Accuracy of IOL power calculations in the very elderly

The effect of patient age on some new and older IOL power calculation formulas

PURPOSE

To assess the accuracy of intraocular lens (IOL) power calculation in different age groups using various IOL calculation formulas.

METHODS

Data from 421 eyes of 421 patients ≥60 years old (ages: 60-69, n = 131; 70-74, n = 105; 75-84, n = 158 and ≥85, n = 27), who underwent uneventful cataract surgery with SN60WF IOL implantation at John A. Moran Eye Center, Salt Lake City, USA, were retrospectively obtained. The SD of the prediction error (PE), median and mean absolute PEs and the percentage of eyes within ±0.25, ±0.50, ±0.75 and ±1.00 D were calculated after constant optimizations for the following formulas: Barrett Universal II (BUII), Emmetropia Verifying Optical (EVO) 2.0, Haigis, Hoffer Q, Hoffer QST, Holladay 1, Kane, Radial Basis Function (RBF) 3.0 and SRK/T. Results were compared between the different age groups.

RESULTS

Predictability rates within 0.25D were lower for the eldest age group compared with the other groups using the EVO 2.0 (33% vs. 37%-53%, p = 0.045), Kane (26% vs. 35%-50%, p = 0.034) and SRK/T (22% vs. 31%-49%, p = 0.002). Higher median absolute refractive errors for all formulas were observed in the oldest group [range: 0.39 D (Haigis, Hoffer QSR)-0.48 D (Kane)], followed by the youngest group [range: 0.30 D (RBF 3.0)-0.39 D (Holladay 1, SRK/T)] but did not reach statistical significance. No significant differences between the groups in the distribution parameter were seen.

CONCLUSION

Current IOL power calculation formulas may have variable accuracy for different age groups. This should be taken into account when planning cataract surgery to improve refractive outcomes.

The Significance of Dry Eye Signs on Preoperative Keratometry Measurements in Patients Scheduled for Cataract Surgery

Purpose

The primary objective was to investigate if subjects with dry eyes had increased variability of keratometry measurements prior to cataract surgery compared to subjects with non-dry eyes. Secondary objectives were to determine which separate signs affected keratometry.

Patients and Methods

This study was part of a prospective interventional randomized controlled trial. After dry eye diagnostics were performed (signs only) subjects were divided into sign of dry eye (SDE) positive and negative groups. To investigate variability, we performed two keratometry measurements for each subject with three different optical biometers: Anterion (OCT optical biometer), Eyestar (combined OCT and reflection-based optical biometer), and Lenstar (reflection based-optical biometer).

Results

One hundred and thirty-one subjects were available for analysis. The variability of astigmatism was significantly higher for subjects with hyperosmolarity compared to normal eyes for the Lenstar, as was the percentage of eyes with variability of astigmatism greater than 0.25 D. The percentage of eyes with variability of average K greater than 0.25 D was higher for subjects with non-invasive keratograph break-up time <10 seconds (NIKBUT positive) compared to normal eyes for the Lenstar.

Conclusion

Combined diagnostic criteria (signs only) showed no statistically significant differences for keratometry measurements between SDE positive and negative. Eyes with hyperosmolarity and NIKBUT positive showed statistically higher variability of keratometry measurements compared to normal eyes for Lenstar, but not for the Anterion or Eyestar biometers.

Anterior Segment Biometry in a Caucasian Population with Cataracts

PURPOSE

To investigate biometric factors of the anterior segment of phakic eyes with cataracts.

METHODS

This population-based study included Caucasian patients with cataracts in the University Eye Hospital, Goethe University Frankfurt, Germany. Biometric parameters were measured using the swept-source optical coherence tomography method. Patients were grouped into intermediate stages based on decades of life.

RESULTS

In total, 6289 eyes of 3615 patients (age: 70.67 ± 8.42 years) were included. Age-related reductions in the anterior chamber depth (mean ± standard deviation) decreased from 3.26 ± 0.42 mm (group A: 55-59 years) to 2.94 ± 0.4 mm (group G: 85-89 years), and those in the axial length decreased from 24.37 ± 1.87 mm (group A) to 23.39 ± 1.07 mm (group G). Likewise, the white-to-white distance decreased from 12.12 ± 0.48 mm (group A) to 11.96 ± 0.47 mm (group G). Lens thickness tended to increase accordingly from 4.39 ± 0.36 µm (group A) to 4.9 ± 0.40 µm (group G). A comparison of the eyes showed no detectable lateral difference regarding the biometric parameters between the groups (axial length: p = 0.26, Rosenthal effect size = 0.03; lens thickness: p = 0.12, R = 0.03; anterior chamber depth: p = 0.63, Rosenthal effect size = 0.01). The axial length and anterior chamber depth differed significantly between sexes (r = 0.22, p < 0.0001 and r = 0.16, p < 0.0001, respectively). Multiple regression analysis of the anterior chamber depth as a function of biometry parameters as well as age and sex additionally indicated a positive correlation of anterior chamber depth with white-to-white distance (b = 0.32, p = 10-5), axial length (b = 0.10, p = 10-5), keratometry (b = 0.07, p = 10-5), and lens thickness (b=-0.05, p = 10-5) with a high effect size (Cohen f2=1.866, p = 10-5) and strong multiple correlation coefficient (Rosenthal effect size = 0.80, p = 10-5).

CONCLUSIONS

In the anterior segment, there are age- and sex-dependent changes in biometric parameters. In addition, changes in anterior chamber depth were noted in relation to white-to-white distance, axial length, keratometry, and lens thickness. These data should be considered in lens calculation formulas.

Efficacy of Toric Intraocular Lens Implantation in Patients Older Than 80 Years with Cataracts and Corneal Astigmatism

INTRODUCTION

This study analyzed the visual outcome following cataract surgery with toric intraocular lenses (IOLs) in patients older than 80 years with corneal astigmatism.

METHODS

A total of 159 patients (159 eyes) older than 80 years with corneal astigmatism (≥ 0.75 D) were included. Fifty-three eyes received Acrysof IQ® toric IOLs (SN6AT2-5), while the others received non-toric IOLs: 51 eyes received Acrysof IQ® IOLs (SN60WF) and 55 eyes received A1-UV IOLs. The uncorrected distance visual acuity, corrected distance visual acuity, and refraction (spherical equivalent, refractive cylinder) were assessed at 3 months postoperatively. The prediction error of refractive outcome and percentages of eyes within ± 0.50 D and ± 1.00 D in the toric IOL group obtained using five toric IOL formulas (Barrett predicted posterior corneal astigmatism (PCA), Barrett measured PCA, Kane, EVO 2.0 and Næser-Savini) were compared.

RESULTS

At 3 months postoperatively, the average uncorrected distance visual acuity was better in the toric IOL group than the non-toric IOL group (p < 0.001). The mean residual refractive cylinder was lower in the toric IOL group than the non-toric IOL group (p < 0.001). The Næser-Savini formula achieved the lowest mean absolute error (0.39 D) and had the highest percentages of eyes within an absolute error of 0.50 D and 1.00 D (72% and 98%) compared to the other formulas.

CONCLUSION

The results demonstrate the efficacy of toric IOL implantation in patients older than 80 years with corneal astigmatism and provide strong evidence for cataract surgeons to encourage such patients to choose toric IOLs.

Advancements in intraocular lens power calculation formulas

PURPOSE OF REVIEW

We review recent studies comparing intraocular lens (IOL) formulas with an emphasis on selection of the highest performing formulas based on patient axial length, age, and history of previous corneal refractive surgery.

RECENT FINDINGS

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. Although newly developed and updated IOL formulas have improved refractive prediction in patients with short or long axial length eyes or prior history of corneal refractive surgery, these challenging cases still require special consideration. The Barrett True-K formula has shown accurate results regardless of preoperative data in eyes with previous myopic refractive surgery.

SUMMARY

Advancements in optical biometry and IOL calculation formulas continue to improve refractive outcomes. The clinician can optimize refractive outcomes in the majority of patients with the use of formulas that have shown consistent results and accuracy in several large studies.

Cataract Surgery in Very Old Patients: A Case-Control Study

Advancements in surgical techniques and increased life expectancy have made cataract surgery more common among very old patients. However, surgical outcomes seem impaired in patients older than 90 years, especially with ocular comorbidities. A retrospective case-control study of 53 eyes of 53 very old patients (mean 92.6 ± 3.0) and 140 eyes of 140 matched patients (mean 75.2 ± 7.6) was undertaken. Groups were matched in terms of gender and systemic and ocular comorbidities. In very old patients, higher phacoemulsification energy (cumulative dissipated energy [CDE], 25.0 ± 22.4 vs. 16.1 ± 10.7, p = 0.01) and rate of intraoperative floppy iris syndrome (IFIS, 9.4% vs. 1.4%, p = 0.02) were observed compared to controls. Uncorrected (UCVA) and best-corrected distance visual acuity (BCVA) gains were significantly poorer among the very old patients than among the control at postoperative day 30 (0.20 ± 0.70 vs. 0.56 ± 0.61 logMAR, p < 0.001 and 0.27 ± 0.64 vs. 0.55 ± 0.62 logMAR, p = 0.006, respectively). Even after including CDE and IFIS as covariates, age remained an independent factor for poor visual gain at 30 days (p < 0.001). Cataract surgery in very old patients may demand more experienced surgeons due to higher nuclear density and the rates of IFIS. Expectations in visual acuity gains should be aligned with the patient’s age.

Prediction Error of Intraocular Lens Power Calculation in Very Elderly Patients over 90 Years Old

BACKGROUND

To investigate the influence of age on prediction error (PE) after cataract surgery in very elderly (VE) patients aged more than 90 years.

METHODS

We retrospectively analyzed 66 eyes of patients aged ≥90 years (VE group) who underwent phacoemulsification and intraocular lens (IOL) implantation. As the control group (CG), we investigated 121 eyes of patients aged 70-89 years who underwent the same surgery. PE was calculated 1 month post-surgery as the actual postoperative spherical equivalent minus the target diopter, which was calculated using the Sanders-Retzlaff-Kraff/T formula. The absolute and arithmetic PE were compared between the two groups. The factors affecting absolute PE outside ±0.5 diopter (D) and ±1.0 D were determined through logistic regression analysis with the variables age, sex, axial length (AL), average corneal power, preoperative best-corrected visual acuity, target diopter, and coexisting pseudoexfoliation syndrome.

RESULTS

The absolute PE was significantly larger in the VE group than that in the CG (0.60 ± 0.52 D and 0.34 ± 0.25 D, respectively; P < .001). There was no significant difference in terms of arithmetic PE between the two groups (-0.06 ± 0.79 D and -0.07 ± 0.42 D, respectively; P = .653). In the logistic regression analysis, age was significantly associated with absolute PE outside ±0.50 D (Odds ratio [OR]: 1.05). Age and AL were significantly associated with absolute PE outside ±1.0 D (OR: 1.24 and 0.20, respectively).

CONCLUSIONS

Absolute PE tended to increase in the cataract surgery of VE patients.

Intraocular lens power calculation in the elderly population using the Kane formula in comparison with existing methods

PURPOSE

To assess the accuracy of the Kane formula for intraocualr lens (IOL) power calculation in comparison with established formulas in the elderly population.

SETTING

Shiley Eye Institute, University of California San Diego, USA.

DESIGN

Retrospective cohort.

METHODS

Retrospective data from 90 patients (90 eyes) aged 75 years or older who underwent uneventful cataract surgery with SN60WF intraocular lens (IOL) implantation were evaluated. The first operated eyes of patients with final corrected distance visual acuity 20/40 or better and axial length 22 to 26 mm were included. Prediction errors were calculated for Barrett Universal (BU) II, Haigis, Hoffer Q, Holladay 1, Kane, and SRK/T formulas. A subgroup analysis based on age (75-84 and ≥85 years old) was performed.

RESULTS

Use of both BUII and Kane formulas resulted in the highest percentage of eyes with prediction errors within ±0.50 diopters (D) (72% each) and significantly higher than Hoffer Q, Holladay 1, and SRK/T (P = .001). Rates of predictability within ±0.25 D and ±1.00 D were 31% to 38% and 87% to 92%, respectively, with no significant differences between formulas. No statistically significant difference was seen between formulas in the median absolute error. These tendencies remained consistent in both age groups when analyzed separately. Subgroup analysis showed better predictability of all formulas in the younger age group.

CONCLUSIONS

To the authors' knowledge, this is the first study evaluating the Kane formula exclusively in the elderly population. The Kane formula was found to be of equal accuracy to the BUII and superior to the Hoffer Q, Holladay 1, and SRK/T formulas. Very elderly patients might have reduced refractive precision using all formulas.