Original article
Effect of pharmacological pupil dilation on measurements and iol power calculation made using the new swept-source optical coherence tomography-based optical biometerEffet de la dilatation pharmacologique de la pupille sur les mesures biométriques et la prédiction de l’implant intraoculaire avec le nouveau biomètre optique basé sur la tomographie par cohérence optique swept-source

https://doi.org/10.1016/j.jfo.2016.09.003Get rights and content

Summary

Purpose

To determine whether pupil dilation affects biometric measurements and intraocular lens (IOL) power calculation made using the new swept-source optical coherence tomography-based optical biometer (IOLMaster 700©; Carl Zeiss Meditec, Jena, Germany).

Procedures

Eighty-one eyes of 81 patients evaluated for cataract surgery were prospectively examined using the IOLMaster 700© before and after pupil dilation with tropicamide 1%. The measurements made were: axial length (AL), central corneal thickness (CCT), aqueous chamber depth (ACD), lens thickness (LT), mean keratometry (MK), white-to-white distance (WTW) and pupil diameter (PD). Holladay II and SRK/T formulas were used to calculate IOL power. Agreement between measurement modes (with and without dilation) was assessed through intraclass correlation coefficients (ICC) and Bland-Altman plots.

Results

Mean patient age was 75.17 ± 7.54 years (range: 57–92). Of the variables determined, CCT, ACD, LT and WTW varied significantly according to pupil dilation. Excellent intraobserver correlation was observed between measurements made before and after pupil dilation. Mean IOL power calculation using the Holladay 2 and SRK/T formulas were unmodified by pupil dilation.

Conclusions

The use of pupil dilation produces statistical yet not clinically significant differences in some IOLMaster 700© measurements. However, it does not affect mean IOL power calculation.

Résumé

Propos

Déterminer si la dilatation pupillaire modifie les mesures biométriques et le calcul de la puissance de l’implant intraoculaire obtenus avec un nouveau biomètre optique basé sur la tomographie par cohérence optique swept-source (IOLMaster 700© ; Carl Zeiss Meditec, Jena, Allemagne)

Méthodes

Nous avons évalué prospectivement 81 yeux de 81 patients prévus pour la chirurgie de la cataracte au moyen du biomètre IOLMaster 700©, avant et après dilatation pupillaire avec tropicamide 1 %. Les mesures réalisées ont été : longueur axiale (AL), épaisseur cornéenne centrale (CCT), profondeur de la chambre antérieure (épaisseur cornéenne exclue) (ACD), épaisseur cristallinienne (LT), kératométrie moyenne (MK), distance blanc à blanc (WTW) et diamètre pupillaire (PD). Les formules Holladay II et SRK/T ont été employées pour calculer la puissance de l’implant intraoculaire. Nous avons évalué la concordance entre les deux méthodes de mesure (sous dilatation pupillaire et sans) au moyen des coefficients de corrélation intraclasse (ICC) et des graphiques de Bland-Altman.

Résultats

La moyenne d’âge des patients était de 75,17 ± 7,54 ans (intervalle : 57–92). Parmi les variables mesurées, la CCT, l’ACD, la LT et la WTW montraient des variations significatives en fonction de la dilatation pupillaire. On a observé une excellente corrélation intra-observateur entre les mesures réalisées avant et après la dilatation pupillaire. Celle-ci ne modifiait pas la prédiction de la puissance moyenne de l’implant avec Holladay 2 et SKR/T.

Conclusions

L’emploi de tropicamide 1 % produit des différences significatives du point de vue statistique mais pas clinique sur certaines mesures réalisées avec IOLMaster 700©. Cependant, la mesure de la puissance moyenne de l’implant intraoculaire n’est pas affectée.

Introduction

The success of cataract surgery depends on many factors, one of the most important being accurate calculation of intraocular lens (IOL) power [1]. Three main measurements are used for IOL calculation: axial length (AL), anterior chamber depth (ACD) and corneal power. In addition, some fourth generation formulas such as Holladay 2, also requires lens thickness (LT) and white-to-white distance (WTW). AL and ACD are normally determined through ultrasound or optical biometry. Currently used optical methods include the IOLMaster 500© (Carl Zeiss Meditec AG, Jena, Germany) based on partial coherence interferometry, the LENSTAR 900© (Haag-Streit AG, Koeniz, Switzerland), which uses optical low-coherence reflectometry (OLCR) powered by a superluminescent diode (SLD) and the newly developed IOLMaster 700© (Carl Zeiss Meditec AG, Jena, Germany) based on Swept Source optical coherence tomography (SS-OCT) technology. For more than 15 years, the IOLMaster 500© has been the benchmark for optical biometry measurements, offering high precision and good resolution for axial length (AL), anterior chamber depth (ACD) and corneal curvature [2]. Moreover, the LENSTAR©, which also measures lens thickness (LT) and central corneal thickness (CCT), has shown good reproducibility [3] and good correlation with the IOLMaster 500© [4]. The new IOLMaster 700©, the first SS-OCT-based biometer, has so far shown excellent repeatability and reproducibility, along with very high agreement with the IOLMaster 500© [5].

The effects of pupil dilation on optical biometry measurements have been fairly well established. Thus according to several reports, pharmacological mydriasis does not seem to significantly affect IOLmaster 500© measurements and IOL predictions [6], [7], [8] and similar results have been reported for LENSTAR© [9], [10].

To the best of our knowledge, no studies have hitherto studied the effect of pupil dilation on the accuracy of IOLMaster 700© measurements.

The purpose of the current study was to determine the influence of pharmacological pupil dilation on measurements using the new IOLMaster 700©. To determine the clinical significance of possible differences in measurements, we also calculated IOL powers.

Section snippets

Patients and methods

The subjects for this randomized diagnostic technology evaluation study were consecutively recruited among patients scheduled for cataract surgery at our department. The inclusion criterion was age-related cataract (including mild cataract). Exclusion criteria were prior eye surgery, an active ocular pathology such as uveitis or retinal degeneration and inability to fixate because of an eye disease and prior contact lens use. When both eyes met these criteria, only the right eye was included

Results

The study sample was comprised of 81 eyes of 81 patients (52 women) of mean age 75.17 ± 7.54 years (range: 57–92). In 71 (86.6%) participants, the eye examined was the right eye.

Of the data determined (Table 1), CCT, ACD, LT and WTW differed significantly before and after pupil dilation (Table 2). Good correlation was indicated by the ICC (Table 2) for all the variables. The IOL power prediction data are provided in Table 3. No statistical differences were detected in IOL power predictions based

Discussion

The results of our study indicate that pupil dilation affect some IOLMaster 700© measurements. Given the established excellent intraobserver repeatability of the IOLMaster 700© [5], we can assume that the differences observed were attributable to pupil dilation. Notwithstanding, these statistical differences were clinically insignificant since IOL power predictions were unaffected. Only in four IOL power predictions (with the Holladay 2 formula) did the difference exceed 1D. In addition, there

Disclosure of interest

The authors declare that they have no competing interest.

Acknowledgements

Authors acknowledge Ana Burton for the English edition of the manuscript.

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