Journal of Refractive Surgery

Original Article Supplemental Data

Intraoperative Aberrometry Versus Preoperative Biometry for IOL Power Selection After Radial Keratotomy: A Prospective Study

Sebastião Xavier Curado, MD; Wilson Takashi Hida, MD, PhD; César Martins Cortez Vilar, MD; Virgílio Luiz Ordones, MD; Mário Augusto Pereira Chaves, MD; Patrick Frensel Tzelikis, MD, PhD

Abstract

PURPOSE:

To compare the accuracy of Optiwave Refractive Analysis (ORA) intraoperative aberrometry (Alcon Laboratories, Inc., Fort Worth, TX) with preoperative biometry in predicting residual refractive error after cataract surgery in eyes that underwent radial keratotomy.

METHODS:

This was a prospective consecutive case series of patients with cataract and prior radial keratotomy. Each patient underwent a preoperative intraocular lens (IOL) power calculation using partial coherence interferometry (IOLMaster version 5; Carl Zeiss Meditec, Jena, Germany). For each eye, the Barrett True-K formula was used to select an IOL targeting emmetropia. Residual refractive error was predicted preoperatively using the SRK/T, Hoffer Q, Haigis, and Holladay formulas 1 and 2, and the ORA intraoperatively. Between 8 and 12 weeks after cataract extraction with IOL implantation, the postoperative refraction was compared with the preoperative and intraoperative predictions.

RESULTS:

The study comprised 52 eyes of 34 patients. The median absolute errors associated with each method were as follows: Barrett True-K formula (0.34), ORA aberrometer (0.53), and SRK/T (0.54), Hoffer Q (0.51), Haigis (0.54), SRK/T (0.57), and Holladay formulas 1 and 2 (0.44) (P = .08). The proportion of patients within ±0.50 diopters of the predicted error was 63.5%, 48.1%, 44.2%, 48.1%, 53.8%, 36.5%, and 57.7%, respectively (P = .03). No statistically significant difference was observed in the number of eyes with hyperopic outcomes (P = .68).

CONCLUSIONS:

In eyes with prior radial keratotomy surgery, the ORA aberrometer performance was similar to the Barrett True-K formula and all of the other established formulas, with no significant difference between median absolute error and mean absolute error. The Barrett True-K formula produced significantly more eyes within ±0.50 diopters than the SRK/T, Hoffer Q, and Holladay 1 formulas.

[J Refract Surg. 2019;35(10):656–661.]

Abstract

PURPOSE:

To compare the accuracy of Optiwave Refractive Analysis (ORA) intraoperative aberrometry (Alcon Laboratories, Inc., Fort Worth, TX) with preoperative biometry in predicting residual refractive error after cataract surgery in eyes that underwent radial keratotomy.

METHODS:

This was a prospective consecutive case series of patients with cataract and prior radial keratotomy. Each patient underwent a preoperative intraocular lens (IOL) power calculation using partial coherence interferometry (IOLMaster version 5; Carl Zeiss Meditec, Jena, Germany). For each eye, the Barrett True-K formula was used to select an IOL targeting emmetropia. Residual refractive error was predicted preoperatively using the SRK/T, Hoffer Q, Haigis, and Holladay formulas 1 and 2, and the ORA intraoperatively. Between 8 and 12 weeks after cataract extraction with IOL implantation, the postoperative refraction was compared with the preoperative and intraoperative predictions.

RESULTS:

The study comprised 52 eyes of 34 patients. The median absolute errors associated with each method were as follows: Barrett True-K formula (0.34), ORA aberrometer (0.53), and SRK/T (0.54), Hoffer Q (0.51), Haigis (0.54), SRK/T (0.57), and Holladay formulas 1 and 2 (0.44) (P = .08). The proportion of patients within ±0.50 diopters of the predicted error was 63.5%, 48.1%, 44.2%, 48.1%, 53.8%, 36.5%, and 57.7%, respectively (P = .03). No statistically significant difference was observed in the number of eyes with hyperopic outcomes (P = .68).

CONCLUSIONS:

In eyes with prior radial keratotomy surgery, the ORA aberrometer performance was similar to the Barrett True-K formula and all of the other established formulas, with no significant difference between median absolute error and mean absolute error. The Barrett True-K formula produced significantly more eyes within ±0.50 diopters than the SRK/T, Hoffer Q, and Holladay 1 formulas.

[J Refract Surg. 2019;35(10):656–661.]

Radial keratotomy was the most frequently performed refractive procedure for the treatment of myopia in the late 1970s and 1980s.1 In 1981, the National Eye Institute began a multicenter prospective trial, the Prospective Evaluation of Radial Keratotomy (PERK) study, to establish the outcome of a single radial keratotomy technique and long-term predictability of a refractive procedure for which there was weak published data.2 The PERK study recruited 427 patients (793 eyes), and 374 patients (88%) returned for the 10-year examination. Between 6 months and 10 years, the refractive error of 43% of eyes changed in the hyperopic direction by 1.00 diopters (D) or more, and 3% of eyes lost two or more lines of corrected distance visual acuity (CDVA). Overcorrection and diurnal fluctuations remain the most common persistent complications of radial keratotomy.3

Furthermore, many patients have experienced cataract and presbyopia with age. Studies have demonstrated that refractive outcomes after cataract surgery in such patients are difficult to predict because radial keratotomy incisions alter corneal curvatures, making the shape more oblate through central flattening and peripheral steepening, leading to errors when measuring the corneal power and predicting effective lens position.4–6 Both of these errors lead to an underestimation of the required intraocular lens (IOL) power, which leaves the patient hyperopic.7

Conventional methods of IOL power calculation have been based on preoperative biometry using keratometry, axial length, and, in some formulas, additional measurements such as anterior chamber depth.8,9 Radial keratotomy flattens both the anterior and posterior corneal surfaces in a small, central optical zone, changing the corneal power but not the depth of the lens, and leading to an error in effective lens placement prediction in the standard formulas.5,7 The Internet-based IOL power calculator at the American Society of Cataract and Refractive Surgery (ASCRS) website has a specific module for eyes with prior radial keratotomy.10,11 Another Internet-based IOL power calculator is the Barrett True-K formula, which can be accessed from the Asian-Pacific Association of Cataract and Refractive Surgeons (APACRS) and ASCRS websites.12

Another recent method in eyes after radial keratotomy is intraoperative aberrometry. The Optiwave Refractive Analysis (ORA) (Alcon Laboratories, Inc., Fort Worth, TX) is an intraoperative wavefront aberrometer used to measure the refractive power of an aphakic eye intraoperatively and to calculate the expected residual refractive error after placement of an IOL. However, the accuracy of its use in patients who underwent radial keratotomy has not been well evaluated in the literature.11,13

The purpose of this prospective study was to compare the ORA aberrometer with the Barrett True-K formula and other established formulas based on preoperative biometry in predicting residual refractive error in a series of eyes with previous radial keratotomy.

Patients and Methods

Study Design

A prospective single-center study was conducted between July 1, 2017, and September 30, 2018, in accordance with the ethical principles of the Declaration of Helsinki and the principles of current Good Clinical Practices. The study protocol was approved by the institutional review board of Hospital Oftalmológico de Brasília. All patients provided written informed consent.

Patient Enrollment

Patients were enrolled at only one study center in Brasília, Brazil. Eligible patients were aged 40 years or older, had undergone previous radial keratotomy surgery, had age-related cataract that required cataract extraction by phacoemulsification, and had a normal ophthalmologic examination except for senile cataract and radial keratotomy incisions. Exclusion criteria were any corneal pathology, additional keratorefractive surgery (laser-assisted in situ keratomileusis (LASIK) or photorefractive keratectomy), glaucoma or intraocular pressure (IOP) of greater than 21 mm Hg, amblyopia, central endothelial cell count of less than 2,000 cells/mm2, retinal abnormalities, uveitis, diabetes mellitus, connective tissue diseases, trauma, or steroid or immunosuppressive treatment. Enrolled patients who had surgical complications (eg, posterior capsule rupture, vitreous loss, or an IOL not placed in the capsular bag), posterior capsule opacification, or a postoperative CDVA of 20/40 or worse were subsequently excluded.

Study Protocol

Preoperatively, patients underwent an extensive ophthalmologic examination, including measurement of uncorrected distance visual acuity (UDVA), CDVA, refraction, slit-lamp biomicroscopy, IOP, and dilated fundus examination. Spherical equivalent (SE) refractions were recorded for each eye before surgery. UDVA and CDVA were assessed with the Early Treatment Diabetic Retinopathy Study eye meter chart under standardized conditions. The visual acuity measurements were recorded in logMAR units.

IOL Power Calculation Methods

Preoperative biometry measurements were performed using a partial coherence interferometry device (IOLMaster version 5; Carl Zeiss Meditec, Jena, Germany). The IOL with the smallest possible myopic outcome was chosen for implantation in all eyes. IOL power calculations were measured using the following seven methods: (1) the Barrett True-K formula, (2) ORA aberrometer in the aphakic state, (3) SRK/T, (4) Hoffer Q, (5) Haigis, (6) Holladay 1, and (7) Holladay 2.

Surgical Technique

All operations were performed in a standard way by the same experienced surgeon. Briefly, phacoemulsification surgery was performed via a 2.4-mm temporal, clear corneal incision. Intraoperatively and after cortical clean-up, each eye was reinflated with sodium hyaluronate 1% (Provisc; Alcon Laboratories, Inc.) to an IOP of between 18 and 20 mm Hg, which was confirmed with the Barraquer tonometer. The ORA aberrometer measured the eye in the aphakic state and estimated the postoperative refractive error for the IOL that the surgeon had selected for implantation based on preoperative biometry. Where there was a difference, the surgeon was allowed to use either the ORA-calculated IOL power or the IOL power previously selected based on the Barrett True-K formula.

Outcome Measurements

Outcomes of the seven formulas in the study were evaluated as follows: the Barrett True-K formula, SRK/T, Hoffer Q, Haigis, Holladay 1 and 2, and the ORA aberrometer. The primary outcome measure of this study was the median absolute error. The median absolute error represents the central location of the absolute errors and is less affected by outliers in a dataset. The secondary outcomes were the arithmetic mean prediction error, mean absolute error, and the percentage of eyes within ±0.50 and ±1.00 D of the predicted refraction error. To back-calculate the prediction error, the difference between the postoperative refractive SE and predicted SE for each of the tested formulas was calculated. The median absolute error and mean absolute error values were calculated with data derived after reducing the arithmetic mean error to zero. A 3-month postoperative subjective refraction was chosen as the final CDVA and end point.

Statistical Analysis

Data were entered into a Microsoft Office Excel spreadsheet (Microsoft Corporation, Redmond, WA) and analyzed using SPSS software (version 17.0; SPSS, Inc., Chicago, IL). Outcome measures were the median absolute error, mean absolute error, and percentage of eyes achieving absolute errors within the dioptric range of predicted refraction (0.50 to 1.00 D). All data were analyzed preoperatively and 3 months postoperatively.

Quantitative variables are described using mean ± standard deviation or median and range where appropriate. The normality of data was assessed with the Shapiro–Wilk test. Depending on the data distribution, within-subject analysis of variance, the Friedman test, or the Cochran Q test were used for comparisons between groups and comparisons of percentages of eyes within certain refractive prediction errors. Bonferroni correction was applied for multiplex tests. Any differences showing a P value of less than .05 (ie, at the 5% level) were considered statistically significant.

Results

Patient Characteristics

A total of 39 patients were screened to participate in this study. One patient decided not to participate and three were excluded due to previous LASIK and glaucoma; for these reasons, four were withdrawn from the analysis set. Thirty-five patients started the study, underwent surgery, and were included in the full analysis set. One patient was lost to follow-up after the first postoperative visit. A total of 34 patients (52 eyes) completed the protocol. There were no intraoperative complications.

Eighteen patients (52.9%) were men and 16 (47.1%) were women. The mean age of the patients was 62.09 ± 4.60 years (range: 53 to 70 years); they all had a cataract with four (41 eyes; 78.8%) or eight (11 eyes; 21.2%) radial keratotomy incisions. Patients were followed up for 8- to 12-week postoperative refraction. Table 1 shows the demographics of the study population and Table A (available in the online version of this article) lists the IOL models implanted.

Demographics of the Study Population

Table 1:

Demographics of the Study Population

Models of the Implanted IOL

Table A:

Models of the Implanted IOL

Table 2 compares the outcomes of the seven methods. There was no difference in median absolute error and mean absolute error between the seven groups (P > .05), although the Barrett True-K formula resulted in the lowest value (Figures 12). The number of patients in our study is small with unequal radial keratotomy sized groups. For this reason, we have inadequate power to detect any difference between the two groups of radial keratotomy (four and eight incisions) performed in the study.

Comparison of the Six Calculation Methods

Table 2:

Comparison of the Six Calculation Methods

Box plot of the median absolute error (MedAE) associated with each different intraocular lens calculation formula in eyes with prior radial keratotomy. ORA = Optiwave Refractive Analysis intraoperative aberrometer (Alcon Laboratories, Inc., Fort Worth, TX)

Figure 1.

Box plot of the median absolute error (MedAE) associated with each different intraocular lens calculation formula in eyes with prior radial keratotomy. ORA = Optiwave Refractive Analysis intraoperative aberrometer (Alcon Laboratories, Inc., Fort Worth, TX)

Box plot of the mean absolute error associated with each different intraocular lens calculation formula in eyes with prior radial keratotomy. ORA = Optiwave Refractive Analysis intraoperative aberrometer (Alcon Laboratories, Inc., Fort Worth, TX)

Figure 2.

Box plot of the mean absolute error associated with each different intraocular lens calculation formula in eyes with prior radial keratotomy. ORA = Optiwave Refractive Analysis intraoperative aberrometer (Alcon Laboratories, Inc., Fort Worth, TX)

The seven groups differed significantly in the proportion of patients with ±0.50 D of the predicted error. The Barrett True-K formula was significantly better than the SRK/T, Hoffer Q, and Holladay 1 at predicting an SE within ±0.50 D of actual postoperative SE (Table B, available in the online version of this article). The Barrett True-K formula was also significantly better than the Haigis at predicting an SE within ±1.00 D of actual postoperative SE. The Holladay 2 performed significantly better than the Holladay 1 and SRK/T.

P Values for Pairwise Comparisons of Percentage of Eyes Within ±0.50 and ±1.00 D of the Target SE for Each IOL Calculation Method

Table B:

P Values for Pairwise Comparisons of Percentage of Eyes Within ±0.50 and ±1.00 D of the Target SE for Each IOL Calculation Method

The seven groups also differed significantly in the proportion of patients with hyperopic outcomes (P = .03). The Barrett True-K formula significantly reduced hyperopic outcomes compared with the SRK/T and Holladay 1 formulas (P = .02 and .005, respectively). The difference in hyperopic outcomes between the Barrett True-K formula (18 of 52 [34.6%]) and ORA aberrometer (22 of 52 [42.3%]) did not reach significance (P = .28).

Discussion

The accuracy of IOL power calculation in eyes with prior refractive surgery remains a major challenge. Our study reports the largest series of outcomes using the ORA aberrometer for IOL power calculation in eyes with previous radial keratotomy. The results from 52 consecutive eyes demonstrate predictive accuracy similar to IOL power estimation using the ORA aberrometer compared with the Barrett True-K formula and conventional preoperative methods.

Recent advances in modern phacoemulsification techniques have raised patient expectations that better refractive outcomes can be achieved. One of these advances is the use of real-time biometry during cataract surgery, such as intraoperative aberrometry, which could improve refractive outcomes, especially after laser vision correction or more challenging cases such as after radial keratotomy. However, in a study evaluating the efficacy and reliability of intraoperative wavefront aberrometry (Hartmann-Shack aberrometer) in patients with no risk factors impacting optical media transparency, Huelle et al.14 found several factors that may impair the precision and quality of the intraoperative wavefront aberrometry measurements, such as eyelid speculum, corneal wound integrity and hydration, eye movements, hydration of the vitreous, refractive index difference between ophthalmic viscosurgical device and aqueous humor, and large variations in anterior chamber depth and IOP intraoperatively.

Our study also investigated the ORA aberrometer. Other authors have used the intraoperative aberrometer and presented promising results in eyes that underwent refractive surgery.13,15 In a retrospective study involving 246 eyes, Ianchulev et al.15 achieved 67% of eyes within ±0.50 D of target refraction in myopic patients who underwent myopic LASIK/photorefractive keratectomy with the ORA aberrometer method. The authors reported a median absolute error of 0.35 D and a mean absolute error of 0.42 D. In a retrospective study involving a total of 39 eyes that underwent previous laser vision correction, Fram et al.13 also reported 74% of eyes within ±0.50 D of target refraction, with a median absolute error of 0.29 D and a mean absolute error of 0.34 D for the ORA aberrometer.

The two previously mentioned studies presented results superior to those of the current study because they did not include patients after radial keratotomy, who represent an even greater challenge regarding the refractive results of surgery. In the current study, 48.1% of eyes achieved ±0.50 D of target refraction, and the median absolute error and mean absolute error were 0.53 and 0.55 D, respectively. One study by Canto et al.16 that also included eyes after radial keratotomy and used an older version of the ORA aberrometer reported a ±0.50 D postoperative refractive error in 39% of eyes.

In our study involving patients who underwent radial keratotomy, the Barrett True-K formula presented the best results with the lowest values of median absolute error (0.34 D) and mean absolute error (0.50 D). The proportion of patients within ±0.50 and ±1.00 D of the predicted error was 63.5% and 88.5%, respectively. In a retrospective case series that measured the accuracy of the Barrett True-K formula in eyes that underwent laser vision correction, Abulafia et al.17 reported a median absolute error of 0.33 in eyes with previous refractive data. Furthermore, the percentage of eyes with a refractive prediction error within ±0.50 and ±1.00 D was significantly higher with the Barrett True-K formula than with all other cited formulas (67.2% and 94.8%, respectively). Wang et al.9 prospectively demonstrated that the Barrett True-K formula is a promising formula for eyes after corneal refractive surgery with a median prediction error of 0.42 and 58.7% and 90.4% of eyes within ±0.50 and ±1.00 D of refractive prediction error, respectively.

Our study has some limitations. One important limitation is the small sample size. Further analysis should include more patients and possibly elucidate the true superiority or equivalence among methodologies of lens selection in eyes undergoing cataract surgery after radial keratotomy. Second, we performed assessments of CDVA with subjective refraction 8 to 12 weeks after cataract surgery. This time period was selected to avoid the initial hyperopic shift caused by swelling around incisions during cataract surgery, which can induce an early postoperative corneal flattening described in the literature. However, capsular bag changes within that time could affect outcomes. Third, we included both eyes for some patients because of the small sample size, which is not ideal. However, we did use a statistical method to adjust for dependence using repeated-measures analysis of variance to account for the potentially correlated errors. Finally, we also included a range of differing IOL designs (monofocal, toric, and multifocal IOLs), which makes analysis and generalization more difficult. The strengths of our study are that only one observer took intraoperative measurements and the variety of differing IOLs used in this study is representative of the true assortment used in clinical practice.

The current study shows promising results with the use of this new technology in IOL calculation in eyes with previous radial keratotomy. Although no significant differences were observed in median absolute error and mean absolute error between the methodologies used for IOL calculation, the Barrett True-K formula produced significantly more eyes within ±0.50 D than the SRK/T, Hoffer Q, and Holladay 1 formulas.

References

  1. Cowden JW. Radial keratotomy. A retrospective study of cases observed at the Kresge Eye Institute for six months. Arch Ophthalmol. 1982;100(4):578–580. doi:10.1001/archopht.1982.01030030580004 [CrossRef]7073568
  2. Waring GO III, Moffitt SD, Gelender H, et al. Rationale for and design of the National Eye Institute Prospective Evaluation of Radial Keratotomy (PERK) Study. Ophthalmology. 1983;90(1):40–58. doi:10.1016/S0161-6420(83)34603-0 [CrossRef]6338438
  3. Waring GO III, Lynn MJ, McDonnell PJ. Results of the prospective evaluation of radial keratotomy (PERK) study 10 years after surgery. Arch Ophthalmol. 1994;112(10):1298–1308. doi:10.1001/archopht.1994.01090220048022 [CrossRef]7945032
  4. Kwitko S, Gritz DC, Garbus JJ, Gauderman WJ, McDonnell PJ. Diurnal variation of corneal topography after radial keratotomy. Arch Ophthalmol. 1992;110(3):351–356. doi:10.1001/archopht.1992.01080150049026 [CrossRef]1543452
  5. Ma JX, Tang M, Wang L, Weikert MP, Huang D, Koch DD. Comparison of newer IOL power calculation methods for eyes with previous radial keratotomy. Invest Ophthalmol Vis Sci. 2016;57(9):162–168. doi:10.1167/iovs.15-18948 [CrossRef]
  6. Geggel HS. Intraocular lens power selection after radial keratotomy: topography, manual, and IOLMaster keratometry results using Haigis formulas. Ophthalmology. 2015;122(5):897–902. doi:10.1016/j.ophtha.2014.12.002 [CrossRef]25601534
  7. Awwad ST, Dwarakanathan S, Bowman RW, et al. Intraocular lens power calculation after radial keratotomy: estimating the refractive corneal power. J Cataract Refract Surg. 2007;33(6):1045–1050. doi:10.1016/j.jcrs.2007.03.018 [CrossRef]17531701
  8. Hill DC, Sudhakar S, Hill CS, et al. Intraoperative aberrometry versus preoperative biometry for intraocular lens power selection in axial myopia. J Cataract Refract Surg. 2017;43(4):505–510. doi:10.1016/j.jcrs.2017.01.014 [CrossRef]28532936
  9. Wang L, Tang M, Huang D, Weikert MP, Koch DD. Comparison of newer IOL power calculation methods for post-corneal refractive surgery eyes. Ophthalmology. 2015;122(12):2443–2449. doi:10.1016/j.ophtha.2015.08.037 [CrossRef]26459996
  10. Demill DL, Hsu M, Moshirfar M. Evaluation of the American Society of Cataract and Refractive Surgery intraocular lens calculator for eyes with prior radial keratotomy. Clin Ophthalmol. 2011;5(8):1243–1247.21966194
  11. Wang L, Hill WE, Koch DD. Evaluation of IOL power prediction methods using the ASCRS post-keratorefractive IOL power calculator. J Cataract Refract Surg. 2010;36(9):1466–1473. doi:10.1016/j.jcrs.2010.03.044 [CrossRef]20692556
  12. Barrett GD. An improved universal theoretical formula for intraocular lens power prediction. J Cataract Refract Surg. 1993;19(6):713–720. doi:10.1016/S0886-3350(13)80339-2 [CrossRef]8271166
  13. Fram NR, Masket S, Wang L. Comparison of intraoperative aberrometry, OCT-based IOL formula, Haigis-L, and Masket formulae for IOL power calculation after laser vision correction. Ophthalmology. 2015;122(6):1096–1101. doi:10.1016/j.ophtha.2015.01.027 [CrossRef]25766733
  14. Huelle JO, Druchkiv V, Habib NE, Richard G, Katz T, Linke SJ. Intraoperative aberrometry-based aphakia refraction in patients with cataract: status and options. Br J Ophthalmol. 2017;101(2):97–102. doi:10.1136/bjophthalmol-2015-307594 [CrossRef]
  15. Ianchulev T, Hoffer KJ, Yoo SH, et al. Intraoperative refractive biometry for predicting intraocular lens power calculation after prior myopic refractive surgery. Ophthalmology. 2014;121(1):56–60. doi:10.1016/j.ophtha.2013.08.041 [CrossRef]
  16. Canto AP, Chhadva P, Cabot F, et al. Comparison of IOL power calculation methods and intraoperative wavefront aberrometer in eyes after refractive surgery. J Refract Surg. 2013;29(7):484–489. doi:10.3928/1081597X-20130617-07 [CrossRef]23820231
  17. Abulafia A, Hill WE, Koch DD, Wang L, Barrett GD. Accuracy of the Barrett True-K formula for intraocular lens power prediction after laser in situ keratomileusis or photorefractive keratectomy for myopia. J Cataract Refract Surg. 2016;42(3):363–369. doi:10.1016/j.jcrs.2015.11.039 [CrossRef]27006324

Demographics of the Study Population

ParameterMean ± SDRange
K1 (D)
  Preoperative39.11 ± 2.3533.45 to 43.27
  Postoperative39.34 ± 2.5633.25 to 44.14
K2 (D)
  Preoperative40.54 ± 2.0735.56 to 44.06
  Postoperative40.77 ± 2.1235.45 to 45.17
Corneal astigmatism
  Preoperative1.43 ± 1.310.50 to 5.12
  Postoperative1.43 ± 1.210.14 to 5.02
  AL (mm)24.97 ± 1.0523.09 to 28.03
  ACD (mm)3.37 ± 0.252.89 to 3.93
  IOL power (D)22.30 ± 2.8611.50 to 27.50
  Post-cataract MRSE−0.32 ± 0.70−1.75 to 1.50

Comparison of the Six Calculation Methods

MethodMedian Absolute ErrorMean Absolute ErrorWithin ±0.50 D (%)Within ±1.00 D (%)Within Hyperopic (%)
Barrett True-K0.340.50 ± 0.4663.588.534.6
ORA0.530.55 ± 0.4148.180.742.3
SRK/T0.540.60 ± 0.4044.276.944.2
Hoffer Q0.510.60 ± 0.4748.184.644.2
Haigis0.540.60 ± 0.4953.875.044.2
Holladay 10.570.62 ± 0.3836.576.944.2
Holladay 20.440.52 ± 0.4257.784.642.3
P.08.16

Models of the Implanted IOL

IOLModeln (%)
MonofocalSN60WF2 (3.8%)
AAB008 (15.4%)
ZCB005 (9.6%)
SN6ATx15 (28.8%)
MultifocalZMB003 (5.9%)
ZMT001 (1.9%)
EDOFZXR16 (30.8%)
ZXT2 (3.8%)

P Values for Pairwise Comparisons of Percentage of Eyes Within ±0.50 and ±1.00 D of the Target SE for Each IOL Calculation Method

MethodTrue-KORASRK/THoffer QHaigisHolladay 1Holladay 2
True-K.07.01a.02a.16.003a.40
.24.08.41.03a.08.41
ORA.681.0.51.22.29
.59.56.31.63.59
SRK/T.61.25.31.02a
.24.781.0.15
Hoffer Q.36.11.16
.02a.251.0
Haigis.05.61
.78.13
Holladay 1.01a
.28
Holladay 2
Authors

From the Department of Ophthalmology, Hospital Oftalmológico de Brasília, Brasilía, Brazil.

The authors have no financial or proprietary interest in the materials presented herein.

AUTHOR CONTRIBUTIONS

Study concept and design (SXC, WTH, CMCV, MAPC, PFT); data collection (SXC, VLO, PFT); analysis and interpretation of data (SXC, WTH, CMCV, VLO, MAPC, PFT); writing the manuscript (SXC, CMCV, MAPC, PFT); critical revision of the manuscript (SXC, WTH, CMCV, VLO, MAPC, PFT); statistical expertise (SXC, CMCV, MAPC, PFT); administrative, technical, or material support (WTH); supervision (SXC, WTH, CMCV, VLO, MAPC, PFT)

Correspondence: Patrick Frensel Tzelikis, MD, PhD, SQN 203, Block K, Apartment 502, Brasilía, DF, Brazil 70833-110. E-mail: tzelikis@gmail.com

Received: May 19, 2019
Accepted: September 12, 2019

10.3928/1081597X-20190913-01

Sign up to receive

Journal E-contents