Accuracy Of Intraocular Lens Power Calculation Research Articles

Accuracy of recent intraocular lens power calculation methods in post-myopic LASIK eyes

This retrospective study compared postoperative prediction errors of recent formulas using standard- or total keratometry (K or TK) for intraocular lens (IOL) power calculation in post-myopic LASIK patients. It included 56 eyes of 56 patients who underwent uncomplicated cataract surgery, with at least 1-month follow-up at Keio University Hospital in Tokyo or Hayashi Eye Hospital in Yokohama, Japan. Prediction errors, absolute errors, and percentage of eyes with prediction errors within ± 0.25 D, ± 0.50 D, and ± 1.00 D were calculated using nine formulas: Barrett True-K, Barrett True-K TK, Haigis-L, Haigis TK, Pearl-DGS, Hoffer QST, Hoffer QST PK, EVO K, and EVO PK. Statistical comparisons utilized Friedman test, Conover’s all-pairs post-hoc, Cochran’s Q, and McNemar post-hoc testing. Root-Mean-Square Error (RMSE) was compared with heteroscedastic testing. Barrett True-K TK had the lowest median predicted refractive error (-0.01). EVO PK had the smallest median absolute error (0.20). EVO PK had the highest percentage of eyes within ± 0.25 D of the predicted value (58.9%), significantly better than Haigis-L (p = 0.047). EVO PK had the lowest mean RMSE value (0.499). The EVO PK formula yielded the most accurate IOL power calculation in post-myopic LASIK eyes, with TK/PK values enhancing accuracy.

Comparison of intraocular lens power formulas for negative-diopter intraocular lens implantation for high myopia.

To compare the accuracy of intraocular lens (IOL) power calculation formulas for myopic eyes requiring negative diopter powered IOLs. Retrospective case series. K… hospital and Y… Hospital, …, …. Sixty-one eyes that underwent phacoemulsification with implantation of a negative power IOL were investigated. The trueness, precision and accuracy of IOL power calculation were assessed for the Barrett Universal II (BUII), EVO 2.0, Haigis, Hoffer QST, Holladay 1 and SRK/T formulas using the Eyetemis online tool. The analysis was performed using 1) the ULIB IOL constants and 2) after constant optimization. With ULIB constants, the Haigis, Holladay 1 and SRK/T resulted in a hyperopic mean prediction error (PE) >1.00 diopter (D), which was significantly different from zero (adjusted p <0.05). The mean PE of the remaining formulas was closer to zero. The absolute PE was significantly higher with the Holladay 1 and SRK/T (adjusted p <0.05) with respect to the remaining formulas. After constant optimization, the outcomes of traditional formulas improved and no statistically significant differences were found among any of the formulas in terms of trueness, precision and accuracy. The percentage of eyes with an absolute PE within 0.50 D was low (<50%) even after constant optimization. With ULIB constants, the BUII, EVO 2.0 and Hoffer QST were more accurate than traditional formulas in eyes with negative-diopter IOLs. The results of IOL power calculation in these eyes remain poor even after constant optimization.

Accuracy comparison of total keratometry and standard keratometry in intraocular lens power calculations for post-corneal refractive surgery cataract patients

Objective: To compare the accuracy of intraocular lens (IOL) power calculations using total keratometry (TK) versus standard keratometry (K) in post-corneal refractive surgery cataract patients. Methods: This retrospective case series study included 30 patients (36 eyes) with a history of laser corneal refractive surgery who underwent cataract extraction and IOL implantation at Qingdao Eye Hospital, Affiliated to Shandong First Medical University, from September 2022 to December 2023. The cohort comprised 16 males and 14 females, with an average age of (53.6±8.1) years. IOL power was calculated using the K-based Haigis-L and Barrett True-K formulas, as well as the TK-based Haigis and Barrett Universal Ⅱ formulas. Postoperative objective refraction was performed to obtain the actual refractive status of the operated eyes. The refractive prediction error (RPE) was defined as the difference between the actual spherical equivalent and the predicted refraction. The absolute value of the RPE was taken as the refractive absolute error (RAE). Differences in errors calculated by the four formulas were compared. Results: TK showed good consistency with K, with TK being on average 0.50 D lower than K. Analysis of variance revealed statistically significant differences in RPE among the four formulas (P<0.001). The RPE for the TK-based Haigis formula was (0.17±0.09) D, and for the Barrett Universal Ⅱ formula, it was (0.21±0.11) D, both significantly better than the K-based Haigis-L formula (-0.61±0.12) D and Barrett True-K formula (-0.57±0.11) D (all P<0.001). The percentage of eyes with postoperative RPE<±1.00 D was higher for the TK-based Haigis (92%, 33 eyes) and Barrett Universal Ⅱ (86%, 31 eyes) formulas compared to the TK-based Barrett True-K (75%, 27 eyes) and Haigis-L formulas (67%, 24 eyes), with statistically significant differences (P<0.05). Conclusions: Compared with K, TK improves the accuracy of IOL power calculation in post-corneal refractive surgery patients. Both the TK-based Barrett Universal Ⅱ and Haigis formulas demonstrate high accuracy.

Accuracy of intra ocular lens calculation formulae in patients with pseudoexfoliation syndrome

BackgroundThe purpose of this study was to investigate the visual and refractive outcomes in patients with pseudoexfoliation (PXF) undergoing routine cataract surgery and to compare the accuracy of intraocular lens (IOL) power calculation formulae.MethodsRetrospective case-series study from Shamir medical center, a public hospital, Israel. Medical records of patients who underwent routine cataract surgery between January 2019 and August 2021 were investigated. Postoperative visual acuity and manifest refraction were examined. The error in predicted refraction and IOL power calculation accuracy within a range of ± 0.50 to ± 1.00 diopters were compared between different IOL calculating formulae.Results151 eyes of 151 patients ages 73.9 ± 7.1 years were included in this study- 58 eyes in the PXF group and 93 eyes in the control group. The mean absolute error (MAE) for the BUII formula was 0.63D ± 0.87 for the PXF group and 0.36D ± 0.48 for the control group (p < 0.05). The MAE for the Hill-RBF 3.0 formula was 0.61D ± 0.84 for the PXF group and 0.42D ± 0.55 for the control group (p = 0.05). There were significant differences in MAE and MedAE between PXF group and control group measures (p < 0.05). In the PXF group there were no significant differences between the different formulae.ConclusionsThere were significant differences in accuracy of IOL power calculations in all formulae between PXF group and control group measures. PXF patients show hyperopic shift from predicted refraction. Barret universal II formula had the highest proportion of eyes with absolute error in prediction below or equal to 0.50 D in both PXF and control groups.

Predictability of Existing IOL Formulas After Cataract Surgery in Patients with a Previous History of Radial Keratotomy: A Retrospective Cohort Study and Literature Review.

This study aims to evaluate the accuracy of 12 different intraocular lens (IOL) power calculation formulas for post-radial keratotomy (RK) eyes. The investigation utilizes recent advances in topography/tomography devices and artificial intelligence (AI)-based calculators, comparing the results to those reported in current literature to assess the efficacy and predictability of IOL calculations for this patient group. In this retrospective study, 37 eyes from 24 individuals with a history of RK who underwent cataract surgery at Hoopes Vision Center were analyzed. Biometry and corneal topography measurements were taken preoperatively. Subjective refraction was obtained 6 months postoperatively. Twelve different IOL power calculations were used, including the American Society of Cataract and Refractive Surgery (ASCRS) post-RK online formula, and the Barrett True K, Double K modified-Holladay 1, Haigis-L, Panacea, Camellin-Calossi, Emmetropia Verifying Optical (EVO) 2.0, Kane, and Prediction Enhanced by Artificial Intelligence and output Linearization-Debellemanière, Gatinel, and Saad (PEARL-DGS) formulas. Outcome measures included median absolute error (MedAE), mean absolute error (MAE), arithmetic mean error (AME), and percentage of eyes achieving refractive prediction errors (RPE) within ± 0.50 D, ± 0.75 D, and ± 1 D for each formula. A search of the literature was also performed by two independent reviewers based on relevant formulas. Overall, the best performing IOL power calculations were the Camellin-Calossi (MedAE = 0.515 D), the ASCRS average (MedAE = 0.535 D), and the EVO (MedAE = 0.545 D) and Kane (MedAE = 0.555 D) AI-based formulas. The EVO and Kane formulas along with the ASCRS calculation performed similarly, with 48.65% of eyes scoring within ± 0.50 D of the target range, while the Equivalent Keratometry Reading (EKR) 65 Holladay formula achieved the greatest percentage of eyes scoring within ± 0.25 D of the target range (35.14%). Additionally, the EVO 2.0 formula achieved 64.86% of eyes scoring within the ± 0.75 D RPE category, while the Kane formula achieved 75.68% of eyes scoring within the ± 1 D RPE category. There was no significant difference in MAE between the established and newer generation formulas (P > 0.05). The Panacea formula consistently underperformed when compared to the ASCRS average and other high-performing formulas (P < 0.05). This study demonstrates the potential of AI-based IOL calculation formulas, such as EVO 2.0 and Kane, for improving the accuracy of IOL power calculation in post-RK eyes undergoing cataract surgery. Established calculations, such as the ASCRS and Barrett True K formula, remain effective options, while under-utilized formulas, like the EKR65 and Camellin-Calossi formulas, show promise, emphasizing the need for further research and larger studies to validate and enhance IOL power calculation for this patient group.

Assessing the Impact of Tropicamide on Anterior Segment Parameters in Diabetic Patients: A Randomized Clinical Trial.

Evaluation of anterior segment parameters is crucial in ophthalmic procedures such as intraocular surgeries and contact lens fitting. However, the use of tropicamide in diabetic patients presents challenges due to its potential impact on biometric measurements. This study aims to investigate and compare the effects of 0.5% and 1% tropicamide on anterior segment parameters in diabetic patients. This double-masked randomized clinical trial enrolled 98 patients with diabetes mellitus. Participants were randomly assigned to receive either 0.5% or 1% tropicamide. Anterior segment parameters were measured using Pentacam HR (Oculus Optikgeräte GmbH, Wetzlar, Germany) before and 30 minutes after tropicamide administration. Parameters included anterior chamber depth (ACD), anterior chamber volume (ACV), anterior chamber angle (ACA), keratometry, central corneal thickness (CCT), white-to-white distance (WTW), and pupillary diameter (PD). Both concentrations of 0.5% and 1% tropicamide induced significant changes in anterior segment parameters. There was a notable increase in PD (2.99 ± 0.62, 3.11 ± 0.55, respectively, both P-values < 0.001), ACD (both 0.10 ± 0.05, both P-values < 0.001), ACV (16.69 ± 9.56, 17.51 ± 9.26, respectively, both P-values < 0.001), and WTW (0.06 ± 0.14,0.03 ± 0.30, respectively, both P-values < 0.001), along with a decrease in ACA (-3.50 ± 10.65, -3.30 ± 6.87, P-value< 0.001 and P-value=0.001,respectively), and CCT (-6.10 ± 8.06,-6.39 ± 9.97,respectively, both P-values < 0.001) post-dilation. However, no significant changes were observed in keratometry (front Km (-0.03 ± 0.19, -0.04 ± 0.21, respectively), back Km (0.01 ± 0.05, 0.004 ± 0.05, respectively), P-values> 0.05). Both concentrations of tropicamide exhibited comparable effects on anterior segment parameters in diabetic patients. These post-dilation changes should be considered for accurate intraocular lens power calculation and decision-making for cataract, phakic intraocular lens, and refractive surgeries.

Normative data of corneal diameter and palpebral fissure height in a large cohort of South Indian children.

The purpose of this study was to establish the normative data of horizontal visible iris diameter (HVID), vertical visible iris diameter (VVID), and palpebral fissure height (PFH) in a cohort of South Indian children. The study included 1,234 children from six schools of different regions of Tamil Nadu state, India. HVID, VVID, and PFH were measured using a simple millimeter ruler by three optometrists. Based on their age, the children were divided into three groups: preprimary school children (4-5 years), primary school children (6-10 years), and high school children (11-15 years). Mean age was 4.49 ± 0.50 years, 8.00 ± 1.41 years, and 12.87 ± 1.42 years in the three groups, respectively. Mean HVID was 10.45 mm, 10.54 mm, and 10.73 mm, respectively. Mean VVID was 9.18 mm, 9.32 mm, and 9.57 mm, respectively. Similarly, mean PFH was 8.15 mm, 8.30 mm, and 8.52 mm, respectively. There was a significant difference in HVID, VVID, and PFH among the three age groups (P ≤ 0.001), as well as among male and female children in the 6-10 years age group (P ≤ 0.05) but not in the other groups. Intraclass correlation coefficient values (0.78-0.95) show good agreement among the three optometrists for all parameters. The normal range of HVID, VVID, and PFH presented in the current study can help practitioners in the diagnosis of corneal disorders, serve as a basis for the design of contact lenses, and enable accurate intraocular lens power calculations for South Indian children.

Comparison of Optical Biometry and Scheimpflug Device Keratometric Readings Accuracy in Predicting Intraocular Lens Power in Cataract Surgery

Abstract Background: A correct preoperative intraocular lens (IOL) power measurement in cataract surgery depends on accurate assessment of axial length (AL), anterior segment parameters, and using the suitable formula for the calculation of the power. Objectives: To determine the accuracy of IOL power calculations using keratometric measurements of the IOL Master compared to the Pentacam and to determine whether the results obtained can be used interchangeably in clinical practice in calculating IOL power in routine cataract surgery. Patients and Methods: In this prospective study, the biometric data including AL, keratometric readings, and anterior chamber depth (ACD) were obtained by both the IOL Master 500 and Pentacam Scheimpflug devices added to these measures the white-to-white (WTW) distance by IOL Master and central corneal thickness by Pentacam and calculation of the IOL power using SRK/T formula for the enrolled patients who undergone uneventful cataract surgery with IOL implantation. Postoperatively, spherical equivalent refraction was measured and the mean arithmetic error and the mean absolute error (MAE) for both keratometric readings were calculated to compare the accuracy between them in calculating the IOL power. Results: The study evaluated 57 eyes of 57 patient, the mean K value for the IOL Master was 43.92 (D) ± 1.5 (standard deviation [SD]) and the mean K value for the Pentacam was 43.77 (D) ± 1.7 (SD) (P = 0.62), ACD values between the two groups, was 3.19 ± 0.44 mm measure by IOL Master compared to 3.22 ± 0.48 mm in Pentacam (P = 0.769), with a very strong positive correlation between the two values (r = 0.995, P &lt; 0.001). MAE for the IOL Master was 0.230 (D) ± 0.187 (SD), while for the Pentacam was 0.255 (D) ± 0.204 (SD), with no statistically significant differences between two devices’ values (P = 0.54). Conclusions: Pentacam Scheimpflug measured keratometric and ACD data had good correlation with IOL Master data with good interchangeability between two devices readings in measuring the IOL power in routine cases of cataract surgeries.

Surgeons need to know more about IOL design for accurate power calculation.

Improvement in biometry and formulas have raised the bar for accurate IOL power calculation. However, when we look closely at the performance of a specific IOL model, we often find that the prediction error varies with the implant power. This phenomenon has no explanation other than the optic design of the IOL has shifted over the power range, thereby disrupting the assumptions of the calculations. By this report we call the industry to be more transparent and disclose the basic information about the IOL design that is important for accurate IOL power calculation. The relevant information concerns: the refractive index, the central optic thickness, the anterior and posterior curvature radii, the toricity location, the spherical aberration and haptic angulation. The goal is to predict possible shifts in principal planes or IOL position over the power range causing a refractive surprise if not corrected for.

Theoretical Impact of Intraocular Lens Design Variations on the Accuracy of IOL Power Calculations.

To ascertain the theoretical impact of optical design variations of the intraocular lens (IOL) on the accuracy of IOL power formulas based on a single lens constant using a thick lens eye model. This impact was also simulated before and after optimization. We modeled 70 thick-lens pseudophakic eyes implanted with IOLs of symmetrical optical design and power comprised between 0.50 D and 35 D in 0.5-step increments. Modifications of the shape factor resulting in variations in the anterior and posterior radii of an IOL were made, keeping the central thickness and paraxial powers static. Geometry data from three IOL models were also used. Corresponding postoperative spherical equivalent (SE) were computed for different IOL powers and assimilated to a prediction error of the formula due to the sole change in optical design alone. Formula accuracy was studied before and after zeroization on a uniform and non-uniform realistic IOL power distribution. The impact of the incremental change in optic design variability depended on the IOL power. Design modifications theoretically induce an increase in the standard deviation (SD), Mean Absolute Error (MAE), and Root Mean Square (RMS) of the error. The values of these parameters reduce dramatically after zeroization. While the variations in optical design can affect refractive outcomes, especially in short eyes, the zeroization of the mean error theoretically reduces the impact of the IOL's design and power on the accuracy of IOL power calculation.

Visual Outcomes of Cataract Surgery in Patients With Keratoconus Using Toric and Non-toric Lenses

To compare the accuracy and outcomes of different intraocular lens (IOL) power calculation formulas in eyes with keratoconus undergoing cataract surgery with toric and non-toric IOLs. This was a consecutive retrospective case series study including patients from the Cornea Service at the Department of Ophthalmology and Visual Sciences at the University of British Columbia, Vancouver, Canada, from 2000 to 2020. Keratoconus was diagnosed based on corneal topography and clinician opinion. Patients who underwent topography-guided photorefractive keratectomy, intracorneal ring segments implantation, or corneal transplant were excluded. The manifest spherical equivalent, prediction errors, and median absolute errors were calculated. Descriptive statistics were expressed as mean ± standard deviation. There were 160 eyes from 101 patients; 136 eyes received non-toric lenses and 24 eyes received toric lenses. Most patients had mild disease (< 48.00 diopters [D]) when stratified by steep keratometry values. Patients with severe disease (> 53.00 D) were significantly more hyperopic following surgery (P < .05). The Barrett Universal II (0.26 D, inter-quartile range [IQR] = 0.4), Holladay 2 (0.31, IQR = 1.2), and SRK/T (0.42, IQR = 0.86) formulas had the lowest median absolute error. The postoperative prediction error following toric lens insertion was not significantly different than following non-toric lens insertion, and the mean absolute astigmatism was significantly reduced with toric lenses. The Barrett Universal II, Holladay 2, and SRK/T were the most accurate IOL power calculation formulas in patients with keratoconus undergoing cataract surgery. Hyperopic surprise was increased in severe keratoconus. Toric IOLs may be considered in patients with mild keratoconus. [J Refract Surg. 2023;39(5):319-325.].

Comparison of Intraocular Lens Power Calculation formulas with and without Total Keratometry and Ray tracing in patients with previous myopic SMILE.

This study evaluated the prediction error (PE) variance and absolute median PE of different IOL calculation formulae including last generation formulae such as Barrett True-K with K, Okulix and Total Keratometry (TK) based calculations with Haigis and Barrett True-K in a simulation model in post-SMILE eyes. Department of Ophthalmology, University Hospital Marburg, Germany. Design: Prospective study. Preoperative measurements included IOL power calculation before and after SMILE surgery. The target refraction was set to be the lowest myopic refractive error in pre-SMILE eyes. The IOL power targeting at the lowest myopic refractive error in pre-SMILE eyes was selected for the post-SMILE IOL calculation of the same eye. The difference between the predicted refraction of pre- and post-SMILE eyes with the same IOL power was defined as IOL-Difference (IOL-Diff). The refractive change induced by SMILE was defined as the difference between preoperative and postoperative manifest refraction (SMILE-Diff). 98 eyes from 49 patients underwent bilateral myopic SMILE. The PE variance of Okulix was not significantly different compared to Barrett True-K with TK (P=0.471). The standard deviation (SD) of the mean PEs were ±0.413 D (Haigis-TK), ±0.453 D (Okulix), ±0.471 D (Barrett True-K with TK), ±0.556 D (Haigis-L) and ±0.576 D (Barrett True-K with K). The mean absolute PE were 0.340 D, 0.353 D, 0.404 D, 0.511 D and 0.715 D for Haigis-TK, Okulix, Barrett True-K with TK, Barrett True-K with K and Haigis-L respectively. The highest percentage of eyes within ± 0.50 D was achieved by Okulix followed by Haigis TK, Barrett True-K with TK, Barrett True-K with K and Haigis-L. Our results suggest that Haigis in combination with TK, Okulix and Barrett True-K with and without TK offer good options for accurate IOL power calculation after SMILE. Haigis-L showed a tendency for myopic shift in eyes after previous SMILE.

Comparison of the accuracy of three intraocular lens power calculation formulas in cataract patients with prior radial keratotomy

PurposeTo compare the accuracy of three intraocular lens (IOL) formulas in Chinese cataract patients with prior radial keratotomy (RK).MethodsMedical records of cataract patients with prior RK at Beijing Tongren Hospital were retrospectively analysed. The absolute error (AE) was calculated as the absolute difference between the actual postoperative spherical equivalent and the predicted spherical equivalent. The AE and percentages of eyes with AE within 0.5D, 1.0D, and 2.0D for three formulas [Barrett True-K, Holladay 1 (D–K), Haigis] were calculated and compared.ResultsForty-seven eyes of 28 cataract patients were included. The Median AE (MedAE) was significantly different among the three formulas (P < 0.001). The MedAE was lowest for the Barrett True-K formula (0.62), followed by the Haigis (0.76), and Holladay 1 (D–K) (1.16). The percentages of eyes with AE within 0.5D, and 1.0D were significantly different among the 3 formulas (P = 0.009, and P < 0.001). The Barrett True-K formula achieved the highest percentages (46.8%) of eyes with AE within 0.5D. Haigis achieved the highest percentages (70.21%) of eyes with AE within 1.0 D.ConclusionsBarrett True-K is the most accurate IOL power calculation formula among the 3 formulas and Haigis is an alternative choice. Considering the relatively lower accuracy of IOL formulas in cataract patients with prior RK, newer and more accurate IOL formulas are desirable.

Accuracy of Intraocular Lens Power Calculation in Pediatric Secondary Implantation: In-the-Bag Versus Sulcus Placement

To compare the effects of secondary in-the-bag vs ciliary sulcus intraocular lens (IOL) implantation on the accuracy of IOL power calculation in pediatric eyes. Prospective nonrandomized interventional study. Pediatric aphakic eyes that underwent either in-the-bag or ciliary sulcus secondary IOL implantation were included. The mean prediction error (PE), mean absolute error (MAE), median absolute error, and percentages of eyes with PE within ±0.25 diopter (D), ±0.50 D, ±0.75 D, and ±1.00 D were calculated and compared using SRK/T formula. One hundred fourteen eyes (38.26%) received in-the-bag IOL implantation and 184 (61.74%) underwent ciliary sulcus IOL implantation. Compared with the sulcus group, the capsular group displayed significantly lower MAE and higher percentage of eyes within ±0.50 D of PE (MAE: 0.90 vs 1.56 D; ±0.50 D: 40.40% vs 14.29%, both P < .001). The eyes receiving in-the-bag IOL implantation (sulcus IOL implantation β: -1.060, 95% CI: -1.415 to -0.705; P < .001), unilateral (β: 0.647, 95% CI: 0.144-1.150; P=.012), or with deeper anterior chamber depth (β: 0.362, 95% CI: 0.068-0.656; P=.016) were prone to maintain hyperopia (PE > 0). To reduce PE, when the predicted capsular IOL power was between 11.50 and 30.00 D, the power of a sulcus-implanted IOL should be reduced by 0.50 to 2.50 D accordingly (the exact amount of reduction is positively related to the predicted power). In-the-bag implantation yielded smaller PE in pediatric eyes undergoing secondary IOL implantation. Adjustment of IOL power for ciliary sulcus implantation is required to reduce PE, and the amount of adjustment is positively correlated with the IOL power predicted by SRK/T formula.

Assessment of the influence of keratometry on intraocular lens calculation formulas in long axial length eyes.

Hyperopic surprises tend to occur in axial myopic eyes and other factors including corneal curvature have rarely been analyzed in cataract surgery, especially in eyes with long axial length (≥ 26.0mm). Thus, the purpose of our study was to evaluate the influence of keratometry on four different formulas (SRK/T, Barrett Universal II, Haigis and Olsen) in intraocular lens (IOL) power calculation for long eyes. Retrospective case series. A total of 180 eyes with axial length (AL) ≥ 26.0mm were divided into 3 keratometry (K) groups: K ≤ 42.0 D (Flat), K ≥ 46.0 D (Steep), 42.0 < K < 46.0 D (Average), and all the eyes were underwent phacoemulsification cataract surgery with Rayner (Hove, UK) 920H IOL implantation. Prediction errors (PE) were compared between different formulas to assess the accuracy of different formulas. Multiple regression analysis was performed to investigate factors associated with the PE. The mean absolute error was higher for all evaluated formulas in Steep group (ranging from 0.66 D to 1.02 D) than the Flat (0.34 D to 0.67 D) and Average groups (0.40 D to 0.74D). The median absolute errors predicted by Olsen formula were significantly lower than that predicted by Haigis formula (0.42 D versus 0.85 D in Steep and 0.29 D versus 0.69 D in Average) in Steep and Average groups (P = 0.012, P < 0.001, respectively). And the Olsen formula demonstrated equal accuracy to the Barrett II formula in Flat and Average groups. The predictability of the SRK/T formula was affected by the AL and K, while the predictability of Olsen and Haigis formulas was affected by the AL only. Steep cornea has more influence on the accuracy of IOL power calculation than the other corneal shape in long eyes. Overall, both the Olsen and Barrett Universal II formulas are recommended in long eyes with unusual keratometry.

IOL Power Calculations and Cataract Surgery in Eyes with Previous Small Incision Lenticule Extraction.

Small incision lenticule extraction (SMILE), with over 5 million procedures globally performed, will challenge ophthalmologists in the foreseeable future with accurate intraocular lens power calculations in an ageing population. After more than one decade since the introduction of SMILE, only one case report of cataract surgery with IOL implantation after SMILE is present in the peer-reviewed literature. Hence, the scope of the present multicenter study was to compare the IOL power calculation accuracy in post-SMILE eyes between ray tracing and a range of empirically optimized formulae available in the ASCRS post-keratorefractive surgery IOL power online calculator. In our study of 11 post-SMILE eyes undergoing cataract surgery, ray tracing showed the smallest mean absolute error (0.40 D) and yielded the largest percentage of eyes within ±0.50/±1.00 D (82/91%). The next best conventional formula was the Potvin–Hill formula with a mean absolute error of 0.66 D and an ±0.50/±1.00 D accuracy of 45 and 73%, respectively. Analyzing this first cohort of post-SMILE eyes undergoing cataract surgery and IOL implantation, ray tracing showed superior predictability in IOL power calculation over empirically optimized IOL power calculation formulae that were originally intended for use after Excimer-based keratorefractive procedures.

Evaluation of IOL power calculation with the Kane formula for pediatric cataract surgery.

To assess the accuracy of the Kane formula for intraocular lens (IOL) power calculation in the pediatric population. The charts of pediatric patients who underwent cataract surgery with in-the-bag IOL implantation with one of two IOL models (SA60AT or MA60AC) between 2012 and 2018 in The Hospital for Sick Children, Toronto, Ontario, CanFada, were retrospectively reviewed. The accuracy of IOL power calculation with the Kane formula was evaluated in comparison with the Barrett Universal II (BUII), Haigis, Hoffer Q, Holladay 1, and Sanders-Retzlaff-Kraff Theoretical (SRK/T) formulas. Sixty-two eyes of 62 patients aged 6.2 (IQR 3.2-9.2) years were included. The SD values of the prediction error obtained by Kane (1.38) were comparable with those by BUII (1.34), Hoffer Q (1.37), SRK/T (1.40), Holaday 1 (1.41), and Haigis (1.50), all p > 0.05. A significant difference was observed between the Hoffer Q and Haigis formulas (p = 0.039). No differences in the median and mean absolute errors were found between the Kane formula (0.54 D and 0.91 ± 1.04 D) and BUII (0.50 D and 0.88 ± 1.00 D), Hoffer Q (0.48 D and 0.88 ± 1.05 D), SRK/T (0.72 D and 0.97 ± 1.00 D), Holladay 1 (0.63 D and 0.94 ± 1.05 D), and Haigis (0.57 D and 0.98 ± 1.13 D), p = 0.099. This is the first study to investigate the Kane formula in pediatric cataract surgery. Our results place the Kane among the noteworthy IOL power calculation formulas in this age group, offering an additional means for improving IOL calculation in pediatric cataract surgery. The heteroscedastic statistical method was first implemented to evaluate formulas' predictability in children.

Update and understanding of optical biometer

With advances in technology that allow for more accurate measurement of ocular biometric characteristics and the availability of sophisticated methods for calculating intraocular lens (IOL) power, cataract surgery has evolved into a refractive operation. Patient expectations have been raised as a result of this, as well as free and simple access to information about the latest technology. After cataract surgery, there is a greater demand than ever for life without spectacles. Newer advances in optical biometry, such as swept-source optical coherence tomography, combined with the availability of highly accurate IOL power calculation formulae, including artificial intelligence-based formulae, have the potential to enable surgeons to achieve near-perfect outcomes in the majority of their patients. Understanding the benefits and limitations of currently available cutting-edge technologies and equations and applying them to the cataract surgical practice is required to hit the bull’s eye in terms of goal refraction.

Accuracy of intraocular lens power calculation using Scheimpflug tomography and OKULIX ray-tracing software in paracentral corneal scarring not interfering with postoperative refraction

Purpose The aim of this study was to evaluate the accuracy of intraocular lens (IOL) power calculation using Scheimpflug tomography and OKULIX ray-tracing software in cases of paracentral corneal scarring. Patients and methods The study was conducted on 40 consecutive eyes: 20 with corneal scarring and coexisting cataract and 20 controls with clear cornea, for whom uneventful phacoemulsification and IOL implantation was performed. Preoperatively, Scheimpflug tomography and OKULIX ray-tracing software and third-generation IOL power calculation formulas were used for IOL power calculation. Accuracy of IOL power calculation was evaluated by subtracting the expected and achieved spherical refraction, 3 months postoperatively and was recorded as the mean absolute error (MAE). The distance uncorrected visual acuity for each eye was measured preoperatively and 3 months postoperatively; the visual acuity was scored and converted to the logarithm of the minimum angle of resolution (LogMar) for statistical analysis. Results In cases of corneal scarring, all eyes (100%) yielded a postoperative spherical refraction which differed by less than 1 D from the predicted. In 16 (80%) eyes, the postoperative spherical refraction was within 0.50 D from the expected. The MAE was 0.2 D in cases of corneal scarring, which did not differ significantly from the controls (MAE=0.1 D), P=0.142. In corneal scarring cases, the distance uncorrected visual acuity showed significant improvement from 1.3 LogMar (Snellen’s equivalent 20/400), preoperatively, to 0.5 LogMar (Snellen’s equivalent 20/60), 3 months postoperatively. Conclusion Scheimpflug tomography combined with OKULIX ray-tracing software for the calculation of IOL power provided accurate results in cases of corneal scarring.

OKULIX ray-tracing software versus third generation formulas: compatibility or superiority?

Purpose The aim of this retrospective study was to compare the accuracy of intraocular lens (IOL) power calculation using the OKULIX ray-tracing software compared with third generation IOL power calculation formulas. Patients and methods The study included 80 consecutive eyes of 80 patients (26 males and 54 females, with a mean age of 58.8±15.1 years), for whom phacoemulsification and IOL implantation was performed following biometry using the OKULIX ray-tracing software and third-generation IOL power calculation formulas for IOL power calculation. Accuracy of IOL power calculation was investigated by subtracting the attempted and achieved spherical equivalent 1 month postoperatively and was recorded as the mean absolute error. Results OKULIX ray-tracing software calculated IOL power was 17.1±8.5 diopters (D), which was statistically significantly different from Sanders, Retzlaff, Kraff (SRK)-T, Hoffer Q, SRK II, and Holladay formulas (16.7±8.3, 16.6±8.7, 16.8±8, and 16.7±8.5 D, respectively, P<0.001). The OKULIX ray-tracing software mean absolute error was 0.2±0.2 D, which was statistically significantly less than that of the SRK-T, Hoffer Q, SRK II, and Holladay formulas (0.5±0.5, 0.6±0.5, 0.8±0.7, and 0.6±0.5 D, respectively, P<0.001). Conclusions The OKULIX ray-tracing software seems to deliver reliable and more accurate results in comparison to the third generation IOL power calculation formulas.