T2 formula in a highly myopic population, comparison with other methods and description of an improved approach for estimating corneal height

Abstract Background To determine the accuracy of the T2 formula as applied to highly myopic eyes, to compare the T2 formula to the SRK/T and Holladay 1 formulas, and to describe possible ways to improve the estimation of corneal height and prediction error in two settings, the Hadassah Hospital, Ophthalmology Department, Jerusalem, Israel and Clínica Barraquer, Bogotá, Colombia. Methods In this retrospective case series, optical biometer measurements were taken for 63 highly myopic patients (> 25 mm) undergoing uneventful crystalline lens phacoemulsification and insertion of an acrylic intraocular lens. Prediction errors were obtained, with estimations of ±0.50 D, ± 1.00 D, and greater than ±2.00 D. A method to improve the corneal height calculation is described. Results The SRK/T formula (mean absolute error [MAE] = 0.418; median absolute error [MedAE] = 0.352) was the most accurate, followed by the T2 (MAE = 0.435; MedAE = 0.381) and Holladay 1 (MAE = 0.455; MedAE = 0.389) formulas. Both the SRK/T and T2 formulas overestimated corneal height, but values were higher with the T2 formula. Corneal height was more precisely estimated using an alternative method that, when combined with axial length optimization, resulted in lower MAE (0.425) and MedAE (0.365) values than when applying the T2 formula alone. Conclusions The T2 formula seems to be less accurate than the SRK/T formula in highly myopic eyes. An improved corneal height estimation method is described for the the T2 formula.

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T2 formula in a highly myopic population, comparison with other methods and description of an improved approach for estimating corneal height

10.21203/rs.2.9499/v1 ◽

2019 ◽

Author(s):

Carlos Alberto Idrobo ◽

Gisella Santaella ◽

Ángela María Gutiérrez

Keyword(s):

Mean Absolute Error ◽

Estimation Method ◽

Case Series ◽

Crystalline Lens ◽

Absolute Error ◽

Prediction Errors ◽

Retrospective Case ◽

Population Comparison ◽

Median Absolute Error ◽

Optical Biometer

Abstract Background: To determine the accuracy of the T2 formula as applied to highly myopic eyes, to compare the T2 formula to the SRK/T and Holladay 1 formulas, and to describe possible ways to improve the estimation of corneal height and prediction error in two settings, the Hadassah Hospital, Ophthalmology Department, Jerusalem, Israel and Clínica Barraquer, Bogotá, Colombia. Methods: In this retrospective case series , optical biometer measurements were taken for 63 highly myopic patients (spherical power ≤ 5 D) undergoing uneventful crystalline lens phacoemulsification and insertion of an acrylic intraocular lens. Prediction errors were obtained, with estimations of ± 0.50 D, ± 1.00 D, and greater than ± 2.00 D. A method to improve the corneal height calculation is described. Results: The SRK/T formula (mean absolute error [MAE] = 0.418; median absolute error [MedAE] = 0.352) was the most accurate, followed by the T2 (MAE = 0.435; MedAE = 0.381) and Holladay 1 (MAE = 0.455; MedAE = 0.389) formulas. Both the SRK/T and T2 formulas overestimated corneal height, but values were higher with the T2 formula. Corneal height was more precisely estimated using an alternative method that, when combined with axial length optimization, resulted in lower MAE (0.425) and MedAE (0.365) values than when applying the T2 formula alone. Conclusions: The T2 formula seems to be less accurate than the SRK/T formula in highly myopic eyes. An improved corneal height estimation method is described for the the T2 formula.

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T2 formula in a highly myopic population, comparison with other methods and description of an improved approach for estimating corneal height

10.21203/rs.2.9499/v2 ◽

2019 ◽

Author(s):

Carlos Alberto Idrobo ◽

Gisella Santaella ◽

Ángela María Gutiérrez

Keyword(s):

Intraocular Lens ◽

Estimation Method ◽

Case Series ◽

Crystalline Lens ◽

Absolute Error ◽

Prediction Errors ◽

Retrospective Case ◽

Height Estimation ◽

Population Comparison ◽

Intraocular Lens Calculation

Abstract ABSTRACT Background: To determine the accuracy of the T2 formula as applied to highly myopic eyes, to compare the T2 formula to the SRK/T and Holladay 1 formulas, and to describe possible ways to improve the estimation of corneal height and prediction error in two settings, the Hadassah Hospital, Ophthalmology Department, Jerusalem, Israel and Clínica Barraquer, Bogotá, Colombia. Methods: In this retrospective case series , optical biometer measurements were taken for 63 highly myopic patients (> 25 mm ) undergoing uneventful crystalline lens phacoemulsification and insertion of an acrylic intraocular lens. Prediction errors were obtained, with estimations of ± 0.50 D, ± 1.00 D, and greater than ± 2.00 D. A method to improve the corneal height calculation is described. Results: The SRK/T formula (mean absolute error [MAE] = 0.418; median absolute error [MedAE] = 0.352) was the most accurate, followed by the T2 (MAE = 0.435; MedAE = 0.381) and Holladay 1 (MAE = 0.455; MedAE = 0.389) formulas. Both the SRK/T and T2 formulas overestimated corneal height, but values were higher with the T2 formula. Corneal height was more precisely estimated using an alternative method that, when combined with axial length optimization, resulted in lower MAE (0.425) and MedAE (0.365) values than when applying the T2 formula alone. Conclusions: The T2 formula seems to be less accurate than the SRK/T formula in highly myopic eyes. An improved corneal height estimation method is described for the the T2 formula. Key words: T2 formula, high myopia, corneal height estimation, cataract surgery, intraocular lens calculation .

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Assessment of the Influence of Keratometry on Intraocular Lens Calculation Formulas in Long Axial Length Eyes

10.21203/rs.3.rs-639671/v1 ◽

2021 ◽

Author(s):

Shengjie Yin ◽

Chengyao Guo ◽

Kunliang Qiu ◽

Tsz Kin Ng ◽

Yuancun Li ◽

...

Keyword(s):

Intraocular Lens ◽

Axial Length ◽

Case Series ◽

Absolute Error ◽

Power Calculation ◽

Prediction Errors ◽

Retrospective Case ◽

Iol Power Calculation ◽

Iol Power ◽

Intraocular Lens Calculation

Abstract Purpose: 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 (≥ 26.0 mm). 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.Methods: Retrospective case-series. 180 eyes with axial length (AL) ≥ 26.0 mm were divided into 3 keratometry (K) groups: K ≤ 42.0 D (Flat), K ≥ 46.0 D (Steep), 42.0 < K < 46.0 D (Average). Prediction errors (PE) were compared between different formulas. Multiple regression analysis was performed to investigate factors associated with the PE.Results: 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. Conclusions: 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.

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Anterior chamber depth, lens thickness and intraocular lens calculation formula accuracy: nine formulas comparison

British Journal of Ophthalmology ◽

10.1136/bjophthalmol-2020-317822 ◽

2020 ◽

pp. bjophthalmol-2020-317822

Author(s):

Diogo Hipólito-Fernandes ◽

Maria Elisa Luís ◽

Rita Serras-Pereira ◽

Pedro Gil ◽

Vitor Maduro ◽

...

Keyword(s):

Anterior Chamber ◽

Intraocular Lens ◽

Prediction Error ◽

Anterior Chamber Depth ◽

Case Series ◽

Absolute Error ◽

Power Calculation ◽

Retrospective Case ◽

Lens Thickness ◽

Mean Prediction Error

Background/AimsTo investigate the influence of anterior chamber depth (ACD) and lens thickness (LT) on 9 intraocular lens (IOL) power calculation formulas accuracy, in patients with normal axial lengths.MethodsRetrospective case series, including patients having uncomplicated cataract surgery with insertion of a single IOL model, divided into three groups according to preoperative ACD. Each group was further subdivided into three subgroups, according to the LT. Using optimised constants, refraction prediction error was calculated for Barrett Universal II, Emmetropia Verifying Optical (EVO) V.2.0, Haigis, Hill-RBF V.2.0, Hoffer Q, Holladay 1, Kane, PEARL-DGS and SRK/T formulas. Mean prediction error, mean and median absolute error (MedAE) and the percentage of eyes within ±0.25D, ±0.50D and ±1.00D were also calculated.ResultsThe study included 695 eyes from 695 patients. For ACD ≤3.0 mm and ≥3.5 mm, mean prediction error of SRK/T, Hoffer Q and Holladay 1 was significantly different from 0 (p<0.05). PEARL-DGS, Kane, EVO V.2.0 and Barrett Universal II were more accurate than the Hoffer Q in ACD ≤3.0 mm (p<0.05). Kane, PEARL-DGS, EVO V.2.0 and Barrett Universal II revealed the lowest variance of mean and MedAE by ACD and LT subgroup. Haigis and Hill-RBF V.2.0 were significantly influenced by LT, independently of the ACD, with a myopic shift with thin lenses and a hyperopic shift with thick lenses (p<0.05).ConclusionNew generation formulas, particularly Kane, PEARL-DGS and EVO V.2.0, seem to be more reliable and stable even in eyes with extreme ACD-LT combinations.

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Corneal topographic ring vs zone in trifocal IOL calculation

Modern technologies in ophtalmology ◽

10.25276/2312-4911-2021-2-184-186 ◽

2021 ◽

pp. 184-186

Author(s):

A.D. Loginova ◽

◽

S.V. Shukhaev ◽

S.S. Kudlakhmedov ◽

E.V. Boiko ◽

...

Keyword(s):

Power Distribution ◽

Mean Absolute Error ◽

Absolute Error ◽

Accurate Calculation ◽

Iol Implantation ◽

Topographic Data ◽

Trifocal Iol ◽

Iol Calculation ◽

Km Value ◽

Median Absolute Error

Purpose. To compare the results of trifocal IOL calculation using various corneal topographic data (ring and zone). Methods. This retrospective study involved 35 patients (40 eyes), underwent cataract surgery (FLACS) with trifocal IOL implantation (AcrySof IQ PanOptix). The calculation was performed using IOL-Master 500 according to 4 formulas (Haigis, HofferQ, Holladay 1, SRK / T) and Tomey OA-2000 according to 2 formulas (Barrett II Universal, Olsen). Topographic values included Km collected from Pentacam HR Power Distribution Apex map with diameter of 3.0 and 5.0 mm on a ring and zone. Predicted and actual refraction were compared after surgery. Results. Mean Km value on 3 mm zone and ring was: 42.75±1,46 D and 42.91±1.43 D, respectively (p<0.0001). Mean Km value on 5 mm zone and ring was: 43.09±1.5 D and 43.55±1.48 D, respectively (p<0.0001). According to 6 formulas Mean Absolute Error (MAE) calculated using 3 mm zone data was significantly less then on 3mm ring: 0.3± 0.28; 0.48±0.3 and Median Absolute Error (MedAE) was 0.225 (0.3); 0.465 (0.397) respectively (p<0.01). The same data were obtained on 5mm zone and ring: MAE was 0.29±0.28; 0.35±0.29 and MedAE amounted to 0.225 (0.3); 0.29 (0.38) respectively (p=0.02). Conclusion. Mean Km value on Power Distribution Apex map according to ring is significantly greater then according to zone. 1) Predicted refraction using corneal topographic ring data deviates towards hyperopia relative to the actual postoperative refraction. 2) The use of topographic data on zone allows to obtain more accurate calculation of trifocal IOL than when using the data on the ring. Key words: IOL calculation, Trifocal IOL, corneal topography.

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Multicenter validation of a formula predicting postoperative spinopelvic alignment

Journal of Neurosurgery Spine ◽

10.3171/2011.8.spine11272 ◽

2012 ◽

Vol 16 (1) ◽

pp. 15-21 ◽

Cited By ~ 47

Author(s):

Virginie Lafage ◽

Neil J. Bharucha ◽

Frank Schwab ◽

Robert A. Hart ◽

Douglas Burton ◽

...

Keyword(s):

Spinal Deformity ◽

Predictive Value ◽

Adult Spinal Deformity ◽

Case Series ◽

Absolute Error ◽

Interquartile Range ◽

Successful Outcome ◽

Sagittal Imbalance ◽

Spinopelvic Alignment ◽

Median Absolute Error

Object Sagittal spinopelvic imbalance is a major contributor to pain and disability for patients with adult spinal deformity (ASD). Preoperative planning is essential for pedicle subtraction osteotomy (PSO) candidates; however, current methods are often inaccurate because no formula to date predicts both postoperative sagittal balance and pelvic alignment. The authors of this study aimed to evaluate the accuracy of 2 novel formulas in predicting postoperative spinopelvic alignment after PSO. Methods This study is a multicenter retrospective consecutive PSO case series. Adults with spinal deformity (> 21 years old) who were treated with a single-level lumbar PSO for sagittal imbalance were evaluated. All patients underwent preoperative and a minimum of 6-month postoperative radiography. Two novel formulas were used to predict the postoperative spinopelvic alignment. The results predicted by the formulas were then compared with the actual postoperative radiographic values, and the formulas' ability to identify successful (sagittal vertical axis [SVA] ≤ 50 mm and pelvic tilt [PT] ≤ 25°) and unsuccessful (SVA > 50 mm or PT > 25°) outcomes was evaluated. Results Ninety-nine patients met inclusion criteria. The median absolute error between the predicted and actual PT was 4.1° (interquartile range 2.0°–6.4°). The median absolute error between the predicted and actual SVA was 27 mm (interquartile range 11–47 mm). Forty-one of 54 patients with a formula that predicted a successful outcome had a successful outcome as shown by radiography (positive predictive value = 0.76). Forty-four of 45 patients with a formula that predicted an unsuccessful outcome had an unsuccessful outcome as shown by radiography (negative predictive value = 0.98). Conclusions The spinopelvic alignment formulas were accurate when predicting unsuccessful outcomes but less reliable when predicting successful outcomes. The preoperative surgical plan should be altered if an unsuccessful result is predicted. However, even after obtaining a predicted successful outcome, surgeons should ensure that the predicted values are not too close to unsuccessful values and should identify other variables that may affect alignment. In the near future, it is anticipated that the use of these formulas will lead to better surgical planning and improved outcomes for patients with complex ASD.

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Accuracy of biometric formulae in hypermetropic patients undergoing cataract surgery

European Journal of Ophthalmology ◽

10.1177/1120672118803509 ◽

2018 ◽

Vol 29 (5) ◽

pp. 510-515

Author(s):

Mohammad Z Mustafa ◽

Ashraf A Khan ◽

Harry Bennett ◽

Andrew J Tatham ◽

Mark Wright

Keyword(s):

Cataract Surgery ◽

Anterior Chamber ◽

Axial Length ◽

Mean Absolute Error ◽

Anterior Chamber Depth ◽

Absolute Error ◽

University Hospital ◽

Prediction Errors ◽

Refractive Outcomes ◽

Significant Difference

Purpose: To audit and analyse the accuracy of current biometric formulae on refractive outcomes following cataract surgery in patients with axial length less than 22 mm. Methods: A total of 84 eyes from 84 patients with axial length <22 mm were identified from consecutive patients undergoing cataract surgery retrospectively at a single university hospital. All subjects had biometry using the IOLMaster (Carl Zeiss Meditec, Inc, Dublin, CA, USA) and a Sensar AR40 intraocular lens implant (Abbott Medical Optics, CA, USA). One eye from each patient was randomly selected for inclusion. Prediction errors were calculated by comparing expected refraction from optimized formulas (SRK/T, Hoffer Q, Haigis and Holladay 1) to postoperative refraction. A national survey of ophthalmologists was conducted to ascertain biometric formula preference for small eyes. Results: The mean axial length was 21.00 ± 0.55 mm. Mean error was greatest for Hoffer Q at −0.57 dioptres. There was no significant difference in mean absolute error between formulae. SRK/T achieved the highest percentage of outcomes within 0.5 dioptres (45.2%) and 1 dioptre (76.2%) of target. Shallower anterior chamber depth was associated with higher mean absolute error for SRK/T (p = 0.028), Hoffer Q (p = 0.003) and Haigis (p = 0.016) but not Holladay (p = 0.111). Conclusion: SRK/T had the highest proportion of patients achieving refractive results close to predicted outcomes. However, there was a significant association between a shallower anterior chamber depth and higher mean absolute error for all formulae except Holladay 1. This suggests that anterior chamber depth with axial length should be considered when counselling patients about refractive outcome.

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Lenstar LS 900 versus Pentacam-AXL: analysis of refractive outcomes and predicted refraction

Scientific Reports ◽

10.1038/s41598-021-81146-2 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Henrique Aragão Arruda ◽

Joana M. Pereira ◽

Arminda Neves ◽

Maria João Vieira ◽

Joana Martins ◽

...

Keyword(s):

Refractive Error ◽

Prediction Error ◽

Mean Absolute Error ◽

Absolute Error ◽

Spherical Equivalent ◽

Refractive Outcomes ◽

Iol Calculation ◽

Median Absolute Error ◽

The Difference ◽

Mean Prediction Error

AbstractAnalysis of refractive outcomes, using biometry data collected with a new biometer (Pentacam-AXL, OCULUS, Germany) and a reference biometer (Lenstar LS 900, HAAG-STREIT AG, Switzerland), in order to assess differences in the predicted and actual refraction using different formulas. Prospective, institutional study, in which intraocular lens (IOL) calculation was performed using the Haigis, SRK/T and Hoffer Q formulas with the two systems in patients undergoing cataract surgery between November 2016 and August 2017. Four to 6 weeks after surgery, the spherical equivalent (SE) was derived from objective refraction. Mean prediction error (PE), mean absolute error (MAE) and the median absolute error (MedAE) were calculated. The percentage of eyes within ± 0.25, ± 0.50, ± 1.00, and ± 2.00 D of MAE was determined. 104 eyes from 76 patients, 35 males (46.1%), underwent uneventful phacoemulsification with IOL implantation. Mean SE after surgery was − 0.29 ± 0.46 D. Mean prediction error (PE) using the SRK/T, Haigis and Hoffer Q formulas with the Lenstar was significantly different (p > 0.0001) from PE calculated with the Pentacam in all three formulas. Percentage of eyes within ± 0.25 D MAE were larger with the Lenstar device, using all three formulas. The difference between the actual refractive error and the predicted refractive error is consistently lower when using Lenstar. The Pentacam-AXL user should be alert to the critical necessity of constant optimization in order to obtain optimal refractive results.

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Comparison of Accuracy of Intraocular Lens Power calculation for Eyes with an Axial Length Greater Than 29.0 mm

10.21203/rs.3.rs-709508/v1 ◽

2021 ◽

Author(s):

Chengyao Guo ◽

Shengjie Yin ◽

Kunliang Qiu ◽

Mingzhi Zhang

Keyword(s):

Intraocular Lens ◽

Axial Length ◽

Case Series ◽

Pairwise Comparison ◽

Absolute Error ◽

Power Calculation ◽

Prediction Errors ◽

Intraocular Lens Power Calculation ◽

Iol Power Calculation ◽

Significant Difference

Abstract PurposeTo evaluate and compare the accuracy of six different formulas (EVO 2.0, Kane, SRK/T, Barrett Universal II, Haigis and Olsen) in intraocular lens (IOL) power calculation for extremely long eyes.MethodsRetrospective case-series. 73 eyes with axial length (AL) ≥ 29.0 mm and 920H IOL implantation were included. Prediction errors (PE) were calculated and compared between different formulas. Multiple regression analysis was performed to investigate factors associated with the PE.ResultsThe Kane formula had mean prediction error close to zero (-0.01 D, P = 0.841), whereas the EVO 2.0, SRK/T, Barrett Universal II, Haigis and Olsen formulas produced hyperopic outcomes (all P < 0.001). The median absolute error produced by the EVO 2.0, Kane, Barrett Universal II and Olsen formulas showed no significant difference (0.33 D, 0.30 D, 0.29 D, 0.34 D, respectively, pairwise comparison P > 0.05), but was significantly lower than that of the SRK/T and Haigis formulas (0.85 D, 0.80 D, respectively, pairwise comparison P＜ 0.001). The accuracy of the SRK/T formula in extremely myopic eyes was affected by the AL, suggesting that a longer AL was always associated with a hyperopic surprise and a shorter AL was always associated with a myopic surprise, whereas the accuracy of other formulas was less affected by the AL.ConclusionsFor cataract patients with axial length greater than 29.0 mm, the accuracy of the EVO 2.0, Kane, Barrett Universal II and Olsen formulas is comparable and significantly better than that of the SRK/T and Haigis formulas.

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A 3D map of englacial attenuation rate from radar reflections at Law Dome, East Antarctica

10.5194/essd-2020-146 ◽

2020 ◽

Author(s):

Syed Abdul Salam ◽

Jason L. Roberts ◽

Felicity S. McCormack ◽

Richard Coleman ◽

Jacqueline A. Halpin

Keyword(s):

Root Mean Square Error ◽

Sea Level ◽

Mean Square Error ◽

Mean Absolute Error ◽

Absolute Error ◽

Radar Data ◽

Mean Square ◽

Ice Cap ◽

Attenuation Rate ◽

Median Absolute Error

Abstract. The East Antarctic Ice Sheet (EAIS) is the largest source of potential sea-level rise, containing approximately 52 m of sea-level equivalent. To constrain estimates of sea-level rise into the future requires knowledge of ice-sheet properties and geometry and ice-penetrating radar offers a means to estimate these properties (e.g. ice thickness, englacial temperatures). One of the regions that have been extensively surveyed using ice-penetrating radar from the Investigating the Cryospheric Evolution of the Central Antarctic Plate (ICECAP) project in East Antarctica is Law Dome, a small independent ice cap situated to the west of Totten Ice Shelf. The ice cap is slow-moving, has a low melt-rate at the surface and moderate wind speeds, making it a useful study site for estimating the radar attenuation. A new method is proposed for the estimation of attenuation rate from radar data which is mathematically modelled as a constrained regularised l2 minimisation problem. In the proposed method, only radar data is required and the englacial reflectors are automatically detected from the radar data itself. To validate our methodology, attenuation differences at flight crossover points are calculated and statistical analyses performed to assess the accuracy of the results. For spatial analyses, the errors are of the order 22.6 %, 15.2 %, and 32.8 % for mean absolute error, median absolute error, and root mean square error respectively. Also, for the depth analyses, up to the depth of 800 m, the errors are under 29.9 %, 24.2 %, and 38.8 % for mean absolute error, median absolute error, and root mean square error respectively. A final product of 3D attenuation rates and uncertainty estimates is provided. The generated dataset is publicly available at https://doi.org/10.25959/5e6851e266f4a (Abdul Salam, 2020).

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