A formula to improve the reliability of optical axial length measurement in IOL power calculation

Bernardo, Maddalena De; Cione, Ferdinando; Capasso, Luigi; Coppola, Alessia; Rosa, Nicola

doi:10.1038/s41598-022-23665-0

Cited by 42 publications

(37 citation statements)

References 41 publications

(58 reference statements)

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“…We are aware that axial length measurements are not very precise and some corrections are needed, but they should be precise enough for checking relationships. 4 Dove Medical Press encourages responsible, free and frank academic debate. The contentTxt of the Clinical Ophthalmology 'letters to the editor' section does not necessarily represent the views of Dove Medical Press, its officers, agents, employees, related entities or the Clinical Ophthalmology editors.…”

Section: Dear Editormentioning

confidence: 99%

Choroidal Thickness and Retinal Vein Occlusions [Letter]

Marino¹,

Gioia²,

Reda³

et al. 2023

OPTH

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Section: Dear Editormentioning

confidence: 99%

Choroidal Thickness and Retinal Vein Occlusions [Letter]

Marino¹,

Gioia²,

Reda³

et al. 2023

OPTH

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“…Biometry is indispensable for the diagnosis and treatment of ophthalmic diseases. Keratometry (K), axial length (AL), and anterior chamber depth (ACD) are important variables in the initial intraocular lens (IOL) calculation formulas [ 1 – 3 ]. Newer algorithms such as the Holladay 2 and Barrett Universal II formulas also use corneal diameter (CD) and lens thickness (LT) to improve accuracy [ 4 , 5 ].…”

Section: Introductionmentioning

confidence: 99%

Agreement between a new optical low coherence reflectometry biometer and an anterior segment optical coherence tomographer

et al. 2023

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Background To assess agreement of measurements between a new optical low coherence reflectometry (OLCR) biometer (SW-9000, Suoer, Tianjin, China) and a spectral-domain optical coherence tomographer (SD-OCT)/Placido topographer (MS-39, CSO, Florence, Italy) in healthy subjects. Methods A total of 66 right eyes from 66 healthy subjects were enrolled in this prospective study. Three consecutive measurements were randomly obtained with both devices by the same experienced operator to assess agreement. Bland-Altman plots and 95% limits of agreement (LoA) were used to verify the agreement between the devices. Results are presented as mean ± standard deviation (SD). Results The SD-OCT/Placido tomographer showed high agreement with the OLCR biometer for all parameters included in this study. The mean differences of central corneal thickness (CCT), anterior chamber depth (ACD), aqueous depth (AQD), mean keratometry (Km) and corneal diameter (CD) were 2.21 ± 2.67 μm (P < 0.001), − 0.10 ± 0.03 mm (P < 0.001), − 0.10 ± 0.04 mm (P < 0.001), − 0.01 ± 0.22 D (P = 0.773) and 0.20 ± 0.16 mm (P < 0.001), respectively. This implies that the inter-device difference in Km was not statistically significant, while the differences in CCT, ACD, AQD, CD were statistically but not clinically significant. The 95% LoAs of CCT, ACD, AQD, Km and CD were − 3.01 to 7.44 μm, − 0.16 to − 0.05 mm, − 0.18 to − 0.03 mm, − 0.45 to 0.43 D, and − 0.12 to 0.51 mm, respectively. Conclusions For CCT, ACD, AQD, Km, and CD in healthy subjects, the new OLCR biometer has high agreement with the SD-OCT/Placido tomographer and can be used interchangeably due to the narrow range of 95% LoAs.

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“…In fact, De Bernardo et al recently reported that cataract can modify the lens refractive index, and this could alter AL obtained by biometers using the group refractive index. 2 On these bases, they proposed a correction factor to improve the reliability of AL measurement, applicable to the entire range of AL. This corrected AL (ALc) can eliminate any systematic error resulting from the biometer.…”

mentioning

confidence: 99%

Comment on: Efficacy of segmented axial length and artificial intelligence approaches to intraocular lens power calculation in short eyes

Cione,

Pellegrino,

Di Paola

2023

J Cataract Refract Surg

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Comment on: Efficacy of segmented axial length and artificial intelligence approaches to intraocular lens power calculation in short eyes We read with great interest the article by Kenny et al. concerning intraocular lens (IOL) power calculation in short eyes. 1 In this article, 15 IOL power calculation formulas were compared using traditional axial length (AL) measurements and the segmented AL calculated with the Cooke-modified AL nomogram (CMAL). The authors found that the use of segmented AL for calculating IOL power in short eyes did not improve the formula performances. We congratulate the authors for their interesting study, but we would like to make a few comments.The authors correctly reported that IOL power calculation is challenging in short eyes, and they declared that although the Wang-Koch and Holladay adjustments have reduced prediction errors (PEs) for long eyes, no such solution exists in short eyes. This is not completely true. In fact, De Bernardo et al. recently reported that cataract can modify the lens refractive index, and this could alter AL obtained by biometers using the group refractive index. 2 On these bases, they proposed a correction factor to improve the reliability of AL measurement, applicable to the entire range of AL. This corrected AL (ALc) can eliminate any systematic error resulting from the biometer. 2 Because the authors used LENSTAR LS900, based on a group refractive index combined with the Grieshaber correction algorithm to measure AL, they should have taken in consideration ALc. From this point of view, ALc could be considered an alternative to CMAL or an additional correction in case of formulas that already correct AL to CMAL, like the Castrop formula.The authors did not perform lens constant optimization through zeroing out the mean error (ME), but they used IOL Con website lens factors. These constants are recommended when the sample size is small or more IOL models are included, but this is not the case. 3 Lens constant optimization appears imperative: in fact, Table 2 of their study shows that 5 formulas have high ME (>±0.15 diopters), meaning that a systematic error is present. These formulas cannot be compared with each other without eliminating any systematic error. 3 We have also some concerns regarding the statistical analysis. We applaud the adoption of the generalized estimating equation to account correlations between both eyes of the same patient, which is mandatory in this scenario. 4 On the other hand, we wonder why the authors chose the mean absolute error (MAE) instead of the median absolute error (MedAE). The MedAE is less affected by outliers than the MAE, and the distribution of the absolute PE is not Gaussian, as reported by the same authors, and it is described better by the MedAE than by the MAE. 5 In conclusion, the authors reported as a point of strength of the study that it analyzed firstly ZEISS AI IOL Calculator in short eyes, but they did not specify when and how they analyzed this method. Did they access to an online website, or did they u...

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A formula to improve the reliability of optical axial length measurement in IOL power calculation

Cited by 42 publications

References 41 publications

Choroidal Thickness and Retinal Vein Occlusions [Letter]

Choroidal Thickness and Retinal Vein Occlusions [Letter]

Agreement between a new optical low coherence reflectometry biometer and an anterior segment optical coherence tomographer

Comment on: Efficacy of segmented axial length and artificial intelligence approaches to intraocular lens power calculation in short eyes

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