly create in-text citations and bibliographies in APA and 2,500 other formats

Citation generator

Get explanations, summaries, and answers on academic papers

Ease up your research workflow with {scispace}'s cohort of exciting AI tools

Elevate your academic writing skills and convey your ideas the way you want

Paraphraser

Explore our range of reading and writing tools

Your file is being prepared and should be ready in a few minutes. If it's a large file, it might take a bit longer. You can close this window, and we'll email you the file when it's done.

You have reached a maximum limit of <strong>{limit}</strong> columns in the table. Remove at least <strong>1</strong> column to add or create another one.

de Fez D

Author Tools

Chat about Author

Papers

Minimizing the IOL power error induced by keratometric power.