Vecto-keratometry: determination of anterior corneal astigmatism in manual keratometers using power vectors

ABSTRACT

Background

A new keratometric routine that employs power vector management for manual keratometers is described. This study evaluates the agreement of the new proposed keratometric technique with the classical one.

Research design and methods

The applicability of a new keratometric routine was verified using Helmholtz’s and Javal’s keratometers. Results were obtained by two different and well-trained examiners over two different samples, one including 65 and the other 74 eyes, respectively. Both conventional keratometry and the newly proposed routine (named vecto-keratometry) were used in each eye to obtain the results. The clinical agreement between the methods was evaluated using Bland–Altman and Passing–Bablok analysis.

Results

For Helmholtz’s keratometer, Bland–Altman plots showed good agreement between methods for both astigmatic components being J₀ = 0.04 ± 0.20 D and J₄₅ = −0.07 ± 0.17 D. For Javal’s keratometer, Passing–Bablok regression test determined regression line for J₀ difference as y₀ = 1.03, confidence interval: [0.98, 1.10] and regression line for J₄₅ difference as y₄₅ = 0.97, confidence interval: [0.83, 1.12].

Conclusions

Vecto-keratometry provides accurate clinical results. It has been demonstrated that there are no significant differences between methods in any of the power vector astigmatic components; thus, both methods can be applied interchangeably.

KEYWORDS:

• Cornea
• power vector formalism
• corneal astigmatism
• keratometry
• Javal keratometer
• Helmholtz keratometer

Declaration of interest

The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.

Reviewers disclosure

Peer reviewers on this manuscript have no relevant financial relationships or otherwise to disclose.

Ethics approvals

Approval was obtained from the ethics committee of University of Valencia. The procedures used in this study adhere to the tenets of the Declaration of Helsinki.

Consent statement

Informed consent was obtained from all individual participants included in the study.

Additional information

Funding

This work was supported by the Spanish Ministerio de Universidades under Grant FPU20/05624 awarded to Raquel Salvador-Roger and Grant FPU21/05151 awarded to Rosa Vila-Andrés.