Biometry and Intraocular Lens Power Calculation in Eyes with Prior Laser Vision Correction (LVC) – A Review

Abstract

Background An intraocular lens (IOL) calculation in eyes that have undergone laser vision correction (LVC) poses a significant clinical issue in regards to both patient expectation and accuracy. This review aims to describe the pitfalls of IOL power calculation after LVC and give an overview of the current methods of IOL power calculation after LVC.

Review Problems after LVC derive from the measurement of anterior corneal radii, central corneal thickness, asphericity, and the predicted effective lens position. A central issue is that most conventional 3rd generation formulas estimate lens position amongst other parameters on keratometry, which is altered in post-LVC eyes.

Conclusion An IOL power calculation results in eyes with prior LVC that are notably impaired in eyes without prior surgery. Effective corneal power including anterior corneal curvature, posterior corneal curvature, CCT (central corneal thickness), and asphericity is essential. Total keratometry in combination with the Barrett True-K, EVO (emmetropia verifiying optical formula), or Haigis formula is relatively uncomplicated and seems to provide good results, as does the Barrett True-K formula with anterior K values. The ASCRS ( American Society of Cataract and Refractive Surgery) calculator combines results of various formulae and averages results, which allows a direct comparison between the different methods. Tomography-based raytracing and the Kane and the Castrop formulae need to be evaluated by future studies.

Zusammenfassung

Hintergrund Die Berechnung der Intraokularlinse (IOL) bei Augen, die einer refraktiven Laserkorrektur (LVC) unterzogen wurden, stellt ein bedeutendes klinisches Problem dar, sowohl im Hinblick auf die Erwartungen der Patienten als auch auf die refraktive Treffgenauigkeit. Ziel dieser Übersichtsarbeit ist es, die Fallstricke der IOL-Berechnung nach LVC zu beschreiben und einen Überblick über die aktuellen Methoden der IOL-Berechnung nach LVC zu geben.

Überblick Probleme nach LVC ergeben sich aus der Messung der vorderen Hornhautradien, der zentralen Hornhautdicke (CCT), der Asphärizität und der voraussichtlichen effektiven Linsenposition. Ein zentrales Problem ist, dass die meisten konventionellen Formeln der 3. Generation die effektive Linsenposition neben anderen Parametern anhand der Keratometrie abschätzen, die bei Augen nach LVC verändert ist.

Schlussfolgerung Die Ergebnisse der IOL-Brechkraftberechnung bei Augen mit vorheriger LVC sind deutlich schlechter als bei Augen ohne vorherige Operation. Die effektive Hornhautbrechkraft einschließlich der vorderen Hornhautkrümmung, der hinteren Hornhautkrümmung, der CCT und der Asphärizität ist von wesentlicher Bedeutung. Total Keratometry in Kombination mit der Barrett-True-K-, EVO- oder Haigis-Formel ist relativ unkompliziert und scheint gute Ergebnisse zu liefern. Gleiches gilt für die Barrett-True-K-Formel mit anterioren K-Werten. Der ASCRS-Rechner kombiniert die Ergebnisse der verschiedenen Formeln und bildet einen Mittelwert, was einen direkten Vergleich zwischen den verschiedenen Methoden ermöglicht. Das tomografiebasierte Raytracing, die Kane- und die Castrop-Formel müssen in zukünftigen Studien evaluiert werden.

Key words

cataract - biometry - laser vision correction - intraocular lens - IOL formula

Schlüsselwörter

Katarakt - Biometrie - Laserkorrektur - Intraokularlinse - IOL-Formel

Publication History

Received: 27 June 2022

Accepted: 30 June 2022

Article published online:
16 August 2022

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