Comparison of different methods to calculate the axial length measured by optical biometry

Savini, Giacomo; Hoffer, Kenneth J.; Carballo, Laura; Taroni, Leonardo; Schiano-Lomoriello, Domenico

doi:10.1097/j.jcrs.0000000000000821

Cited by 17 publications

(21 citation statements)

References 18 publications

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“…They found statistically significant differences between ALs, with a traditional AL shorter in short eyes and longer in long eyes. Savini et al 27 described how also an SS-OCT optical biometer based on the GRI (IOLMaster 700; Carl Zeiss Meditec, AG) overestimates AL compared to the device using segmented AL in long eyes (Argos). The effect of these differences on IOL power calculation were not evaluated in both studies.…”

Section: Discussionmentioning

confidence: 99%

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

Bernardo

Cione

Capasso³

et al. 2022

Sci Rep

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To verify the influence of axial length (AL) variations after cataract surgery in IOL power calculation. Patients underwent ophthalmic evaluation before surgery, including optical biometry with IOLMaster 500. Same exams were repeated 2 months after surgery: AL of operated eye was evaluated using two modes (pseudophakic/aphakic options). Mean Keratometry and AL changes were analyzed. Furthermore, refractive prediction error (PE) was back-calculated with Barrett Universal-II, Hoffer-Q, Holladay-1 and SRK/T formulas. To eliminate any systematic error, the mean error (ME) was zeroed-out for each formula. MEs and median absolute errors (MedAEs) of PEs were analyzed. Two-hundred-one operated eyes of 201 patients and 201 opposite eyes were evaluated. In operated eyes, mean AL difference was − 0.11 ± 0.07 mm (p < 0.001) with pseudophakic option and 0.00 ± 0.07 mm (p = 0.922) with aphakic option. There were not-statistically significant differences between MedAE of PEs calculated after zeroing-out the ME with different ALs (p > 0.05). Instead, only MEs of PEs obtained with postoperative ALs-pseudophakic option were not-statistically different from zero (p > 0.05). AL measurement change after cataract surgery is probably due to a systematic error in optical biometer in case of phakic eyes. A correction factor applied to preoperative AL could eliminate any systematic error in IOL power calculation without modifying the lens constant.

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Section: Discussionmentioning

confidence: 99%

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

Bernardo

Cione

Capasso³

et al. 2022

Sci Rep

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“…In the medium-long eyes, especially, the predictive accuracy of SS-OCT for IOL calculations was higher than PCI [ 23 ]. However, it is known that the SS-OCT biometer with group refractive index (IOLMaster 700) overestimates AL compared to the device providing segmented AL in the long eyes, and Cooke-modified AL (CMAL) is the adjusting method that gives the AL values closest to the segmented axial length [ 24 ]. In our research, we used the self-control method which compared one patient's preoperative and postoperative data, and thus, we considered that adjusted AL was not a must in this study.…”

Section: Discussionmentioning

confidence: 99%

Effect of Implantable Collamer Lens on Anterior Segment Measurement and Intraocular Lens Power Calculation Based on IOLMaster 700 and Sirius

Zhang

Liu

et al. 2021

Journal of Ophthalmology

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Purpose. To investigate the possible effect of an implantable collamer lens (ICL) on ocular biometrics and intraocular lens (IOL) power calculation. Methods. Ocular measurements were taken preoperatively and at the two-month follow-up using IOLMaster 700 and Sirius in 85 eyes (43 patients) who had previously undergone ICL surgery. IOL power was calculated using either IOLMaster 700 (Barrett Universal II formula) or Sirius (ray-tracing). All data were compared using the paired t-test. Results. The difference between preoperative and postoperative anterior chamber depth (ACD), lens thickness (LT), and keratometry on the steep axis (K2) measured by IOLMaster 700 was statistically significant (p < 0.001). In 11 of 85 eyes, IOLMaster misjudged the anterior surface of the ICL as that of the lens, leading to an error in ACD and LT. There were no significant differences between preoperative and postoperative axial length (AL) (p = 0.223), white to white (WTW) (p = 0.100), keratometry on flat axis (K1) (p = 0.117), or central corneal thickness (CCT) (p = 0.648), measured using IOLMaster. The difference in IOL power calculated using the Barrett II formula was significant (p = 0.013). Regression analysis showed that AL and K had the greatest influence on IOL calculation (p < 0.001), and ACD and LT had less influence (p = 0.002, p = 0.218, respectively). K1 and K2 were modified to exclude the influence of K2, and modified IOLs showed no difference between pre and postoperation (p = 0.372). Preoperative and postoperative ACD measured using Sirius were significantly different (p < 0.001); however, the IOL power calculated using ray-tracing technology showed no significant differences (p > 0.05). Conclusions. The ocular biometric apparatus may misjudge the anterior surface of the lens, resulting in measurement errors of ACD and LT, which has little effect on the calculation of IOL power when using IOLMaster 700 (Barrett Universal II formula) and Sirius (ray-tracing).

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“…In pseudophakic eyes, optical biometers modify AL calculation according to the corrections recommended by Haigis. 1 These corrections are applied throughout the whole AL range, and for this reason, De Bernardo et al found a similar AL shortening in long, medium, and short eyes. Other authors have also reported almost identical outcomes using sweptsource optical coherence tomography optical biometry.…”

mentioning

confidence: 95%

“…2 The results by Savini et al (AL obtained by Argos vs AL obtained by IOLMaster 700) are similar to those obtained in the paper by De Bernardo et al because a similar AL difference (−0.10 mm) was found between preoperative AL measurements with the phakic option vs postoperative AL with the pseudophakic option, both obtained by IOLMaster 500. 1 The reason why we wrote in part is because in the paper by De Bernardo et al, the AL shortening was obtained not only in long but also in short and normal eyes. 2 For this reason, we wonder whether the AL shortening after cataract surgery could be related not only to the group refractive index, but other reasons could be involved.…”

mentioning

confidence: 96%

Comment on: Comparison of different methods to calculate the axial length measured by optical biometry

Cione¹,

Bernardo²,

Rosa³

2022

J Cataract Refract Surg

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a swept-source optical coherence tomography optical biometer based on the group refractive index technology (IOLMaster 700). These results were explained by different methods used by the 2 machines, mainly in long eyes. In our opinion, these results could help to explain in part the findings of a previously published paper by De Bernardo et al. in which longer AL was measured in eyes before cataract surgery compared with the same eyes measured after surgery using the pseudophakic option obtained with an IOLMaster 500. 2 The results by Savini et al. (AL obtained by Argos vs AL obtained by IOLMaster 700) are similar to those obtained in the paper by De Bernardo et al. because a similar AL difference (À0.10 mm) was found between preoperative AL measurements with the phakic option vs postoperative AL with the pseudophakic option, both obtained by IOLMaster 500. 1The reason why we wrote in part is because in the paper by De Bernardo et al., the AL shortening was obtained not only in long but also in short and normal eyes. 2 For this reason, we wonder whether the AL shortening after cataract surgery could be related not only to the group refractive index, but other reasons could be involved.

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Comparison of different methods to calculate the axial length measured by optical biometry

Abstract: The optical biometer using group refractive index overestimates AL compared with the device based on segmented AL. Cooke-modified AL is the closest to segmented AL.

Cited by 17 publications

References 18 publications

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

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

Effect of Implantable Collamer Lens on Anterior Segment Measurement and Intraocular Lens Power Calculation Based on IOLMaster 700 and Sirius

Comment on: Comparison of different methods to calculate the axial length measured by optical biometry

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