Intraocular lens power formulae

Summary of Evidence

Evidence

1. Across entire axial length range

Review

2022 Chung et.al.

2022
Review

The Barrett Universal II formula based on a theoretical model has consistently demonstrated high accuracy.

The Olsen four-factor formula using ray tracing optics and the Hill-RBF calculator using artificial intelligence have also demonstrated good prediction results after being updated.

Notably, the Kane formula, incorporating artificial intelligence, has overall shown the best performance for all axial lengths.

The Barrett True-K formula has shown accurate results regardless of preoperative data in eyes with previous myopic refractive surgery.{Chung J, Bu JJ, Afshari NA. Advancements in intraocular lens power calculation formulas. Curr Opin Ophthalmol. 2022 Jan 1;33(1):35-40.}

Review

2021 Kane and Chang

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2021
Review

For IOL power formulas, the Kane formula was the most accurate formula over the entire axial length (AL) spectrum and in both the short eye (AL, ≤22.0 mm) and long eye (AL, ≥26.0 mm) subgroups.

Other formulas that performed well in the short-eye subgroup were the Olsen (4-factor), Haigis, and Hill-radial basis function (RBF) 1.0. In the long-eye group, the other formulas that performed well included the Barrett Universal II (BUII), Olsen (4-factor), or Holladay 1 with Wang-Koch adjustment.

Intraoperative aberrometry generally improved outcomes for spherical and toric IOLs in eyes both with and without prior refractive surgery when the BUII and Hill-RBF, Barrett toric calculator, or Barrett True-K formulas were not used. When they were used, IA did not result in better outcomes.{Kane JX, Chang DF. Intraocular Lens Power Formulas, Biometry, and Intraoperative Aberrometry: A Review. Ophthalmology. 2021 Nov;128(11):e94-e114. }

2. Previous refractive surgery

Review

2021 Wang and Koch

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2021
Review

Review of the methods and outcomes of IOL power calculations in eyes with previous LASIK, excimer laser photorefractive keratectomy (PRK), or radial keratotomy (RK). Tools like the ASCRS postrefractive IOL calculator are useful for the clinician by incorporating a variety of formulas. Toric, EDOF, and multifocal IOLs may provide excellent outcomes in selected cases that meet certain corneal topographic criteria.{Wang L, Koch DD. Intraocular Lens Power Calculations in Eyes with Previous Corneal Refractive Surgery: Review and Expert Opinion. Ophthalmology. 2021 Nov;128(11):e121-e131.}

In eyes with previous myopic LASIK or PRK, hyperopic LASIK or PRK, and RK, 0% to 85%, 38.1% to 71.9%, and 29% to 87.5% of eyes, respectively, showed refractive prediction errors within ±0.5 diopter (D); in eyes with toric IOL implantation that met certain inclusion criteria, 80%, 84%, and 69% of eyes, respectively, achieved postoperative astigmatism of 0.50 D or less. Intraocular lenses with negative spherical aberration (SA) will reduce the positive corneal spherical aberration induced in eyes by myopic LASIK or PRK or by RK. Intraocular lenses with 0 SA on average best match corneal SA in eyes with prior hyperopic LASIK or PRK. Studies have reported excellent outcomes of postrefractive eyes implanted with multifocal or EDOF IOLs; however, corneal topographic enrollment criteria were not specified.

Review

2021 Pantanelli et.al.

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2021
Review

Review of the literature of outcomes of intraocular lens (IOL) power calculation in eyes with a history of myopic LASIK or photorefractive keratectomy (PRK). Calculation methods requiring both prerefractive surgery keratometry and manifest refraction are no longer considered the gold standard. Strategies that averaged several methods yielded the lowest reported MedAEs (0.31-0.35 D) and highest (66%-68%) proportions within 0.5 D of target SE. Even after using the best-known methods, refractive outcomes were less accurate in eyes that had previous excimer laser surgery for myopia compared with those that did not have it.{Pantanelli SM, Lin CC, Al-Mohtaseb Z, Rose-Nussbaumer JR, Santhiago MR, Steigleman WA 3rd, Schallhorn JM. Intraocular Lens Power Calculation in Eyes with Previous Excimer Laser Surgery for Myopia: A Report by the American Academy of Ophthalmology. Ophthalmology. 2021 May;128(5):781-792. }

Meta-analysis

2021 Wei et.al.

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2021
Meta-analysis

In eyes with previous myopic laser refractive surgery, the Barrett True-K formula, optical coherence tomography (OCT), and optiwave refractive analysis (ORA) methods seemed to offer greater accuracy than others in calculating the IOL power for postrefractive surgery eyes. {Wei L, Meng J, Qi J, Lu Y, Zhu X. Comparisons of intraocular lens power calculation methods for eyes with previous myopic laser refractive surgery: Bayesian network meta-analysis. J Cataract Refract Surg. 2021 Aug 1;47(8):1011-1018.}

A network meta-analysis revealed that compared with the Haigis-L method, the OCT, Barrett True-K formula, and optiwave refractive analysis (ORA) methods performed better on the % ±0.50 D, whereas the Barrett True-K formula and ORA methods performed better on the % ±1.00 D.

Review

2016 Chen et.al.

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2016
Review

Evaluation of the accuracy of intraocular lens (IOL) power calculation methods after laser refractive surgery in myopic eyes. Compared with the Haigis-L method, the clinical history method, corneal bypass method, and Feiz-Mannis method were associated with lower odds of prediction error; the Masket method showed higher odds.{Chen X, Yuan F, Wu L. Metaanalysis of intraocular lens power calculation after laser refractive surgery in myopic eyes. J Cataract Refract Surg. 2016 Jan;42(1):163-70.}

3. Keratoconus

Review

2020 Garzon et.al.

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2020
Review

There are few publications that show in detail how IOL power is calculated in these particular cases. If the keratometric value used was based on the standard refractive index (1.3375), it resulted in a postoperative refractive error with a tendency to hyperopia. The SRK/T formula yielded the best outcomes. {Garzón N, Arriola-Villalobos P, Felipe G, Poyales F, García-Montero M. Intraocular lens power calculation in eyes with keratoconus. J Cataract Refract Surg. 2020 May;46(5):778-783.}

Review

2020 Smith et.al.

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2020
Review

There is still no consensus on which formula is best for IOL calculation in keratoconic eyes. On the basis of the most recent literature, we recommend using the Barrett II Universal in conjunction with the SRK/T formula for mild-to-moderate eyes.{Smith RG, Knezevic A, Garg S. Intraocular lens calculations in patients with keratoectatic disorders. Curr Opin Ophthalmol. 2020 Jul;31(4):284-287.}

Review

2019 Ghiasian et.al.

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2019
Review

SRK II formula may provide the most accurate IOL power in mild KCN. There is still not a comprehensive consensus of which formula is the best one in moderate and severe KCN, as the literature is limited in this subject.{Ghiasian L, Abolfathzadeh N, Manafi N, Hadavandkhani A. Intraocular lens power calculation in keratoconus; A review of literature. J Curr Ophthalmol. 2019 Mar 15;31(2):127-134. }

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Intraocular lens power formulae

Summary of Evidence

Evidence

1. Across entire axial length range

2. Previous refractive surgery

Details

Details

3. Keratoconus

References

Comments